CA2259090A1 - Rock drill - Google Patents
Rock drill Download PDFInfo
- Publication number
- CA2259090A1 CA2259090A1 CA002259090A CA2259090A CA2259090A1 CA 2259090 A1 CA2259090 A1 CA 2259090A1 CA 002259090 A CA002259090 A CA 002259090A CA 2259090 A CA2259090 A CA 2259090A CA 2259090 A1 CA2259090 A1 CA 2259090A1
- Authority
- CA
- Canada
- Prior art keywords
- drill
- drill bit
- cutting
- ductile iron
- rock
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/36—Percussion drill bits
- E21B10/38—Percussion drill bits characterised by conduits or nozzles for drilling fluids
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
Abstract
A rock drilling bit for drilling bores in rock, more particularly to a percussion rock drilling bit. Specifically, a rock drilling bit having hard material cutting inserts affixed to an austempered ductile iron (ADI) drill body, and a method of drilling rock using said bit.
Description
_ I _ 31 ~I (1-7 ROCK DR1I,L
1. Field of the Invention This invention relates to rock drilling bits for drilling bores in rock) more particularly to percussion rock drilling bit,S. Specifically, the invention is directed to rock drilling bits having hard material cutting inserts affixed to an austemPered ductile iron (ADI) body, and a method of drilling rock using such a bit.
1. Field of the Invention This invention relates to rock drilling bits for drilling bores in rock) more particularly to percussion rock drilling bit,S. Specifically, the invention is directed to rock drilling bits having hard material cutting inserts affixed to an austemPered ductile iron (ADI) body, and a method of drilling rock using such a bit.
2. $ack~rouud of the invention:
'1'hc invention is particularly suited for use in producing rock drilling bits of the type generally referred to as percussion drilling bits and will be described with reference thereto;
however, as ~yill becortac apparent, the invention could equally well be used to produce roller cone bits, polycrystalline diamond compact (PCU) bits, and siulilar bits of the type wherein the cutting is perfozmed by hard material inserts carried in a drill hody.
A conventional percussion drill bit comprises a steel drill body having a generally cylindrical mounting shank carrying an axially aligned cylindrical head defining a cutting face.
A multiplicity of cylindrical, hard material cutting inserts, generally formed of sintered tungsten carbide, press-fitted in precision drilled openings iu the cutting face. The exposed ends of the cutting inserts perform the actual rock cutting by abrading or crushing the rock into rock dust and small particles. The dust and particles are flushed from the drill hole by compressed air or other pressurized fluid supplied through a central passageway in the drill bit and out branch passageways opening on the cutting face. Figure 1 is a depict ion of such a conventional percussion type down-the-hole ("L~TI-I") drill bit. Specifically. F~~iQure 1 shows a conventional DTH drill bit (10) comprising a drill body (?0) having a connecting section (30), defining a rotational axis) means for coupling (35) the drill bit ( 10) to a percussive unit or oilier drill device (not shown), a cutting face (40) having a plurality of holes (~2) tlxcrein (not shown)) the cutting face being rigid with the connecting section, a central passageway (-1_5) rherethrough (not shown) with at least. one branch passageway (50) exlendinfi from the central passageway and opening onto the cutting face and at least one recess (60); a ph~utality of cueing inserts (70) affixed to the cutting face in the plurality of laoles, including gauge row im;erts (7?.) located along the outermost periphery of the cutting fact:, embedded in tire cutting f5ce, each cutting insert comprising a carbide body having a rear mounting portion (not shown) embedded in the drill body and a cutting end portion protruding from tire drill body.
Typically) fire life of a rock drill bit is dependent on the life of the hard material cutting inserts. L-Iov~~ever, in certain rock formations) such as soft) fractured formations, the bit body IS itself is subjected to signific.~tnt erosive wear. lu cutting operations in such rock formations, failure of the drill bit often occurs prematurely because of erosion of the drill body, particularly in the area surrounding the culling inserts. ~1'his erosion results in the weakening of the drill body in general. This erosion also may result irt a. loss of support for the cutting inserts.
Specifically) erosion of the drill body at the site of fixation of the cutting inserts weakens the ;ZO hoed between the drill body and the cutting inserts. wcntnally, i:rusion at the site of fixation results in the separation of the cutting insert from the drill body. Once one or more cutting inserts are sepazated from the drill body, the cutting inserts must be reaffixed to the drill. If reaffixalion is not possible, the drill hit must be retired. The separation of cutting inserts from the drill body is a particular concern with respect to the outer day "gage"
row of inserts located 25 along tire periphery of the cutting face because the outer periphery of the cutting face is subjected to more erosive conditions than the rest of the cutting fact.
In an effort to increase the durability of rock drill bits and to overcome the cutting insert separation problems noted above, various methods have been employed such as increasing the hardness of conventional steel bia bodies by using a higher carbon content steel and heat treating for high hardness; forming the drill bodies fTOtn a low carbon c~ntenl steel and subsequently carburizing and case hardening the drill body; and carburizing and case hardening the cutting face while selectively preventing the penetration of carbon into the cueing face in tlae azeas when the cutting inserts are to be affixed. Notwithstanding) materials of construction and designs which result in rock drill bits which can drill faster and last longer ate constantly being sought.
3. Summary of the Inyention:
The invention provides rock drill hits having drill bodies comprised of austcmperod ductile iron- The auslernpered ductile iron drill bits of the invention have been determined to exhibit exceptional durability and ease of tnanufacmre. The austempered ductile iron drill bits of the invention tray also be produced more economically than conventional steel drill bits.
It is an object of the invention to provide rock drill bits having a drill body comprised of austempered ductite iron.
It is another object of the invention to provide a drill bit for drilling rock, comprising:
as austempered ductile iron drill body having a cutting face, a plurality of openings formed in the drill body at the cutting face) and cutting inserts mounted in said openings with cutting end portions extending outwardly from the cutting face.
1t is another object of the invention to provide austemhered ductile iron drill bodies having a hardness on the Rockwell C scale of at least 40.
It is another object of the invention to provide austempered ductile iron drill bodies having a central passageway and at least one branch passageway fur a flushing medium, wherein die branch passageway opens onto the cutting face and extends tn the central passageway.
It is another object of the invention to provide austempcred ductile iron drill bodies having at Least one branch passageway with a non-circular cross section.
It is another object of the invention to provide austetnpered ductile iron drill bodies having at least one branch passageway having a cross-sect ion shaped to facilitate the incorporation of a maximtun number of cutting inserts on the cutting face.
- 'I - 31d0-7 1l is another object of the invention tn Provide austernpered ductile iron drill bodies traving at least one recess for facilitating the removal of drill dn,st and debris.
It is another object of the invention to provide drill bodies comprised of austcmpered ductile iron produced from ductile iron by a process comprising: heating the drill holly cast in ductile iron to an austeniti~itlg temperature of 1.550 to 1750"P, preferably 1550 to 1650°r;
isothermally treating the drill body at the austenitiziog temperamrc for an austerlitiziztg period sufficient to produce a fully austenitic matrix, saturated with carhon;
quenching the drill body to an austempering temperature of 450 to G00°F rapidly enough to inhihit the forrrtation of pearIite and to initiate the formation of ausfetiite; isothermally rreating the drill body at the austempering temperature for an austempering period to produce ausferrite;
and, recovering the austempered ductile iron drill body.
It is another object of the invention to provide drill bodies compritcd of austempered ductile iron having an austenite carbon content in the range of I . R to 4 wt 3~ ) preferably 1.8 to 2.4 wt%.
It is another object of the invention to provide a percussion drill bit for drilling a bore through rock, cozuprising a drill body having a connecting section at a rear end thereof for connection to a percussive unit and defining a rotational axiR of the drill bit, and a plurality of cutting inserts embedded in a cutting fatx at a front end of the drill holy, the cutting face being rigid witli respect to the connecting section) each cutting insert comprising a hard material body having a rear mounting portion embedded in the drill body, and a cutting end portion protruding from the drill body, wherein the drill body is comprised of austentpered ductile iron.
It is also an object of the invention to provide a method for drilling rock, comprising.
providing a drill hit having a drill body made of austempered ductile iron having a connecting section defining a rotational axis and a cutting face with a plurality of cutting inserts, including gauge row inserts) embedded therein) the cutting face being rigid with the cmtnecting section, each cutting insert comprising a hard material body having a rear mounting portion embedded In the drill body and a cutting end portion protruding from the drill body;
and, rotating the drill bit about the rotational axis such that the gauge row inserts define a diameter of a bore being drilled.
S. Brief Descri tion o the Drawings:
There are shown in the drawings certain excrlplary ernhc~dimentc of the invention as presently preferred. It should be understood that the invention is nut limited to the embodiments disclnsetl as examplec, and is capable of variation within the spirit and scope of the appended claims. 1n the drawings, Figure 1. is a side perspective vietv of a conventional down the hole rock drill bit;
rigure 2 is a de(ailc~i front plan view of the cuttinfi face of a rock drill bit de.9ign of the invention wherein the branch passageway openings are different and nova-circular;
Figure 3 is a detailed front plan view of the cutting face of a rock drill bit design of the invention wherein the branch passageway openings are identical and non-circular;
Figure 4 is a partial cutaway side plan view of a rock drill showing the central passageway anal tile branch passageway;
Figure 5 is a front plan view of the rock drill bit a ;ed in the rock drilling test described in Example l;
Figure 6 is a cido profile view of the rock drill bit used in the rock drilling test described in E~tample 1;
Figure 7 i~ a frunt plan view of the rock drill bit used in the rock drilling test described in Example 2;
Figure 8 is a side profile view of the rock drill bit used in the rock drilling test described ZU in fixatnple 2;
Figure 9 is a front plan view of the rock drill bit used in the ruck drilling test described in Example 5; and Figure IO is a side profile view of the rock drill bit used in the rock drilling teat deBCribed in Example S.
' 6 - 3140-7 C. Detailed Description of the Preferred Embodiments of the Inyentio~l:
The following detailed description is of the best prcsPntly contemplated mode of carrying out tile invention. The description is not intended in a limiting Sense, and is is made solely for the purpose of illustratizlg the general principles of the invention. The various features and advantages of the present invention may be more readily understood cvi~h reference to the following detailed description taken in conjunction with the accompanying drawings.
The rock drill bits of the invention are characterized by having drill bodies constructed of austempered ductile iron_ The rock drill bits of the invention may comprise percussion drill bits, roller cone bits, polycrystalline diamond compact bits, and the like, particularly percussion drill bits.
The austempered ductile iron used in the rock drill bits of the invention consists of acicular ferrite in a high carbon austenite matrix called ausferrite. The austemnered ductile iron is produced by heat treating conventional ductile iron which is derived from gray (cast) iron, which exhibits exceptional ca.stibility when compared witll steel.
Specifically, austempered IS ' ductile iron is produced by subjecting conventional ductile iron to a known heat treatment process called austempering. The austempering heat treatment process generally comprises. (1 ) heating the ductile iron work piece to au auslenitizing temperature; (2) isothermally treating the work piece at the austenitizing temperature for an austenitizing period until s fully austenitic matrix saturated with carbon is obtained; (3) quenching the work piece to an.
austempering temperature rapidly enough to inhibit the formation of pearlitc and to initiate the formation of ausferrite; (4-) isothemtally treating the work piece at the austempering temperature for an austempering period; and (5) recovering the austempered ductile iron work piece. The critical variables in the austempering process are: ( 1 ) the austeuitizing temperature, (2) the length of the austenitiziztg period, (3) the cooling rate during the quenching step from the austenitizing temperature to the austempering temperature, (4) the austempering temperature, and (S) the length of the austempering period.
The allowable process conditions during the austemperirtg process and the resultant physical properties of the au_stempered ductile iron producod thereby are dependant upon the quality and material content of the ductile icon being treated. Defects in the mechanical 7 ' 3110-7 properties of the ductile iron such as shrinkage. slag stringers and poor miGrostrucmral features are magnified in the auttempered ductile iron produced therefrom. Accordingly) it is important to use high quality ductile iron when manufacturing the austempered ductile iron drill bits according to the invention. For the purposes of austempering, high qualit3~
ductile iron has been defined as that which has: (1) a uniform nodule distribution with a minimum of nodules/mm', (2) a nodnlarity excxeding 8096, (3) a carbide and nonmetallic inclusion content not exceeding 0.5 % , and (4) a porosity or microshrinkage volume not exceeding 19b .
Tlte drill bits of the invention are produced by first ca.5ting the drill body with high quality ductile iron. The rough cast product may be machinfxl fls needed before austempering while tlae drill body material is still relatively soft and easily machineable. Notwithstanding, many features that must be machined into conventional steel drill bits may be incorporated into the drill bits according to the invention during casting due to the castability of ductile iron. The castability of ductile iron drzll bits according to the invention allows for the elimination of up tv 90% to 95°6 of the machining costs associated with conventional steel drill biLS. The castibility of ductile izon also makes possible drill bit body configurations which would be difficult and costly and in some cases impossible to achieve using conventional machicting techniques. For example, branch passageways (50) in steel drill bodies conventionally have a circular cross-secaion. Figure I depicts the conventional circular czoss-section of the branch passageways. While acceptable for use with the invention, branch passages having a circular cross-section may limit on the total number of cutting inserts whiclmlay be incorporated on the cutting face. Because the cutting inserts perform the actual drilling, it is advantageous to iutcorporate as many cutting inserts as structurally possible on the cutting face of a given drill bit. In some configurations, the use of unique non-circular cross-sections for the branch passageways may facilitate the incorporation of more cutting inserts than would be conceivable on a similar drill bit having branch passageway openings with a circular cross-section. For example, Figure 2 is a detailed frontal view of the cutting face for a DTH
drill bit design of the invention. Specifically, Figure 2 demonstrates the use of non-circular cross-sections for the branclx passageways (50) . Furthermore) Pigure 2 demonstrates the use of two or more passageways having different, non-ciurcular cross-sections. Alternatively, Figure 3 is a detailed frontal view of another cutting face for a threaded button drill bit design of ttte invention wherein the two branch passageways (50) are of identical nun-circular crc,ss section. I3y using such non-circular cross-sectional branch passageways, the number of cutting inserts which ma_y be incorporated into the cutting face tray be maxituized.
The optionally machined cast ductile iron drill body is then converted into austctrtpercd ductile iron using the austempering heat treatment procedure describext herein. Specifically, high quality ductile iron in ASTM A897-90 Grade 3, ~! or 5, may be used to form the drill hodit~s_ The ductile iron drill bodies may be converted to austempered ductile iron using a thermal austempering treatment generally comprising; (1) heating the ductile iron chill body to an austenitiring temperature crf 1_550 to 1750°F, preferably 1550 to 1650°P; (2) isothermally treating the drill body at the auslenitizing temperature for an austenitizing period sufficient to produce a fully austenitic matrix, saturated with carbon; (3) quenching the drill body to an austempering temperature of 400 tn 6~0°F, rapidly enough to inhibit the formation of pearlite and to initiate the formation of ausferrite, preferably at a rate of 30,000°F/mln.; (4) isothermally treating the drill body al the austempering temperature for an austetnpering period, producing ausferrite having an austcnite carbon content in the range of 1.8 to 4 wt~, preferably 1 _8 to 2.4 wt9b; and, (5) recovering the austempered ductile iron drill body.
The austempcred drill body may be further processed by, for example, shot peering, as required to provide the drill body with the desired surface hardness. The auslempered dirclile iron drill body may also be work ltardened. Specifically, percussion rock drill bits operate by breaking rvc:k in front of the drill bit into small pieces or rock dust. Tlte percussion rack drill bits are used in conjunction with a percussive unit which operates to rotate the dz~ll bit about its axis and to simultaneously propel the drill bit into the rock formation to be drilled in a reciprocating manner. Also, high velocity flushing fluid is passed through the central passageway into the branch passageways out the cutting face into the bore during the drilling process. Figure 4 is a partial cueaway view of a cnnventi~~nal rock drill bit showing the central passageway (45) and the at least one branch passageway (50) _ This high velocity fluid forces the rock dust out from in front of the drill bit to the periphery of the cutting face, through recesses on die drill bit and up and out of the bore. During this process, broken pieces of rock are constantly impacting on the surfaces of the drill hit. Conventional steel drill bid are abraded and worn down by this constant impacting. The surface of austcrnpered ductile iron rock drill bits, however, become harder as a result of tlli5 constant impacting. 'thus, the constant impacting associated with use, operates to work harden austemPered ductile iron drill bits, thereby enhancing their surface wean resistance.
Getting inserr.5 useful with the invention may be made of a material selected from the grouF consisting of tungsten carbide, coated tungsten carbide, diamond enhanced tnngstcn carbide) txramic, last-dened steel, amd ADI.
The cutting inserts preferably have a rrar mounting portion and a cutting end portion.
Tlte roar mounting portion is designed to engage one of the plurality of openings on the drill body, cutting face. The cutting inserts may be interfaced with the drill body using conventional attachment methods, including but not limited to, cementing, glueing) welding, cotnpre~sion fitting, and threading.
Preferably, the cutting inserts are atflxed to the drill body using a compression fit affixation method, i. e. the cutting inserts are press-fitted into the drill body.
The concepts of the invention will now be illustrated by the following Exarnples, which are intended to be purely exemplary and not Iimitinfi. In each of the following examples the drill body used was obtained by first casting the drill body in ductile iron under the designation ADI grade 2. The drill body was then ntaehined as follows: (l j the outside radial elements were turned on a lathe in two (2) separate operations; (2) the center hr.~le was gundrilled; (3) the splines were hobbed; (4) the air flats were milled; (5) the blowtube seat was bored on a lathe and (6) the scallops and blow holes were done on a horizontal atlachining center. The machined drill body was then subjected to 2tn rtustempering heat treatment process consisting of: (1) treating the drill body to an austenitizing temperature of 1550 l0 1750°1", preferably 1550 to 1650°h'; (2) isothermally treatiulg the drill body at the austenitizing temperature for an austenitiiing period of 100 to 140 minutes; (3) cooling the drill body to acr austempering temperature of 575 to G25°F at a rate of 30,000°F/min.; (4) isothermally treating the drill body at the austempering temperature for an austempering period of 100 to 240 min_;
(5) recovering the austempered ductile iron drill body having a hardness on the Rockwell C
scale of 37. Tlte drill body was then finish machined using the following processes: ( 1 ) the critical guide diameter were turned on a lathe, (2) the insert holes were drilhxl on a horizontal machining center. Tungsten carbide cutting inserts were then incorporated imo the drill body by press fit using a hand-held pneumatic impact hammer.
Using a rock drill bit of the iulvention comprising a 61h " diameter concave rock drill bit of the general design depicted in Figures 5 and 6, a series of test bores were drilled at the Vulcan Quarry in Stafford, Virginia. The rock in which the test bores were drilled consisted of granite, the hammer used waa an Ingersole-Rand Percussion Air-Hauimer Model No. SF6 rotating at 34-36 rpm and operating at a pressure of 320 psi. Before drilling, the rock drill bit had a total weight of 5 x .89 pounds and had a gage row button diameter of 6.5 t5 inc>zes and a drill body diameter of 6 _ 453 inelies. The rock dri I I bit was then used to drill rock at an average rate of 86 ft/hour. After drilling about 490 feet of rock) the rock drill bit had a total weight of 50.86 pounds and had a gage row button diameter of 6.92 inches and a drill body diameter of 6.318 inches.
>;.X_A_MPLE Z
Using a rock drill bit of the invention comprising a G'/x" diameter flat rock drill bit of the general design depicted in Figures 7 and $, a series of bores were drilled at the Vulcan Quarry in Stafford, Virginia. T'he rock in which the test bores were drilled consisted of granite, the hammer used was an Ingersole->Zand Percussion Air-Hammer Model SFG
rotating at 34-3G
rpm and operating at a pressure of 320 psi. Before drilling) the rock drill hit had a tots( weight of 52.45 pounds and had a gage row button diameter of 6.510 inches and a drill body diameter of 6.455 inches. The rock drill bit was then used to drill rock at an average rate of 88 filhour.
After drilling about 350 feet of rock) the rock drill bit had a total weight of 51.40 pounds and ?S had a gage row button diameter of 6.488 inches and a drill body diameter of 6.358 inches.
Using a rock drill bit like that used in Example 2) bores were drilled at the Vulcan Quarry in Stafford, Virginia. The rock in which the test bores were drilled consisted oC granite, the hammer used was an Zngersole-Rand Percussion Air-Hammer Model SFf rotating at 34-36 - 11 ' 3140-7 rlntt and operating at a pressure of 320 psi. l3eforc drilling, the rock drill hit had a total weight of 52.45 pounds and had a gage row button diuueter of 6.505 inches and a drill body diameter of 6.451 iltches. The rock drill bit was then used to drill rock at an average rate of 8li ft/hour.
After drilling about 415 feet of ruck, the rock drill bit had a total weight of S I _ 19 pounds and had a gage row button diameter of 6.480 inches and a drill hotly diantete~ of 6.355 inches.
Using a rock bit like that used in Example 2, bores were drilled al the lvtaryland Materials Quarry in Harvc de Grace, Maryland. The rock in which the test bores were drilled coltsisted of granite_ The hamumer need was a Loudon lndusirirs I'r~rcussion Air-lifiammer Model No_ RI~6S rotating al 34-3G tpln and operating at a pressure of 32(1 psi.
Before drilling, tlve rock drill hit had a weight of 5Z-45 pounds and had a diameter aver the gage row buttons of 6.508 inches and a drill body diameter of 6.453 inches. The rock drill hit was then used to drill rock at a rate of 80 ftlhour. After drilling 240 feet of rock, the rock drill bit had a total weight of 51.22 pounds and had a diameter over the gage row buttons of 6.459 inches and a drill body 1S diameter of 6.330 inches.
Using a rock drill bit of the invention comprising a 3ci4" diuneter flat roc><
drill bit of the general design depicted in Figures 9 and I0, a series of test bores were drilled at the Newmont Gvld Company in Elko Nevada. T'lte rock in which the test hores were drilled consisted of siltstone_ The hammer used was a 'i'amrock Model No. 111, 645 rotatiutg at 60 rpm and operating at a pressure of 1,200 psi. Before drilling, the rock drill hit had a diar~oeter over tltc gage row buttotls of 3.50b" and a drill body diameter of 3.450" . The rock drill bit was then used to drill rock at a rate of 90 ft/hvur. The rock drill bit drilled through 4,120 feet of rock before losing four (4) carbide inserts.
2.5 While certain present preferred embodiments of the invention have been illustrated and described, it is to tae understood that the invention is not limited thereto and nmy be otherwise practiced within the scope of the following claims.
_.~._..___~_.~ _._. ._.____ . ~ ...~_ .~...~_
'1'hc invention is particularly suited for use in producing rock drilling bits of the type generally referred to as percussion drilling bits and will be described with reference thereto;
however, as ~yill becortac apparent, the invention could equally well be used to produce roller cone bits, polycrystalline diamond compact (PCU) bits, and siulilar bits of the type wherein the cutting is perfozmed by hard material inserts carried in a drill hody.
A conventional percussion drill bit comprises a steel drill body having a generally cylindrical mounting shank carrying an axially aligned cylindrical head defining a cutting face.
A multiplicity of cylindrical, hard material cutting inserts, generally formed of sintered tungsten carbide, press-fitted in precision drilled openings iu the cutting face. The exposed ends of the cutting inserts perform the actual rock cutting by abrading or crushing the rock into rock dust and small particles. The dust and particles are flushed from the drill hole by compressed air or other pressurized fluid supplied through a central passageway in the drill bit and out branch passageways opening on the cutting face. Figure 1 is a depict ion of such a conventional percussion type down-the-hole ("L~TI-I") drill bit. Specifically. F~~iQure 1 shows a conventional DTH drill bit (10) comprising a drill body (?0) having a connecting section (30), defining a rotational axis) means for coupling (35) the drill bit ( 10) to a percussive unit or oilier drill device (not shown), a cutting face (40) having a plurality of holes (~2) tlxcrein (not shown)) the cutting face being rigid with the connecting section, a central passageway (-1_5) rherethrough (not shown) with at least. one branch passageway (50) exlendinfi from the central passageway and opening onto the cutting face and at least one recess (60); a ph~utality of cueing inserts (70) affixed to the cutting face in the plurality of laoles, including gauge row im;erts (7?.) located along the outermost periphery of the cutting fact:, embedded in tire cutting f5ce, each cutting insert comprising a carbide body having a rear mounting portion (not shown) embedded in the drill body and a cutting end portion protruding from tire drill body.
Typically) fire life of a rock drill bit is dependent on the life of the hard material cutting inserts. L-Iov~~ever, in certain rock formations) such as soft) fractured formations, the bit body IS itself is subjected to signific.~tnt erosive wear. lu cutting operations in such rock formations, failure of the drill bit often occurs prematurely because of erosion of the drill body, particularly in the area surrounding the culling inserts. ~1'his erosion results in the weakening of the drill body in general. This erosion also may result irt a. loss of support for the cutting inserts.
Specifically) erosion of the drill body at the site of fixation of the cutting inserts weakens the ;ZO hoed between the drill body and the cutting inserts. wcntnally, i:rusion at the site of fixation results in the separation of the cutting insert from the drill body. Once one or more cutting inserts are sepazated from the drill body, the cutting inserts must be reaffixed to the drill. If reaffixalion is not possible, the drill hit must be retired. The separation of cutting inserts from the drill body is a particular concern with respect to the outer day "gage"
row of inserts located 25 along tire periphery of the cutting face because the outer periphery of the cutting face is subjected to more erosive conditions than the rest of the cutting fact.
In an effort to increase the durability of rock drill bits and to overcome the cutting insert separation problems noted above, various methods have been employed such as increasing the hardness of conventional steel bia bodies by using a higher carbon content steel and heat treating for high hardness; forming the drill bodies fTOtn a low carbon c~ntenl steel and subsequently carburizing and case hardening the drill body; and carburizing and case hardening the cutting face while selectively preventing the penetration of carbon into the cueing face in tlae azeas when the cutting inserts are to be affixed. Notwithstanding) materials of construction and designs which result in rock drill bits which can drill faster and last longer ate constantly being sought.
3. Summary of the Inyention:
The invention provides rock drill hits having drill bodies comprised of austcmperod ductile iron- The auslernpered ductile iron drill bits of the invention have been determined to exhibit exceptional durability and ease of tnanufacmre. The austempered ductile iron drill bits of the invention tray also be produced more economically than conventional steel drill bits.
It is an object of the invention to provide rock drill bits having a drill body comprised of austempered ductite iron.
It is another object of the invention to provide a drill bit for drilling rock, comprising:
as austempered ductile iron drill body having a cutting face, a plurality of openings formed in the drill body at the cutting face) and cutting inserts mounted in said openings with cutting end portions extending outwardly from the cutting face.
1t is another object of the invention to provide austemhered ductile iron drill bodies having a hardness on the Rockwell C scale of at least 40.
It is another object of the invention to provide austempered ductile iron drill bodies having a central passageway and at least one branch passageway fur a flushing medium, wherein die branch passageway opens onto the cutting face and extends tn the central passageway.
It is another object of the invention to provide austempcred ductile iron drill bodies having at Least one branch passageway with a non-circular cross section.
It is another object of the invention to provide austetnpered ductile iron drill bodies having at least one branch passageway having a cross-sect ion shaped to facilitate the incorporation of a maximtun number of cutting inserts on the cutting face.
- 'I - 31d0-7 1l is another object of the invention tn Provide austernpered ductile iron drill bodies traving at least one recess for facilitating the removal of drill dn,st and debris.
It is another object of the invention to provide drill bodies comprised of austcmpered ductile iron produced from ductile iron by a process comprising: heating the drill holly cast in ductile iron to an austeniti~itlg temperature of 1.550 to 1750"P, preferably 1550 to 1650°r;
isothermally treating the drill body at the austenitiziog temperamrc for an austerlitiziztg period sufficient to produce a fully austenitic matrix, saturated with carhon;
quenching the drill body to an austempering temperature of 450 to G00°F rapidly enough to inhihit the forrrtation of pearIite and to initiate the formation of ausfetiite; isothermally rreating the drill body at the austempering temperature for an austempering period to produce ausferrite;
and, recovering the austempered ductile iron drill body.
It is another object of the invention to provide drill bodies compritcd of austempered ductile iron having an austenite carbon content in the range of I . R to 4 wt 3~ ) preferably 1.8 to 2.4 wt%.
It is another object of the invention to provide a percussion drill bit for drilling a bore through rock, cozuprising a drill body having a connecting section at a rear end thereof for connection to a percussive unit and defining a rotational axiR of the drill bit, and a plurality of cutting inserts embedded in a cutting fatx at a front end of the drill holy, the cutting face being rigid witli respect to the connecting section) each cutting insert comprising a hard material body having a rear mounting portion embedded in the drill body, and a cutting end portion protruding from the drill body, wherein the drill body is comprised of austentpered ductile iron.
It is also an object of the invention to provide a method for drilling rock, comprising.
providing a drill hit having a drill body made of austempered ductile iron having a connecting section defining a rotational axis and a cutting face with a plurality of cutting inserts, including gauge row inserts) embedded therein) the cutting face being rigid with the cmtnecting section, each cutting insert comprising a hard material body having a rear mounting portion embedded In the drill body and a cutting end portion protruding from the drill body;
and, rotating the drill bit about the rotational axis such that the gauge row inserts define a diameter of a bore being drilled.
S. Brief Descri tion o the Drawings:
There are shown in the drawings certain excrlplary ernhc~dimentc of the invention as presently preferred. It should be understood that the invention is nut limited to the embodiments disclnsetl as examplec, and is capable of variation within the spirit and scope of the appended claims. 1n the drawings, Figure 1. is a side perspective vietv of a conventional down the hole rock drill bit;
rigure 2 is a de(ailc~i front plan view of the cuttinfi face of a rock drill bit de.9ign of the invention wherein the branch passageway openings are different and nova-circular;
Figure 3 is a detailed front plan view of the cutting face of a rock drill bit design of the invention wherein the branch passageway openings are identical and non-circular;
Figure 4 is a partial cutaway side plan view of a rock drill showing the central passageway anal tile branch passageway;
Figure 5 is a front plan view of the rock drill bit a ;ed in the rock drilling test described in Example l;
Figure 6 is a cido profile view of the rock drill bit used in the rock drilling test described in E~tample 1;
Figure 7 i~ a frunt plan view of the rock drill bit used in the rock drilling test described in Example 2;
Figure 8 is a side profile view of the rock drill bit used in the rock drilling test described ZU in fixatnple 2;
Figure 9 is a front plan view of the rock drill bit used in the ruck drilling test described in Example 5; and Figure IO is a side profile view of the rock drill bit used in the rock drilling teat deBCribed in Example S.
' 6 - 3140-7 C. Detailed Description of the Preferred Embodiments of the Inyentio~l:
The following detailed description is of the best prcsPntly contemplated mode of carrying out tile invention. The description is not intended in a limiting Sense, and is is made solely for the purpose of illustratizlg the general principles of the invention. The various features and advantages of the present invention may be more readily understood cvi~h reference to the following detailed description taken in conjunction with the accompanying drawings.
The rock drill bits of the invention are characterized by having drill bodies constructed of austempered ductile iron_ The rock drill bits of the invention may comprise percussion drill bits, roller cone bits, polycrystalline diamond compact bits, and the like, particularly percussion drill bits.
The austempered ductile iron used in the rock drill bits of the invention consists of acicular ferrite in a high carbon austenite matrix called ausferrite. The austemnered ductile iron is produced by heat treating conventional ductile iron which is derived from gray (cast) iron, which exhibits exceptional ca.stibility when compared witll steel.
Specifically, austempered IS ' ductile iron is produced by subjecting conventional ductile iron to a known heat treatment process called austempering. The austempering heat treatment process generally comprises. (1 ) heating the ductile iron work piece to au auslenitizing temperature; (2) isothermally treating the work piece at the austenitizing temperature for an austenitizing period until s fully austenitic matrix saturated with carbon is obtained; (3) quenching the work piece to an.
austempering temperature rapidly enough to inhibit the formation of pearlitc and to initiate the formation of ausferrite; (4-) isothemtally treating the work piece at the austempering temperature for an austempering period; and (5) recovering the austempered ductile iron work piece. The critical variables in the austempering process are: ( 1 ) the austeuitizing temperature, (2) the length of the austenitiziztg period, (3) the cooling rate during the quenching step from the austenitizing temperature to the austempering temperature, (4) the austempering temperature, and (S) the length of the austempering period.
The allowable process conditions during the austemperirtg process and the resultant physical properties of the au_stempered ductile iron producod thereby are dependant upon the quality and material content of the ductile icon being treated. Defects in the mechanical 7 ' 3110-7 properties of the ductile iron such as shrinkage. slag stringers and poor miGrostrucmral features are magnified in the auttempered ductile iron produced therefrom. Accordingly) it is important to use high quality ductile iron when manufacturing the austempered ductile iron drill bits according to the invention. For the purposes of austempering, high qualit3~
ductile iron has been defined as that which has: (1) a uniform nodule distribution with a minimum of nodules/mm', (2) a nodnlarity excxeding 8096, (3) a carbide and nonmetallic inclusion content not exceeding 0.5 % , and (4) a porosity or microshrinkage volume not exceeding 19b .
Tlte drill bits of the invention are produced by first ca.5ting the drill body with high quality ductile iron. The rough cast product may be machinfxl fls needed before austempering while tlae drill body material is still relatively soft and easily machineable. Notwithstanding, many features that must be machined into conventional steel drill bits may be incorporated into the drill bits according to the invention during casting due to the castability of ductile iron. The castability of ductile iron drzll bits according to the invention allows for the elimination of up tv 90% to 95°6 of the machining costs associated with conventional steel drill biLS. The castibility of ductile izon also makes possible drill bit body configurations which would be difficult and costly and in some cases impossible to achieve using conventional machicting techniques. For example, branch passageways (50) in steel drill bodies conventionally have a circular cross-secaion. Figure I depicts the conventional circular czoss-section of the branch passageways. While acceptable for use with the invention, branch passages having a circular cross-section may limit on the total number of cutting inserts whiclmlay be incorporated on the cutting face. Because the cutting inserts perform the actual drilling, it is advantageous to iutcorporate as many cutting inserts as structurally possible on the cutting face of a given drill bit. In some configurations, the use of unique non-circular cross-sections for the branch passageways may facilitate the incorporation of more cutting inserts than would be conceivable on a similar drill bit having branch passageway openings with a circular cross-section. For example, Figure 2 is a detailed frontal view of the cutting face for a DTH
drill bit design of the invention. Specifically, Figure 2 demonstrates the use of non-circular cross-sections for the branclx passageways (50) . Furthermore) Pigure 2 demonstrates the use of two or more passageways having different, non-ciurcular cross-sections. Alternatively, Figure 3 is a detailed frontal view of another cutting face for a threaded button drill bit design of ttte invention wherein the two branch passageways (50) are of identical nun-circular crc,ss section. I3y using such non-circular cross-sectional branch passageways, the number of cutting inserts which ma_y be incorporated into the cutting face tray be maxituized.
The optionally machined cast ductile iron drill body is then converted into austctrtpercd ductile iron using the austempering heat treatment procedure describext herein. Specifically, high quality ductile iron in ASTM A897-90 Grade 3, ~! or 5, may be used to form the drill hodit~s_ The ductile iron drill bodies may be converted to austempered ductile iron using a thermal austempering treatment generally comprising; (1) heating the ductile iron chill body to an austenitiring temperature crf 1_550 to 1750°F, preferably 1550 to 1650°P; (2) isothermally treating the drill body at the auslenitizing temperature for an austenitizing period sufficient to produce a fully austenitic matrix, saturated with carbon; (3) quenching the drill body to an austempering temperature of 400 tn 6~0°F, rapidly enough to inhibit the formation of pearlite and to initiate the formation of ausferrite, preferably at a rate of 30,000°F/mln.; (4) isothermally treating the drill body al the austempering temperature for an austetnpering period, producing ausferrite having an austcnite carbon content in the range of 1.8 to 4 wt~, preferably 1 _8 to 2.4 wt9b; and, (5) recovering the austempered ductile iron drill body.
The austempcred drill body may be further processed by, for example, shot peering, as required to provide the drill body with the desired surface hardness. The auslempered dirclile iron drill body may also be work ltardened. Specifically, percussion rock drill bits operate by breaking rvc:k in front of the drill bit into small pieces or rock dust. Tlte percussion rack drill bits are used in conjunction with a percussive unit which operates to rotate the dz~ll bit about its axis and to simultaneously propel the drill bit into the rock formation to be drilled in a reciprocating manner. Also, high velocity flushing fluid is passed through the central passageway into the branch passageways out the cutting face into the bore during the drilling process. Figure 4 is a partial cueaway view of a cnnventi~~nal rock drill bit showing the central passageway (45) and the at least one branch passageway (50) _ This high velocity fluid forces the rock dust out from in front of the drill bit to the periphery of the cutting face, through recesses on die drill bit and up and out of the bore. During this process, broken pieces of rock are constantly impacting on the surfaces of the drill hit. Conventional steel drill bid are abraded and worn down by this constant impacting. The surface of austcrnpered ductile iron rock drill bits, however, become harder as a result of tlli5 constant impacting. 'thus, the constant impacting associated with use, operates to work harden austemPered ductile iron drill bits, thereby enhancing their surface wean resistance.
Getting inserr.5 useful with the invention may be made of a material selected from the grouF consisting of tungsten carbide, coated tungsten carbide, diamond enhanced tnngstcn carbide) txramic, last-dened steel, amd ADI.
The cutting inserts preferably have a rrar mounting portion and a cutting end portion.
Tlte roar mounting portion is designed to engage one of the plurality of openings on the drill body, cutting face. The cutting inserts may be interfaced with the drill body using conventional attachment methods, including but not limited to, cementing, glueing) welding, cotnpre~sion fitting, and threading.
Preferably, the cutting inserts are atflxed to the drill body using a compression fit affixation method, i. e. the cutting inserts are press-fitted into the drill body.
The concepts of the invention will now be illustrated by the following Exarnples, which are intended to be purely exemplary and not Iimitinfi. In each of the following examples the drill body used was obtained by first casting the drill body in ductile iron under the designation ADI grade 2. The drill body was then ntaehined as follows: (l j the outside radial elements were turned on a lathe in two (2) separate operations; (2) the center hr.~le was gundrilled; (3) the splines were hobbed; (4) the air flats were milled; (5) the blowtube seat was bored on a lathe and (6) the scallops and blow holes were done on a horizontal atlachining center. The machined drill body was then subjected to 2tn rtustempering heat treatment process consisting of: (1) treating the drill body to an austenitizing temperature of 1550 l0 1750°1", preferably 1550 to 1650°h'; (2) isothermally treatiulg the drill body at the austenitizing temperature for an austenitiiing period of 100 to 140 minutes; (3) cooling the drill body to acr austempering temperature of 575 to G25°F at a rate of 30,000°F/min.; (4) isothermally treating the drill body at the austempering temperature for an austempering period of 100 to 240 min_;
(5) recovering the austempered ductile iron drill body having a hardness on the Rockwell C
scale of 37. Tlte drill body was then finish machined using the following processes: ( 1 ) the critical guide diameter were turned on a lathe, (2) the insert holes were drilhxl on a horizontal machining center. Tungsten carbide cutting inserts were then incorporated imo the drill body by press fit using a hand-held pneumatic impact hammer.
Using a rock drill bit of the iulvention comprising a 61h " diameter concave rock drill bit of the general design depicted in Figures 5 and 6, a series of test bores were drilled at the Vulcan Quarry in Stafford, Virginia. The rock in which the test bores were drilled consisted of granite, the hammer used waa an Ingersole-Rand Percussion Air-Hauimer Model No. SF6 rotating at 34-36 rpm and operating at a pressure of 320 psi. Before drilling, the rock drill bit had a total weight of 5 x .89 pounds and had a gage row button diameter of 6.5 t5 inc>zes and a drill body diameter of 6 _ 453 inelies. The rock dri I I bit was then used to drill rock at an average rate of 86 ft/hour. After drilling about 490 feet of rock) the rock drill bit had a total weight of 50.86 pounds and had a gage row button diameter of 6.92 inches and a drill body diameter of 6.318 inches.
>;.X_A_MPLE Z
Using a rock drill bit of the invention comprising a G'/x" diameter flat rock drill bit of the general design depicted in Figures 7 and $, a series of bores were drilled at the Vulcan Quarry in Stafford, Virginia. T'he rock in which the test bores were drilled consisted of granite, the hammer used was an Ingersole->Zand Percussion Air-Hammer Model SFG
rotating at 34-3G
rpm and operating at a pressure of 320 psi. Before drilling) the rock drill hit had a tots( weight of 52.45 pounds and had a gage row button diameter of 6.510 inches and a drill body diameter of 6.455 inches. The rock drill bit was then used to drill rock at an average rate of 88 filhour.
After drilling about 350 feet of rock) the rock drill bit had a total weight of 51.40 pounds and ?S had a gage row button diameter of 6.488 inches and a drill body diameter of 6.358 inches.
Using a rock drill bit like that used in Example 2) bores were drilled at the Vulcan Quarry in Stafford, Virginia. The rock in which the test bores were drilled consisted oC granite, the hammer used was an Zngersole-Rand Percussion Air-Hammer Model SFf rotating at 34-36 - 11 ' 3140-7 rlntt and operating at a pressure of 320 psi. l3eforc drilling, the rock drill hit had a total weight of 52.45 pounds and had a gage row button diuueter of 6.505 inches and a drill body diameter of 6.451 iltches. The rock drill bit was then used to drill rock at an average rate of 8li ft/hour.
After drilling about 415 feet of ruck, the rock drill bit had a total weight of S I _ 19 pounds and had a gage row button diameter of 6.480 inches and a drill hotly diantete~ of 6.355 inches.
Using a rock bit like that used in Example 2, bores were drilled al the lvtaryland Materials Quarry in Harvc de Grace, Maryland. The rock in which the test bores were drilled coltsisted of granite_ The hamumer need was a Loudon lndusirirs I'r~rcussion Air-lifiammer Model No_ RI~6S rotating al 34-3G tpln and operating at a pressure of 32(1 psi.
Before drilling, tlve rock drill hit had a weight of 5Z-45 pounds and had a diameter aver the gage row buttons of 6.508 inches and a drill body diameter of 6.453 inches. The rock drill hit was then used to drill rock at a rate of 80 ftlhour. After drilling 240 feet of rock, the rock drill bit had a total weight of 51.22 pounds and had a diameter over the gage row buttons of 6.459 inches and a drill body 1S diameter of 6.330 inches.
Using a rock drill bit of the invention comprising a 3ci4" diuneter flat roc><
drill bit of the general design depicted in Figures 9 and I0, a series of test bores were drilled at the Newmont Gvld Company in Elko Nevada. T'lte rock in which the test hores were drilled consisted of siltstone_ The hammer used was a 'i'amrock Model No. 111, 645 rotatiutg at 60 rpm and operating at a pressure of 1,200 psi. Before drilling, the rock drill hit had a diar~oeter over tltc gage row buttotls of 3.50b" and a drill body diameter of 3.450" . The rock drill bit was then used to drill rock at a rate of 90 ft/hvur. The rock drill bit drilled through 4,120 feet of rock before losing four (4) carbide inserts.
2.5 While certain present preferred embodiments of the invention have been illustrated and described, it is to tae understood that the invention is not limited thereto and nmy be otherwise practiced within the scope of the following claims.
_.~._..___~_.~ _._. ._.____ . ~ ...~_ .~...~_
Claims (19)
1. A drill bit for drilling rock, comprising:
an austempered ductile iron drill body having a cutting face, a plurality of openings formed in the drill body at the cutting face, and cutting inserts mounted in said openings with cutting end portions extending outwardly from the cutting face.
an austempered ductile iron drill body having a cutting face, a plurality of openings formed in the drill body at the cutting face, and cutting inserts mounted in said openings with cutting end portions extending outwardly from the cutting face.
2. The drill bit of claim 1, wherein the drill body has a hardness on the Rockwell C scale of at least 40.
3. The drill bit of claim 1, wherein the drill bit is selected from the group consisting of a percussion drilling bit, a roller cone bit, and a polycrystalline diamond compact bit.
4. The drill bit of claim 1, wherein the drill bit is a percussion drilling bit.
5. The drill bit of claim 1, wherein the cutting inserts are made of a material selected from the group consisting of tungsten carbide, coated tungsten carbide, diamond enhanced tungsten carbide, ceramic, hardened steel and austempered ductile iron.
6. The drill bit of claim 1, further comprising a central passageway and at least one branch passageway for a flushing medium, wherein the branch passageway opens onto the cutting face and extends to the central passageway.
7. The drill bit of claim 6, wherein the branch passageway has a non-circular cross-section.
8. The drill bit of claim 6, whereizt the drill bit comprises at least two branch passageways.
9. The drill bit of claim 8, wherein the branch passageways have different cross-sections.
10. The drill hit of claim 1, wherein the drill body is provided with at least one recess for facilitating the removal of drill dust and debris.
11. The drill bit of claim 1, wherein the austempered ductile iron drill body is made by heat treating a ductile iron casting as follows:
(a) heating the casting to an austenitizing temperature of 1550 to 1750° F;
(b) isothermally treating the casting at the austenitizing temperature for an austenitizing period sufficient to produce a fully austenitic matrix, saturated with carbon;
(c) quenching the casting to an austempering temperature of 450 to 600°F, wherein the quenching rate is rapid enough to inhibit the formation of pearlite and to initiate the formation of ausferrite;
(d) isothermally treaties the casting at the austempering temperature for an austempering period to produce ausferrite; and, (e) recovering the austempered casting.
(a) heating the casting to an austenitizing temperature of 1550 to 1750° F;
(b) isothermally treating the casting at the austenitizing temperature for an austenitizing period sufficient to produce a fully austenitic matrix, saturated with carbon;
(c) quenching the casting to an austempering temperature of 450 to 600°F, wherein the quenching rate is rapid enough to inhibit the formation of pearlite and to initiate the formation of ausferrite;
(d) isothermally treaties the casting at the austempering temperature for an austempering period to produce ausferrite; and, (e) recovering the austempered casting.
12. The drill hit of claim 11, wherein the austempered ductile iron has an austenite carbon content in the range of 1.8 to 4.0 wt%.
13. A percussion drill bit for drilling a bore through rock, comprising a drill body having a connecting section at a rear end thereof for connection to a percussive unit and defining a rotational axis of the drill bit, and a plurality of cutting inserts embedded in a culling face at a front end of the drill body, the cutting face being rigid with respect to the connecting section, each cutting insert comprising a hard material body having a rear mounting portion embedded in the drill body, and a cutting end portion protruding from the drill body, wherein the drill body is comprised of austempered ductile iron.
14. A method of drilling rock, comprising:
(a) providing a drill bit having: a drill body made of austempered ductile iron having a connecting section defining a rotational axis and a calling face with a plurality of cutting inserts, including gauge row inserts, embedded therein, the cutting face being rigid with the connecting section, each cutting insert comprising a hard material body having a rear mounting portion embedded in the drill body and a cutting end portion providing from the drill body; and, (b) rotating the drill bit about the rotational axis such that the gauge cow inserts define a diameter of a bore being drilled.
(a) providing a drill bit having: a drill body made of austempered ductile iron having a connecting section defining a rotational axis and a calling face with a plurality of cutting inserts, including gauge row inserts, embedded therein, the cutting face being rigid with the connecting section, each cutting insert comprising a hard material body having a rear mounting portion embedded in the drill body and a cutting end portion providing from the drill body; and, (b) rotating the drill bit about the rotational axis such that the gauge cow inserts define a diameter of a bore being drilled.
15. The method of claim 14, wherein drill bit further comprises a central passageway and at least one branch passageway for a flushing medium, wherein the at least one branch passageway opens onto the cutting face and extends to the central passageway, and wherein the at least one branch passageway has a non-circular cross-section.
16. The method of claim 15, wherein the at least one branch passageway comprises at least two branch passageways having different cross-sections.
17. The method of claim 15, wherein the drill body is provided with at least one recess for facilitating the removal of drill dust and debris from the bore.
18. The method of claim 15, wherein the austempered ductile iron drill body is made by heat treating a ductile iron casting by a process comprising:
(a) heating the casting to an austenitizing temperature of 1550 to 1750°F;
(b) isothermally treating the casting at the austenitizing temperature for an austenitizing period sufficient to produce a fully austenitic matrix, saturated with carbon;
(c) quenching the casting to an austempering temperature of 450 to 600°F wherein the quenching rate is rapid enough to inhibit the formulation of pearlite and to initiate the formation of ausferrite;
(d) isothermally treating the casting at the austempering temperature for an austempering period to produce ausferrite; and, (e) recovering the austempered casting.
(a) heating the casting to an austenitizing temperature of 1550 to 1750°F;
(b) isothermally treating the casting at the austenitizing temperature for an austenitizing period sufficient to produce a fully austenitic matrix, saturated with carbon;
(c) quenching the casting to an austempering temperature of 450 to 600°F wherein the quenching rate is rapid enough to inhibit the formulation of pearlite and to initiate the formation of ausferrite;
(d) isothermally treating the casting at the austempering temperature for an austempering period to produce ausferrite; and, (e) recovering the austempered casting.
19. The method of claim 18, wherein the austempered ductile iron has an austenite carbon content in the range of 1.8 to 4 wt %.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/042,398 | 1998-03-13 | ||
| US09/042,398 US6039127A (en) | 1998-03-13 | 1998-03-13 | Rock drill |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2259090A1 true CA2259090A1 (en) | 1999-09-13 |
Family
ID=21921719
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002259090A Abandoned CA2259090A1 (en) | 1998-03-13 | 1999-01-15 | Rock drill |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US6039127A (en) |
| CA (1) | CA2259090A1 (en) |
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| CA2030350C (en) * | 1989-11-27 | 1994-08-02 | Tetsuo Nakai | Hard sintered compact for tools |
| SE503323C2 (en) * | 1990-12-21 | 1996-05-28 | Sandvik Ab | Drill bit, preferably lower drill bit |
| SE506207C2 (en) * | 1992-01-22 | 1997-11-24 | Sandvik Ab | Lower Drill |
| DE4339245A1 (en) * | 1993-11-18 | 1995-05-24 | Hilti Ag | Twist drill |
| DE4407119A1 (en) * | 1993-12-11 | 1995-06-14 | Hawera Probst Kg Hartmetall | Rock drill |
| US5555781A (en) * | 1995-02-23 | 1996-09-17 | The Lisle Corporation | Driver or bit construction |
| US5880382A (en) * | 1996-08-01 | 1999-03-09 | Smith International, Inc. | Double cemented carbide composites |
-
1998
- 1998-03-13 US US09/042,398 patent/US6039127A/en not_active Expired - Fee Related
-
1999
- 1999-01-15 CA CA002259090A patent/CA2259090A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1261799A1 (en) * | 2000-03-10 | 2002-12-04 | Downhole Products PLC | Centraliser |
Also Published As
| Publication number | Publication date |
|---|---|
| US6039127A (en) | 2000-03-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |