US3881878A - Large-sized and large thickness composite sleeves - Google Patents

Abstract

Large-sized and large thickness composite sleeves adapted for use with rolls of a universal rolling mill for producing H-shaped beams and having a width which is small relative to the diameter. The sleeves each have an outer diameter of over 900 millimeters and comprises an outer layer of high carbon cast alloy steel having a carbon content in a range between 1.6 and 2.2 percent by weight and a Shore hardness number of over 55, and an inner layer of cast steel of high carbon content in which crystallization of graphite has taken place and which has a Shore hardness number in a range between 35 and 42. The outer and inner layers are both produced by centrifugal casting in such a manner that the ratio of the thickness of the outer layer to that of the inner layer is in a range between 0.5 and 2.6.

Description

0 United States Patent 1 1 1111 3,881,878 Maruta et a1. May 6, 1975 [54] LARGE-SIZED AND LARGE THICKNESS 2,964,251 12/1960 Samuels et a1 241/293 COMP SLEEVES 3.014366 12/1961 Samuels et 29/130 X 3,416,435 12/1968 Dahl et a]. 29/130 X [75] Inventors: Kenzl Maruta, 11-51,

nf wakamatsuku; Primary Examiner-L. Dewayne Rutledge 2: :1 :22;? 1 i' ku Assistant Examiner-Arthur J. Steiner both of Kitakyu'shwshi; Attorney, Agent, or Firm-Craig & Antonelll Tsunelni Tsuji, 200-1-2, Hirowatari, Ongamachi, Onga-gun, Fukuoka, all [57] ABSTRACT of Japan Large-sized and large thickness composite sleeves adapted for use with rolls of a universal rolling mill for [73] Asslgnee' [mach] Metals producing H-shaped beams and having a width which [22] Filed: Mar. 18, 1974 is small relative to the diameter. The sleeves each have an outer diameter of over 900 millimeters and [2]] Appl' 452'269 comprises an outer layer of high carbon cast alloy steel having a carbon content in a range between 1.6 [30] Foreign Application Priority Data and 2.2 percent by weight and a Shore hardness num- Mar. 30, 1973 Japan 48-35681 b of over and an inner layer Of cast Steel of high carbon content in which crystallization of graphite has 52 us. (:1 29/191; 29/1961; 308/237 R taken place and which has a Shore hardness number 51 1111. C1 B32b 15/02;B32b 15/18 in a range between 35 and The Outer and inner 58 Field of Search 308/237 R, 216; 29/130, layers are both produced y centrifugal casting in such 29/132, 196.1, 191; 148/34 a manner that the ratio of the thickness of the outer layer to that of the inner layer is in a range between References Clted 0.5 and 2.6.

2,710,997 6/1955 Krepps 164/67 LARGE-SIZED AND LARGE THICKNESS COMPOSITE SLEEVES This invention relates to large-sized and large thickness composite sleeves adapted for use with horizontal rolls and vertical rolls of the assembly type for a universal rolling mill for producing l-I-shaped beams which has mounted on the shaft large-sized sleeves having a small width relative to the diameter.

Rolls of the assembly type have been widely in use because the shaft can be used again by replacing one sleeve by another one and the rolls of the assembly type are low in roll cost, so that they are more economical than rolls of the solid type. l-leretofore, it has been customary to use sleeves of cast steel of medium carbon content having a Shore hardness number of below 50 for rolls of the asembly type of a universal rolling mill for producing l-l-shaped beams. Some disadvantages are associated with such sleeves. Wear is caused on the lateral surface of each sleeve, scars are formed in the flange by striking, and the sleeve is unable to withstand pressure applied by folding of the metal to be rolled or form other reasons.

On the other hand, with the progress of the rolling art and the increase in efficiency in performing rolling, there has in recent years been an increasingly large demand for sleeves having properties as set forth below for rolls of a universal rolling mill for producing H- shaped beams.

l. The sleeves should be tough and devoid of the possibilities of fractures;

2. The sleeves should be highly resistant to wear and should not produce surface roughness;

3. The sleeves should be highly resistant to crack formation when heated; and

4. The sleeves should be deep hardening or low in the reduction of internal hardness when the range of diameters for effective use is great.

Difficulty has been experienced, however, in producing large thickness sleeves having all the aforementioned properties from a single material. Particularly, it has been impossible to produce such sleeves by casting in a mold because of low strength of the material.

In order to obviate this problem, proposals have been made to produce sleeves of the composite type each comprising outer and inner layers of equal thickness made of dissimilar materials. More specifically, such sleeves would consist of an effective surface layer or outer layer made of a high hardness alloy or high carbon content alloy which is highly resistant to wear, production of surface roughness and crack formation upon heating and which is highly deep hardening, and an inner layer made of a soft and ductile material of low hardness which is so tough that it does not fail when subjected to a shrinkage fitting stress during production or when rolling and thermal stresses are simultaneously applied to the sleeve in service, and which has a reduced internal residual stress.

Composite sleeves of the prior art have hitherto been produced by casting two types of metals by using the fixed mold provided with a partition of an steel plate, or by first casting a molten melt for the outer layer and replacing the inner portion of the poured molten metal by another molten metal for the inner layer after the outer layer has solidified a predetermined distance from the surface. The former has disadvantages in that the outer and inner layers are sometimes not welded together properly, hot top has little effect because the outer and inner layers are separated by the partition, and degasing of the poured molten metals is not effected properly. The latter has disadvantages in that molten for the inner and outer layers tend to mix with each other thoroughly, so that it is impossible to perform the operation in a stable manner because difficulty is experienced in controlling the thickness of each layer and the quantity of the molten metal used for each layer. Thus, the aforementioned methods are not in practical use nowadays.

A pipe of small thickness formed in two layers and made of a ferrous or non-ferrous material can readily be produced by centrifugal casting and the two layers form well-defined concentric circular areas because the pipe has a small thickness and the outer and inner layers quickly solidity. Since such pipe is not subjected to a high load both mechanically and thermally as is the case with rolls, there is no technical problem to be obviated in producing such pipe.

However, when composite sleeves of large size and large thickness which have an outer diameter of over 900 millimeters and in which by ratio of the thickness T to the diameter D of T/D is over 0.20 are to be produced by centrifugal casting for use with a rolling mill, difficulties are experienced because such sleeves must have the aforementioned properties. The problems which should be obviated in producing such composite sleeves bby centrifugal casting are as follows.

a. It takes a long time for both the outer and inner layers to solidify and variations tend to occur in the rate of solidifying of the molten metals from region to region, thereby making it difficult to provide a composite sleeve with concentric circular layers each made of a homogeneous material and separated by a circular boundary layer. The outer and inner layers are either mixed with each other too much and no well-defined outer and inner layers are formed, or the outer and inner layers are welded together improperly.

b. [t is difficult to minimize a residual stress existing in the interior of the boundary layer through which the metals for the outer and inner layers shift from one layer to the other, thereby making it difficult to form a satisfactory boundary layer having no defect throughout the whole sleeve.

c. A sleeve in which the thicknesses of the outer and inner layers are not proper has the possibilities of failures during production or in service.

d. The rate of solidifying of molten metals is low and defective segregation tends to occur in the outer and inner layers.

Thus, the production of large-size and large thickness composite sleeves of high hardness by centrifugal casting has been very difficult.

SUMMARY OF THE INVENTION This invention has as its object the provision of ideal large-sized and large thickness composite sleeves having predetermined properties and adapted for use with rolls of the assembly type for producing H-steels, such composite sleeves being produced by centrifugal casting and obviating the aforementioned disadvantages of the prior art.

According to the invention, there are provided largesized and large thickness composite sleeves produced by centrifugal casting and each having an outer diameter of over 900 millimeters, such composite sleeves each comprising an outer layer of high carbon alloy steel having a carbon content in a range between L6 and 2.2 by weight and a Shore hardness number of over 55, and an inner layer of high carbon cast steel in which crystallization of graphite has taken place and which has a Shore hardness number in a range between 35 and 42.

According to the invention, there are also provided large-sized and large thickness composite sleeves of the type described in which the ratio of the thickness of the outer layer to that of the inner layer is in a range between 0.5 and 2.6.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front view of a composite sleeve according to the present invention;

FIG. 2 is a vertical sectional view of the composite sleeve shown in FIG. 1; and

FIG. 3 is a diagram showing hardness penetration in internal hardness.

The invention will now be described with reference to an embodiment shown in the drawings. FIG. I shows the construction of a composite sleeve of large thickness adapted for use with a horizontal roll of large thickness and small width of the assembly type used with a universal rolling mill for producing H-shaped beams. The sleeve comprises an outer layer 1 of large thickness made of high carbon alloy steel, an inner layer 2 made of tough high carbon cast steel in which crystallization of graphite has taken place and which has a low Shore hardness number, and a boundary layer 3 consisting of a mixture of the materials for the outer and inner layers 1 and 2. 4 designates a shrinkage fitting surface.

Large-sized and large thickness composite sleeves of over 900 millimeters in diameter in which the ratio of the thickness t to the outer diameter D of t/D is in a range between 0.20 and 0.40 are produced as follows. A predetermined quantity of molten alloy steel of high carbon content is poured into a metallic mold for centrifugal casting rotating at high speed on a horizontal centrifugal casting apparatus to form the outer layer 1 which will have a Shore hardness number of over 55 and a carbon content in a range between 1.6 and 2.2 percent after the casting is produced. Immediately before the inner surface of the molten metal for the outer layer 1 completely solidifies after lapse of a predetermined time, a predetermined quantity of molten metal of high carbon content for the inner layer in which crystallization of graphite can be made to take place upon solidification is poured into the mold in such a manner that the ratio 21 of the outer layer 1 to the thickness of :2 of the inner layer 2 or tl/t2 will be in a range between 0.50 and 2.6 and the Shore hardness number of the inner layer 2 will be in a range between 35 and 42 after the casting is produced. Thus, perfect mixing and fusion of the two types of molten metals take place in the boundary layer 3 between the outer and inner layers I and 2 from the metallurgical point of view and no diffusion of the metals occurs, so that the composite sleeve produced has no flaws in the casting. After the casting or composite sleeve has solidified, rotation of the mold is interrupted, thereby finishing the casting operation.

The reason why the diameter of the sleeves according to the invention is limited over 900 millimeters and the ratio of the thickness t to the outer diameter t or t/D is limited to a range between 0.20 and 0.40 is as follows. The object of the invention is to provide large-sized and large thickness composite sleeves of over 900 millimeters in outer diameter. In the case of small thickness sleeves in which the ratio t/D is below 0.20, there is no problem to be obviated because cooling of the sleeves takes place relatively quickly. Thus, the lower limit of the ratio t/D is set at 0.20. On the other hand, when the ratio t/D is over 0.40, the casting has an inordinately large thickness and is not therefore generally referred to as a sleeve. Besides, it takes an extremely long time for the finish of solidification metals to cool and solidify, so that it is impossible to produce composite sleeves by centrifugal casting which meet the aforementioned requirements, no matter how the thicknesses of the outer and inner layers are controlled.

The carbon content of the alloy steel for the outer layer 1 is limited to a range between 1.6 and 2.2 percent by weight according to the invention because, if the carbon content exceeds 2.2 percent, then the material is brittle and surface cracks formation tends to occur when subjected to a heat treatment, and, if the carbon content is below 1.6 percent by weight, then hot rolling causes wear and seizure to occur in the sleeves.

The ratio of the thickness :1 of the outer layer 1 to the thickness 22 of the inner layer 2 or t/t2 of the sleeves according to the invention is limited to a range between 0.50 and 2.6 because of the following reason. In order that the boundary layer 3 may be in a perfect condition for joining the outer layer 1 and the inner layer 2 by fusion of the two metals, a portion of the inner surface of the outer layer 1 should be melted again after solidification by the molten metal for the inner layer 2 and allowed to solidify again. To this end, it is required that the quantity of the molten metal for the inner layer 2 should be such that the ratio tl/t2 does not exceed 2.6 so that the molten metal for the inner layer has a thermal capacity which is high relative to the volume of the outer layer 1, whereby a portion (having a thickness between 15 and 20 millimeters) of the inner surface of the outer layer can be melted again immediately before completion of solidification. If the ratio tl/t2 is below 0.5, then the thickness of the outer layer 1 is extremely small as compared with the thickness of the inner layer 2. When this is the case, the thermal capacity of the molten metal for the inner layer 2 is excessively high relative to the volume of the outer layer 1, with the result that the inner surface of the outer layer 1 is too readily melted again and diffused to enable the outer layer 1 to have a predetermined thickness and to permit the boundary layer 3 to be formed in the form of a circle free from eccentricity.

This makes it difficult to produce a casting in which the outer layer has a thickness as designed and the outer and inner layers are separated by the boundary layer which is circular and free from eccentricity.

The reason why the Shore hardness number of the outer layer 1 should be over 55 is because the sleeves should be sufficiently hard to be resistant to wear and the production of surface roughness. If the Shore hardness number of the inner layer 2 exceeds 42, then the sleeves become exceedingly brittle, thereby producing the possibilities of failures during production and in service. If the Shore hardness number of the sleeves is below 35, then the shrinkage fitting surface of the sleeves lacks rigidity after shrinkage fitting is effected and assembling is effected, thereby posing the problem of slipping of the sleeves. To obviate this problem, therefore, the Shore hardness number of the inner layer 2 is limited to a range between 35 and 42 in which crystallization of spherical graphite form tends to occur. It

dimensions and mounted on a shaft by shrinkage fitting.

The results of inspection carried out by entire surface coloring and supersonic flaw detecting methods show should be noted that the hardness of the inner layer 2 5 h h sleeves d d are f f fl Th is elQSetY related t range between and of the Shore hardness number of the surface of the sleeves ratio 11/12 and that the Shore hardness number of the was between 50 and 61 hfl the Shore hardness ihhel layer 2 is Preferably in the neighborhood of 35 at ber of the inner surface was between 38 and 41. The which the steel is high in toughness and crystallization higmy deep hardness of the sleeves was as shown in of spherical graphite form takes Place a yto FIG. 3. it will be seen that, in spite of the fact that the 3 Show? the hardness p h ofa eempesite sleeves have a large size and a large thickness, a reduc- Sleeve accmdmg to mvemmn' It shows that tion in the thickness of the outer layer is very small and the outer layer is highly deep hardening, the residual the outer layer and the inner layer form separate layers ensue stress apphed by the outer the demarcated by a clear-cut boundary. The sleeves each layer becomes very great when thlckness of h had an outer layer of 250 millimeters in thickness while outer layer of Shore hardness numbfsr of 55 IS the overall thickness of each sleeve was 350 millime- Such i ram) of f iq Steel 15 over ters. Variations in the thickness of the outer layer were "9 twsmlmes less than 6 millimeters. The ratio l/D was 0.25 and the A 9 51.6mm aforemenuoned, a ratio t1/t2 was 2.5, which are in the predetermined meetlng the requirements is sub ected to homogenizing ranges and spherodizing when considered necessary. Then, it Table 2 is cut into sleeves of a smaller size which are subjected to heat :eatment, quenchmg and tempering Layer Tensile Strength Ductility Charby Impact that the final products or sleeves can be produced in (kg/mm!) Test (kgmlcmz) which the ratio 21/22 is in a range between 0.5 and 2.6. 25 The final products are mounted on shafts by shrink- 3 2:: 33 age fitting. Thus, the production of a large-sized and large thlckness composite slgeve completed Horizontal rolls for producing H-shaped beams using EXAMPLE the composite sleeves according to the invention were capable of producing H-shaped beams of L980 tons by Table 1 shows the chemical composition of metals rolling in one operation, as compared with the H- used for producing a composite sleeve for a horizontal shaped beams of 1,000 tons produced by rolling in one roughing roll which has an outer diameter of 1,390 operation by conventionaal rolls having a Shore hardmillimeters, an inner diameter of 650 millimeters and 35 ness number b l 50, a total length of L600 millimeters, and in which re- The amount of wear caused on the side wall was bequired thickness of the outer layer is over 245 millimetween 0.15 and 0.20 millimeter for one operation ters. which was smaller than the amount of wear caused on Table l Chemical composition (36) C Si Mn P S Ni Cr Mo Outer Layer 2.07 0.78 0.8l 0.020 0.003 2.32 0.94 0.89 Inner Laycr L L56 0.77 0.018 0.005 0.42 0.23 0. [5

12,200 kilograms of molten metal for the outer layer conventional T0|tS Whieh was millimeterkept at 1470C was poured into a metallic mold rotat- From the fotegomg description. it will be appreciated ing at 120 G on a horizontal centrifugal molding appathat the Present invention p large-Sized and ratus for producing large-sized sleeves. After lapse of large thickness cmhposite Sleeves which meet the a predetermined time and immediately before complequh'emehts with respect to the material, hardness and tion of solidification of the inner surface of the molten thickness of the Outer layer, and which are free from metal for the outer layer, 3,500 kilograms of molten Casting a s, Solid and high in performance. The metal for the inner layer kept at l500C was poured sleeves according to the invention have no possibilities into the metallic mold again. Rotation of the mold was of fractures, and can have a service life about twice as interrupted when solidification of the molten metals ng as that Of sleeves of the prior art. The use of the was completed in about 5 hours. sleeves according to the invention is economical be- The outer layer had a particularly large thickness and cause the cost of material required for the rolls is low. was made of high carbon alloy steel which is brittle if What is claimed is: not subjected to some treatment after being produced l. A large-size and large thickness composite sleeve by casting in a mold. Therefore, the casting was reproduced by centrifugal casting and having a diameter moved from the metallic mold while being maintained of over 900 millimeters, said composite sleeve comprisat a temperature of over 600C and subjected to hoing an outer layer of high carbon cast alloy steel having mogenizing and spherodizing. Thereafter, the casting a carbon content of about 1.6 to 2.2 percent by weight was cut into smaller pieces by turning, each piece having a required width. After each sleeve was subjected to rough working, it was quenched and tempered. Then, each sleeve was worked to have predetermined and a Shore hardness of over 55, and an inner layer of high carbon cast steel in which crystallization of graph ite has taken place, said inner layer having a Shore hardness of about 35 to 42, the ratio of the thickness of said outer layer to the thickness of said inner layer being about 0.5 to 2.6.

2. A large-size and large thickness composite sleeve produced by centrifugal casting and having an outer diameter of over 900 millimeters and a sleeve thickness to outer diameter ratio (t/D) of from 0.2 to 0.4, said composite sleeve comprising an outer layer of high carbon cast alloy steel having a carbon content of about 1.6 to 2.2 percent by weight and a Shore hardness of over 55, and an inner layer of high carbon cast steel in which crystallization of graphite has taken place, said inner layer having a Shore hardness of about 35 to 42, the ratio of the thickness of said outer layer to the thickness of said inner layer being about 0.5 to 2.6.

3. The composite sleeve of claim 2, wherein the Shore hardness of said inner layer is in the neighborhood of 35.

4. The composite sleeve of claim 2, wherein said outer layer consists essentially of 2.07 percent by weight C, 0.78 weight percent Si, 0.8] weight percent Mn, 0.02 weight percent P, 0.003 weight percent S, 0.32 weight percent Ni, 0.094 weight percent Cr, 0.89 weight percent Mo, and the balance substantially iron.

5. The composite sleeve of claim 4, wherein said inner layer consists essentially of [.45 weight percent C, 1.56 weight percent Si, 0.77 weight percent Mn, 0.018 weight percent P, 0.005 weight percent S, 0.42 weight percent Ni, 0.23 weight percent Cr, 0.15 weight percent Mo, and the balance substantially iron.

6. The composite of claim 5, wherein the Shore hardness of said inner layer is about 38 to 41.

7. The composite sleeve of claim 6, wherein the Shore hardness of said outer layer is about to 61.

8. The composite sleeve of claim 5, wherein the outer diameter of said outer layer is about 1,390 mm.

9. The composite sleeve of claim 2, wherein said composite sleeve is a two-layered article.

i I i i I

Claims (9)

1. A LARGE-SIZE AND LARGE THICKNESS COMPOSITE SLEEVE PRODUCED BY ENTRIFUGAL CASTING AND HAVING A DIAMETER OF OVER 900 MILIMETERS, SAID COMPOSITE SLEEVE COMPRISING AN OUTER LAYER OF HIGH CARBON CAST ALLOY STEEL HAVING A CARBON CONTENT OF ABOUT 1.6 TO 2.2 PERCENT BY WEIGHT AND A SHORE HARDNESS OF OVER 55, AND AN INNER LAYER OF HIGH CARBON CAST STEEL IN WHICH CRYSTALLIZATION OF GRAPHITE HAS TAKEN PLACE, SAID INNER LAYER HAVING A SHORE HARDNESS OF ABOUT 35 TO 42, THE RATIO OF THE THICKNESS OF SAID OUTER AYER TO THE THICKNESS OF SAID INNER LAYER BEING ABOUT 0.5 TO 2.6.

2. A large-size and large thickness composite sleeve produced by centrifugal casting and having an outer diameter of over 900 millimeters and a sleeve thickness to outer diameter ratio (t/D) of from 0.2 to 0.4, said composite sleeve comprising an outer layer of high carbon cast alloy steel having a carbon content of about 1.6 to 2.2 percent by weight and a Shore hardness of over 55, and an inner layer of high carbon cast steel in which crystallization of graphite has taken place, said inner layer having a Shore hardness of about 35 to 42, the ratio of the thickness of said outer layer to the thickness of said inner layer being about 0.5 to 2.6.

3. The composite sleeve of claim 2, wherein the Shore hardness of said inner layer is in the neighborhood of 35.

4. The composite sleeve of claim 2, wherein said outer layer consists essentially of 2.07 percent by weight C, 0.78 weight percent Si, 0.81 weight percent Mn, 0.02 weight percent P, 0.003 weight percent S, 0.32 weight percent Ni, 0.094 weight percent Cr, 0.89 weight percent Mo, and the balance substantially iron.

5. The composite sleeve of claim 4, wherein said inner layer consists essentially of 1.45 weight percent C, 1.56 weight percent Si, 0.77 weight percent Mn, 0.018 weight percent P, 0.005 weight percent S, 0.42 weight percent Ni, 0.23 weight percent Cr, 0.15 weight percent Mo, and the balance substantially iron.

6. The composite of claim 5, wherein the Shore hardness of said inner layer is about 38 to 41.

7. The composite sleeve of claim 6, wherein the Shore hardness of said outer layer is about 60 to 61.

8. The composite sleeve of claim 5, wherein the outer diameter of said outer layer is about 1,390 mm.

9. The composite sleeve of claim 2, wherein said composite sleeve is a two-layered article.

Images