JPS58221661A - Production of composite sleeve for rolling roll with caliber - Google Patents

Abstract

PURPOSE:To improve the using performance, such as abrasion resistance or the like, of this kind of roll by casting a sleeve of an outside layer of high Cr cast iron and an inside layer of ductile cast iron, and hardening only the working layer in the caliber part of the outside layer after a heat treatment. CONSTITUTION:An outside layer 7 of high Cr cast iron is formed by centrifugal casting; thereafter, an inside layer 8 of ductile cast iron is charged by centrifugal casting or static casting in the internal part thereof to cast a composite sleeve wherein both layers having a prescribed wall thickness are welded by fusion to one body is cast. After said sleeve is cooled slowly, the sleeve is subjected to a diffusion heat treatment, the granulation treatment of the inside layer and the soft annealing of the outside layer. Only the working layer 9 of a caliber part 5 which is formed beforehand by casting on the layer 7 or is formed separately by machining is thereafter subjected to a hardening treatment, whereby the hardness of the layer 9 is made to >=75Hs.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a composite sleeve used in a grooved rolling roll for rolling steel pipes, and particularly to the improvement of a composite sleeve with improved wear resistance in the grooved part. Regarding manufacturing methods.

Conventionally, this type of rolling roll with grooves has a sleeve (1) having grooves (5) in the aperture (1), as shown in FIG.
A book with a sleeve assembly structure is used in which 2) is fixed to the body by mechanical coupling means such as shrink fitting or keying (6). At this time, the sleeve (2) is made of chilled material or grain material having a hardness of He 65 to 75, and its hole (5) is formed by cutting or during the casting process.

By the way, the sleeve outer layer (3) is provided with the hole-shaped part (6).
) must be made of a high hardness material such as the above-mentioned high hardness chilled material as wear resistance is required. Problems such as cracks may occur from the parts. Conventionally, in this type of roll, as shown in the figure, the outer layer (3) is formed of the above-mentioned high-hardness material, while the inner layer (4) is often made of a composite sleeve made of a material with excellent toughness. .

However, when using such a composite sleeve,
When the outer layer (3) has a thin wall thickness and the inner layer (4) has a large wall thickness, the residual stress is small and there is no problem even if the outer layer (3) is of high hardness. However, if the outer layer (3) has a thick wall thickness t and the inner layer (4) has a thin wall thickness, the residual stress in the sleeve becomes large and easily leads to breakage. ) Therefore, there is a limit to the increase in hardness of the hole part (5).

In order to solve these problems, the present invention aims to select and improve the sleeve material and structure of the composite sleeve used in the grooved rolling row JvK, as well as improve the heat treatment method such as quenching after casting. We succeeded in reducing the residual stress in the sleeve while increasing the hardness of its outer layer, especially the necessary hole-shaped layer, thereby improving the wear resistance and other performance of this type of sleeve. It is something.

That is, the present invention provides a method for manufacturing a composite sleeve for a mill roll with grooves, in which an outer layer of p-high chromium cast iron is cast by centrifugal force casting, and then ductile cast iron is formed inside the outer layer by centrifugal force casting or static casting. Casting a composite sleeve in which the inner layer is cast and the outer layer and inner layer are integrally welded, and the required heat treatment is applied to the post-filling composite sleeve, and the use of a hole molded in advance by casting or cutting in the outer layer. It is characterized in that only the layer is hardened to make the hardness of the hole portion He75 or higher.

□:1 The present invention will be described in detail below. The composite sleeve according to the present invention is formed by welding an outer layer (18) made of high chromium cast iron and an inner layer (18) made of ductile cast iron by casting, and as shown in FIG. A hardened layer is formed on the layer tsn used in 5). When casting this composite sleeve, the outer layer)
It is then cast to a predetermined thickness by centrifugal force casting. That is, an outer layer molten metal of high chromium cast iron as exemplified later is cast into a rotary mold set on a centrifugal casting machine, and a cylindrical body of the outer layer material is formed on the inner surface of the mold. At this time, the hole shape required for the outer layer can be formed directly during casting by providing a chiller projecting on the inner surface of the mold.
The composite sleeve may be formed by a separate cutting process after casting. Then we move on to casting the inner layer. The inner layer may be subsequently centrifugally cast at a predetermined timing after the outer layer is cast, or the mold may be left standing upright and cast by pouring, and the inner diameter of the sleeve may be polled to obtain the desired composite sleeve. can. The inner layer is made of strong ductile cast iron, but since a part of the inner surface of the outer layer is washed during casting and mixed into the inner layer, the inner layer is ultimately made of a material containing some Cr as exemplified later. In this way, a composite sleeve is cast in which the outer layer and the inner layer, each made of a predetermined material, are welded and integrated.

The material of each layer of the composite sleeve according to the present invention will be specifically explained.

[Outer layer]

The outer layer of the sleeve is made of high chromium cast iron with a target hardness of He75 or higher at the bottom of the hole. vI high chromium cast iron is preferably C1,6-3.4,810.3-1.5, M
nO, 3-t5, N i O, 1-2.0. Cr10
~25, MoO, 5~3.0% by weight, the balance re
and impurities. The reason for limiting the range of each component is that it should be determined according to the target amount of carbide by balancing it with the amount of Cr within the range that specifies the Fs Cr (Fs Cr ) ycs type carbide carbide as shown in the following table. c.
If it is less than 6%, the amount of carbide is small and the wear resistance is insufficient.
Moreover, if the content exceeds 3 or 4%, the amount of carbides is too large, resulting in significant deterioration in mechanical strength, especially toughness.

81 is necessary for deoxidizing the molten metal in an amount of 3% or more, but if it is contained in an amount exceeding 1.5%, the mechanical properties deteriorate, and at the same time the K Arl transformation point is lowered and hardness cannot be obtained. This is because it becomes difficult.

Mn is necessary in an amount of 90.3% or more to assist in deoxidizing the molten metal, but if the content exceeds 1.5%, the deterioration of mechanical properties, especially toughness, will be significant. .

N1 is contained to improve hardenability and actively adjust hardness, and 0.1% or more is necessary, but if it is contained in excess of 2.0%, retained austenite increases and hardness increases. This is because it disappears.

Cr is contained in large amounts for the purpose of improving toughness and wear resistance, but if its content is less than 10%, &C
A large amount of mold carbide crystallizes out, reducing toughness and making it impossible to obtain fine and uniform carbides.If the content exceeds 25%, the amount of &sC-type carbide increases, which is undesirable. This l
&, C-type carbide has lower hardness than 40m-type carbide and cannot provide sufficient wear resistance, and the range in which 160m-type carbide occurs is Cr
Content! Fi should be 10-25%.

Mo is effective in increasing the quenching and tempering resistance and at the same time increasing the hardness of the carbide injected into the carbide and promoting the tempering softening resistance. This is because if the content exceeds 0%, residual austenite will become stabilized in the matrix, and the hardness will actually decrease.

In addition to the above-mentioned components, the high chromium cast iron of the outer layer consists of the remainder Fa and impurities, but this does not preclude the addition of V, W or CO as necessary. These elements are added for the same purpose as MO, but it is uneconomical and the material becomes brittle if added to a large amount of material, so the upper limit of each element is v2.
．． 0%, W5.0%, Go! It shall be 1.0%.

[Inner layer]

The inner layer is made of strong ductile cast iron, and a portion of the inner surface of the outer layer is melted and mixed into the inner layer.

Therefore, considering this compositional variation, the ductile cast iron of the inner layer preferably has a final 1fcc of 2.5 to 3.7,811
．． 8-5.5, Mn 0.2-1.01Ni0.2-
2.5, Cr (1,5-3.0, M.

0.05-1.0, Mg0.03-0.07 each weight%
The remainder consists of Fe and impurities.

2.5% or more of C is required for graphite crystallization, but 3.
This is because if the content exceeds 7%, it becomes brittle.

Since a large amount of Cr is mixed into Sl from the outer layer, it must also contain a large amount of Cr compared to ordinary ductile cast iron in order to achieve graphitization. Therefore, for this purpose, it is necessary to have a content of 811.8% or more, but the upper limit is 3.5% because the excess 81 content causes back-filling and makes the material brittle. An effective means to promote graphitization of the inner layer is to increase the amount of inoculation.

It is desirable that Mn be low in order to improve the toughness of the inner ductile cast iron, but it is necessarily 0.2 to 1.0 to prevent washing of the outer layer.
This is because it is contained at 0%.

0.2% or more of N1 is necessary to improve mechanical properties and remove the harmful effects of cr, but if added in a large amount, it becomes uneconomical and becomes bainite, so it is 2.5%.
is the upper limit.

It is desirable for the Cr content to be as low as possible, and although it is cast without adding Cr, the outer layer is washed away.
．． It is necessarily contained in a range of 5 to 5.0%.

Although 0.05% or more of MO is required to improve mechanical properties, the upper limit is set to 1.0% due to washing of the outer layer.

Mg is contained in a normal range of 0.05 to 0.07%, which is necessary for graphite nodulation in ductile cast iron.

The inner layer ductile cast iron after being welded to the outer layer has the above composition range, with the remainder consisting of Fe and impurities. In addition, the outer layer is V
If it contains CO, some of it will be diffused into the inner layer and will be slightly trapped.

The present invention is characterized in that after a composite sleeve is cast by welding and integrating the outer and inner layers of four predetermined materials as described above, the composite sleeve is further subjected to the following heat treatment. That is, after casting a composite sleeve and cooling it with body,
First, it is preferably subjected to diffusion heat treatment at 900-1100°C, then annealed at 800-950°C, and then
The outer layer is subjected to softening annealing at 700°C to undergo barphite transformation. This heat treatment softens the high chromium cast iron of the outer layer and increases the toughness of the ductile cast iron of the unidirectional layer, which prevents cracking during the subsequent local hardening of the outer layer and accidents during use.

After the required heat treatment is applied to the entire composite sleeve, the present invention provides a hole (6) which is precast or separately cut into the outer layer (7), as shown in FIG.
) The hardening treatment is performed only on the layer +91 used, and the hardness of the hole side layer (9) is set to Hs75 or higher. Specifically, this hardening treatment is performed by medium frequency hardening at 900 to 1100°C and tempering at 400 to 600°C only to the layer (9) used in the cavity (5).

In this way, after softening annealing the entire sleeve, the hole part (
In the heat treatment method of the present invention which employs local hardening in 5),
The feature is that the desired high hardness can be imparted to the necessary hole side layer (9) without increasing residual stress in the sleeve. This means that when the entire non-leap is heated and quenched uniformly to make all of the outer layers have a high hardness of Hs75 or higher, the thickness t of the outer layer + 71 is less than the thickness of the inner layer (8). This is because if the thickness increases, the residual compressive stress generated on the entire surface of the outer layer (1) of the thick wall will generate a large residual tensile stress in the inner layer (8), which is greater than the material strength of the inner layer (8), and this will lead to sleeve failure. . Therefore, the method of the present invention is most effective for rolls with grooves for rolling steel pipes, which have a large outer layer thickness. Since high chromium cast iron has good hardenability and is difficult to crack during hardening, the hardness of the hole side layer (9) of the outer layer 17) can be easily increased to the desired target hardness. In addition, in conventional composite rolls, when the outer layer is made of chilled or grain material, the inner layer is made of ordinary cast iron or ductile cast iron.
In the method of the present invention, the inner layer is also subjected to high temperature heat treatment, thereby making it possible to improve the toughness of the ductile cast iron. After processing, the sleeve manufactured in this manner is shrink-fitted in the negative direction and is ready for use.

Next, specific examples of the present invention will be described.

<Example 1> 11 dimensions m800'X50o11. 1350 of them? JL [11° deep cod composite sleeve was manufactured as follows.

First, an outer layer was cast to a predetermined thickness by centrifugal force casting, followed by an inner layer to a predetermined thickness, and the two were welded and integrated to form a composite sleeve. The composition of each layer after casting is as follows.

Chemical composition of product sleeve (wt%) This composite sleeve was subjected to diffusion heat treatment at 1000°C,
As a result of softening annealing at 0°C and 1650°C, the outer layer had a hardness of H842 to H45. After continuing to process the hole and inner diameter, only the hole was medium-frequency hardened at 950°C and tempered at 480'O. As a result, the hole was H880.
hardness was obtained.

Example 22 A composite sleeve having the same dimensions and shape as in Example 1 was manufactured as follows.

In centrifugal force casting χ, the outer layer was first cast to a predetermined thickness, then the mold was erected at an appropriate timing, the core material forming the inner layer was cast, and both were welded and integrated to cast a composite IJ-spring. The composition of each layer after casting is as follows.

Chemical composition of product sleeve (wt%) This cast product was diffusion heat treated at 950°C, 900°C, 6
As a result of softening annealing at 80°C, the outer layer has a hardness of H84F?
= 4 condolences were obtained. However, after adding hole machining and poling to the cast lever to form a composite sleeve & Ca shape, only the hole portion was medium frequency hardened at 1000°C, and then heated to 520°C.
As a result, a hardness of Hs 86-88 was obtained at the bottom of the hole.

As described above, according to the manufacturing method of the present invention, the outer layer of the composite sleeve is made of high chromium cast iron and the inner layer is made of ductile cast iron. After softening annealing, only the outer layer for the hole side is hardened, so it is possible to increase the hardness of the layer for the hole side without increasing residual stress in the sleeve. Therefore, it is now possible to easily impart a hardness of H875 or higher to the hole portion, which was virtually impossible due to residual stress using conventional methods. In addition, the inner layer of this composite sleeve is made of ductile cast iron that has been heat-treated at high temperature to ensure its toughness, so it is safe without cracking both during hardening and during use. Therefore.

If the composite sleeve obtained by this method is assembled into an arbor and subjected to rolling, it is possible to significantly improve its usability properties such as wear resistance without compromising safety.

The present invention is suitable as a means for manufacturing composite sleeves for assembled rolls used in grooved rolling rolls for rolling copper pipes, and as described above, the outer layer thickness is larger than the inner layer thickness. It is particularly effective against

The basic idea behind the manufacturing method of the present invention is the third
When obtaining a solid roll as shown in the figure, the t
Well, it can be applied. That is, in this case, after centrifugally casting the outer layer in the same way, when standing the mold and casting the inner layer, the inner layer (core material) molten metal is filled into the mold and at the same time the metal part is extended. Casting forms and outer layer (
7), the core material, and the metal portion 101 may be formed into a double-structure solid composite roll in which both the core material and the metal portion 101 are welded and integrated.

In this case, the hole (6) may be formed by casting or forming by processing, and the core material +101 may be cast in multiple steps to substantially have a three-layer or more structure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a conventional mill roll with grooves. FIG. 2 is a sectional view showing the structure of the grooved mill roll according to the present invention. FIG. 3 is a sectional view showing the structure of a solid-hole rolled a-A/ manufactured by applying the manufacturing method of the present invention. (1)...Aper, (3)(7)...Outer layer, (4
) (81...inner layer, (5)...hole shape (part), (
6) Shrink fit fixing surface, (9) °° hole mold side used layer quenched layer).

Claims (1)

[Claims] 1. After forming an outer layer of high chromium cast iron by centrifugal casting, an inner layer of ductile cast iron is cast inside the cast iron by centrifugal casting or static casting, and the outer layer and inner layer are welded together. The hindlimb composite sleeve is cast, and the hindlimb composite sleeve is subjected to the required heat treatment, and only the layer used for the hole portion, which has been cast or cut in advance on the outer layer, is quenched to form the hole portion. A manufacturing method Z for a composite sleeve for a rolling roll with a groove, characterized in that the hardness is H875 or higher.The heat treatment of the composite sleeve and the quenching treatment of the outer layer for the groove side are carried out at 800 to 950°C and 600°C. Softening annealing at ~700°C, 900-1100°C
Quenching only the hole side layer at 400-600℃
A method of manufacturing a composite sleeve according to claim 1 by tempering at. 5. The high chromium cast iron of the outer layer is C1,6~3.4,810
．． 3-1.5, MnQ, 3-1.5, N i O, 1-
2.0, Cr1O~25, MoO, 5~5. The ductile cast iron of the inner layer is C2.5~5.7, 811.8~565.
, Mn0.2-1.0, Ni0.2-2.5, Cr0
．． 5-3. OlMoo, 05-1. Q. 3. The method for producing a composite sleeve according to claim 1 or 2, which contains 0.3 to 0.07 gO in each weight percent, and the remainder is Fe and impurities.