JPS58221660A - 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 graphite cast steel, 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 graphite cast steel 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 steel pipe rolling, and in particular to an improved 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 sleeve assembly structure in which 2) is fixed (6) to the body by mechanical coupling means such as shrink fit or keying is used. At this time, the sleeve (2) is made of chilled material or grain material with a hardness of H865 to H75, and the hole m (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 (5).
) requires wear resistance, so it must be made of a high hardness material such as the high hardness chilled material mentioned above, but on the other hand, this high hardness material has a large residual stress, and the inner layer is It is criticized for causing problems such as cracks in the parts. Therefore, in conventional rolls of this type, as shown in the figure, the outer layer (3) is made of the above-mentioned high hardness material, while the inner layer (4) is made of a composite sleeve made of a material with excellent toughness. There are many.

However, when using such a composite sleeve,
When the outer layer (3) has a small 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 (8) is of high hardness. On the other hand, if the outer layer (3) has a large wall thickness and the inner layer (4) has a small wall thickness tm, the residual stress in the sleeve will increase and it will easily break. 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 develop a composite sleeve for use with grooved rolling rolls, selecting and improving the material and structure of the sleeve, and improving the heat treatment method such as quenching after casting. By devising a new method, the residual stress of the sleeve can be reduced, while the outer layer, especially the necessary hole-shaped layer, can be made even more hard, thereby improving the usability of this type of roll, such as its wear resistance. It was a success.

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 high chromium cast iron is formed by centrifugal force casting, and then graphite cast steel is formed inside the outer layer by centrifugal force casting or static casting. A composite sleeve is cast in which the inner layer is welded and the outer layer and the inner layer are integrally welded, and then the required heat treatment is applied to the hindlimb composite sleeve, and a hole that has been previously cast or cut is formed on the outer layer. It is characterized in that only the used layer is hardened to make the hardness of the hole part 75 or more.

The present invention will be explained in detail below. The composite sleeve according to the present invention is made by integrally welding an outer layer 17) made of high chromium cast iron and an inner layer (8) made of graphite cast steel by casting,
And as shown in FIG. 2, the used layer (
9) with a hardened layer formed thereon. When casting this composite sleeve, the outer layer (7) is cast to a predetermined thickness by centrifugal casting. That is, a molten outer layer of 71-button Kametaka Krim cast iron, as exemplified later, is poured into a rotary mold Kt set on a centrifugal casting machine to form a cylindrical body of the outer layer material on the inner surface of the mold. In this case, the hole shape required for the outer layer can be formed by installing a chiller that protrudes on the inner surface of the mold and forming the hole directly during casting, or by separately cutting the hole shape after casting the composite sleeve. You can pressure them to do so. Then we move on to casting the inner layer. The inner layer can be cast using centrifugal force at a predetermined timing after the outer layer is cast, or the mold can be left standing upright, cast by pouring, and the inner diameter of the sleeve can be bored to obtain the desired composite sleeve. can. The inner layer is made of strong graphite cast steel, 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-temperature cast iron with a target hardness of H875 or higher at the bottom of the hole. The high chromium cast iron is
Preferably C1,6 to 5.4.810. ．． 5-1.5, M
no, s ~ i, s, Ni0.1-2.0, Cr
10~251M o O, 5~! 1.0% by weight, and the remainder consists of Fe and impurities. The reason for limiting the range of each component is as follows.

C should be determined according to the desired amount of carbide by balancing it with the amount of Cr so that the pressure of the (Fe-Cr)yCg type carbide is stable, but if it is less than 1.6%, the amount of carbide will be small. This is because wear resistance is insufficient, and if the content exceeds 64%, the amount of carbide is too large, resulting in significant deterioration in mechanical strength, particularly toughness.

81 is necessary in an amount of 0.3% or more to deoxidize the molten metal, but if it is contained in an amount exceeding 1.5%, mechanical properties deteriorate, and at the same time, the Mr1 transformation point is lowered and hardness is obtained. This is because it becomes difficult.

Mn is necessary in an amount of 0.3% or more to assist in deoxidizing the molten metal, but if it is contained in excess of 1.5%, the mechanical properties will deteriorate! This is because the deterioration in lcu properties becomes significant.

Ml 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 the content is less than 10%, MI
A large amount of CIJ carbides crystallizes, resulting in a decrease in toughness and failure to achieve fine uniformity of the coexisting carbides.If the content exceeds 25%, the amount of MasCa-type carbides increases, which is undesirable.

This 3-type shallow carbide has a lower hardness than M, C, and type carbides and cannot provide sufficient wear resistance. The content is 10 to 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, but if its content is less than 0.5%, the effect is small; This is because if the content exceeds 0%, residual austenite will become stabilized in the matrix, which will actually cause a decrease in hardness.

In addition to the above components, the high chromium cast iron of the outer layer consists of the remainder FIe and impurities, but I! I/cv, W or Co
This prevents the addition of These elements are added for the same purpose as MO, but adding too much is uneconomical and also makes the material brittle, so the upper limits are AV 2.0% and W 5.0%, respectively. , Co5.0%.

[Inner layer]

The inner layer is made of tough graphite cast steel, and a portion of the inner surface of the outer layer is melted and mixed into the inner layer. Considering this compositional variation, the inner layer of graphite cast steel is preferably C1,
0-2.0.811.0-2.5, Mn0.3-1.2
, NiO, 2-2.5, Cr 1.0-3.0, Mo
It is assumed that it contains O.05 to 1.5% by weight, and the remainder consists of Fs and impurities. In addition, when casting the inner layer, the process can be divided into multiple steps to form a composite sleeve having a substantially double layer or more structure. The reason for limiting the range of each component is as follows.

C is required to be 1.0% or more for graphite precipitation, but 2.0% or more is required.
This is because if the content exceeds 5%, the mechanical properties will deteriorate.

81 requires 1.0% or more for graphite precipitation, and 2.
This is because if the content exceeds 5%, the mechanical properties will deteriorate.

Mn is required at least 0.3% for deoxidation, but 1.2% or more is required for deoxidation.
This is because if the content exceeds %, it becomes brittle.

N1 is required to be at least 0.2% for both the purpose of improving mechanical properties and eliminating the harm caused by CR, but if it is included in a large amount, it becomes bainite, which is also uneconomical.
．． The upper limit is 5%.

It is desirable that Cr be low, and Cr is not added during casting, but it is inevitably included in the range of 1:0 to 3.0% in the washed outer layer.

MO is required to be at least 0.05% in order to improve mechanical properties, but the upper limit is set at 1.5% due to washing of the outer layer.

The inner layer of graphite cast steel after welding with the outer layer has the above-mentioned 2m radius, and the remainder consists of re and impurities. In addition, ° the outer layer is V, W
Or, in the case where Co is included, a part of it is diffused into the inner layer and is slightly deposited.

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 the composite sleeve and slowly cooling it,
First, it is preferably subjected to a diffusion heat treatment at 900 to 1100°C, followed by a granulation treatment of the inner layer at 800 to 950°C.
The outer layer is subjected to softening annealing at 00 to 700°C to transform into pearlite. This heat treatment softens the high chromium cast iron of the outer layer, while increasing the toughness of the graphite cast steel of the inner 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 portion (5), which is precast or separately cut, in the outer layer (7), as shown in FIG.
) is subjected to hardening treatment, and the hardness of the hole-side layer (111) is set to Hs75 or higher. Specifically, this hardening treatment 9) by medium frequency quenching at 900-1100°C and tempering at 400-600°C.

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 required hole side layer (lead) can be given the targeted high hardness without increasing the residual stress in the sleeve. When all Hs 75LJ and the above high hardness are summed, the wall thickness t1 of the outer layer 1)) is the wall thickness t of the inner layer (8)! When it becomes larger than , the outer layer (71) with a wall thickness of tm (inner layer + all K
This is because a large residual tensile stress exceeding the material strength is generated, which leads to sleeve failure. Therefore,
The method of the present invention is most effective for materials whose outer layer has a large thickness, such as grooved rolls for steel pipe rolling.
In addition, compared to conventional chilled and grain materials, the outer layer high chromium cast iron has better hardenability and is more difficult to crack during hardening.
The hardness of the material can be easily increased to the desired target hardness. 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, but graphite cast steel is stronger and safer than these materials. Therefore, according to the manufacturing method of the present invention, it is possible to safely manufacture a composite sleeve whose hole side layer has excellent wear resistance. In addition, the inner layer (81
The outer layer (7) of the graphite cast steel is made from high chromium cast iron.
Chromium is mixed in, but if the inner layer is made of cast iron-based materials, it becomes brittle and the safety level decreases, whereas in the case of graphite cast steel, it is possible to absorb this chromium and maintain its original properties. There is no need to worry about material deterioration due to diffusion of chromium. After processing, the sleeve manufactured in this manner is shrink-fitted with a negative edge and is ready for use.

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

<Example 1> 111 dimensions 800'X500'! Inner diameter 550? Jl[
A composite sleeve of 110 deep cod was produced like a manure.

By centrifugal force casting, the outer layer was first cast to a predetermined thickness, followed by the inner layer to a predetermined thickness, and the two were welded together 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 granulation and softening annealing at 0°C and 650°C, the outer layer had a hardness of 11s 40-45. Further, only the hole part was medium frequency hardened at 1060°C, and
As a result of tempering at °C, a hardness of H881 was obtained in the hole portion.

<Example 2> A composite sleeve having the same dimensions and shape as Example 1 was manufactured as follows.

First, the outer layer was cast to a predetermined thickness by centrifugal force casting, and then the mold was erected at an appropriate timing, the core material forming the inner layer was cast, and the two were welded together to form a composite sprue. The composition of each layer in #fc after casting is as follows.

Chemical composition of product sleeve (wt%) This cast product was diffusion heat treated at t-950°C, and then heated at 850°C.
As a result of granulation and softening annealing at 1650°C, the outer layer had a hardness of Hs47 to 49. However, after adding hole machining and boring to the casting of the lever and forming it into a composite sleeve, only the hole portion was medium-frequency quenched at 1000°C.
As a result of tempering at 00°C, Hs87 to 88 at the bottom of the hole.
hardness was obtained.

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 graphite cast steel. After softening annealing, only the outer layer for the hole side is hardened, making it possible to increase the hardness of the layer for the hole side without increasing residual stress in the sleeve. , hole mold part KHs, which was virtually impossible due to residual stress with conventional methods.
It becomes possible to easily impart a hardness of 75 or more. The inner layer of the composite sleeve of the octopus is made of graphite cast steel to ensure toughness, so it is safe without cracking even when scratched during hardening or during use. Therefore, by assembling the composite sleeve obtained by this method into an arbor and subjecting it to rolling, it is possible to significantly improve its use characteristics 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 steel pipes.
, as mentioned above, is particularly effective for those whose outer layer thickness is larger than the inner layer thickness.

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
In other words, in this case, the outer layer is made of phosphorus that has been centrifugally cast in the same way, and when the inner layer is cast with the mold set up, the inner layer (core material) molten metal is filled into the mold. At the same time, the metal part is extended and cast, and the outer layer (
7), the core material and the metal part 11υ are welded together to form a double-structured solid composite roll. It is also possible to form the core material (l
The casting step (O) may be divided into multiple steps to obtain a substantially triple or more structure.

[Brief explanation of drawings]

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 rolling reel with solid holes manufactured by applying the manufacturing method of the present invention. (1)...Aper, (3)(7)...Outer layer, (4
) 181... Inner layer, (6)... Hole shape (part), (
6)... Shrink fitting fixing surface, (9)... Hole side layer (
hardened layer). Figure 1

Claims (1)

[Claims] 1. After forming an outer layer of high chromium cast iron by centrifugal casting, an inner layer of graphite cast steel is cast inside it (by centrifugal casting or static casting) to separate the outer layer and the inner layer. A welded and integrated composite sleeve is cast, and the hindlimb composite sleeve is subjected to the required heat treatment, and only the layer used in the hole portion, which has been previously cast or cut on the outer layer, is quenched. A method for manufacturing a composite sleeve for a grooved expansion roll, characterized in that the hardness of the grooved portion is H875 or higher. λ The heat treatment for the composite sleeve and the quenching treatment for the hole-forming layer of the outer layer are carried out at 800-950℃ and 6
Softening annealing and granulation treatment at 00-70σC and 90
Quenching only the layer used in the hole part at 0 to 1100℃ and 4
A method of manufacturing a composite sleeve according to claim 1 by tempering at 00 to 600°C. 3. The high chromium cast iron of the outer layer is C1,6~5.4,810
．． 5-1.5, Mn0.5-1.5, N i O, 1-
2.0-2.0, Cr10-25, Mo 0.5-5.0, and the balance is Fe and impurities, and the inner layer graphite cast steel contains C1.0-2.0. 5. Mn
0.3~1.2, old, 0.2~2.5, Cr 1.0
~! 1.0, Mo0.05 to 1.5% by weight, and the remainder 1e and impurities.