JPS6223969A - Composite sleeve for rolling h-beam and its manufacture - Google Patents

Abstract

PURPOSE:To provide superior wear and heat cracking resistances by interposing an intermediate layer between an outer layer having a structure whose matrix consists essentially of carbides and bainite and an inner layer of spheroidal graphite steel and by uniting the layers to one body by welding. CONSTITUTION:An outer layer is made of a high Cr material consisting of, by weight, 0.8-2% C, 0.8-2.5% Ni, 0.3-1.5% Si, 7-22% Cr, 0.4-1.5% Mn, 0.5-3% Mo, <0.1% P, <0.1% S and the balance Fe and having a structure whose matrix consists essentially of (Fe,Cr)7C3-base primary and secondary carbides and bainite. An intermediate layer is interposed between the outer layer and an inner layer of tough and hard spheroidal graphite cast steel and the layers are united to one body by welding.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to a new type of composite sleeve roll sleeve (with higher performance) which is mainly used in the rolling field of H-section steel. The present invention relates to a sleeve and a preferred method for manufacturing the same.

(Conventional technology and its problems) When rolling IIH section steel, universal mills are commonly used from the viewpoint of productivity and quality assurance, but the rolls used in this universal mill, Most of the horizontal rolls, rigid rolls, and edge rolls are of the sleeve type.

In casting the sleeve, the method shown in FIG. 1 is generally adopted from the viewpoint of improving material quality and casting yield. That is, first, the outer layer is centrifugally cast, and the inner layer is centrifugally cast when it is unsolidified or after solidification, and the two are welded together.

In the case of the sleeve method, the first major problem is the accident of breakage from the inner surface of the sleeve. However, compared to general solid rolls, since the sleeve is hollow, the residual stress in the tangential direction on the inner surface is large. is added,
This is a problem that does not occur with other general rolls. Therefore, it is necessary to pay attention to the reduction of residual stress and the toughness of the sleeve inner layer material.

The outer layer material is in contact with the rolled material and has wear resistance, crack resistance,
Improving the outer layer material is most important because it is directly linked to rolling performance such as surface roughness resistance. In particular, in the case of the horizontal roll of a universal mill, the sliding wear on the flange of the H-shaped steel is severe, and the heat load at the corner of the flange and web is severe. There is a need to.

Conventionally, adamite material with Hs 55 to 65 has been used as this type of outer layer material, but it has problems in terms of wear resistance, and setting the hardness to Hs 65 or higher is also difficult due to manufacturing technology and during use. Difficult due to accidents.

In addition, high Cr materials with the following components (wt%) as proposed in Japanese Patent Application Nos. 56-155877, etc., are excellent in terms of wear resistance, but when receiving a large heat load on the front stage side, heat In some cases, cracks may occur and the amount of rework may be increased.

C-2, 0~3.2% Ni: 0.8~2.5
%Si: 0.5-1.5% Cr: 10
-25%Mn: 0.5~1.5%Mo
: 0.5-2.0% balance essentially Fe In addition, the welding of the outer and inner layers must be sound to prevent accidents when using rolls, and it is also important for composite technology. It is considered a problem.

Based on such a background of the prior art, the present invention provides a composite sleeve of this type that has superior wear resistance and heat crack resistance than conventional sleeves and has sufficient accident resistance, and a method for manufacturing the same. The purpose is to

(Means for Solving the Problems) The features of the present invention for achieving the above object are as follows:
Outer layer: C: 0.8-2.0%, Cr: 7-22%,
It has Mo 0.5-3.0%, etc., and (Fe, Cr
It is made of a high chromium material of 65% or higher, consisting of primary and secondary carbide mainly composed of hC3 type and a base mainly composed of bainite, and has a strong spherical graphite (an inner layer made of li1 material and an inner layer made of li1 material). The purpose of creating an intermediate layer between them is to turn them into second-hand clothing, and to finish the production, centrifugal force casting is applied using hot water with a specific composition, and a specific heat treatment is applied. The point is to apply

(Example) The materials of the composite sleeve for rolling RF section steel of the present invention (layer, intermediate layer, and inner layer) will be described in detail below.

The outer auror is made of a high chromium material with a hardness of Hs 65 to 1, and the range of each component and the reason for visual determination are explained as follows.

In the case of the present invention, C is the most important element and basically determines wear resistance and crank resistance. Also, (Fe, C
r) It should be determined while maintaining a balance with Cr within a range that stabilizes the 7cx type carbide. If it is less than 0.8%, the amount of carbide is small and wear resistance is insufficient, while if it is more than 2.0%, the carbide becomes too warm, resulting in significant deterioration in mechanical strength, especially toughness and IL. . Therefore, C is 0.
It is defined as 8-2.0%. In addition, patent application 1983-15587
Compared to the high Cr materials described in No. 7 and the like, it has less than 2.0% C and is intended to improve toughness, that is, heat crank resistance.

Si is necessary for deoxidizing the molten metal, and if it is less than 0.3%, it has no effect; on the other hand, if it is contained in more than 1.5%, the mechanical properties deteriorate, and the ^r1 transformation point hardness becomes difficult to obtain. Therefore, the Si content is 0.3 to 1
．． The range shall be 5%.

The content of Mn must be at least 0.4% to assist in deoxidizing Si and to prevent harm from S, and if it is less than 0.4%, there is no deoxidizing effect. But 1.5%
If the content exceeds this amount, the mechanical properties, especially the toughness, will deteriorate significantly. Therefore, the Mn content is also set in the range of 0.4 to 1.5%.

P is an element that is preferably as small as possible especially in the roll material, and is set at 0.1% or less in view of making the material brittle.

Like P, S makes the roll material brittle, so the smaller the content, the more desirable it is, and its content should be 0.1% or less.

N+ is included to improve hardenability and actively adjust hardness, and if it is less than 0.8%, it has no effect;
．． If the content exceeds 5%, residual austenite increases, causing problems such as deterioration of roughness resistance and increase in residual stress. Therefore, the content should be in the range of 0.8 to 2.5%.

Cr is used to improve toughness and wear resistance, but if the content is less than 7%, many M3C type carbides will be produced, making it difficult to obtain toughness and fine uniformity of carbides, and 22 %, the amount of M23C6 type carbide increases. This carbide has lower hardness than M and C3 type carbides and cannot provide sufficient wear resistance. In the present invention, as the range in which M and C3 type carbides occur, the Cr content is defined to be in the range of 7 to 22%, in balance with the above-mentioned defined range of the C content.

Mo enters the carbide and is effective in increasing the hardness of the carbide and improving the tempering softening resistance.
, less than 5%, this effect is small, and 3.0%.
If the content exceeds this amount, residual austenite will stabilize in the matrix and cause problems.

Therefore, the Mo content is set in the range of 0.5 to 3.0%.

The outer layer material contains each of the above components in weight percent, and the remainder is essentially composed of Fe, but other components other than those listed above may be added as supplementary materials, such as the following: Examples include Nb and V.

Nb and (2) exert the tib effect either alone or in combination within the following component ranges.

Nb is effective in refining the casting structure, and the inclusion of Nb promotes precipitation hardening and improves wear resistance.
In particular, in the range of target hardness Hs 65 or more -L, this effect is present when the Nh content is less than 1.0%, and when it exceeds 1.0%, this effect is saturated and costs increase.

V is contained for the same purpose as Nb, and especially in the range of target hardness Hs 65 or higher, the content may be less than 1.0%, and if it is contained in excess of 1.0%, V carbides will be large. This results in deterioration in toughness.

The cast structure of the outer layer high chromium material composed of the above-mentioned composition range consists of hard (Fe, Cr) 7c3 type carbide and a base of retained austenite and some martensite. However, in this structural state, the residual austenite in the matrix begins to partially transform when it comes into contact with the hot rolled material during rolling, making the structure extremely unstable. Poor roughness and wear resistance.

Therefore, in this type of high-chromium outer layer, in order to stabilize the cast structure, and to obtain a structure that cannot be obtained by heating to a temperature higher than the transformation point and further accelerating the cooling rate after casting, Heat treatment is applied during the manufacturing process.

That is, after the high chromium outer layer material and the inner layer material described later are welded and cast together, this is
The temperature of the heated stomach is maintained in the temperature range of 0℃ to precipitate secondary carbide in the matrix, and in the subsequent cooling process, the cooling rate is accelerated to 100℃/llr or more to reach a pearlite nose of about 620℃ or higher. (Fe, Cr)7C
Consisting of primary and secondary carbide mainly of x type and base mainly of bainite, and outer layer hardness IIs 65
It is an object of the present invention to provide a sleeve having the above properties and having excellent wear resistance and roughness resistance.

The reason why the heating temperature is maintained at 900 to 1100°C during the above heat treatment conditions is that at temperatures below 900°C, secondary carbide is precipitated, but its form is (Fe, C).
r) 23C6 type, and the (Fe, Cr)7C3 type carbide having high wear resistance, which is a feature of the present invention, cannot be obtained. In other words, even when comparing the hardness of carbide itself, (FeXCr) 23C6 type has (Fe
This is because it is about 11v400 softer than the Cr>yc3 type. Therefore, in the present invention, a (Fe, Cr)7C3 type is used as a secondary car-hybrid as a base it.
The heating temperature is limited to 900° C. or higher in order to cause the precipitation. On the other hand, the heating holding temperature is set at -1 to 1 based on the viewpoint of preventing tissue enlargement and energy saving for long-term heating and holding.
It is limited to 100℃.

Also, the reason for the limitation on the cooling rate after heating and holding is that when cooling from the above temperature range of 900 to 1100°C, if the temperature is not rapidly cooled to 1 (below 10°C/lIr), the pearlite nose will reach a temperature of about 620°C or more during cold sleep. This is because pearlite transformation occurs at high temperatures, making it impossible to obtain the desired hardness of IIs 65 or higher.
The cooling rate of ~ is achieved by forced air cooling in the atmosphere or spray water cooling.

As is well known, sleeve rolls for rolling YI section steel are used by firing and assembling the sleeve on the arbor, but in this case, there are cases where cracks occur from the firing part with the arbor, that is, from the inner surface of the sleeve, resulting in breakage. many. Although the inner layer material will be described in detail later, the above heat treatment not only modifies the outer layer material, but also promotes graphitization of the eutectic cementite in the inner layer material that is integrated with the outer layer. A great effect can also be obtained by improving the inner layer material by improving its toughness. After the heat treatment, strain relief annealing is of course performed at an appropriate temperature in order to reduce residual stress that is closely related to breakage of the sleeve.

In the following description of the second outer layer material, each component and its heat treatment conditions are explained in relation to its target hardness Hs 65 or higher, which is based on the following extrusion. Generally II
Roll sleeves for shape copper rolling are required to have resistance to abrasion between the side wall and H-beam flange, roughness, cracking, etc., but the wear resistance of the sleeve also has a strong correlation with hardness. If the hardness is less than 65, roughness resistance
Sufficient wear resistance cannot be ensured. That is, in order to ensure excellent roughness resistance, abrasion resistance, accident resistance, and crack resistance, a high chromium material needs to have a hardness of Hs 65 or more.

Although there is no separate regulation regarding the upper limit of the hardness of the outer layer material, depending on the above component range and heat treatment, and considering accident resistance, the outer layer material generally has a hardness of IIs.
It is difficult to achieve a value of 90 or more.

Next, the middle layer will be explained. This intermediate layer is interposed between the first outer layer and the next inner layer, and Cr is mixed and expanded from the outer layer mainly made of a high chromium material to the inner layer 11, and as the inner layer material becomes high Cr, the toughness is deteriorated. (Preventing 1
It is something that has a purpose for each action. The range of each component of the intermediate layer material and the reason for its limitation are explained below.

First, regarding the C content, it is specified in the range of 0.8 to 3.0% by the 28 field component that is used during casting.
In the case of a product in which the outer layer is partially combined with the outer layer, the content is in the range of 0.8 to 2.5%. That is, when the middle layer molten metal is cast on the inner surface of the already cast outer layer,
Part of the inner surface is dissolved, and the C content of the intermediate layer changes, resulting in an ILo of 8 to 3.0% depending on the layer material.
If the amount of the intermediate layer/8m is used, if the amount of dissolved outer layer is completely uniformly mixed into the intermediate layer, the C content will be 0.8 to 2.
．． It becomes 5%. Regarding the reason for this limited ingredient,
When the content of the inner layer becomes less than 18%, the casting temperature of the intermediate layer becomes high, the outer layer becomes easy to melt, the amount of Cr mixed into the intermediate layer further increases, and the diffusion of Cr into the inner layer is prevented. This is because the reason for the existence of the intermediate layer is lost, and if the carbon content exceeds 2.5%, the carbide content becomes large, and the toughness of the intermediate layer deteriorates, which also causes the existence of the intermediate layer to be lost. It is to become something.

Regarding Si, it has a deoxidizing effect of /8 hot water, and has a deoxidizing effect of 0.2% or more.
L is necessary, but if it exceeds 3.0%, it will become brittle and the mechanical properties of the intermediate layer will deteriorate, so it should be 0.2 to 3.0%.
The range shall be .

Mn also has the same effect as Si, and in order to remove the negative effects of S as MnS, it is necessary to have a concentration of 0.3% or more, but if it exceeds 2.0%, the effect is saturated, and Also, since it causes deterioration in mechanical properties, the content is set in the range of 0.3 to 2.0%.

P affects the fluidity of the molten metal, but in the case of roll materials, it lowers the toughness of the material, so it is kept at 0.1% or less.

Like P, S also makes the roll material brittle, so it should be kept at 0.1% or less without causing any actual damage.

As for Ni, it is not necessary to add it separately, and more than 0.1% is contained due to contamination from the first layer material, but compared to the old 2.5%.
There is no problem if the content is up to If it exceeds 2.5%, the hardenability will improve, but this will make the matrix too hard, which is undesirable in terms of toughness, and will also increase residual stress, so it is necessary to limit it to 2.5% or less. .

As for Cr, it is preferable that it is low because of the significance of casting the intermediate layer, and the content of the molten metal for casting is regulated to 3.0% or less, which is easy to control industrially. In other words, if Cr is contained in excess of 3.0%, Cr mixed from the layer after casting
In total, the content of the intermediate layer increases, which in turn leads to an increase in 1l of Cr mixed into the inner layer, which becomes a problem. It is necessary to limit it to 0% or less. Incidentally, when an intermediate layer molten metal with a Cr content of 3.0% or less is cast, the Cr content in the IJ after casting is in the range of 0.5 to 9.0%.

Regarding Mo, i;t: It has the same effect as Ni, but
If it is contained in an amount of 1.5% or more, the intermediate layer becomes too hard, so it is limited to 1.5% or less as long as it does not cause any actual damage.

Middle! The layer material contains each of the above components in weight percent, and the balance is basically composed of Pa, but other components other than the above, and if necessary, the following Ti, 81, Z
r can be added alone or in combination.

That is, since the above-mentioned intermediate layer material is a material that is relatively easily oxidized, by adding less than 0.1% of one or more of Ti, At, and Zr in an amount of less than 0.1% by weight, the material is deoxidized.
This results in an intermediate layer that is more sound in terms of material. Regarding the upper limit of the above added content, all of the above elements are strong deoxidizers, so if these elements are used singly or in combination,
．． If it is contained in an amount of 1% or more, it becomes a state of overoxidation, which is undesirable, and at the same time, it also contains oxides as various reaction products, which leads to deterioration of the mechanical properties of the material.

Next, the inner layer material of the roll according to the present invention will be explained. This inner layer is made of a so-called spherical graphite steel material, and the range of each component and the reason for the limitation will be explained as follows. Regarding the inner layer material, during casting, part of the inner surface of the previous intermediate layer is washed and welded, so for elements with particularly large differences in composition, it is necessary to take this amount of washing into account when determining the composition of the molten metal when pouring the inner layer. .

In the case of graphite steel, C is melted into the matrix and becomes graphite (in some cases, a portion becomes eutectic cementite). If the C content is less than 1.0%, melting and casting temperatures will be high, resulting in increased costs. On the other hand, if it exceeds 2.0%, the graphite tends to lose its spherical shape and its toughness deteriorates. Therefore, it is defined as (J11+, 0 to 20%.

St is closely related to graphite production, and is 0°6%
It is almost difficult to crystallize graphite I below. However, if it exceeds 4.0%, Si melted into the ferrite tends to deteriorate the toughness of the material. (The Si content should be in the range of 0.6 to 4.0%. In general, to promote graphitization, inoculating Si with CaSi, etc. immediately before casting will give good results.) is known, and in the present invention, this technology is applied during production to replace CaSi with Si immediately before casting.
It can be added in an amount of 0.1 to 1.0%. In this case, if it is less than 0.1%, the effect of graphitization is small, while if it exceeds 1.0%, the effect is saturated and it is not economical.

Even when inoculated, if the Si component range is 1-, CaS
It is regulated by the content after addition of i, etc.

MnL: L: Combines with S and acts as MnS to remove the negative effects of S, but if it is less than 0.2%, this effect will not be affected, while if it exceeds 1.0%, the toughness of the material will deteriorate. Since the content becomes significant, the content is set in the range of 0.2 to 1.0%.

I) increases the fluidity of the molten metal, but since it makes the material brittle, a low content is desirable and should be 0.1% or less.

Like P, S makes the material brittle, so the lower its content is, the better (below 0.1%. Note that when Ca5i0') is added, it is deoxidized by Ca, so in general S0 .04% 1g lower. Ni is effective in making the material tougher, but it is required at 0.1% or more and 3.0% or less. Note that if it is less than 0.1%, the effect will be insufficient, but
Due to the fact that roll waste iron is generally used as the raw material for melting,
In fact, it is desirable to obtain a material with -1 to less than 0.1% of old content.

Since the outer layer of Cr is an I-comb material, it is unavoidable that some amount of Cr will be mixed into the inner layer as the outer and inner layers are welded together, and care must be taken in determining the molten metal components of the inner layer. This varies depending on the outer layer components, inner layer components, and casting conditions, but the Cr content of the inner layer material is 0.62~
Increase by 1.0%. The Cr content of the inner layer with the product is 0.2
A range of 2.0% is appropriate. In other words, Cr has a 411 effect on making the material tougher, but if it is less than 0.2%, it has no effect, while if it exceeds 2.0%, it becomes difficult for graphite to crystallize, which actually deteriorates the toughness. be. On the other hand, in order to regulate the Cr content of this inner layer material within a predetermined range, it is necessary to
It is necessary to specify the range of 1.0% or less.

As before, Mo is an important element in terms of ensuring toughness, but if it is less than 0.1%, it has no effect, and on the other hand, if it exceeds 1.0%, it becomes hard and brittle. is in the range of 0.1 to 1.0%.

The inner layer material includes the components listed in % of each mold mouth, and the remainder essentially consists of Fe, but other components other than those listed in ``-'', and if necessary, the following Ti as a deoxidizing agent. , A1. ,
Zr can be added alone or in combination. That is, the inner layer material described in item 1 has a C content of 1.0 to 2.
Since it is within the range of 0%, by adding one or more of Ti, 81, and Zr in a total weight percent of less than 0.1% to deoxidize, the material has better properties and is free from cavities. A sleeve is obtained. Regarding the upper limit of the added content in I-1, all of the elements in I-1 are strong deoxidizing agents, so if they are contained alone or in combination at 0.1% or more, the molten metal will become overoxidized. This is because the fluidity of /8 hot water decreases.

The composite sleeve for rolling steel of type 1 according to the present invention has the structure described above, and the manufacturing method of this composite sleeve by the centrifugal casting method will be explained with reference to the example shown in FIG.

That is, on the rotating roller 6.6 of the centrifugal casting machine, a sleeve 2.2 made of a sand mold or heat-resistant brick is placed at both ends of the inner surface.
A rotary mold 1 in which the outer layer 3 is to be formed is installed, and while the mold 1 is rotating, the molten metal to form the outer layer 3 is first poured into it from the pot 7 through the casting gutter 8, etc., and then the 2 ( 1. The intermediate layer 4 should be formed while the inner surface of the kidney 3 is partially or completely uncoagulated.
Pour 8 hot water, and after it has solidified, while it is still unsolidified,
Should inner layer 5 be formed>=? It is the infusion of E. Thus, the three layers (N3, intermediate layer 4 and inner layer 5) are metallurgically completely bonded to form a single composite sleeve for assembly rolls.

The casting method shown in the figure shows the case where the axis of rotation is horizontal, but of course the axis of rotation is vertical or oblique.
This does not preclude modification and casting in the form , '.

In addition, when casting the inner layer 4, refer to the casting example for the outer layer 3.
It is possible to cast from the opposite side instead of the previous case, and this is effective in ensuring uniform thickness of the first layer. The composite sleeve thus cast is further subjected to a predetermined tassel treatment as described above.

Here, the reasons for centrifugally casting the first layer, middle layer, and inner layer are as follows: 1) Cr in the outer layer can be mixed and expanded into the middle layer and inner layer in January. (In the case of inner N injection, Cr in the inner layer is
In the case of the material of the present invention, it is difficult to add lrl+ to 2.0 layers, and it is difficult to achieve the required strength of 45 kg/piece.) 2) Compared to inner layer pouring casting Since the stiffness is greatly reduced, and due to the cooling effect from the inner space, the solidified structure of the inner layer becomes finer, and the toughness is further improved by +11.

The following effects can be mentioned.

In the case of horizontal rolls, the composite sleeve thus manufactured is subjected to rolling with the composite sleeve 9 assembled to the arch 10 in a tight fit, as shown in FIG. The materials of Ahar 10 are SCM-440, St'-6
0, cast steel, spheroidal graphite cast iron, etc. are selected according to the rolling conditions, and the shrink fit part 11 is 0.8 x 10 in terms of shrink fit ratio.
-3 or so is common. In some cases, a friction-enhancing material or an adhesive is applied to the shrink fit portion to increase the shrink fit rate.

In addition, the wear resistance, which is the rolling characteristic of the sleeve III-ru, is not affected by the material of the ar-har.
Further, the accident resistance (resistance to 10 accidents +!I:) is determined by the tangential direction (circumferential direction) strength of the inner layer of the sleeve and the tangential direction residual stress of the inner surface of the sleeve, and is not directly related to the material of the Ahar.

Incidentally, from past experience, it is known that there is no problem if the tensile strength (tangential direction) of the inner layer of the sleeve is 45 kg/vJ or more and the residual tensile stress (tangential direction) is 15 kg/vJ or less. That is, horizontal [1 to le,
The tangential (circumferential) tensile stress acting on the inner surface of the sleeve is
Rolling load 2kg/■1h, thermal stress during rolling 6kg/
Considering the safety factor based on wlfi, the maximum firing stress of 12 kg/VT (according to past results) and the maximum residual stress of 1.5 kg/-, the strength of the inner surface of the sleeve is 45 kg.
/i

Next, specific examples and comparative examples of the present invention will be described. In the comparative example, the outer layer is made of high C and high Cr material, and the inner layer is made of graphite steel.

(2) Table 1 shows the chemical composition of Solvent 21 of Examples of the present invention and Comparative Examples. Using these /8 hot water, under the production conditions shown below, a sleeve material in which the first layer, middle layer, and inner layer were welded and integrated was cast by the centrifugal force casting method shown in Figure 1.
After the solidification was completed, a heat treatment was performed as shown below, and then a composite sleeve of a predetermined size was collected.

Manufacturing conditions (Examples, Comparative Examples) (general) Mold inner diameter...φ11 (10mm) Casting wall thickness (one side) Outer layer...2001 Marginal middle layer...40mm Inner layer...1001°Heat treatment-=・940℃X1211r cooling i*degree 200
~250°C/llr. Product dimensions (11)...outer diameter 10
60 x inner 1 yen 518 x width 230 (next leaf) ■ Commercialization of the obtained composite sleeve Or silk composition not shown in Table 2. The composition of the outer layer is omitted because it is almost the same as the composition of the molten metal. The sampling position (mm) from the surface of the product tray 1 is as described above for both Examples and Comparative Examples.

Middle class...17f1. Inner layer: 250mm The hardness distribution on the side surface of the sleeves of Examples and Comparative Examples was measured. The results are shown in Figure 3.

From FIG. 3, it can be seen that the total thickness lv range of the outer layer of the example is [1].
It can be seen that a high hardness of approximately 11s70 is achieved.

Further, the weaving at a position 40 degrees from the outer surface of the sleeve of the example is shown in Fig. 4 (+1 and (2). Fig. 4 (1)
is 50 times, and (2) is 400 times. As shown in the same figure, there is a large amount of 2 in the base mainly composed of primary carbide and
Carbide is separated into fine particles11. j It is observed that he is doing so.

■ A +A quality test was conducted using the irradiated composite sleeve.

(1) Wear resistance It is determined by the test results of the Ohkoshi type abrasion test, and it is known that the test results show the same tendency as the actual rolling results.

Thickness 10m1 at 40 degrees from the surface of the sleeve outer layer. A test piece of width 20 x length 5011 was taken in the axial direction, and the specific wear amount without lubrication was measured under the following test conditions.

Slip speed: 3.4m/sec Slip distance 1iill: 200m Final load: 17.6-18.5 kg Rotating wheel:
SUJ 2 (IIRc 60-63) (11) Accident resistance (resistance to split m accidents) 25 from the surface of the sleeve
The inner layer strength (tensile strength) in the tangential direction at 0+n and the residual stress in the tangential direction on the inner surface of the inner rii were measured.

The measurement results of (1) and (ii) are shown in Table 3.

(Next page) Table 3 (iii) Resistance to scraping The outer layer comes into contact with the rolled material and is subjected to repeated heat stress, thereby generating thermal fatigue cranks (so-called heat cracks).

This thermal fatigue crack is due to toughness (elongation in tensile test)
The better the toughness, the higher the resistance to thermal fatigue crank.

Table 4 shows the results of the tensile test at a position 401 from the outer surface of the sleeve.

From Tables 4 and 3, it can be seen that the outer layer of the composite sleeve of the present invention has high hardness and extremely excellent wear resistance. Furthermore, it can be seen from the elongation value of layer 1 in Table 4 that it has excellent crank resistance. Moreover, the strength (and residual stress) of the inner layer of the sleeve is also low, and it can be seen that the accident resistance is also good.

(Effects of the Invention) The present invention has been described in detail below, and in the I-1 section steel rolled composite sleeve according to the present invention, the outer layer is formed of a high chromium material with a specific chemical composition The inner layer is formed of spherical graphite steel with a specific chemical M composition, and C to the inner layer is
In order to prevent R contamination, an intermediate layer with a specific chemical composition is interposed between the outer and inner layers, and these are welded and integrated. ”Because of the treatment, the outer layer is
Consisting of a base mainly composed of bainite containing a large amount of primary and secondary carbides, the target outer layer hardness Its 6
5 or more can be reliably achieved, which results in excellent wear resistance and heat crack resistance, which significantly contributes to reducing uneven wear during actual rolling and reducing heat cracks at the corners of the web and flange. On the other hand, the graphite steel material forming the inner layer has excellent material toughness, and the interposition of the intermediate layer can reliably solve the problem of material embrittlement due to Cr contamination from the outer layer. Toughness is increased because the incidental effects of Tendency 1~ are exhibited.
Due to the synergistic effect of these excellent properties of the outer and inner layers, the sleeve of the present invention has a significant improvement in rolling performance and sleeve life compared to conventional products. This can be extremely useful in the field of one-shape rolling (particularly).

Furthermore, in addition to the manufacturing method of the present invention using centrifugal force casting, for example, the intermediate layer and inner layer are also formed by centrifugal force casting following the outer layer, so there is little mixing between the layers of tiles, and in particular, the amount of Cr in the inner layer molten metal is reduced. Since the amount of contamination from the outer layer is anticipated in advance and the content is regulated to a low level, the inner layer material does not become high in Cr and deteriorate in toughness due to the presence of the intermediate layer, and the inner layer is further protected against hollow centrifugal force. Good results were obtained in terms of the effect of finer weave of the inner layer, that is, improvement of toughness, and the weldability of the inner layer by casting, and furthermore, by implementing the high temperature heat treatment, the above-mentioned remarkable improvement effect on the outer and inner layers was obtained. , is particularly useful as a technical means for obtaining the desired composite sleeve.

[Brief explanation of the drawing]

Fig. 1 is an explanatory cross-sectional view of a centrifugal casting mold in the manufacturing process of the present invention, Fig. 2 is a cross-sectional view of a sleeve roll to which a composite sleeve is shrink-fitted, and Fig. 3 is a cross-sectional view of a composite sleeve according to the present invention. - Diagram representing the hardness distribution for the example, Figure 4+11
．． f2) is a photograph of the metallographic structure of the outer layer according to the present invention. 3...outer layer, 4...middle layer, 5...inner layer.

Claims (1)

[Claims] 1. C: 0.8-2.0%, Ni: 0.8-2.5%S
i: 0.3-1.5%, Cr: 7-22% Mn: 0.4
~1.5%, Mo: 0.5~3.0%, P: 0.1% or less, S: 0.1% or less, and the remainder substantially consists of Fe, and (F
e, Cr)_7C_3 type primary and secondary carbide, and an outer layer of high chromium material consisting of a base mainly composed of bainite, C: 0.8 to 2.5%, Ni: 0.1 to 2 .5%Si:
0.2-3.0%, Cr: 0.5-9.0% Mn: 0.
3 to 2.0%, Mo: 1.5% or less, P: 0.1% or less, S: 0.1% or less, and the remainder substantially consists of Fe, and C: 1.0. ~2.0%, Ni:0.1~3.0%Si:
0.6-4.0%, Cr: 0.2-2.0% Mn: 0.
Inner layer of spheroidal graphite steel material containing 2 to 1.0%, Mo: 0.1 to 1.0%, P: 0.1% or less, S: 0.1% or less, and the remainder substantially consists of Fe. A composite sleeve for rolling H-section steel, characterized in that the outer layer has a hardness of Hs65 or more. 2. By centrifugal casting method, C: 0.8-2.0%, Ni: 0.8-2.5% Si:
0.3-1.5%, Cr: 7-22% Mn: 0.4-1
．． 5%, Mo: 0.5 to 3.0%, P: 0.1% or less, S: 0.1% or less, respectively, by weight, with the remainder essentially consisting of Fe. After that, while the inner surface is partially or completely unsolidified, C: 0.8 to 3.0%, Ni: 2.5% or less, Si: 0.
2-3.0%, Cr: 0.3% or less Mn: 0.3-2.
0%, Mo: 1.5% or less P: 0.1% or less During non-solidification, C: 1.0-2.0%, Ni: 0.1-3.0%, Si:
0.6-4.0%, Cr: 1.0% or less Mn: 0.2-4.0%
1.0%, Mo: 0.1 to 1.0% P: 0.1% or less After casting, welding and integrating the outer layer, intermediate layer, and inner layer, the temperature was maintained at 900 to 1100°C and heated to 100°C.
1. A method for manufacturing a composite sleeve for H-shaped steel rolling, characterized by performing heat treatment for cooling at a cooling rate of /Hr or more.