JPH04191347A - Hollow sleeve material for assembled type rolling roll - Google Patents

Abstract

PURPOSE:To produce a rolling roll having a sleeve material excellent in wear resistance and surface roughing resistance by constituting a hollow sleeve for assembled type rolling roll of an alloy steel with a specific composition. CONSTITUTION:At the time of producing a rolling roll by using a forged steel, etc., as a shaft material and subjecting a hollow sleeve material forming a rolling surface to shrinkage fit on the external surface of this shaft material, a high carbon high alloy steel having a composition which contains, by weight, 1.0-4.O% C, <3.0% Si, <1.5% Mn, 2.0-15.0% Cr, <10.0% Mo, <20.0% W, and 2.0-12.0% V and in which (C+0.4V) is regulated to <=6.0% is used as the sleeve material, or, an alloy steel having a composition prepared by incorporating, into the above composition, <2.0% Ni or incorporating Ni and further <=5.0%, in total, of one or <=2 elements among Ti, Zr, and Nb or incorporating <5.0% Co independently or in combination with Ni and one or more elements among Ti, Zr, and Nb is used as the sleeve material.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the material of sleeves used in assembled type rolling rolls, and particularly relates to materials for sleeves used in assembled type rolling rolls for hot or cold rolling that have excellent wear resistance and surface roughening properties. This relates to the material of the sleeve used for the rolling roll.

[Prior art and invention or problem to be solved] Hot or cold rolling rolls are used to improve product quality and reduce the number of man-hours for changing rolls and calibers when rolling wire rods, steel bars, shaped steel, steel pipes, etc. Abrasion resistance and rough skin resistance are required.

As such a rolling roll, an assembled type rolling roll is used, in which a roll-use layer (sleeve) and a shaft part are made separately, and the two are assembled by methods such as shrink fitting or adhesion.

The above-mentioned assembly type rolling roll has a structure in which only the outer shell used for rolling is made of a highly wear-resistant material, and the arbor is made of forged steel, etc., so it has excellent wear resistance, roughness, and toughness. It is possible to make it into a roll.

In recent years, such prefabricated rolling rolls have been improved in wear resistance and
1. There is a demand for products with excellent skin irritation properties, and various types of 0-ruols have been proposed for this purpose.

Japanese Patent Publication No. 2-206868 consists of an outer layer which is a rolling phase formed by sintering an alloy powder with excellent wear resistance and crack resistance, and an inner layer made of a steel material with excellent toughness. A composite ring sleeve is disclosed in which the outer layer is formed over the entire width of the outer surface of the inner layer, and the outer layer and the inner layer are diffusion bonded by hot isostatic pressing.

However, this composite ring has dramatically improved wear resistance compared to conventional cast iron rolls, is expensive to manufacture, and has poor workability, so it requires advanced processing technology when recutting. There is a problem in that it requires a large amount of processing time and man-hours.

Further, Japanese Patent Publication No. 2-19181 discloses a roll material for hot rolling which is made by containing a large amount of vanadium to crystallize hard MC type carbide.

This hot rolling roll material has excellent abrasion resistance and is easy to process, but (2) VC type carbide tends to precipitate, which tends to cause unevenness in the structure, and even one level of roughness is not necessarily sufficient. ■Since the specific gravity is lower than that of VC-type carbide iron molten metal, it tends to float and segregate on the innermost surface in centrifugal casting and in the riser part in static casting, reducing the yield of ■ and in some cases causing cracks. There's a problem.

Therefore, it is an object of the present invention to provide a hollow sleeve material for assembled rolls for hot or cold rolling, in which MC type carbide such as VC is uniformly distributed, and has excellent wear resistance and surface roughness. It is to be.

[Means to solve the problem]

A problem in manufacturing hollow sleeve materials for assembled rolling rolls containing hard carbides such as VC is that the VC carbides, which have a different specific gravity from the molten metal, are segregated by centrifugation or flotation. As a result of conducting various experiments regarding this problem, the present inventor found that the degree of segregation of VC carbide is extremely small if the chemical composition has a small amount of primary crystallization of VC carbide. In other words, in terms of weight ratio, C1
, 0 to 4.0%, Si 3.0% or less, Mn 1.5% or less, Cr 2.0 to 15.0%, Mo 10° 0% or less, W
20.0% or less, 12.0 to 12.0%, the remainder substantially consisting of Fe and unavoidable impurity elements, and 6% +
If the composition range is in which the value of 0.4v% is 6.0 or less, VC carbide does not crystallize as a primary crystal, so there is little segregation of VC carbide in the inner part, and the sleeve has good wear resistance. In addition, we discovered that if the chemical composition of primary C carbide does not crystallize, the structure of VC carbide is less uneven and has good skin roughness, and we have come up with the present invention. did.

That is, the hollow sleeve material for assembled type rolling rolls of the present invention has chemical components of C1.0 to 4.0% and Si3.0% by weight.
% or less, Mn 1.5% or less, Cr2.0-15.0?4
, Mo10.0% or less, W20.0% or less, V2.0~
12.0%, the remainder substantially consisting of Fe and unavoidable impurity elements, and the value of 6%+0.4V% is 6.0 or less.

The present invention will be explained in detail below.

The reasons for specifying the content (weight ratio) of each element will be described below.

(arc: 1.0-4.0% C is an element constituting carbide necessary for improving wear resistance. If it is less than 1.0%, the amount of carbide is not sufficient and it is difficult to obtain sufficient wear resistance. On the other hand, if the amount of C is increased, primary crystals ■
It is limited because the amount of C carbide crystallized becomes excessive. Is this amount limited by the amount of V? If the amount of V exceeds 4.0%, carbides will crystallize or be excessive in the primary crystals, and there will be significant segregation of VC carbides during casting. This is inconvenient because it occurs. The preferred C content is 1 to
It is 3%.

(bi Si: 3.0% or less S1 is not effective as a deoxidizing agent, but if it exceeds 3.0%, the material becomes brittle, which is disadvantageous. The preferable content of Sl is 0.2 to 2%. It is.

[C) Mn: 1.5% or less Mn is also a deoxidizing agent like Si, or has the effect of fixing S as MnS. However, if it exceeds 1.5%, the material becomes brittle, which is disadvantageous. The preferred Mn content is 0.
It is 1-1%.

(d) Cr: 2.0 to 15.0% Cr is added to improve hardenability and form a hard MTC3-based carbide. If the amount added is less than 2.0%, the effect of the addition is not sufficient. Moreover, if it exceeds 15.0%, the amount of harder VC carbide becomes too small, so the Cr amount is set to 15% or less. The preferred Cr content is 3 to 12%.

(e) Mo: 10.0% or less Mo is added to improve hardenability and temper hardness.

However, if it is added in excess of 10.0%, more M2C or M,C carbides will crystallize, resulting in a harder VC.
or decrease. The preferred MO content is 0.5 to 6%.

(fl W: 20.0% or less W has the effect of improving the tempering hardness, and also has the effect of substituting solid solution in the VC carbide, increasing the specific gravity of the VC carbide, and reducing the degree of gravitational segregation. However, If it is added in excess of 20%, a large amount of W6C carbide will be produced, and the harder VC carbide will be reduced.The preferable W content is 0.5 to 10%.
It is.

fg) V: 2.0 to 12.0% (2) is an element that contributes most to the wear resistance of the sleeve material of the present invention. In other words, (2) is an element that has a very strong carbide-forming effect and forms hard VC. If this V is less than 2.0%, crystallization of VC carbide is not sufficient. On the other hand, if the V content is too high, there will be too much primary crystal granular VC carbide,
Due to the centrifugal force during centrifugal casting, VC carbide with a light specific gravity segregates to the inner part.

Therefore, it is necessary to reduce the V content to 12.0% or less.

The preferred V content is 3 to 8%.

Further, the amount of V is limited mainly by the amount of C. Through various experiments, the present inventors have determined a composition range in which the crystallization of such primary VC carbides is minimal and segregation during casting does not pose a problem. That is, if the composition is such that the weight ratio is 0%+0.4V% or 6°0 or less, the crystallization of VC carbide in the primary crystal will be sufficiently reduced.

Therefore, even if the sleeve material is cast within such a composition range, segregation of V and C toward the inner surface side can be minimized, and it can be formed to have a nearly uniform composition.

Other chemical components In the present invention, in addition to the above-mentioned components, the following elements may be further contained.

■Ni: 2.0% or less Ni forms a solid solution in the base, stabilizes austenite,
In order to improve hardenability, it is effective to add it when manufacturing large rolls. However, if it exceeds 2.0%, austenite becomes too stable and it becomes difficult to decompose residual austenite, making it impossible to obtain sufficient hardness or wear resistance. A more preferable Ni content is 1.5% or less.

■At least one of Ti, Zr and Nb; 5.
0% or less Ti, Zr, and Nb are elements that form hard carbides like (2), and by introducing them into the sleeve material of the roll, it is possible to improve the wear resistance. T1,
The blending ratio of one or more components of Zr and Nb is
The total amount shall be 5.0% or less. Is it the sum of these elements?5.
If the amount exceeds 0%, the amount of VC carbide becomes too small, which is not preferable. A more preferable content is 3% or less.

■Co:15. 0% or less Co is dissolved in the roll base and has the effect of improving the hot strength of the roll. Therefore, the addition of CO is particularly effective in improving the wear resistance and roughness of hot rolling rolls. This effect is sufficient if the amount of CO added is 15.0%, and even if it exceeds 15.0%, there is no improvement in wear resistance or rough skin, so from an economic point of view. 15.
0% or less. More preferable Co content is 3.0~
It is 12.0%.

In addition, the molten metal having the above composition is cast into a mold such as a sand mold in the desired sleeve shape, solidified and cooled, annealed, etc., and subjected to rough processing and various finishing processes as necessary to produce a mold for assembly type rolling rolls. It is possible to manufacture hollow sleeves.

In addition, in order to manufacture a rolling roll using the hollow sleeve for an assembled rolling roll obtained in this way, it may be fixed to a shaft material made of gray cast iron, ductile cast iron, graphite steel, etc. by a method such as shrink fitting. .

〔Example〕

The present invention will be further explained in detail by the following examples.

Examples 1 to 3 A molten metal having the composition shown in Table 1 was prepared with a diameter of 70 mm and a height of 80 mm.
A small roll material for rolling wear test was cast by injecting it into a CO2 sand mold. 1000~l 100' for this material
After heat treatment of quenching from C and tempering at 500-550°C, the outer diameter is 60mm, the inner diameter is 35mm, and the length is 4.
A 0 mm sleeve-shaped test roll was prepared.

Table 2 shows the results of measuring the surface hardness of the outer shell layer of each test roll using a Shore hardness meter. Next, a rolling wear test was conducted on this test roll. As shown in Fig. 3, the rolling wear test machine includes a rolling mill 1, an upper roll 2 and a lower roll 3 incorporated in the rolling mill 1, a heating furnace 4 for preheating the rolled material S, and a heating furnace 4 for cooling the rolled material S. It consists of a cooling water tank 5, a winder 6 that applies constant tension during rolling, and a tension controller 7 that adjusts the tension. The test conditions were as follows.

Rolled material SO3304, thickness 1mm, width 15mm Rolling distance ・800m Rolling temperature ・900″C Reduction ratio .25% Rolling speed 150m/min Roll cooling/water cooling The depth of wear on the surface of the test roll is the rolling width Table 2 shows the results of determining the average wear depth.

As conventional materials for comparison, test rolls were produced in the same manner as in Example 1 using high chromium cast iron (Conventional Example 1) and alloy grain roll material (Conventional Example 2). Tatashi,
Heat treatment was applied to suit these materials. A wear test was conducted in the same manner as in Example 1, and the measured values of wear depth and hardness are shown in Table 2.

Example 4 Inventive material (a) and conventional material (b) having chemical components shown in Table 3.
) was centrifugally cast using a mold with an inner diameter of 450 mmφ and a body length of 750 mm to produce a sleeve roll with a wall thickness of 60 mm. The rotation speed is 140G due to the centrifugal force on the inner surface of the sleeve roll.
It was set so that

FIG. 2 shows the change in the amount of V, which is an indicator of the change in the amount of VC carbide, from the as-cast surface to the inner surface of each sleeve. Also the first
The figure shows a micrograph of the metal structure of the material of the present invention at a magnification of 100 times at a position of 20 mm.

As is clear from Fig. 2, in the present invention material (a), there is less segregation of VC carbide toward the inner surface, whereas in the conventional material (bl
The degree of segregation is large, especially in the inside of the sleeve.
It can be seen that the amount of V has increased significantly.

Example 5 φ285 mm×4 with chemical components shown in Table 4
00 mm sleeve roll is cast and this is SCM4
40 forged steel was used, and an assembly-type rolling roll was manufactured.

Casting was performed by centrifugal casting, and after rough processing, quenching from 1030°C and tempering at 500 to 550°C were repeated three times. The hardness after heat treatment is also shown in Table 4.

A rolling test was conducted on the assembled roll roll thus obtained. In the rolling test, a special steel round bar with a diameter of 8 mm was used as the rolled material, and the amount of rolling, the amount of wear, and the amount of recutting per one recutting when rolled at a rolling reduction of 13% were measured.

The results are shown in Table 5. For comparison, Table 5 also shows the results of rolling in the same manner using a conventional chilled cast iron roll (Comparative Example 1).

As is clear from Table 5, compared to the roll of Comparative Example 1, the roll of Example 5 has a rolling capacity of 2.2 mm before the next reshaping.
7 times as much, and the amount of wear and rework is also 1/2 of that of the comparative example.
, I/4. The roll surface after rolling was good and could be used satisfactorily.

〔Effect of the invention〕

The present invention has made it possible to manufacture at low cost a prefabricated rolling roll having wear resistance more than twice that of conventional cast iron roll materials. This not only extends the life of the rolls, but also reduces the frequency of roll replacement, improves the product shape, and increases the flexibility of the rolling schedule.

[Brief explanation of drawings]

FIG. 1 is a micrograph showing the metallographic structure of the sleeve material of Example 4, FIG. 2 is a graph showing changes in the V amount of the sleeve roll of the present invention and sleeve rolls made of conventional materials, and FIG. FIG. 2 is a diagram schematically showing a rolling abrasion tester used for a roll abrasion test. 1 Rolling mill 2... Upper roll 3... Lower roll S... Rolled material 5... Cooling water tank 6... Winder 7... Tension controller

Claims (4)

[Claims] (1) Chemical components are C1.0 to 4.0% by weight, Si3
．． 0% or less, Mn 1.5% or less, Cr2.0-15.0
%, Mo10.0% or less, W20.0% or less, V2.0
~12.0%, the remainder substantially consisting of Fe and unavoidable impurity elements, and a value of C%+0.4V% of 6.0 or less. (2) In the hollow sleeve material for an assembled rolling roll according to claim 1, the chemical component further includes Ni2.
A hollow sleeve material for an assembled rolling roll, characterized by containing 0% or less. (3) In the hollow sleeve material for assembled rolling rolls according to claim 1 or 2, the chemical components further include Ti, Z
A hollow sleeve material for a prefabricated rolling roll, characterized in that it contains a total of 5.0% or less by weight of one or more components selected from the group consisting of r and Nb. (4) The hollow sleeve material for a prefabricated roll according to any one of claims 1 to 3, wherein the chemical component further contains Co at a weight ratio of 5.0% or less. Hollow sleeve material.