JP3151998B2 - Composite roll for cold rolling and production method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite roll for cold rolling and a method for producing the same.

[0002]

2. Description of the Related Art A large load is applied to a cold rolling roll used for cold rolling of a metal plate such as a steel plate during rolling. In addition, since the roll for cold rolling has a smaller amount of wear on the surface layer than the roll for hot rolling, the amount of grinding for optimizing the roll profile is also small. Accordingly, the fatigue damage and the accumulation of fatigue in the surface layer of the cold rolling roll tend to increase more easily than the hot rolling roll. Therefore, in the roll for cold rolling, resistance to falling off of the surface layer, that is, spalling resistance is extremely important. The spalling resistance required for a cold rolling roll is 1 × 10 ⁶ times or more under a Hertzian contact pressure of 2800 MPa in terms of rolling fatigue life.

[0003] For example, "Steel Handbook, 3rd Edition, III (1) Rolling Basics / Steel Sheet, page 411, Table 7.35" points out a material defect on the roll surface as one of the causes of spalling. Therefore, in order to improve the spalling resistance of a cold rolling roll manufactured from a single ingot (hereinafter, referred to as a “single cold rolling roll”), the amount of nonmetallic inclusions has been suppressed. Therefore, cold rolling rolls have been manufactured using high-purity steel. By the way, the inclusions existing in the roll for cold rolling are roughly classified into oxide-based inclusions and sulfide-based inclusions.

In order to reduce these nonmetallic inclusions in steel, generally, (i) oxide-based inclusions: use of out-of-pile refining by various vacuum degassing methods or ladle refining methods (Ii) Sulfide-based inclusions: Means such as reducing the S content in steel by using secondary melting by ladle refining or ESR are known. However, the methods currently applied to the control of non-metallic inclusions in a single cold rolling roll mainly include electric furnace melting → deoxidation by out-of-pile refining → desulfurization by ESR method and nonmetallic inclusion This process involves a process of finely graining and dispersing the material, and by such a method, the steel quality of the roll for cold rolling is made sound and spalling resistance is secured.

By the way, at present, in order to satisfy both the abrasion resistance required on the body surface of the cold rolling roll and the toughness required inside the body and the shaft of the cold rolling roll, the steel composition is The outer layer material having the same or different steel composition around the core material with excellent toughness, such as continuous casting method, centrifugal casting method, and even ESR outer layer overlay method, wear resistance Improved composite rolls for cold rolling have been manufactured.

[0006] However, the production of this composite roll for cold rolling has the following problems. (i) When manufacturing composite rolls for cold rolling by the continuous casting method or the centrifugal casting method, since the outer layer material is cast into the atmosphere using molten steel, deoxidation and desulfurization of the outer layer material and finer nonmetallic inclusions are required. Granulation and dispersion cannot be performed sufficiently,
Neither the S content nor the amount of nonmetallic inclusions in the outer layer material can be suppressed to appropriate values.

(Ii) When manufacturing a composite roll for cold rolling by the ESR outer layer overlay method, the outer layer material as an electrode is secondarily melted under slag (the surface layer of the core material is melted in the process). In some cases, nonmetallic inclusions contained in the core material move and diffuse into the outer layer material, and the amount of nonmetallic inclusions in the outer layer material cannot be suppressed to a predetermined value.

Conventionally, as a material for limiting the S content of the outer layer material of a composite roll, JP-A-63-114937 discloses C: 0.8 to 1.2% by weight, Si: 0.5 to 1.5% by weight, M:
n: 0.5 to 1.5% by weight, P: 0.08% by weight or less, S: 0.06%
Wt% or less, Ni: 0.5 to 2.0% by weight, Cr: 8 to 16% by weight, Mo: 0.8 to 2.5% by weight, V: 2.0 to 6.0% by weight, low carbon high chromium cast iron consisting of balance Fe and unavoidable impurities With an outer layer material formed by the above, a composite roll for hot rolling excellent in abrasion resistance, skin roughness resistance, slip resistance and crack resistance is disclosed in JP-A-3-254304 in terms of area ratio. High strength and wear resistance with an outer layer material consisting of a structure containing 5 to 30% of granular carbide and 5% or less of non-granular carbide and having a hardness of Vickers hardness of Hv550 or more. And a wear-resistant composite roll having excellent skin roughness resistance have been proposed.

Further, Japanese Patent Application Laid-Open No. 1-129929 discloses that
Ni: A composite material in which an outer layer material of nickel cast iron containing 3.3 to 6% by weight and a steel core material are welded and integrated by an ESR method, and this composite material is annealed at 500 to 600 ° C.
After quenching by holding at a temperature of 1150 ° C for 1 to 10 hours and then cooling, after quenching, it is tempered to a high tempering temperature of 450 to 550 ° C.
A method has been proposed for producing a hot-rolling work roll with high hardness, high wear resistance, and a longer life by increasing the hardness by performing tempering by air cooling and slow cooling after holding for 10 hours. I have.

[0010]

SUMMARY OF THE INVENTION The composite rolls proposed in JP-A-63-114937 or JP-A-3-254304 aim at improving the slip resistance and the surface roughness of the composite roll, respectively. It is not intended to improve the spalling resistance of the composite roll. Further, in each proposal, the S content is limited to 0.06% by weight or less, but the reason for the limitation is merely described as prevention of embrittlement of the composite roll. No effect on gender is mentioned.

[0011] Further, in the work roll for hot rolling proposed in Japanese Patent Application Laid-Open No. 1-129929, the S content is limited to 0.05% by weight or more and 0.15% by weight or less from the viewpoint of preventing embrittlement and improving machinability. No mention is made of the effect of the S content on the spalling resistance as in the case of the composite roll proposed in JP-A-63-114937 or JP-A-3-254304.

Here, an object of the present invention is to provide a composite roll for cold rolling having a desired spalling resistance, specifically, a rolling fatigue life of 1 × 10 ⁶ under a Hertzian contact pressure of 2800 MPa.
It is an object of the present invention to provide a composite roll for cold rolling that is performed more than once and a method for producing the same.

[0013]

The present inventor has investigated various features common to a single cold rolling roll having desired spalling resistance. FIG. 1 shows the occurrence of spalling in a single cold rolling roll manufactured conventionally in relation to the amount of oxide-based inclusions k _o (%) and the amount of sulfide-based inclusions k _s (%). FIG. 2 is a graph showing the arranged results, and FIG. 2 shows the relationship between all the nonmetallic inclusions k _T (%) and the S content (%) in the cold rolling rolls examined in deriving the results of FIG. FIG. In addition, the amount of nonmetallic inclusions (%) is usually the result of measurement by a test method specified in JIS G 0555, and in this specification, the amount of nonmetallic inclusions uses the result of measurement by this method. . That is, the amount of non-metallic inclusions: 0.03% is d60 × 400 = 0.
03%, that is, a cleanliness level of 0.03%.

From the graph shown in FIG. 1, it can be seen that the proportion of sulfide-based inclusions in all non-metallic inclusions is large, and that the amount of oxide-based inclusions is not so large, which is almost the same as the conventional deoxidation. It can be seen that the deoxidation can be sufficiently reduced and that spalling increases when the total amount of nonmetallic inclusions exceeds 0.03%.
From the graph shown in Fig. 7, it was found that it is effective to set the S content to 0.005% by weight or less in order to reduce the amount of all nonmetallic inclusions to 0.03% or less.

Therefore, the present inventor has further studied, and in order to achieve the above-mentioned desired spalling resistance in the production of the composite roll for cold rolling, as in the case of a single cold rolling roll, the cold rolling is performed similarly to the case of a single cold rolling roll. It has been found that it is effective to set the S content of the outer layer material of the composite roll for cold rolling to 0.005% by weight or less and the amount of nonmetallic inclusions to 0.03% or less.

However, as a result of further studies, the present inventor has found that when the outer layer material is overlaid on the core material using the ESR method in order to set only the S content and the amount of nonmetallic inclusions in the outer layer material to predetermined values, It has been found that non-metallic inclusions contained in the core material move and diffuse into the outer layer material during the overlaying, and the amount of non-metallic inclusions in the outer layer material may not be able to be set to a predetermined value.

The present inventor has studied various methods for manufacturing such a composite roll for cold rolling. As a result, not only the S content and the amount of nonmetallic inclusions in the outer layer material, but also the nonmetallic The present invention was completed by finding that a composite roll for cold rolling having a desired level of spalling resistance can be obtained by limiting the physical quantity.

Here, the gist of the present invention is a composite roll for cold rolling composed of a core material having a steel composition and an outer layer material, wherein the amount of nonmetallic inclusions in the material of the core material is 0.03. % And the non-metallic inclusions in the outer layer material are 0.03% or less and the S content of the outer layer material is
A composite roll for cold rolling characterized by being 0.005% by weight or less.

The above-mentioned composite roll for cold rolling according to the present invention is characterized in that an outer layer material having the same or different steel composition is surrounded by a core material having a steel composition having a nonmetallic inclusion content of 0.03% or less. It is manufactured by overlaying by the method so that the amount of nonmetallic inclusions in the outer layer material is 0.03% or less and the S content of the outer layer material is 0.005% by weight or less. The core material and the outer layer material of the composite roll for cold rolling according to the present invention each have a steel composition. The core material and the outer layer material may be the same or different.

[0020]

Hereinafter, the present invention will be described in detail together with the functions and effects. In the composite roll for cold rolling according to the present invention, the S content and the amount of nonmetallic inclusions in the outer layer material and the amount of nonmetallic inclusions in the core material are each suppressed to a predetermined value or less, so that the spalling resistance is reduced. [The rolling fatigue occurrence life is 1 × 10 ⁶ times or more under the Hertzian contact pressure of 2800 MPa].

That is, in the composite roll for cold rolling, when the amount of nonmetallic inclusions in the outer layer material is 0.03% or less, the rolling fatigue generation life is 1 × 10 ⁶ times or more under the Hertz contact pressure of 2800 MPa. Is obtained. As described above, most of the non-metallic inclusions are sulfide-based inclusions. Therefore, in the present invention, by controlling the S content of the outer layer material to 0.005% by weight or less, the sulfide-based inclusions and thus the non-metallic inclusions are reduced. Reduce the total amount of inclusions.

In order to manufacture a composite roll having such an outer layer material having an S content and a non-metallic inclusion amount, a core material is disposed inside an electrode made of the outer layer material, and the ESR meat for re-dissolving the electrode is prepared. The same or different outer layer materials may be build-up welded around the core material using the build-up method.

However, the amount of nonmetallic inclusions in the core material is 0.03% or less. If the amount of nonmetallic inclusions in the core material exceeds 0.03%,
Non-metallic inclusions contained in the core material are transferred to the outer layer material because the surface of the core material in contact with the high-temperature slag or molten steel melts when the electrode is formed as an outer layer material by the ESR overlaying method around the core material. This is because the material moves and the amount of nonmetallic inclusions in the outer layer material exceeds 0.03%.

As the core material and the outer layer material of the composite roll for cold rolling according to the present invention, the steel used for the core material and the outer layer material of the known composite roll for cold rolling may be applied. For example, C: 0.35 to 1.2% by weight, Si: 0.15 to 1.
0% by weight, Mn: 0.15 to 1.0% by weight, Cr: 0.5 to 5.0% by weight, Mo: 0.70% by weight or less, Ni: 2.0% by weight or less, C: 0.5 to 1.7% by weight, Si: 0.15-3.
0% by weight, Mn: 0.15 to 5.0% by weight, Cr: 3 to 13% by weight,
An outer layer material having a steel composition containing Mo: 11.0% by weight or less, V: 6.0% by weight or less, Co: 13% by weight or less, W: 20.0% by weight or less, and Ni: 5.0% by weight or less can be exemplified. Further, the present invention will be described in detail with reference to examples, but this is an exemplification of the present invention, and the present invention is not limited thereto.

[0025]

EXAMPLES (Example 1) C: 1.50% by weight, Si: 0.35% by weight, Mn: 0.35%
% By weight, P: 0.01% by weight, S: 0.008% by weight, Cr: 12.0
Weight: 0.90% by weight, Mo: 0.90% by weight, V: 0.55% by weight, balance of steel composition (equivalent to alloy tool steel SKD11) consisting of Fe and unavoidable impurities. Electrode, C: 0.40% by weight, Si: 0.25% by weight, Mn:
0.75% by weight, P: 0.01% by weight, Cr: 1.05% by weight, Mo: 0.
Steel composition consisting of 25% by weight, balance Fe and unavoidable impurities
Outer diameter of 500 mm (equivalent to SCM440 steel for machine structural use), length 1500 mm
ESR in a copper mold with an inner diameter of 750 mm
After the dissolution, the electrode was re-dissolved around the core material and was overlaid as an outer layer material. In addition, at the time of ESR melting, the S content of the core material and the amount of nonmetallic inclusions were changed at five levels, and a composite steel ingot was manufactured for each core material.

Samples No. 1 to No. 5 were collected from the outer layers of these composite steel ingots, and the amount of nonmetallic inclusions and the S content were measured by the test method specified in JIS G 0555. Table 1 shows the results. From Table 1, it can be seen that the amount of non-metallic inclusions in the outer layer material of the steel ingot should be 0.03% or less, and the amount of non-metallic inclusions in the core material should be 0.03% or less.

Further, with respect to these samples, the number of times of occurrence of rolling fatigue was measured under the condition of a Hertzian contact pressure of 2800 MPa. The results are shown in Table 1. From Table 1, it can be seen that according to the present invention, the goal of spalling resistance (Hertz contact pressure 28
It can be seen that the rolling fatigue occurrence life under 00 MPa was at least 1 × 10 ⁶ times).

[0028]

[Table 1]

Example 2 Using the composite roll for cold rolling from which the data of FIG.
A rolling fatigue life test was performed under the condition of 00 MPa, and the relationship between nonmetallic inclusions in the outer layer material of the composite roll for cold rolling and rolling fatigue occurrence life was investigated. The results are shown in FIG. FIG. 3 shows that when the amount of nonmetallic inclusions in the outer layer material exceeds 0.03%, the rolling fatigue occurrence life is significantly reduced.

Further, a sample was cut out from the outer layer portion of the composite steel ingot manufactured in Example 1, and a rolling fatigue test was performed to measure a rolling fatigue generation life. The results are shown in the graph (グ ラ フ) in FIG. FIG. 3 shows that when the amount of nonmetallic inclusions in the core material exceeds 0.03%, the rolling fatigue occurrence life is significantly reduced.

[0031]

As described in detail above, the present invention makes it possible to improve the spalling resistance of a composite roll for cold rolling.

[Brief description of the drawings]

FIG. 1 shows the occurrence of spalling in a single cold roll manufactured conventionally, in relation to the amount of oxide-based inclusions K _o (%) and the amount of sulfide-based inclusions K _s (%). It is a graph which shows the result of arrangement.

FIG. 2 shows the total amount of nonmetallic inclusions K _T (%) and S content in the cold rolling rolls investigated in deriving the results of FIG.
6 is a graph showing the relationship with (% by weight).

FIG. 3 is a graph showing the relationship between the rolling fatigue occurrence life and the amount of nonmetallic inclusions in Example 2.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-157836 (JP, A) JP-A-4-365836 (JP, A) JP-A-1-240635 (JP, A) JP-A-4- 358046 (JP, A) JP-A-63-157707 (JP, A) JP-A-4-182011 (JP, A) JP-A-57-134013 (JP, A) JP-A-4-297565 (JP, A) JP-A-63-235006 (JP, A) JP-A-1-129929 (JP, A) JP-A-6-226309 (JP, A) JP-A-6-128686 (JP, A) JP-A-1-104750 (JP, A) JP-A-58-171552 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 27/00

Claims (2)

(57) [Claims] 1. A composite roll for cold rolling comprising a core material and an outer layer material each having a steel composition, wherein the material of the core material has a non-metallic inclusion content of 0.03% or less. A composite roll for cold rolling, wherein the amount of nonmetallic inclusions in the material is 0.03% or less and the S content of the outer layer material is 0.005% by weight or less. 2. An outer layer material having the same or different steel composition is built up by an ESR method around a core material having a steel composition in which the amount of nonmetallic inclusions is 0.03% or less. A method for producing a composite roll for cold rolling, comprising producing a non-metallic inclusion: 0.03% or less and an S content of the outer layer material: 0.005% by weight or less.