JPH0741899A - Centrifugally cast high wear resistant roll - Google Patents

Abstract

PURPOSE:To produce a composite roll in which metal carbides having high hardness are uniformly precipitated and excellent in wear resistance, at the time of producing a composite roll for rolling by a centrifugal casting method, by constituting the external layer of the roll of high carbon-high Cr cast iron steel having a specified compsn. CONSTITUTION:High Cr alloy steel or high Cr allay cast iron contg., by weight, 1.0 to 3.0% C, 0.1 to 2.0% Si, 0.1 to 2.0% Mn, 11 to 20% Cr, 0.1 to 3.0% Mo, 1.5 to 7.0% W and 1.0 to 3.0% V or furthermore contg. one or two kinds of 0.01 to 0.5% Al and 0.01 to 0.5% Ti, and the balance Fe is cast in the inside face of a cylindrical mold by a centrifugal casting method into an external layer, and in the hollow inside, high strength iron steel such as high grade cast iron is cast as an external layer material. Or, an adamite material is interposed between the external layer and internal layer as an intermediate layer to produce a composite roll for rolling steel. The composite roll in which the fine grains of Cr7C3, MoC, VC, W2C or the like having high hardness are uniformly precipitated into the external layer directly contacted with the material to be rolled and excellent in wear resistance can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll material used as an outer layer which is a rolling use layer of a composite roll.

[0002]

2. Description of the Related Art Conventionally, a high chromium cast iron material or a graphite crystallized high chromium cast iron material with improved seizure resistance is used as a material for the rolling use layer of a steel rolling roll which is particularly required to have wear resistance. It had been. With the recent severer rolling conditions,
Since higher wear resistance is required, one or two kinds of Nb and V are added to the cast iron in a total amount of 2% or less,
Attempts have been made to generate the fine carbides as crystal nuclei, thereby making the structure finer and denser and thereby improving the wear resistance, but it is said that the demand for improvement of the wear resistance is sufficiently met. The reality is that I can't say it.

On the other hand, in order to significantly improve the wear resistance in hot rolling, a large amount of W may be added to the material. However, since the outer layer of the composite roll is mainly cast by centrifugal casting, there is a problem that W is separated due to the difference in specific gravity, segregation occurs in the circumferential direction, and it is difficult to obtain a uniform material. The cause of the above segregation (solidification segregation) is M
This is because a C and M ₂ C-based carbide that is stable at a relatively high temperature is generated during solidification and is localized due to a difference in specific gravity and the like.

According to the present invention, by adopting a specific chemical composition, by preferentially crystallizing M ₇ C ₃ type carbides, macroscopic uniform solidification can be achieved over the entire solidification, and at the same time, optimum Provided is a centrifugally cast high wear-resistant roll, which is made to precipitate carbides such as W, Mo, V, etc. exhibiting excellent wear resistance by various quenching and tempering heat treatments and has significantly improved wear resistance without segregation. With the goal.

[0005]

The roll material of the present invention made to achieve the above object has a chemical composition of wt%,
C: 1.0 to 3.0%, Si: 0.1 to 2.0%, M
n: 0.1 to 2.0%, Cr: 11 to 20%, Mo: 0.1
~ 3.0%, W: 1.5 ~ 7.0%, V: 1.0 ~ 3.0
%, The balance consisting essentially of Fe and impurities was formed by centrifugal force casting.

At this time, Al: 0.01 instead of part of Fe
.About.0.5%, Ti: 0.01 to 0.5%, and one or two kinds may be added.

[0007]

The chemical composition of the high wear resistant roll material of the present invention is limited for the following reasons. The unit is% by weight. C: 1.0 to 3.0% C mainly combines with Fe and Cr to form a high hardness composite carbide of M ₇ C ₃ type, and combines with Mo, V and W to obtain high hardness of MC type and M ₂ C type. Form a composite carbide.
Due to the formation of this high hardness composite carbide, C% of 1.0% or more
is necessary. On the other hand, when C is contained in excess of 3.0%, MC type carbides increase and cause segregation. Si: 0.1 to 2.0% Si is an element necessary for ensuring the melt flowability because the material of the present invention is a casting alloy, and at the same time, from the raw materials used
About 0.1% is unavoidably contained. However, if it exceeds 2.0%, the toughness is deteriorated, which is not preferable. Mn: 0.1 to 2.0% Mn is an element that increases the hardening ability and also combines with S to form MnS to prevent embrittlement due to S. At the same time, about 0.1% is inevitably contained from the raw materials used. But 2.0
%, It is not preferable because the toughness is deteriorated. Cr: 11 to 20% Cr combines with C to form M ₇ C ₃ type carbide and exhibits high temperature wear resistance. If less than 11%, M due to Mo, W, V
Solidification segregation is exhibited due to preferential formation of C and M ₂ C type carbides. On the other hand, if it is contained in excess of 20%, it becomes a hypereutectic and causes deterioration of the material, which is not preferable. Mo: 0.1-3.0% Mo easily combines with C along with Fe, Cr, V and W,
Mainly during solidification and heat treatment, MC type composite carbide is formed, and hardness at normal temperature and high temperature is increased to contribute to improvement of wear resistance. Mo exhibits its effect when added in a small amount as compared with W. At this time, if it is less than 0.1%, the desired wear resistance cannot be obtained, and the effect is saturated at 3%. On the other hand, if it exceeds 3.0%, it is associated with C and solidification segregation occurs. W: 1.5-7.0% W similarly easily combines with Fe, Cr, Mo, and V together with C to form a composite carbide during solidification and heat treatment, which improves the room temperature and high temperature hardness to improve wear resistance. Contribute. 1.5
If it is less than%, the desired wear resistance cannot be obtained, while
If it exceeds 7.0%, macrosegregation is easily generated during centrifugal casting. Therefore, it should be 7.0% or less. V: 1.0 to 3.0% V easily combines with C along with Fe, Cr, Mo and W,
Mainly during solidification and heat treatment, MC type composite carbide is formed, and hardness at normal temperature and high temperature is increased to contribute to improvement of wear resistance. The effect appears at 1.0% or more. However, if the amount added exceeds 3%, macrosegregation tends to occur during centrifugal casting. Therefore, it should be 3.0% or less.

In the first roll material of the present invention, in addition to the above components, the balance is formed of Fe and impurities. Although P and S are inevitably mixed in from the raw materials, they are preferably made less as they make the material brittle, and it is preferable to keep P: 0.2% or less and S: 0.1% or less. In the second roll material of the present invention, in addition to the alloy element of the first roll material, a part of Fe is replaced by Al:
One or two of 0.01 to 0.50% and Ti: 0.01 to 0.50% is contained. Al and Ti form an oxide in the molten metal, reduce the oxygen content in the molten metal, improve the soundness of the product, and make the solidification structure finer because the generated oxide acts as a crystal nucleus. Has an effect on. 0.01
If it is less than 0.5%, this effect is not sufficient, and if it exceeds 0.50%, it remains as inclusions, which is not preferable. still,
In the present invention, Al and Ti are added mainly for the purpose of improving the wear resistance by refining the cast structure, and are not simply added for the purpose of degassing.

The roll material of the present invention is usually centrifugally cast as an outer layer of a composite roll, but vertical centrifugal casting has a variation of G in the vertical centrifugal casting as compared with horizontal centrifugal casting, and a die for centrifugal casting is used. Since the vibration of No. 2 is small, the components of the molten metal cast in the mold do not easily change, so that a roll material having excellent structure uniformity can be easily obtained. For this reason, vertical centrifugal casting can raise the casting temperature as compared with horizontal centrifugal casting, and the casting operation has more time, which facilitates the work. It is also possible to prevent casting defects due to inclusion of an oxide film or the like formed on the surface.

[0010]

EXAMPLES Examples of the composite roll include those in which the shaft core is welded to the outer layer which is the layer used for rolling, and those in which the composite sleeve in which the inner layer is welded to the inner surface of the outer layer are fixed to the roll shaft by shrink fitting or the like. Any type of roll material can be used as the outer layer material. Incidentally, in order to prevent deterioration of the toughness of the shaft core material or the like due to mixing of alloy elements from the outer layer to the shaft core portion or the inner layer, an intermediate layer may be formed by casting therebetween. As the shaft core material and the inner layer material, high-strength cast iron, ductile cast iron, graphite steel, and other tough materials exemplified in Table 1 below (molten metal composition) are used, and as the intermediate layer material, adamite material is used.

[0011]

[Table 1]

When these shaft core materials are welded to the outer layer (when the intermediate layer is formed between the outer layer and the shaft core material, to the intermediate layer adamite), V, W, etc. are removed from the outer layer (or the intermediate layer). Alloying elements are also mixed. Also in the intermediate layer adamite, alloy elements such as V and W are mixed from the outer layer during welding with the outer layer.

The outer layer of the composite roll is formed by centrifugal casting. The roll material of the present invention is cast as an outer layer of a composite roll or a composite sleeve and then cast at 950 to 1100 ° C.
After holding for 1 to 5 hours at 200 to 700 ° C / H, 400 to
After cooling to 550 [deg.] C., gradual cooling at 10 to 100 [deg.] C./H, cooling to room temperature, and tempering heat treatment at 500 to 600 [deg.] C. for 10 to 20 hours may be performed once or several times.

The term "roll material" as used in the present invention means a material applicable not only to the above-described rolling roll but also to a roller in an auxiliary equipment for rolling, and is not limited to the outer layer material of the rolling roll, for example, hot run. It can also be applied as an outer layer material of a hollow cylindrical roller such as a table roller. Next, specific production examples of the composite roll in which the roll material of the present invention is applied to the outer layer which is the rolling use layer will be described. (Example A) (1) Table 2 shows a mold for horizontal centrifugal casting of the molten outer layer material (inner diameter φ).
600 mm) was cast at a solidification start temperature + 50 ° C. The casting amount was 60 mm in wall thickness.

[0015]

[Table 2]

(2) After casting the outer layer, a die having an inner layer was erected vertically, an upper die and a lower die were connected in series at both ends, and a shaft core material (high-grade cast iron) molten metal was cast inside the die. . (3) At a later date, the mold was disassembled, the roll material was taken out, and after rough processing, it was held at 1000 ° C for 2 hours, forcedly cooled to 420 ° C at 420 ° C / Hr, and then cooled to room temperature at 50 ° C / Hr. After that, tempering heat treatment at 500 ° C. for 10 hours was repeated twice. The outer layer surface hardness after the heat treatment is shown in Table 3.

[0017]

[Table 3]

(4) When the outer layer end cross section was visually observed,
No segregation of components was observed. Further, a plate-shaped test piece was sampled from the outer layer, and a rotary wheel was pressed against the fixed test piece to measure the specific wear amount. The results are shown in Table 4. Rotating wheel SUJ-1 Carburizing and quenching (HRC60 ~ 6
2) Initial load 18 kgf Sliding speed 3.4 m / sec Sliding distance 200 m

[0019]

[Table 4]

As a result of observing the macrostructure of the longitudinal section, segregation was not found in Examples 1 and 2 and Comparative Example 2, but
Segregation was observed in Comparative Example 1.

[0021]

As described above, the centrifugal casting high wear resistance roll of the present invention can improve the wear resistance. Moreover, even if centrifugal casting is used, macro segregation hardly occurs,
Excellent in tissue uniformity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Kimura 1-247 Shikitsuhigashi, Naniwa-ku, Osaka City, Osaka Kubota Corporation

Claims (2)

[Claims] 1. The chemical composition is% by weight, C: 1.0-3.0%, Si: 0.1-2.0%, M
n: 0.1 to 2.0%, Cr: 11 to 20%, Mo: 0.1 to 3.0%, W
: 1.5 to 7.0%, V: 1.0 to 3.0%, centrifugally cast high wear-resistant roll, characterized in that a used layer consisting essentially of Fe and impurities is formed by centrifugal casting. 2. The chemical composition is% by weight, C: 1.0-3.0%, Si: 0.1-2.0%, M
n: 0.1 to 2.0%, Cr: 11 to 20%, Mo: 0.1 to 3.0%, W
: 1.5 to 7.0%, V: 1.0 to 3.0%, Al: 0.01 to 0.5%, Ti: 0.01 to 0.5%, one or two kinds, the balance consisting of Fe and impurities. A centrifugal wear high wear resistant roll characterized by being formed by.