JPH08127838A - Adamite or special cast iron material excellent in cracking resistance and surface roughening resistance - Google Patents

Abstract

PURPOSE: To improve the surface roughening resistance and cracking resistance of adamite or special cast iron material by adding a specified amt. of B to the compsn. thereof and uniformly dispersing graphite and carbides therein. CONSTITUTION: The chemical components in adamite or special cast iron material are constituted of, by weight, 1.5 to 2.5% C, 0.4 to 1.5% Si, 0.4 to 1.5% Mn, <=0.05% P, <=0.05% S, 0.4 to 3.0% Ni, 0.4 to 3.0% Cr, 0.1 to 2.0% Mo, 0.01 to 0.10% B, and the balance substantial Fe with impurities. By the addition of B by the content in a specified range, there is no adverse effect such as its convertion into white pig iron, and it can finely be dispersed into graphite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adamite or special cast iron material having excellent strength, particularly improved crack resistance and surface roughening resistance, and having an extremely uniform metal structure distribution.

[0002]

2. Description of the Related Art Generally, as a roll material when the biting and impact of the steel material at the time of rolling such as shaped steel rolling is large,
Prioritizing material strength, cast adamite material, forged adamite material, or special cast iron material is used. However, in recent years, due to the increasing demand for higher precision of steel products, the rolling conditions have become more severe, and the use conditions of rolls have become more severe.
As a result, conventional materials such as adamite and special cast iron materials have problems with crackability and surface roughness. That is,
It is difficult to improve the surface roughening resistance and the crack resistance in the roll using conditions in which the matrix, the carbide and the graphite constituting the metal structure are conventional components.

Carbides in the structure of adamite or special cast iron materials have high hardness and high melting point per se, and have a great effect on wear resistance. However, an excessive amount of carbides causes embrittlement of the material, lowers workability, and significantly deteriorates crack resistance, so that there is a limit.

Further, although graphite has a great effect on the wear resistance as a solid lubricant, the strength of cast iron itself decreases if the amount thereof is too large as in the case of carbides, so that the amount of graphite also has a limit.

For this reason, in order to improve the surface roughness and crack resistance while maintaining the wear resistance, it is necessary to uniformly finely disperse the graphite and carbide without changing the amounts thereof.
This improves skin roughness due to uneven graphite structure,
Further, by finely dispersing, the pinning effect of the graphite structure suppresses the propagation of cracks and improves the crackability. The method is to increase the casting solidification rate and the quickest method is the quickest, but for adamite and special cast iron materials, there is a limit to the solidification rate during casting due to the manufacturing process, and if it is too large, such as casting cracks. Defects occur. In particular, carbides can be finely dispersed at a relatively low cooling rate, but graphite cannot obtain a finely dispersed structure until the roughening resistance and crack resistance are improved unless a certain cooling rate is obtained. Absent.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a cast adamite material which is obtained by uniformly finely dispersing graphite at a cooling rate at which carbide can be finely dispersed to improve surface roughness and crack resistance, and forging. We provide adamite or special cast iron materials.

[0007]

According to the present invention, B is added to uniformly and finely disperse graphite, and the chemical components are C: 1.5 to 2.5% by weight and Si: 0.4 to 1 by weight. .5%, M
n: 0.4 to 1.5%, P: 0.1% or less, S: 0.0
5% or less, Ni: 0.4 to 3.0%, Cr: 0.4 to
3.0%, Mo: 0.1 to 2.0%, B: 0.01 to
The gist is an adamite or special cast iron material excellent in surface roughness resistance and crack resistance, which is characterized by comprising 0.10% and the balance impurities and substantially Fe.

[0008]

With the above structure, graphite and carbide are uniformly dispersed to improve the surface roughening resistance and crack resistance. The reason why the alloy components are limited to the above range will be described below.

C: Regarding the limitation of 1.5% to 2.5%,
As is the case with conventional forged adamite rolls, if C is less than 0.8% of the lower limit value, there are few hard carbides and the wear resistance of the roll material itself cannot be expected. On the other hand, when C exceeds 2.0% of the upper limit value, the amount of coarsened chromium carbide increases, and the black skin locally peels off from this, causing rough skin to grow.

Si: Regarding the limitation of 0.4% to 1.5%, Si is an element indispensable for crystallization of graphite, but if Si is less than 0.4%, the effect of crystallization of graphite is not observed. However, improvement in wear resistance cannot be expected. On the other hand, if Si exceeds 1.5%, the effect of crystallizing graphite is not improved.
%.

Mn: Regarding the limitation of 0.4% to 1.5%, Mn generally has a deoxidizing effect on cast steel, and the lower limit of 0.4% is the minimum addition amount at which the effect appears. it is conceivable that. Further, when Mn exceeds the upper limit of 1.5%, mechanical properties, particularly toughness deteriorate, so the upper limit was made this amount.

Regarding P: 0.1% or less, P is set to 0.1% or less from the viewpoint of making the material brittle.

S: Regarding the limit of 0.05% or less, S is set to 0.05% or less from the viewpoint of making the material brittle.

Ni: With respect to the limitation of 0.4% to 3.0%, Ni is an element that improves the strength and toughness of the matrix and promotes graphitization. If the Ni content is less than 0.4%, the effect of improving the strength of the matrix cannot be seen. On the other hand, when Ni exceeds 3.0%, the synergistic effect with Si does not improve the effect of promoting graphitization, so the upper limit was made 3.0%.

Cr: For the limits of 0.4% to 3.0%, Cr combines with C to form hard Cr carbides,
If it is less than 0.4%, the amount of the carbides is small and the effect of improving the material quality cannot be seen.

On the other hand, if Cr exceeds 3.0%, which is the upper limit value, the amount of coarsened chromium carbide increases, which deteriorates the surface roughening resistance and crack resistance.

Mo: Regarding the limitation of 0.1% to 2.0%, Mo has the effect of maintaining quenching and tempering resistance and entering the carbide to increase the carbide strength, but if it is less than 0.1%, the effect is obtained. Can't expect. Further, since Mo is an expensive alloy, its addition amount is limited to 2.0% or less.

B: Regarding the limitation of 0.01% to 0.10%, B is generally added to steel in a very small amount to form a boride having high hardness and improve wear resistance. Are known. On the other hand, in a cast iron material, a B layer is applied to the inner surface of the mold to obtain a high hardness chill layer, but the applicable material is limited, and it is generally not a very preferable element.

The present invention focuses on the eutectic cell increasing effect of B, and when B within a certain range of the above component system is added, it is found that graphite can be dispersed uniformly and finely without adverse effects such as white pig iron formation. It is a thing.

If the amount of B added is 0.01% or less, there is no effect of increasing the amount of graphite crystallization. On the other hand, if it exceeds 0.1%, the B-containing carbide is preferentially generated rather than the uniform fine dispersion effect, and the amount of graphite is increased. Decrease and cause embrittlement of the material. Therefore, the addition amount is set to the range of 0.01% to 0.10%.

In addition to the above components, the component according to the present invention is composed of the balance impurities and substantially Fe.

Next, an example of basic data of the cast material according to the present invention will be described. FIG. 1 shows the relationship between graphite and addition of B. The amount of graphite has an increasing effect on crystallization of graphite from 0.01% of B, but sharply decreases when it exceeds 0.1%. Regarding the relationship between the number of graphite particles, which represents the degree of fineness of graphite, and the addition of B, B is 0.
The number of grains is increased from 01%, but if it exceeds 0.1%, the effect is reduced.

The relationship between the amount of carbide and the addition of B is as follows:
There is no large fluctuation up to the B addition amount of 0.1%, but it rapidly increases when the B addition amount exceeds 0.1%. This suggests that B hindered graphitization and preferentially produced B-containing carbide, based on the relationship between the amount of graphite and the number of particles.

Similarly, the relationship between material strength and B addition is shown. The strength of the material (corresponding to the change in the microstructure, the strength (tensile strength at room temperature, tensile strength at high temperature, elongation and drawing)) is B
If the added amount exceeds 0.1%, the amount of B-containing carbide increases, and the amount of B-containing carbide decreases sharply.

[0025]

[Example] Product body diameter 600 mmφ, body length 800 mm, total length 2
500mm forged adamite roll is manufactured as follows,
It was subjected to various investigations. As a material component, using the molten metal having the chemical composition shown in Table 1,
This was cast into a predetermined forging steel ingot at a casting temperature of 1,460 ° C. Component 1-1 in Table 1 is the forged adamite roll manufactured by the present invention, and component 2-1 is the molten metal chemical component of the forged special cast iron roll manufactured by the present invention. After casting, forging was performed at a predetermined temperature to obtain an integral roll for shaped steel. As a comparative material, the component 1 shown in Table 1 without addition of B 1
Rolls having the same shape were manufactured by the above-described roll manufacturing method using the molten metal chemical components of 2, 2-2, and the two were compared and investigated.

FIG. 2 shows the structures of both body parts. It was confirmed that the target graphite in which B was added was crystallized by uniformly finely dispersing it. Further, Table 3 shows the manufacturing quality of both rolls. As is clear from the table, the B-added roll of the present invention has a larger amount of graphite and a larger number of graphite particles than the conventional material without B, and achieves finer graphite without lowering the material strength.

As described above, in the roll of the present invention,
B: By adding 0.01 to 0.1%, graphite can be uniformly finely dispersed and crystallized, and it is particularly effective in improving crack resistance and surface roughening resistance.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

As described above, the adamite and the special cast iron materials of the present invention have crack resistance and surface roughening resistance by crystallizing graphite finely and uniformly as compared with conventional adamite and special cast iron materials. I was able to improve.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the amount of crystallized graphite and B addition, a diagram showing the relationship between the number of graphite particles and B addition, a diagram showing the relationship between carbide amount and B addition, and a diagram showing the relationship between material strength and B addition. .

FIG. 2 is a photograph of the metallographic structures of the B-added material and the non-added material.

Claims (1)

[Claims] 1. Chemical ratio by weight of C: 1.5 to 2.5% Si: 0.4 to 1.5% Mn: 0.4 to 1.5% P: 0.1% or less S: 0.05% or less Ni: 0.4 to 3.0% Cr: 0.4 to 3.0% Mo: 0.1 to 2.0% B: 0.01 to 0.10% Residual impurities and substantial An adamite or special cast iron material having excellent crack resistance and surface roughening resistance, which is made of Fe.