JPH03281753A - High alloy cast iron material having excellent resistance to roughening of surface - Google Patents

Abstract

PURPOSE:To improve the resistance to the roughening of the surface in a high alloy cast iron material by adding a specified amt. of B to high alloy cast iron having a specified compsn. and uniformly and finely dispersing and crystallizing out graphite without changing the amounts of graphite and carbide. CONSTITUTION:This high alloy cast iron material is constituted of, by weight, 3.0 to 4.0% C, 0.5 to 1.5% Si, 0.4 to 1.5% Mn, <=0.1% P, <=0.05% S, 3.0 to 5.0% Ni, 1.2 to 2.5% Cr, 0.1 to 2.0% Mo, 0.01 to 0.20% B and the balance Fe. Because C forms Cr carbide and crystallizes out fine graphite by Si and Ni, its content is regulated to the range where the Cr carbide and graphite are coexistent and the deterioration of the wear resistance is made small. The content of Ni is regulated to the range where the improvement of the matrix structure and the effect of promoting graphitization can be obtd., the content of Cr is regulated to the range where the deterioration of the wear resistance and resistance to the roughening of the surface does not occur and the content of Mo is regulated to the range where the hardness of carbide can be increased. As for the content of B, the range where the wear resistance can be improved as well as graphite can uniformly and finely be dispersed, and in excess, it reduces the amt. of graphite to cause its embrittlement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-alloy cast iron material that has excellent strength, particularly improved roughness resistance, and has an extremely uniformly distributed cast structure.

[Prior art] JP-A-1-191746 discloses a component containing Ti,
This is a roll material for hot rolling that is transformed into a bainite structure through isothermal transformation and is further heat-treated to impart compressive stress to the surface. However, in this composition range of rolling roll material, according to the findings of the present inventors, the matrix, carbide, and graphite that make up the metal structure cause microscopic abrasion differences on the sliding surface, resulting in uneven surface roughness. The problem is that it is easy.

[Problems to be Solved by the Invention] For example, in products such as rolling rolls that directly affect the surface of the rolled material, unevenness tends to become a problem.

Graphite in the spinning iron structure has a great effect on the wear resistance properties as a solid lubricant, but if its amount is too large, the strength of the spinning iron white body decreases, so there is a natural limit to the amount of graphite.

Further, some carbides themselves have high hardness and high melting points, and have a large effect on wear resistance properties. However, like graphite, excessive amounts of carbides cause cast iron to become brittle and reduce workability, so there is still a limit.

For this reason, in order to improve roughness resistance while maintaining wear resistance, it is necessary to uniformly and finely disperse graphite and carbide without changing the amount of graphite and carbide. The easiest way to do this is to increase the casting solidification rate and quench it, but high-alloy hammered iron materials are highly susceptible to cracking, so if the solidification rate is too high, defects such as casting cracks will occur. In particular, carbides can be finely dispersed at a relatively low cooling rate, but graphite cannot obtain a finely dispersed structure that improves roughness resistance unless the cooling rate exceeds a certain level. .

An object of the present invention is to provide an elevated hammered iron material in which graphite is uniformly and finely dispersed at a cooling rate that allows fine dispersion of carbides, thereby improving roughness resistance.

[Means for Solving the Problems] The present invention aims at homogeneous and fine dispersion of graphite by adding B, and the chemical component is C: 3.0 to 4.0% by weight.

Si: 0.5-1.5%, Mn: 0.4-1
．． 5%, P: 0.1% or less, S: 0.05% or less, N
i: 3.0-5.0%, Cr: 1.2-2.5%,
Mo: 0.1~2.0%, B: 0.01~
This is a high-alloy spun iron material with excellent skin roughness resistance, characterized by consisting of 0.20% balance impurities and substantially Fe.

[Function] By using the above composition, graphite and carbide are uniformly and finely dispersed, and the roughness resistance is improved.

The reason why the alloy components were limited to the above range will be described below.

C: Regarding the limit of 3.0 to 4.0%, C is a Cr carbide-forming element, and fine graphite is crystallized by the graphitization-forming elements of Si and Ni, which will be described later. Therefore, chromium carbide and graphite coexist, resulting in less deterioration of wear resistance.
It was set to 0%.

Regarding the limitation of Si: 0.5 to 1.5%, Si is an essential element for producing graphite products, and the amount required for producing graphite products and 0.5 to 1.5% that does not deteriorate wear resistance. range. This component system is adjusted within the above range with the components of the final product in order to control the amount of graphite produced by the amount of inoculation.

Regarding the limitation of M n 80 , 4 to 1.5%, Mn is 0.4 to 1.5 which does not cause deterioration of mechanical properties, especially toughness.
% range.

Regarding the limitation of P: 0.1% or less, P was set to 0.1% or less since it makes the material brittle.

Regarding the limitation of S: 0.05% or less, S was set to 0.05% or less since it makes the material brittle.

Regarding the limitation of Ni: 3.0 to 5.0%, Ni is an element that improves the matrix structure and is an element that promotes graphitization, as is clear in nihard cast iron. Therefore, the content was determined to be in the range of 3.0 to 5.0%, which provides the effect of improving the matrix structure and promoting graphitization.

Cr: Regarding the limitation of 1, 2~2, 5%, Cr
Although Cr combines with C to form a hard Cr carbide, the content is set in a range of 1.2 to 2.5% so as not to deteriorate wear resistance and roughness resistance.

Mo: 0, for the limitation of 1-2.0%, M.O.
was set in the range of O01 to 2.0%, which maintains quenching and tempering resistance and enters into carbides to increase carbide hardness.

B: O, O As for the O limit of 1 to 0.20%, B is generally added in a very small amount to steel to form a high hardness boride and improve wear resistance.

On the other hand, in cast iron materials, a high hardness chill layer is obtained by applying B powder to the inner surface of the mold, but the applicable materials are limited, and it is used as a whitening promoting element for general iron visiting materials. It is not a very desirable element.

The present invention focuses on the effect of increasing the common cell of B, and it has been discovered that by adding 13 within a certain range to the above component system, it is possible to uniformly and finely disperse graphite without having any negative effects such as whitening. It is.

That is, if B is added in an excessive amount, B-containing carbides are preferentially generated rather than having a uniform and fine dispersion effect, reducing the amount of graphite and causing embrittlement of cast iron. Therefore 0.01~0.
The range was set at 20%.

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

Next, an example of basic data that led to the present invention will be explained.

Figure 1 shows the relationship between graphite content and B addition. 13 is 0.01
%, it has an increasing effect on graphite products, and it is 0.2%.
When it exceeds this value, it decreases rapidly and is lower than that without additives.

Figure 2 shows the relationship between the number of graphite grains, which represents graphite fineness, and the addition of 13. B increases the number of grains from 0.01%, and 0.2%
%, the amount of graphite decreases rapidly.

Figure 3 shows the relationship between carbide content and B addition. The amount of carbide is
There is no big change up to 0.2% B addition, but 0.2%
It increases rapidly when it exceeds. This is shown in Figures 1 and 2 above.
The figure suggests that B inhibited graphitization and produced B-containing carbide preferentially.

Figure 4 shows the relationship between material strength and B addition. The material strength is I
When the amount of 3 added exceeds 0.2%, the B-containing carbide increases and the content rapidly decreases.

[Example] A high-base metal cast iron composite roll having a product body diameter of 80011+01φ, a body length of 2500 mm, and a total length of 5120 mm was manufactured as described below and subjected to various investigations.

■A molten metal with the chemical composition shown in Table 1 is used as the outer layer material, and it is poured into a cylindrical metal mold with a coating on the inner surface, which is rotated by a centrifugal spinning machine, at a casting temperature of 1320℃. 105o
uo (spinning 4900kg) B included.

Table 1 shows the chemical composition of the molten metal of the elevated gold cast iron composite roll manufactured according to the present invention.

■After the outer layer was completely solidified (22.5 minutes after the start of casting), the molten metal for the shaft core material at 1350°C was similarly spun on a centrifugal casting machine, and the outer and inner layers were completely welded. It was a body roll.

■ After the inner layer is poured, the mold is erected and completely cooled.
The roll was extracted from the mold and subjected to the required heat treatment.

Rolls of the same shape were manufactured using the above-mentioned roll manufacturing method using the chemical components of the molten metal shown in Table 2, and the two were compared and investigated.

Figure 5 shows the structure of the outer layer material of both. Those with B added are
It was confirmed that the target graphite was crystallized in a uniform and finely dispersed manner.

Furthermore, Table 3 shows the manufacturing quality of both rolls. The B-added roll achieves finer graphite without reducing material strength.

As mentioned above, in the roll of the present invention, B: 0°01~
By adding 0.2%, graphite can be uniformly and finely dispersed and crystallized, and is particularly effective in improving rough skin resistance.

[Effects of the Invention] As explained below, the high alloy U iron material of the present invention improves roughness resistance by uniformly and finely dispersing graphite and crystallizing it compared to conventional high alloy cast iron materials. was completed.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the amount of crystallized graphite and 13 addition, Figure 2 is a diagram showing the relationship between the number of graphite grains and B addition, Figure 3 is a diagram showing the relationship between the amount of carbide and B addition, and Figure 4 is a diagram showing the relationship between the amount of carbide and B addition. The figure shows the relationship between material strength and addition of 13, and Figure 5 is a photograph of the metal structure of the B-added material and the non-additive material.

Claims (1)

[Claims] The chemical components are C: 3.0 to 4.0%, Si: 0.5 to 1.5%, and Mn in weight ratio.
: 0.4-1.5%, P: 0.1% or less, S: 0.05
% or less, Ni: 3.0-5.0%, Cr: 1.2-2.
5%, Mo: 0.1-2.0%, B: 0.01-0.2
High-alloy cast iron material with excellent surface roughness resistance characterized by 0% balance impurities and substantially Fe.