JPH0386306A - Process roll for iron making machine having excellent wear resistance - Google Patents

Abstract

PURPOSE:To obtain a process roll for iron making machines having excellent wear resistance by limiting the thickness of a film to be formed on the surface of a roll main body and the component compsn. thereof. CONSTITUTION:The component compsn. of the film on the surface of the process roll for iron making machines is composed to contain, by weight, 10 to 25% chromium carbide and 5 to 15% Ni and to consists of the balance one or two kinds of the carbide and boride of tungsten. The wear resistance is not obtd. when the ratio of the chromium carbide is below 10wt.%. Peeling is liable to arise when the ratio exceeds 25wt.%. The Ni is required to be incorporated at least at 5wt.% in order to assure the wear resistance and lubricity. The hardness is degraded and the wear resistance is lowered as well when the ratio exceeds 15wt.%. The thickness of the surface film layer of the roll body is <=200mum and the optimum range thereof is 7 to 200mum. The wear resistance and heat resistance are not obtd. when the thickness is below 7mum. The peeling is liable to arise when the thickness exceeds 200mum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a steel making machine and a process roll in its manufacturing process equipment.

(Problems to be Solved by the Invention) An object of the present invention is to provide a process roll for iron-making machinery that has excellent wear resistance and heat resistance.

More specifically, in order to impart wear resistance and heat resistance to the roll surface, a process roll for iron-making machinery, preferably a high-speed gas The present invention aims to provide a process roll with a small surface roughness, in which a thermal spray layer with a thickness of 7 to 200 nm is formed on the roll surface using a thermal spray system.

(Means for solving problems) The gist of the present invention is as follows.

(1) The surface film layer of the roll body with a thickness of 2004 mm or less is chromium carbide: 10 to 25%, Ni: 5 to 15% by weight
A steel manufacturing machine process roll having excellent wear resistance, characterized in that the remainder consists of one or two of tungsten carbides and borides and unavoidable impurities.

(2) The surface film layer is further made of titanium carbide.

1. A process roll for iron-making machinery with excellent wear resistance as described in 1 above, which contains one or more of niobium carbide, zirconium carbide, titanium boride, zirconium boride, and the like.

The present invention will be explained in detail below.

Chromium carbide and tungsten carbide have high hardness;
Although it has high abrasion resistance, it is difficult to weld it to the roll surface at first glance.

Therefore, Ni is welded and buried as a matrix, but high adhesion strength cannot be obtained by ordinary gas spraying or the like.

In the present invention, we have studied a thermal spraying method in which particles are sprayed at high speed, and have achieved the intended purpose.

As a component of the surface film layer, chromium carbide has a content of 10 to 2
5%. If the chromium carbide content is less than 10%, the desired wear resistance cannot be obtained, and if it exceeds 25%, the toughness of the film will be lost and peeling will occur easily.

Therefore, chromium carbide was limited to the above component range.

Tungsten carbide and tungsten boride have high hardness and provide wear resistance. Therefore, in the present invention, these compounds are used in combination to stabilize chromium carbide and improve wear resistance. However, if it is too much, the toughness of the surface film layer will be reduced, so the method is to ensure the amount of Ni as a matrix and the necessary amount of chromium carbide, and then make the rest of these carbides and borides. . Also, similar to tungsten carbide and boride, carbide and boride which have high hardness and provide wear resistance are tungsten carbide,
It was confirmed that boride can be partially replaced. For example, the surface coating layer according to the present invention is NbC+TiC+ZrC, Ti
It may additionally contain one or more of Bg + Zrfh and the like.

Ni is a binder component of the matrix, and it was found that a minimum content of 5% is required to prevent the loss of chromium carbide and tungsten carbide and to ensure wear resistance and lubricity of the structure. However, when N1fi exceeded 15%, the average hardness decreased and the wear resistance also tended to decrease. Therefore, the amount of Ni is limited to 5 to 15%.

In addition, when thermal spraying is used, the temperature of the thermal spray flame becomes a problem, but since chromium carbide and tungsten carbide tend to be oxidized at relatively low temperatures, the speed, temperature,
Attention must be paid to the high temperature residence time of the particles. The present inventors conducted repeated experiments with various thermal spraying methods, and found that high-energy density high-velocity gas spraying is suitable! Approved.

The optimum value of the surface coating layer thickness also varies slightly depending on the thermal spraying method, but the optimum range is 7 to 2001 rm. In other words, if the speed is less than 7 trm, there is no use in wear resistance or heat resistance.
It was found that when it exceeds 00Q, the residual stress in the coating layer becomes large and it becomes easy to peel off.

Next, the effects of the present invention will be explained based on examples.

Table 1 compares the characteristics of the surface coating layer by high-velocity gas spraying method and plasma spraying method for a surface coating layer having a component composition according to the present invention and a surface coating layer other than the present invention.

According to this, with the plasma spraying method, the hardness and adhesion strength are slightly reduced even with the surface coating layer having the composition according to the present invention, but with the high-velocity gas spraying method, extremely excellent wear resistance and adhesion strength can be obtained. I understand.

(Effects of the Invention) According to the present invention, it is possible to provide a process roll for iron-making machinery having a surface film layer with excellent wear resistance, heat resistance, and adhesion strength.

Claims (2)

[Claims] (1) The surface coating layer of the roll body with a thickness of 200 μm or less is chromium carbide: 10 to 25%, Ni: 5 to 15% by weight.
%, and the remainder consists of one or two of tungsten carbides and borides and unavoidable impurities. (2) The wear resistance according to claim 1, wherein the surface film layer further contains one or more of titanium carbide, niobium carbide, zirconium carbide, titanium boride, zirconium boride, etc. Excellent steelmaking machinery process roll.