JPH031384B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a high-strength wear-resistant member in which a cast iron layer is formed on the surface of a steel base material to improve wear resistance.

Various parts for internal combustion engines such as piston rings, tappets, rocker arms, compressor parts, rocker rings, etc. are required to have wear resistance and mechanical strength. One of the conventional materials that has both of these features is a material that is made by thermally spraying a high-hardness metal, especially Mo, on the surface of a steel base material to locally impart wear resistance to the surface layer. However, this Mo spraying method has various problems. In other words, Mo is expensive as a raw material, difficult to cut due to its high hardness, and has pores that promote oxidation or corrosion inward, causing thermal spray particles to fall off or from the main body. Peeling is likely to occur.
In particular, Mo oxides have a low vaporization temperature, and this tendency is remarkable. In addition, pores tend to become points where cracks occur due to the edge effect, and serve as transmission routes for the generated cracks, reducing the strength of the sprayed layer. Furthermore, in the case of thermal spraying, mechanical bonding is the main component rather than complete metallurgical bonding, so there is a high risk of peeling off due to impact.

The object of the present invention is to provide a method for producing a material that is inexpensive and has both wear resistance and mechanical strength, in place of Mo-sprayed steel, which has such drawbacks.

In detail, the method for producing the material according to the present invention is as follows:
First, after applying C and Si powder to the steel base material, TIG
Steel, C, and Si are simultaneously melted using an arc or other high-density energy beam to form a solid solution of C and Si in the steel. At this time, the surface layer of the steel base material, C, and Si melt instantly, and because the beam has good heat concentration, the temperature of the base metal other than the molten part does not rise much. Therefore, the rapidly melted portion is rapidly cooled by the cooling effect of the base material, and a chilled structure is formed.

Then, heat at 850-950℃ for 30-120 minutes,
The reaction of [FeC (carbide) → 3Fe (base) + C (graphite)] is carried out to precipitate graphite, and the mixture is further cooled under conditions that allow a desired base structure such as pearlite or martensite to be obtained.

The amount of C and Si powder to be applied is adjusted so that the cast iron layer contains 2.0 to 5.5% of C and 0.9 to 3.5% of Si, or Cr, W,
A trace amount of Nb, Mo, B, V, Cu, and Ni powder may also be added.

Explain the reason for limiting C and Si. C is 2.0 to 5.5%, but if it exceeds 5.5%, the toughness of the cast iron layer will deteriorate,
In addition, if the amount of C powder applied is too large, it will scatter more due to the impact of the beam, and the yield of the amount of C that should be included in the cast iron layer will be worse, so it should be reduced to 5.5%.
is the limit. Moreover, if it is less than 2.0%, the amount of precipitated tempered graphite decreases, making machinability difficult. Furthermore, as the amount of C decreases, the wear resistance also deteriorates. Si is 0.9
~3.5%, but if it exceeds 3.5%, the amount of ferrite in the cast iron layer becomes large, resulting in a decrease in hardness and wear resistance. Moreover, if it is less than 0.9%, graphitization will be difficult to occur during annealing. Regarding other additive elements, Cr, W, Nb, V, and B form highly hard carbides. Furthermore, BC generated by the addition of B
is easily thermally decomposed and promotes the precipitation of graphite during tempering. Mo, Cu, and Ni also contribute to strengthening the base of the cast iron layer.

Figure 1 shows carburized and hardened steel (JIS standard, SCM415H) selected as the steel base material, and a conventional Mo sprayed material and a material with a cast iron surface according to the present invention (heated at 910℃ for 60 minutes and annealed. This is a comparison of the results of a scuffing test conducted after cooling (after cooling in air). The sample number and the composition (wt%) in the cast iron layer on the surface were as follows.

No.1...Mo sprayed material No.2...Invention material (C: 3.0, Si: 2.5, Mn: 0.4,
Remaining Fe) No. 3… 〃 (C: 3.0, Si: 2.5, Mn: 0.4,
Cr: 1.0, Cu: 0.5, remaining Fe) No. 4…〃 (C: 3.0, Si: 2.5, Mn: 0.4,
(Cr: 1.0, Mo: 0.4, residual Fe) Samples Nos. 1 to 4 were used as fixed pieces in a plane contact sliding wear tester, and these fixed pieces were pressure welded to the mating material, that is, a disk-shaped sample made of carburized and hardened steel. Then, the disk-shaped sample was rotated while constantly supplying lubricating oil to the pressure contact surface. Starting from surface pressure 25Kg/mm 5
A load was applied in kg/mm increments to measure the critical surface pressure when scuffing occurred.

(Test conditions) Lubricating oil amount: 0.5 l/min Lubricating oil: SAE #30 + white kerosene (1:1) Wear rate: 5 m/sec As is clear from these results, the parts obtained by the manufacturing method of the present invention were It showed wear resistance comparable to that of Mo sprayed materials.

[Brief explanation of drawings]

FIG. 1 is a graph showing the results of a scuffing resistance comparison test between a Mo sprayed material and a material according to the present invention.

Claims (1)

[Claims] 1. After applying C powder and Si powder to the surface of the steel base material, they are melted with a high-density beam to form a chill layer on the surface of the base material, and then graphitized annealing treatment is performed to form the base material. A method for manufacturing a high-strength, wear-resistant member, characterized by forming a cast iron layer on the surface.