JPH0321619B2 - - Google Patents

Description

[Detailed description of the invention]

Stainless steels include iron, chromium, nickel, nickel, chromium, molybdenum, and iron.
Chromium-based, iron/chromium/nickel/titanium-based,
Iron/chromium/nitrogen systems are known, and chromium/cobalt systems (those with an extremely small amount of iron or close to zero) are also known. Stainless steel is rust-free and has excellent corrosion resistance, but in order to improve its strength and hardness, it is made with metal oxides, nitrides, etc. such as aluminum and titanium.
Conventionally, dispersion and inclusion of a small amount of carbide has been carried out. In addition, in order to improve the uniform dispersion of oxides, nitrides, and carbides contained in the dispersed materials and to improve work efficiency, instead of adding oxides, nitrides, and carbides such as aluminum and titanium themselves, these It is also practiced to add metals such as oxidizing agents, nitriding agents, and carbonizing agents to produce oxides, nitrides, and carbides of these metals during heating and sintering. The purpose of the present invention is to improve the wear resistance of the stainless steel manufactured in this way, which has improved strength and hardness. ,Titanium,
Adding and mixing an appropriate amount of powder "hereinafter referred to as (for compound formation)" for forming one or more oxides, nitrides, or carbides arbitrarily selected from silicon, boron, and aluminum, and further for forming compounds. Add and mix an appropriate amount of one or more powders arbitrarily selected from among rare earth metals as a uniformly dispersed mixture,
The mixture is brought into contact with an oxidizing agent, a nitriding agent, a carbonizing agent, or a mixture thereof, and sintered under pressure and heat, and during sintering, the oxides, nitrides, and The present invention is characterized in that one or more types of carbides are generated and dispersed in the sintered compact. As the rare earth metal to be added, for example, one or more metals can be arbitrarily selected and used from among Mitsushi metal, lanthanum, cerium, samarium, praseodymium, yttrium, neodymium, promethium, etc. Wear resistance is significantly improved by adding 0.1 to 1.0% by weight of rare earth metal. In addition, air, oxygen, ozone, hydrogen peroxide, chloric acid, hypochlorous acid, etc. are used as the oxidizing agent, and nitrogen gas is used as the nitriding agent.
Generally, nitrogen generated when ammonia decomposes at high temperatures is used, and as the carbonizing agent, those commonly used as carburizing agents can be used, such as powdered charcoal, coke, bone ash, graphite, etc. Gaseous substances such as carbon dioxide, natural gas, carbon monoxide, methane, ethane, propane, alcohol, and oil vapor are used. Furthermore, carbonization and nitridation can be performed simultaneously using a mixed gas of carbon monoxide, methane, and ammonia, that is, a mixture of a carbonizing agent and a nitriding agent. Further, carbonization and nitridation can be performed simultaneously using carbon monoxide and nitrogen generated by heating in a molten salt containing molten cyanide, for example, potassium cyanide as a main component; in this case, the molten cyanide is Acts as both an agent and a nitriding agent. In this way, the oxidizing agent, nitriding agent, and carbonizing agent used can be solid, liquid,
If a gaseous substance is present, and if a solid substance is used, the solid is mixed with the uniformly dispersed mixture to be heated and sintered, and if a liquid substance is used,
The uniformly dispersed mixture is immersed in the liquid, or the uniformly dispersed mixture is impregnated with the liquid, or when a gaseous one is used, the uniformly dispersed mixture is placed in an atmosphere of the gas. Heating and sintering is performed in a state where the Next, the present invention will be explained using experimental examples. A conventional powder metallurgy method in which 18-8 stainless steel 300 mesh powder is mixed with 5% by weight of titanium as a compound-forming powder and 5% by weight of graphite as a carbonizing agent powder, compacted by pressure, and then heated and sintered. The sintered body A formed and sintered by the method has high strength, corrosion resistance, and wear resistance as shown in Table 1. In addition, sintered body B in which 2% by weight of titanium and 3% by weight of titanium oxide were added instead of 5% by weight of the titanium powder for forming a compound had similar good properties as shown in Table 1. showed that. Next, 5% by weight of titanium, 5% by weight of graphite, and further 0.5% by weight of lanthanum as a compound-forming powder were added and mixed to the 18-8 stainless steel powder and obtained by the same usual powder metallurgy method as above. As shown in Table 1, the sintered body C exhibited better corrosion resistance, strength, and wear resistance than those of the two experimental examples.
Further, sintered body D was obtained by adding 5% by weight of titanium, 5% by weight of graphite, 0.5% by weight of lanthanum, and further 0.5% by weight of boron as powder for forming a compound to the 18-8 stainless steel powder. Further improved properties were obtained as shown in Table 1.

【table】

[Table] As shown in Table 1, the sintered body to which rare earth elements were added had particularly marked improvement in wear resistance. Comparing the above-mentioned sintered bodies C and D, D is superior to C not only in hardness but also in underwater wear, but this is due to boron carbide (carbide) produced during sintering. It is thought that boron) also contributes to the improvement of wear resistance due to its high hardness. In addition, from the above experimental results, the rare earth metal added becomes a carbide during sintering and has the effect of significantly improving wear resistance, and also acts as a catalyst to promote the production of titanium carbide. Seem. In the above experiment, the above-mentioned results also apply when other types of stainless steel are used instead of stainless steel, and when other carbonizing agents are arbitrarily selected from commercially available products instead of graphite. Almost the same results were obtained. In addition, when boron, aluminum, or silicon is used in place of titanium as the powder for forming compounds in the above experimental example, and in place of the rare earth element lanthanum added as the powder for forming other compounds. Table 2 shows the results of experimental examples using Mitsushimetal and one or more other rare earth elements.

[Table] According to the experimental results in Table 2, boron, aluminum, silicon, etc. can be used as substitutes for titanium, and rare earth elements other than lanthanum can be used as substitutes for lanthanum. It can be seen that a useful wear-resistant stainless steel can be obtained. In addition, although specific experimental examples are not given, oxides and nitrides of titanium, silicon, boron, aluminum, and rare earth metals can be produced by adding an oxidizing agent or nitriding agent instead of the carbonizing agent in the above experimental example. The strength also increases when
In addition to improving hardness, it was also possible to significantly improve wear resistance. As described above, according to the present invention, one or more oxides, nitrides, and carbides of metals such as titanium, silicon, boron, and aluminum are dispersed in the sintered compact, and oxides and nitrides of rare earth metals are dispersed in the sintered compact. By dispersing and containing one or more types of carbides, it is possible to improve the strength and hardness of stainless steel, which is inherently excellent in rustlessness and corrosion resistance, and to significantly improve wear resistance. Focusing on extremely good corrosion resistance and wear resistance in seawater, we have developed submersible pumps, seawater pumps, sludge pumps,
Trial use of the material on parts such as concrete pumps showed extremely low wear and high corrosion resistance. It is optimal for these uses. It has extremely good heat resistance as well as corrosion resistance, and the ease of molding is also extremely improved.

Claims (1)

[Claims] 1 Stainless steel powder and an appropriate amount of powder for forming one or more oxides, nitrides, or carbides (hereinafter referred to as "for compound formation") arbitrarily selected from titanium, silicon, boron, and aluminum. and an appropriate amount of one or more powders arbitrarily selected from rare earth metals for forming a compound, and an oxidizing agent, a nitriding agent, a carbonizing agent, or any of these is placed in contact with the mixture and sintered under pressure and heat, and during sintering, one or more of the oxides, nitrides, and carbides of the added and mixed powder are generated and dispersed in the sintered compact. A method for producing wear-resistant stainless steel, characterized by comprising: