JPH026827B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an iron-based sintered material having excellent corrosion resistance. In recent years, there has been a gradual increase in demand for sintered materials with excellent corrosion resistance for use in office machine parts such as electronic copiers, computer parts, measuring instrument parts, watch exterior parts, and the like. Conventionally, sintered materials with excellent corrosion resistance are known as SUS 316 and SUS according to the JIS standard.
Most of them have the composition of stainless steel such as 304, but when manufactured using normal powder metallurgy, the porosity is less than 10% by volume. However, there was a problem in that only a large amount of corrosion resistance could be obtained, and therefore, the desired corrosion resistance could not be obtained. Furthermore, as a method to reduce such pores, it is considered that the obtained sintered material is subjected to cold or hot forging, HIP (hydrostatic pressing) treatment, etc. In this case, special equipment is required, the work is complicated, and the problem of cracking and chipping during forging remains unsolved. From the above-mentioned viewpoints, the present inventors conducted intensive research in order to obtain iron-based sintered materials with low porosity and superior corrosion resistance. Based on the composition, a specific amount of Co and B is added and sintered.
During the sintering process, a liquid phase containing Co and B is generated and is uniformly dispersed in the matrix to fill the pores, so that the amount of pores in the resulting sintered material is less than 10% by volume. They came to the knowledge that corrosion resistance improves as the amount decreases. At the stage of detailed examination of the various properties of the above-mentioned sintered material containing Co and B to improve corrosion resistance, the present inventors added Mo, Cu, Nb to the sintered material. , Ti, and Ta, the strength and corrosion resistance of the sintered material are further improved. Therefore, this invention has been made based on the above knowledge, and the corrosion-resistant sintered material is made of Cr: 10.0 to 25.0% (hereinafter, % indicating the composition ratio is expressed as weight %), Ni: 4.0 to 20.0. %, Co: 0.5 to 10.0%, B: 0.01 to 1.00%, and if necessary, (a) one or two of Mo and Cu: 0.01
~5%, (b) One or more of Nb, Ti, and Ta: 0.01~1%, Contains either or both of (a) and (b) above, and the rest is Fe. By composing the material with a composition consisting of unavoidable impurities, the amount of pores is reduced to 10% by volume or less, and a structure is formed in which compounds containing Co and B are uniformly dispersed in the matrix, further improving corrosion resistance. It is characterized by its sharpness. Next, in the corrosion-resistant sintered material of this invention,
The reason why the composition range of each component and the amount of pores are limited as described above will be explained. (a) Cr The Cr component has the effect of imparting corrosion resistance and oxidation resistance to the sintered material, but its content is 10.0%.
If the content is less than 25.0%, the desired excellent corrosion resistance and oxidation resistance cannot be secured, and if the content exceeds 25.0%, no further improvement effect will be obtained. Established. (b) Ni The Ni component lowers the Ms point and stabilizes austenite, thus improving toughness, corrosion resistance, and oxidation resistance, but its content is 4.0%.
If the content is less than 20%, the desired effect cannot be obtained, and on the other hand, if the content exceeds 20%, no further improvement effect can be obtained.
Its content was set at 4.0-20.0%. (c) Co Co is an austenite-forming element, and
Co itself forms intermetallic compounds and shows precipitation hardening,
It also acts as a solid solution in the base material to strengthen it.
Furthermore, when it coexists with B, it forms a eutectic, significantly improving sinterability and reducing the amount of pores, but if its content is less than 0.5%, the desired effect is not achieved. cannot obtain the effect of
On the other hand, even if the content exceeds 10.0%, no further improvement effect can be obtained, and the content was determined to be 0.5 to 10.0%, taking economic efficiency into consideration. (d) B The B component forms a eutectic with Co to improve sinterability,
As a result, the corrosion resistance is further improved, and it has the effect of solid solution in the base material to strengthen it, and also has the effect of dispersing compounds containing Co and B to harden the material. If the content is less than 0.01%, the desired effect cannot be obtained, while if the content exceeds 1.00%, toughness and corrosion resistance will deteriorate.
It was set at 0.01-1.00%. (e) Mo, Cu, Nb, Ta, and Ti These components have the same effect of increasing the strength of the sintered material and improving the corrosion resistance, so improvement of these properties is required. It is added as necessary in the case, but in particular,
Mo and Cu components form a solid solution in the base material and have a remarkable effect of strengthening it, and Nb, Ta and Ti have an excellent effect of fixing carbides and improving corrosion resistance, but one type of Mo or Cu Or, if the total content of the two types exceeds 5%, the impact value and corrosion resistance will deteriorate, while on the other hand, if the total content of one or more of Nb, Ta and Ti exceeds 1%. Since no further improvement effect can be obtained with Mo or Cu, the content should be reduced to 5% or less for one or more of Mo or Cu.
The content of one or more of Nb, Ta, or Ti was set at 1% or less. It should be noted that each of these components can have the effect of improving each of the above characteristics even when added in a small amount, but the content of each component is 0.01.
If the content is less than 0.01%, the effect of addition decreases rapidly, so it is preferable to contain 0.01% or more. (f) Amount of pores If the amount of pores in the sintered material exceeds 10% by volume, the corrosion resistance of the material itself will rapidly deteriorate, making it unsuitable for use as a corrosion-resistant material. is set at 10% by volume or less. Furthermore, if each additive element is blended to achieve the composition of the sintered material of this invention and normal sintering is performed, a material with a porosity of less than 10% by volume will inevitably be obtained. . Further, impurities included in the sintered material of the present invention include Mn, Si, P, S, C, etc., but from the viewpoint of corrosion resistance and sinterability, the content of these impurities is 2.0% or less. This is desirable. Next, the corrosion-resistant sintered material of the present invention will be explained through examples and in comparison with comparative examples. Example Various types of Fe-Cr alloy and Fe-Cr-Ni alloy powders, each with a particle size of -150mesh, were prepared as raw material powders, and Ni with an average particle size of 3 μm was prepared.
Powder, Co powder, Mo powder, Nb powder, Ti powder, Ta
Powder, Cu powder, and Fe with -200mesh
Prepare B alloy powder (containing 20% B), mix these powders in the composition shown in Table 1, mix for 30 minutes with a miniute mixer, and mix for 5 minutes.
By molding the compact at a pressure of ~7 ton/cm ² and then heating and sintering it in a vacuum furnace to a predetermined temperature in the range of 1250 to 1300°C, the composition is substantially the same as that of the compound. Sintered materials 1 to 2 of the present invention having a component composition of
9 and comparative sintered material 30 were manufactured. Note that the comparative sintered material 30 has a composition equivalent to that of SUS 304. The resulting materials of the present invention and comparative materials were measured for pore content, high temperature oxidation resistance, and corrosion resistance, and the results are also shown in Table 1. High-temperature oxidation resistance is determined by heating each sample with dimensions: 10 x 10 x 10 to 800°C in the air for 50 hours.

【table】

[Table] Corrosion resistance is evaluated based on weight increase rate after holding.
It was evaluated using the salt spray test specified in JIS20H. The salt spray test results are as follows: △: Rust occurred, ○: Some rust occurred, ◎: No rust occurred.
It was done in stages. From the results shown in Table 1, it is clear that all the corrosion-resistant sintered materials of the present invention have excellent properties. As described above, according to the present invention, it is possible to obtain a sintered material with excellent corrosion resistance without requiring any special post-processing, and it can be used not only for office machine parts, computer parts, and measuring instrument parts. In addition to exhibiting excellent performance in applications such as exterior parts for watches that have particularly strict requirements on the appearance finish, when subjected to cold or hot forging, the density is further improved and the performance is improved. This brings about industrially useful effects, such as making it an even better material.

Claims (1)

[Claims] 1 Cr: 10 to 25%, Ni: 4 to 20%, Co: 0.5 to 10%, B: 0.01 to 1%. % by weight), a structure in which a compound containing Co and B is uniformly dispersed in the matrix, and a porosity of 10% by volume or less. 2 Contains Cr: 10-25%, Ni: 4-20%, Co: 0.5-10%, B: 0.01-1%, and further contains one or two of Mo and Cu: 0.01-20%.
5%, with the remainder consisting of Fe and unavoidable impurities (wt%), a structure in which compounds containing Co and B are uniformly dispersed in the matrix, and a porosity of 10% by volume or less. A corrosion-resistant sintered material characterized by: 3 Contains Cr: 10-25%, Ni: 4-20%, Co: 0.5-10%, B: 0.01-1%, and further contains one or more of Nb, Ti, and Ta. : 0.01 to 1%, with the remainder consisting of Fe and unavoidable impurities (more than % by weight), a structure in which compounds containing Co and B are uniformly dispersed in the matrix, and pores of 10% by volume or less A corrosion-resistant sintered material characterized by having a quantity of 4 Contains Cr: 10-25%, Ni: 4-20%, Co: 0.5-10%, B: 0.01-1%, and further contains one or two of Mo and Cu: 0.01-1%.
5%, and one or more of Nb, Ti, and Ta: 0.01 to 1%, and the remainder is Fe and unavoidable impurities (weight %), Co and B in the matrix. A corrosion-resistant sintered material characterized by having a structure in which a compound containing the above is uniformly dispersed, and a porosity of 10% by volume or less.