Method of manufacturing powder metallurgy nitrogen/high nitrogen containing stainless steel parts

A high-nitrogen stainless steel and powder metallurgy technology, applied in the field of powder metallurgy, can solve the problems of undisclosed preparation methods, uneven composition and structure, and decreased impact toughness, and achieve the effects of improved dimensional accuracy, uniform composition and structure, and controllable nitrogen content

Active Publication Date: 2009-01-14
ADVANCED TECHNOLOGY & MATERIALS CO LTD
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Problems solved by technology

The high / nitrogen-containing steel parts produced by conventional powder metallurgy methods have low sintering density, low nitrogen content, and uneven composition and structure. Compared with nitrogen-free stainless steel, although the strength is greatly improved, the impact toughness is significantly reduced. , which is a fatal flaw for some powder metallurgy parts
The hot isostatic pressing method needs to prepare a sheath, which is obviously not suitable for lighter parts products, and the preparation method of nitrogen-containing / high-nitrogen stainless steel parts products is not disclosed in the prior art

Method used

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  • Method of manufacturing powder metallurgy nitrogen/high nitrogen containing stainless steel parts

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Experimental program
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Embodiment 1

[0043] Raw materials: Nitrogen-containing stainless steel powder, composition (weight percent): 16.74% Cr, 12.02% Mn, 2.08% Mo, 0.5% Si, 0.8% N, the rest is iron; average particle size 9.1 μm, bulk density 4.0 g cm -3 , tap density 4.6g·cm -3 , D10 = 3.5 μm, D50 = 9.00 μm, D90 = 16 μm, N wt% = 0.85%; thermoplastic wax-based binder is used, and the powder loading rate is 55%.

[0044] Heat and knead the powder and binder evenly, and then granulate to obtain a uniform granular injection material; wherein the binder is composed of 70% paraffin, 29% high-density polyethylene, and 1% stearic acid (both by weight percentage) . Install the mold on an injection molding machine for injection molding to obtain a part blank. Soak the obtained blank in an organic solvent for a certain period of time to ensure that more than 80% of the wax is dissolved. Dry in a vacuum oven at a temperature of 100° C. for 120 minutes. After drying, thermal degreasing is carried out in a resistance furn...

Embodiment 2

[0046] The molding and degreasing process of raw materials and parts is the same as in Example 1. After degreasing, in sintering isostatic pressing, a mixed gas of 0.15 MPa nitrogen and hydrogen is used, wherein the partial pressure of nitrogen is 0.1 MPa, and the temperature is raised at a heating rate of 7 °C / min. Carry out sintering at 1400°C and keep it warm for 120min. When the sintering density reaches more than 95%, and the connected pores basically disappear, increase the gas pressure to 9MPa, of which the nitrogen partial pressure is 0.1MPa, and the rest is argon partial pressure. Keep it for 180min, and the sintering density of the parts is close to 100%, reduced pressure, quick cooling. The whole process keeps the partial pressure of nitrogen consistent with the solubility of nitrogen in the alloy system, so that the nitrogen content in the alloy does not fluctuate significantly, and δ-ferrite is not formed. Finally, the relative density>99% can be obtained, R p0.2...

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Abstract

The present invention relates to a method for preparing powder metallurgic nitrogen-contained/high-nitrogen stainless steel components, and comprises the following steps: raw materials preparation, forming, degreasing treatment, sintering and other static press, wherein, during the static press such as the sintering, the temperature increasing speed is 3 to 10 DEG C per minute; the sintering gas is the pure nitrogen or the mixed gas of the nitrogen, hydrogen and the argon; the pressure/partial pressure of the nitrogen is consistent with the solubility of the nitrogen in the alloy system; the sintering temperature is 1200 to 1450 DEG C, and the heat preservation period is 10 to 20 minutes; after the density is more than 90 to 95 percent, the pressure is increased to 3 to 10 MPa; the partial pressure is maintained the same during the pressure increasing process, and the pressure is distributed on the argon and the hydrogen, and the heat preservation period is 60 to 240 minutes; after the density is more than 99 percent, the pressure is decreased and rapid cooling is performed. The content of the nitrogen of the component that is made with the method hereinabove can be controlled to the highest level; the composition constitution is uniform, the density is high, the flexibility is good, the deformation is less, the precision is high and the corrosion-resistance is good.

Description

technical field [0001] The invention belongs to the technical field of powder metallurgy, in particular to a method for preparing nitrogen-containing / high-nitrogen stainless steel parts in powder metallurgy. Background technique [0002] High-nitrogen stainless steel has good mechanical and corrosion resistance properties, and nitrogen is a strong austenite stable element with rich sources, which can partially or completely replace nickel in austenitic stainless steel, saving expensive resources and reducing costs; nitrogen is an effective solid Solvent strengthening elements increase the effect of fine grain strengthening, which can significantly improve the strength of stainless steel. While nitrogen significantly improves the mechanical properties of stainless steel, it can also improve the corrosion resistance of steel, especially the local corrosion resistance, such as resistance to pitting corrosion, crevice corrosion and intergranular corrosion. Nickel ions are carci...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B22F3/16
Inventor 毕景维贾成厂匡星徐自伟曹丹曹勇家程东凯钟海林况春江
Owner ADVANCED TECHNOLOGY & MATERIALS CO LTD
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