CN1332055C - Stainless steel powder composite material and its warm-pressing method - Google Patents

Abstract

The invention provides a precipitation-hardenable stainless steel powder composite material and a warm-pressing method thereof. The components of the powder material and their mass percentage content ranges are as follows: 0.02-0.07% carbon, 15.0-17.5% chromium, 3.0-5.0% nickel, 3.0-5.0% copper, 0-0.6% manganese, 0.15- 0.45% niobium, 0-0.1% molybdenum, and the rest iron and unavoidable impurity elements; add 5-10% niobium carbide particles and 0.1-0.3% lubricant based on the total mass of the above components. This method uses electrostatic spraying to spray EBS wax powder on the inner cavity of the mold as a lubricant for the mold wall, and the coating thickness is 0.01-0.1mm. The density of the green body formed by warm pressing is 0.15-0.25g/cm ³ higher than that of cold pressing, and the strength of green body is 6.2-15% higher than that of cold pressing. The invention has the characteristics of high density, low cost, easy operation and control, and the green body is not prone to lamination, and can greatly increase the density and strength of the green body of stainless steel powder composite parts, and can be widely used in construction machinery, automobiles, and chemical industries. Parts manufacturing in other industries.

Description

A kind of stainless steel powder composite material and its warm pressing method

technical field

The invention relates to powder metallurgy technology, in particular to a stainless steel powder composite material for manufacturing high-density and high-strength powder metallurgy parts and a warm-pressing method thereof.

Background technique

The advantage of using the traditional powder metallurgy method to produce stainless steel parts is that it can produce final shape or near-net shape powder metallurgy parts at a lower cost, which can realize less cutting and no machining, but the disadvantage is that the density of the parts is not high, and the corrosion resistance and mechanical properties are relatively high. lower. Although the density of isostatic pressing and injection molding parts is high, their application is greatly limited due to the complicated process and high cost. The warm-pressing technology, which was successfully developed in the 1990s and has been industrialized, not only overcomes the disadvantage of low density of parts, but also has the advantage of low cost. It is the latest advanced powder metallurgy technology. At present, there are many technologies related to powder temperature pressing, mainly Swedish HOEGANAES company, American NORTH AMERICA HOEGANAES company and Canadian QMP METAL POWDERS company. However, the above powder warm pressing is mainly based on pure iron powder or partly pre-alloyed powder or iron-based powder, and for the warm pressing method of stainless steel powder, Xiao Zhiyu et al. ), 2004, 14(4) pp. 756-761 "Warm compacting behavior of stainless steel powders (temperature-compression behavior of stainless steel powder)" studied the temperature-compression of 304L, 316L, 410L, 430L stainless steel, only limited to ferrite , Austenitic and martensitic stainless steels. There is no report on the warm-pressing of precipitation-hardening stainless steel powder composites.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of the above-mentioned prior art, especially for the disadvantages of poor formability, low green density and poor green strength of traditional cold-pressed precipitation-hardened stainless steel and its composite material powder, and to provide a A precipitation-hardening stainless steel powder composite material with high density, high green strength, low cost, easy to control operation, and less prone to lamination in the green body, and a warm-pressing method thereof.

The purpose of the present invention can be achieved through the following measures:

A composite material component and its mass percent content range of a precipitation-hardenable stainless steel powder are as follows: 0.02-0.07% carbon, 15.0-17.5% chromium, 3.0-5.0% nickel, 3.0-5.0% copper, 0 ~0.6% of manganese, 0.15~0.45% of niobium, 0~0.1% of molybdenum, and the rest are iron and unavoidable impurity elements; additionally add 5~10% of the total mass of the above components, with a particle size of 1~3μm Niobium carbide and 0.1-0.3% lubricant, the lubricant refers to lithium stearate, long-chain fatty acid amide or their mixture.

The warm pressing of the above-mentioned stainless steel powder composite material includes powder mixing, heating, and pressing processes. It is characterized in that the ingredients are formulated according to the following components and their mass percentage content ranges: 0.02-0.07% carbon, 15.0-17.5% chromium, 3.0-17.5% 5.0% nickel, 3.0-5.0% copper, 0-0.6% manganese, 0.15-0.45% niobium, 0-0.1% molybdenum, and the rest are iron and unavoidable impurity elements; 5-10% by mass, niobium carbide with a particle size of 1-3μm and 0.1-0.3% lubricant; the temperature and pressure of the composite material adopts the mold wall lubrication process, specifically, the electrostatic spraying method is used to spray EBS wax powder on the inner cavity of the mold , the coating thickness is 0.01-0.1mm; the powder heating temperature is 80-130°C, and the mold heating temperature is 80-110°C.

Compared with the prior art, the present invention has the following outstanding advantages:

1. The present invention successfully applies the powder metallurgy warm-pressing process to the forming of precipitation-hardening stainless steel powder and its composite material powder, and realizes the low-cost and high-density forming of precipitation-hardening stainless steel powder and its composite material powder.

2. In the present invention, the lubricant is evenly sprayed on the inner wall of the mold, which can reduce the amount of lubricant added in the powder, thereby effectively improving the green density and green strength of powder metallurgy parts, and reducing the stainless steel parts caused by low density. Increased scrap rate during handling.

3. For the first time, the present invention applies the warm pressing process to the forming of precipitation-hardenable stainless steel powder composite material, which solves the problem of poor formability and compressibility of stainless steel powder composite material. The stainless steel powder composite material is warm-pressed under a pressure of 500-800MPa, and the green density is 0.15-0.25g/cm ³ higher than that of conventional cold-pressed green bodies, and the green body strength is 6.2-15% higher than that of cold-pressed bodies. crack.

4. The present invention can realize near-final high-density forming of precipitation-hardened stainless steel powder and its composite material parts, with simple process and good practicability. It can be used to manufacture high-performance and corrosion-resistant structural parts in machinery, automobile, chemical and other industries, and has good And broad prospects for industrialized production.

Detailed ways

The present invention will be further described by following examples:

Example 1

The components of precipitation hardening stainless steel powder and their mass percentage content ranges are as follows: 0.038% carbon, 16.2% chromium, 4.6% nickel, 4.6% copper, 0.55% manganese, 0.30% niobium, 0.09% molybdenum, Composed of 73.62% iron and unavoidable impurity elements. The particle size of the stainless steel powder is ≤74μm.

In addition, 0.2% lubricant is added according to the total mass of the above components, and the lubricant is a long-chain fatty acid amide. The stainless steel powder with lubricant was mixed on a V-blender for 15 minutes and preheated to 100°C. Electrostatic spraying is used to spray EBS wax on the inner cavity of the mold with a coating thickness of 0.05mm, and the mold is heated to 80°C. Then fill the powder into the mold and warm press at different unit pressures to obtain the following results: the density of the green compact under warm pressing at 500MPa is 5.97g/cm ³ , which is 0.20g/cm ³ higher than that of traditional cold pressing; The green density is 6.18g/cm ³ , which is 0.21g/cm ³ higher than that of traditional cold pressing; the green density of warm pressing at 700MPa is 6.38g/cm ³ , which is 0.22g/cm ³ higher than that of traditional cold pressing; the green density of warm pressing at 800MPa is 0.22g/cm 3 The density is 6.56g/cm ³ , which is 0.22g/cm ³ higher than that of traditional cold pressing; the green strength of warm pressing at 500MPa is 13.7MPa, which is 15% higher than that of traditional cold pressing; the green strength of warm pressing at 600MPa is 19.4MPa, which is higher than that of traditional cold pressing 8% increase; 700MPa warm-pressed green body strength 23.8MPa, 9.2% higher than traditional cold-pressed; 800MPa warm-pressed green body strength 27.3MPa, 6.2% higher than traditional cold-pressed.

Example 2

The components of the stainless steel powder composite material and their mass percentage content ranges are as follows: 0.047% carbon, 17.03% chromium, 4.02% nickel, 3.97% copper, 0.37% niobium, 74.56% iron; the particle size of the stainless steel powder is ≤ 74 μm. In addition, 10% of niobium carbide with a particle size of 2.5 μm and 0.3% of lubricant are added based on the total mass of the above components. The lubricant is a mixture prepared according to the ratio of lithium stearate:long-chain fatty acid amide=20:80 (mass ratio). The stainless steel composite powder with lubricant was mixed on a V-blender for 50 minutes and preheated to 130 °C. EBS wax was sprayed on the inner cavity of the mold by electrostatic spraying with a coating thickness of 0.03mm, and the mold was heated to 110°C. Then the powder is filled in the mold and warm-pressed under different unit pressures, the following results can be obtained: the density of the green compact under warm pressing at 500MPa is 5.90g/cm ³ , which is 0.15g/cm ³ higher than that of traditional cold pressing; The density of pressed green body is 6.12g/cm ³ , which is 0.17g/cm ³ higher than that of traditional cold pressing; the density of warm pressed green body at 700MPa is 6.32g/cm ³ , which is 0.19g/cm ³ higher than that of traditional cold pressing; The green density is 6.52g/cm ³ , which is 0.20g/cm ³ higher than that of traditional cold pressing; the green strength of warm pressing at 500MPa is 12.SMPa, which is 12% higher than that of traditional cold pressing; the green strength of warm pressing at 600MPa is 14.3Mpa, higher than that of traditional cold pressing The cold pressing is increased by 7.2%; the green strength of warm pressing at 700MPa is 18.5Mpa, which is 7.0% higher than that of traditional cold pressing; the green strength of warm pressing at 800MPa is 22.6MPa, which is 6.5% higher than that of traditional cold pressing.

Example 3

The components of the stainless steel powder composite material and their mass percentage content ranges are as follows: 0.047% carbon, 17.03% chromium, 4.02% nickel, 3.97% copper, 0.37% niobium, 74.56% iron; the particle size of the stainless steel powder is ≤ 74 μm. In addition, 5% of niobium carbide particles with a particle size of 3 μm and 0.1% of lubricant were added based on the total mass of the above components. The lubricant was lithium stearate. The stainless steel powder composite with lubricant was mixed on a V-blender for 60 minutes and preheated to 80 °C. Electrostatic spraying is used to spray EBS wax on the inner cavity of the mold with a coating thickness of 0.1mm, and the mold is heated to 100°C. Then the powder is filled in the mold and warm-pressed under different unit pressures, the following results can be obtained: the density of the green compact under warm pressing at 500MPa is 5.94g/cm ³ , which is 0.18g/cm ³ higher than that of traditional cold pressing; The density of pressed green body is 6.15g/cm ³ , which is 0.20g/cm ³ higher than that of traditional cold pressing; the density of warm pressed green body at 700MPa is 6.35g/cm ³ , which is 0.21g/cm ³ higher than that of traditional cold pressing; The green density is 6.54g/cm ³ , which is 0.21g/cm ³ higher than that of traditional cold pressing; the green strength of warm pressing at 500MPa is 13.0MPa, which is 13% higher than that of traditional cold pressing; the green strength of warm pressing at 600MPa is 16.2MPa, which is higher than that of traditional cold pressing. The pressure is increased by 7.6%; the green strength of warm pressing at 700MPa is 19.8Mpa, which is 8.2% higher than that of traditional cold pressing; the green strength of warm pressing at 800MPa is 24.5MPa, which is 6.4% higher than that of traditional cold pressing.

Claims (2)

1. A stainless steel powder composite material, characterized in that the composition of the precipitation hardenable stainless steel powder composite material and its mass percentage content range are as follows: 0.02-0.07% carbon, 15.0-17.5% chromium, 3.0-5.0% nickel, 3.0-5.0% copper, 0-0.6% manganese, 0.15-0.45% niobium, 0-0.1% molybdenum, and the rest are iron and unavoidable impurity elements; 5-10% niobium carbide with a particle size of 1-3 μm and 0.1-0.3% lubricant, the lubricant refers to lithium stearate, long-chain fatty acid amide or their mixture. 2. A warm-pressing method for stainless steel powder composite materials, including powder mixing, heating, and pressing processes, characterized in that the ingredients are formulated according to the following components and their mass percentage content ranges: 0.02-0.07% carbon, 15.0-17.5% carbon Chromium, 3.0-5.0% nickel, 3.0-5.0% copper, 0-0.6% manganese, 0.15-0.45% niobium, 0-0.1% molybdenum, and the rest are iron and unavoidable impurity elements; The total mass of the above components is 5-10%, niobium carbide with a particle size of 1-3μm and 0.1-0.3% lubricant; the temperature and pressure of the composite material adopts the mold wall lubrication process, specifically, the EBS wax powder is sprayed by electrostatic spraying method In the mold cavity, the coating thickness is 0.01-0.1mm; the powder heating temperature is 80-130°C, and the mold heating temperature is 80-110°C.