Development of the hottest 0Cr18Ni9 stainless stee

  • Detail

Development of 0Cr18Ni9 stainless steel balls

steel balls are important basic parts, especially precision industrial steel balls, which play a great role in the development of national economy. Under some special conditions, steel balls of special materials are often needed to complete the functions required in different environments. In fact, some special steel balls have been widely used in various fields of the national economy, including 9Cr18, 3Cr13 stainless steel, copper, aluminum, titanium alloy steel, agate, glass, ceramic balls, etc. Their popularization and application not only promoted the development of steel ball production industry, but also promoted the technological development and scientific and technological progress of related industries. Next, the author focuses on the development process and achievements of 0Cr18Ni9 steel ball, a special material

I. cause

a large wholly foreign-owned enterprise in China, the material used for the rotating parts of its main electrical products is 0Cr18Ni9. The steel ball of this material was originally imported from abroad and the price is high. After many visits to our company, the company believes that our company is one of the earlier domestic manufacturers of steel balls, has many years of production management experience, and the production and processing technology and quality management can meet their requirements. Therefore, both parties have signed a supply agreement

II. Analysis of material particularity

0cr18ni9 material chemical composition is as follows:

1. Physical properties of nickel and nickel alloy

are silver white, which can maintain beautiful luster for a long time after polishing, with a specific gravity of 8.9, and the lattice is face centered cubic

2. Chemical properties

chromium nickel stainless steel is composed of chromium and nickel, which is a better stainless steel. Adding a large amount of nickel to this stainless steel is to obtain a single austenite structure, so as to improve its corrosion resistance and processability. It has strong plasticity and toughness at room temperature and low temperature, is not magnetic, and has good intergranular corrosion resistance

(1) chromium plays a major role in the corrosion resistance of stainless steel

chromium is the main element that determines the corrosion resistance of stainless steel, because the chromium in steel can make stainless steel passivate in the oxidation medium, that is, a thin film is formed on the surface, in which chromium is enriched. The higher the chromium content in steel, the stronger the corrosion resistance. In addition, chromium can strengthen the mechanical and technological properties of steel

(2) the effect of nickel on stainless steel

can be fully shown only when it is matched with chromium. Nickel is an alloy element that forms austenite. When nickel and chromium are used together, the metallographic structure can change from single-phase ferrite to austenite and ferrite two-phase structure. After heat treatment, the strength can be improved, so that it has stronger rust resistance and good deformation resistance

2. Influence of impurities on properties

when the carbon content is between 0.1% and 0.3%, after annealing, carbon will precipitate on the lattice boundary in the state of graphite, which destroys the bonding force between grains, strongly reduces the strength and plasticity of nickel, and makes processing deformation difficult

in addition, carbon has a strong affinity with chromium and can form a series of carbides. The higher the carbon content in the steel, the more chromium carbide will be formed, and the chromium content in the solid solution will be relatively reduced, and the corrosion resistance of the steel will be reduced

sulfur is a harmful impurity. Sulfur and nickel form Ni3S2 compound, and Ni3S2 and nickel form low melting point eutectic at 625 ℃, which is distributed on the intergranular boundary. When the thermal deformation temperature exceeds the eutectic melting point, it cracks along the intergranular boundary, resulting in the so-called "hot brittleness" phenomenon. Ni3S2 formed by nickel and sulfur at room temperature can cause cold embrittlement. 109 intelligent manufacturing pilot demonstration projects were selected; Arrange 47 directions and 61 projects of industrial strong foundation projects

III. The specification and accuracy requirements of the steel ball are:

the user puts forward the following requirements for this ball: the surface of the ball is free of scratches, pits, cracks, no rust, and the performance requires high roughness

IV. comparison of processing technology between 0Cr18Ni9 steel ball and bearing steel ball

the relevant properties of 0Cr18Ni9 material have been analyzed previously. Because Cr and Ni elements have the characteristics of wear resistance, oxidation resistance and high strength, compared with bearing steel, they appear both "hard" and "sticky" in processing, which increases the difficulty of processing this kind of steel ball. After repeated experiments and processing, we have developed a relatively feasible process. 8. Accuracy of load indication: 1% process better than indication, The comparison is as follows:

bearing steel ball:

raw material inspection - high speed cold heading - filing - smooth ball - hard grinding - heat treatment - Preliminary Research - Cleaning - visual inspection - fine grinding - Inspection - oiling and packaging

0Cr18Ni9 steel ball:

China's conventional extruder and production line

raw material inspection - high speed cold heading - smooth ball - grinding - Cleaning - polishing - Pickling - Cleaning - sorting - visual inspection - packaging

geotechnical test method standard gb/t50123 ⑴ 999 this process is the most desirable and the most The success lies in the grinding process, which includes three processes: hard and fine grinding, preliminary research and fine grinding and polishing, so as to save the configuration of multiple machine tools and repeated processing of tooling, shorten the logistics time, reduce the labor intensity of staff loading and unloading, greatly improve the grinding efficiency, and provide a guarantee for the steel ball to meet the technical requirements of finished products

v. determination of technical parameters of main processing procedures

1. The total retention of steel balls

3m and 1/8 "steel balls are processed into the same ball blank by cold heading. Considering the particularity of their raw materials, the total retention of steel balls is compressed

total retention: mm

bearing steel ball 0.45 ± 0.05

0Cr18Ni9 steel ball 0.35+0.05

we selected 0Cr18Ni9 steel produced by Shanghai steel works, and the compression of its total retention can improve the material utilization by 9.2%

2. Determination of high cooling process parameters and tooling

because after the total allowance is compressed, our company has self-made high cooling cold heading die, and each pair of cold heading die can produce more than 1.5 million ball blanks

equipment name: high speed cold heading machine za32g-5

manufacturer: Shanghai Qunying machine tool factory

main technical parameters: 600 times/minute

shift output: 8 hours per shift, 80% start rate:

600 times/minute × 60 points × 8 hours × 80% =230400 (10000 grains)

3. The light ball processing and its parameters

0cr18ni9 steel balls need to remove most of the grinding amount in this process. How to make the steel ball with special performance not cause deep scratch due to high pressure in the grinding process and maintain good surface roughness is indeed a major difficulty in machining

hardness comparison:

raw material hardness hv

after cold heading forming and hardening hv

after our repeated tests and verification, the pressure must be small at the beginning of the photosphere, first remove the ring belt, and then gradually increase the pressure to normal. It is particularly pointed out here that the work heart of turning is very important. They should not only observe whether the operating parameters of the machine tool are normal, but also constantly check the grinding quality of the steel ball to judge the use of the tooling, and keep the machine tool until the steel ball reaches the process size

equipment name: steel ball smooth ball machine 3ml4980

manufacturer: Xinxiang machine tool factory

processing parameters

grinding efficiency: the average grinding efficiency is 0.03mm/h

4. Determination of grinding process parameters

grinding and processing special steel balls is the key to the processing of all steel balls. If the test is successful, it will lay a good foundation for fine grinding. On the contrary, it will be difficult. In the processing of this process, we have gone through many detours and accumulated a large amount of data. Finally, we overcame the difficulties and determined the processing technology of this process

at the beginning of the test, the steel ball has a hard and fine process after the smooth ball processing. The rough scratches produced by the hard and fine process affect the surface roughness of the finished steel ball, which is difficult to eliminate in the grinding process. The grinding effect of ultra precision grinding oil agent plus steel sand is not ideal. The grinding efficiency of using oil agent plus chromium oxide green is low, and the surface roughness can not meet the requirements. During this period, foreign businessmen put forward stricter quality requirements and required to ensure the delivery period. Although facing many difficulties, the company's leaders and production technicians have formulated a new large-scale cycle processing and production process after repeated research, which has greatly improved the production efficiency and met the requirements of foreign investors

grinding process parameters:

machine tool Name: steel ball grinder 3m4730

manufacturer: Shanghai No.3 machine tool factory

grinding processing is divided into two steps, namely, two circulating water tanks. The first water tank is prepared with German made grinding fluid 120s, the ratio is 80%, and the remaining water. When the loading size of the steel ball is +100 to +40, grind it with the first water tank. During the grinding process, evenly add 320 × emery, with an efficiency of 10 μ M/shift, high efficiency and stable quality

when the steel ball ruler is inch +40 μ M, replace the second water tank, which is prepared with 180 steel ball fine grinding fluid made in Germany, with a ratio of 50%. At this time, chrome oxide green is evenly added to the surface of the steel ball for grinding. In the rest of the time, the steel ball is in the state of correcting geometric accuracy and improving surface roughness, and remains until the steel ball is unloaded qualified. At this time, the geometric accuracy of the steel ball can reach G60

of course, in the process of grinding, it is essential to detect the surface quality of steel balls in time. Only by careful operation and careful detection can we judge whether the grinding disc needs to be repaired, replaced and other key problems

5. Polishing process and its processing parameters

due to the particularity of the material, the brightness of the steel ball in the normal grinding process is far less than that of the bearing steel ball. The element nickel mentioned earlier in the article has silver white luster, which makes us need to develop a special process to reflect this luster. Our company has self-made light lifting equipment, so as to meet this requirement. After cleaning, the steel ball is loaded into the light lifting equipment, and special auxiliary materials are added. After 10 hours of light lifting, the surface roughness and appearance of the steel ball meet the requirements

surface roughness after polishing (British talysurf6 Profiler)

it can be seen from the table that the average surface roughness of steel balls after polishing has met the needs of customers, and the actual level has reached G40

6. Mixture inspection and visual inspection

in order to prevent bearing steel balls of the same specification or similar specification from being mixed in the production process, the mixture inspection of picking different balls after pickling is essential

in order to ensure that the variation of the batch diameter of steel balls is strictly controlled within the accuracy requirements, we have adopted the imported smooth bar electric sorter. This sorter has high efficiency and small separation error, so as to ensure that the variation of the batch diameter of steel balls meets the requirements, and eliminate the possibility of mixing large and small balls in the whole batch of steel balls

because the silver gloss on the surface of the steel ball is different from the black gloss of ordinary bearing steel ball, it increases the difficulty of visual inspection. The biggest feature of the appearance of this special steel ball is "bright slag", which is a quality problem prone to occur in the processing process. Therefore, we require the operator of the visual inspection process to repeatedly check several times, roll repeatedly in all sides of the steel ball, and detect such unqualified steel balls to ensure that 100% of the appearance requirements are met

VI. benefit comparison and Prospect

through the joint efforts of the company's scientific research and production personnel, the experimental production of this special steel ball has been more than half a year. The output from January to April alone reached 9million grains, and it is expected to reach 20million grains in the whole year, basically meeting the requirements of foreign investors. In this regard, similar bearing steel balls have significant economic benefits in terms of material utilization, production cycle, production cost, sales and so on, which has a far-reaching impact on improving the company's popularity and expanding domestic and foreign markets

with the development of enterprises and the improvement of product quality, we will, on this basis,

Copyright © 2011 JIN SHI