Production process and advantages of precision steel pipes

First, the basic use of precision steel pipes: precision steel pipes are widely used in automobiles, motorcycles, electric vehicles, petrochemicals, electricity, ships, aerospace, bearings, pneumatic components, medium and low-pressure boiler seamless steel pipes, and other fields, and can also be used in steel sleeves, bearings, hydraulics, mechanical processing, and other fields!

Second, the production process of precision steel pipes: the production process of precision steel pipes is the same as that of ordinary seamless pipes, except that there is an additional final pickling and cold rolling procedure.

Third, the process flow of precision steel pipes: pipe blanks - inspection - peeling - inspection - heating - perforation - pickling and passivation - grinding - lubrication and air drying - cold rolling - degreasing - cutting - inspection - marking - finished product packaging

Fourth, the difference between steel pipes

1. The main feature of seamless steel pipes is that they have no welding seams and can withstand greater pressure. The product can be a very rough cast or cold-drawn part.

2. Precision steel pipes are products that have appeared in recent years, mainly with strict tolerances and roughness for the inner hole and outer wall dimensions.

Fifth, the characteristics of precision steel pipes

1. Smaller outer diameter

2. High precision can be produced in small batches.

3. Cold-drawn finished products have high precision and good surface quality.

4. The cross-sectional area of the steel pipe is more complex.

5. The performance of the steel pipe is superior and the metal is denser.

3. Cold-drawn finished products have high precision and good surface quality.

4. The cross-sectional area of the steel pipe is more complex.

5. The performance of the steel pipe is superior and the metal is denser.

Precision steel pipe calculation formula: [(outer diameter-wall thickness)*wall thickness]*0.02466=kg/meter (weight per meter)

Sixth, precision steel pipe heat treatment process

Prelude: vacuum annealing of high-quality spring steel, tool steel, precision steel pipe wire, stainless steel products, and titanium alloy materials, bright annealing can be vacuum treated. The lower the annealing temperature, the higher the vacuum degree required. To prevent the evaporation of chromium and accelerate heat conduction, the carrier gas heating (insulation) method is generally used, and it is noted that nitrogen should not be used for stainless steel and titanium alloys, but argon should be used.

Process: Vacuum quenching furnaces are divided into oil quenching and gas quenching according to the cooling method and are divided into single-chamber and double-chamber types according to the number of workstations. 904 is a periodic operation furnace. Vacuum oil quenching furnaces are all double-chamber, with electric heating elements in the rear chamber and an oil tank below the front chamber. After the workpiece is heated and insulated, it is moved into the front chamber. After closing the middle door, the front chamber is filled with inert gas to about 2.66×10~1.01×10 Pa (200~760mm mercury column), and oil is added. Oil quenching can easily cause surface deterioration of the workpiece. Due to the high surface activity, significant thin-layer carburization can occur under the action of a short high-temperature oil film. In addition, the adhesion of carbon black and oil on the surface is not conducive to simplifying the heat treatment process. The development of vacuum quenching technology mainly lies in the development of gas-cooled quenching furnaces with excellent performance and a single workstation. The aforementioned double-chamber furnace can also be used for gas quenching (jet cooling in the front chamber), but the double-station operation makes it difficult to produce large-scale furnaces, and it is also easy to cause deformation of the workpiece during high-temperature movement or change the orientation of the workpiece to increase quenching deformation. The single-station gas-cooled quenching furnace is jet-cooled in the heating chamber after heating and insulation. The cooling rate of gas cooling is not as fast as oil cooling and is also lower than the molten salt isothermal and graded quenching in the traditional quenching method. Therefore, continuously increasing the pressure of the spray chamber, increasing the flow rate, and using inert gases helium and hydrogen with a molar mass smaller than nitrogen and argon are the mainstream of the development of vacuum quenching technology today. In the late 1970s, the pressure of nitrogen spray cooling was increased from (1~2)×10Pa to (5~6)×10Pa, making the cooling capacity close to oil cooling under normal pressure. In the mid-1980s, ultra-high pressure gas quenching appeared, using (10~20)×10Pa of helium, and the cooling capacity was equal to or slightly higher than oil quenching, which has entered industrial use. In the early 1990s, 40×10Pa hydrogen was used, which was close to the cooling capacity of water quenching and was still in its infancy. Industrially developed countries have progressed to high-pressure (5-6)×10. Pa gas quenching is the main method, while the relationship between the vapor pressure (theoretical value) and temperature of some metals produced in China is still in the general pressurized gas quenching (2×10Pa) stage.

Results Vacuum carburizing is a vacuum carburizing-quenching process curve. After heating to the carburizing temperature in a vacuum and keeping warm to purify and activate the surface, a thin carburizing enriched gas (see controlled atmosphere heat treatment) is introduced, and the infiltration is carried out under a negative pressure of about 1330Pa (10T0rr), and then the gas is stopped (pressure reduction) for diffusion. The quenching of precision steel pipes after carburizing adopts a one-time quenching method, that is, the power is turned off first, and the workpiece is cooled to below the critical point A, through nitrogen to make the internal phase change, and then the gas is turned off, the pump is turned on, and the temperature is raised to between Ac1, and Accm. The quenching method can be air cooling or oil cooling. The latter is austenitized and then moved into the front chamber, filled with nitrogen to normal pressure, and then filled with oil. The temperature of vacuum carburizing is generally higher than that of ordinary gas carburizing. It is usually 920-1040℃. Infiltration and diffusion can be divided into two stages as shown. Pulse ventilation, gas stop, and multi-stage infiltration and diffusion can also be used, which has better effects. Due to the high temperature, especially the clean and active surface, the vacuum carburizing layer is formed faster than ordinary gas, liquid, and solid carburizing. If the carburizing layer is required to be 1mm, it only takes 5h at 927℃ and only 1h at 1033℃.