In the past 10 years, China's automobile industry has developed by leaps and bounds. With an annual increase of millions of vehicles, it has become a major automobile manufacturing country with an annual output of nearly 20 million passenger cars, commercial vehicles and special vehicles. The automobile industry has already become a country. One of the pillar industries.
In the automobile manufacturing process, about 70% to 80% of the parts need to be heat treated. Heat treatment is an important process in the automobile manufacturing process. Important parts such as engine, transmission, middle bridge and rear axle need to be heat treated to ensure the safety, reliability and service life of the whole vehicle. The precision, low noise and long life requirements of auto parts have become the development trend of auto parts processing.
In the past 10 years, with the rapid development of the automobile industry, the heat treatment process and equipment level of domestic auto parts have been greatly improved. Advanced heat treatment technology and equipment have been widely promoted, vacuum heating quenching, low pressure vacuum carburizing, vacuum ion nitriding, high pressure gas. Quenching, protective atmosphere heat treatment, controlled atmosphere carburizing and carbonitriding, laser heat treatment, modern induction heat treatment process, etc., have no oxidation heat treatment, and become the mainstream of heat treatment of automotive parts. At the same time, intelligent continuous carburizing automatic production line, sealed box type multi-purpose furnace and its automatic production line, low-pressure vacuum carburizing and high-pressure gas quenching equipment, synchronous dual-frequency induction heat treatment equipment and laser heat treatment equipment are widely used. Because these advanced heat treatment equipments use advanced computer technology (including software technology), the heat treatment production (including procedures, processes) process is automatically controlled, and advanced sensors and their control systems are used to precisely control the heat treatment process parameters, thereby The increase in the heat treatment quality of the parts makes the intrinsic quality of the auto parts close to or reach the international advanced level.
Vacuum heat treatment process and high pressure gas quenching process and equipment
Vacuum heat treatment has a series of advantages: no oxidation, no decarburization, good surface quality, small deformation, excellent heat treatment parts, long service life, no pollution, no pollution, high degree of automation, so it has developed rapidly in China. In recent years, the use of new testing technology and computer control technology has enabled the continuous development of vacuum and controlled atmosphere heat treatment technology to program and automation. The energy-saving, environmentally-friendly and precision heat treatment process led by vacuum heat treatment has become one of the development directions of today's heat treatment. The vacuum heat treatment process includes vacuum heating quenching, low pressure carburizing quenching, low pressure ion carburizing, vacuum ion nitriding and the like. Vacuum heat treatment equipment has single chamber, double chamber, three chamber and oil quenching, gas quenching, oil and gas quenching, high pressure gas quenching, ultra high pressure gas quenching vacuum furnace and low pressure carburizing high pressure gas quenching furnace, multi-chamber low pressure carburizing high pressure gas quenching Semi-continuous production lines, etc.
After the parts are heated at the austenitizing temperature, 0.5~2MPa high-pressure gas quenching can be applied to achieve the quenching effect of static oil or high-speed circulating oil or even water. The biggest advantage is to avoid the smoke pollution caused by oil quenching, and the surface of the treated parts is cleaned. High degree, no need for subsequent cleaning and cleaning shot blasting process.
The gas quenching of steel is different from the quenching mechanism of liquid medium, which can achieve uniform cooling from the surface to the inner layer, so the gas quenching deformation is small, and less grinding can be achieved. High-pressure gas quenching uses nitrogen, hydrogen, argon, and helium. These gases are released into the atmosphere without pollution. The new rapid atmosphere circulation cooling process uses high-pressure gas injection into the cooling chamber, and the flow rate and flow rate are controlled by the computer to achieve the cooling rate in a specific time, thereby achieving the required cooling curve during the heat treatment process, and ensuring the parts. Heat treatment quality. Instead of nitrogen, argon, helium and other gas quenching methods, the air is strongly sprayed, so that the parts are cooled at an extremely fast speed. After quenching, there is only a very thin oxide film on the surface, which is grayish white, and the color of the parts is still beautiful, thus saving a lot of Nitrogen and inert gases further reduce heat treatment costs. This process will become the development trend of high pressure gas quenching.
Vacuum low pressure carburizing combined with high pressure gas quenching is an advanced carburizing and quenching process. It has high carburizing speed, excellent carbide structure, small quenching cracking and deformation tendency, energy saving and carburizing agent raw materials, carburizing. The surface quality of the parts is good and it is beneficial to environmental protection.
1. Vacuum heating quenching and high pressure gas quenching process and equipment
With the development of China's automobile industry, the manufacturing level of automotive molds has also been greatly improved. The key process of mold manufacturing - heat treatment technology has also developed from the original low level to the international level, such as vacuum heating quenching technology, induction hardening Technology and laser quenching technology have been widely used and developed.
In the production of automobiles, almost all types of molds are used, such as cold die, hot forging die, cold die, hot die, die-casting die and casting die. For China's auto companies, with the in-depth development of the market economy, the original decades-old models have now changed to several models in a year. Generally, the modification of medium-sized trucks requires more than 4,000 sets of molds and weighs 2000 tons. At present, automotive mold heat treatment is widely used in vacuum furnace heating and oil quenching, or vacuum heating high pressure gas quenching furnace above 0.6MPa for heat treatment to replace the salt bath furnace to avoid emissions. Compared with other heat treatment processes, not only the heat treatment of the mold is small, there is no oxidative decarburization, and the service life can be increased by 1 to 3 times.
2. Vacuum carburizing and high pressure gas quenching process and equipment
The carburizing heat treatment of automobile parts mainly adopts a gas carburizing process and a vacuum carburizing process. Gas carburizing process is one of the most widely used heat treatment processes for automotive parts due to its excellent processing quality and low cost. In the past decade, vacuum carburizing processes and equipment have also been used in the automotive industry. The combination of low-pressure vacuum carburizing and high-pressure gas quenching technology can meet the requirements for high-quality heat treatment of car transmissions and engine parts.
The low-pressure vacuum carburizing furnace is developed on the basis of vacuum furnace according to the characteristics of vacuum carburizing. Compared with the conventional carburizing furnace, the low-pressure vacuum carburizing furnace is easy to operate; the furnace is very clean and has no carbon black; it has no pollution to the environment. In addition, the furnace has a high heating rate, is convenient to open and stop the furnace, and saves electric energy, and the gas consumption is low. The actual production proves that the production cost is significantly lower than conventional carburizing. Compared with the periodic vacuum carburizing furnace, the production efficiency of the semi-continuous and continuous vacuum carburizing furnace can be increased by 25% and 40%, respectively. Semi-continuous and continuous low-pressure carburizing high-pressure gas quenching automatic production line will become one of the development trends of high-quality automotive parts carburizing heat treatment equipment. Figure 1 shows a continuous low pressure vacuum carburizing automatic production line.
Figure 1 Continuous low pressure vacuum carburizing automatic production line
At present, the cyclic low-pressure carburizing high-pressure gas quenching furnace and the semi-continuous low-pressure carburizing production line have been applied in Shanghai Automotive Industry Group, FAW Group, and Shenlong Automobile Company for load transmission and engine parts, car engines and automatic transmissions. Heat treatment of parts, main reducer sun gear shafts, gear sleeves and gears for heavy-duty vehicles.
In addition to the advantages of low-pressure carburizing, low-pressure ion carburizing is faster because the methane is easily decomposed. After the workpiece is ion-carburized, it can be quenched by oil quenching or high-pressure gas quenching in a vacuum furnace to achieve high carburizing quality requirements. The main equipment is a vacuum ion carburizing furnace, which has been applied in the automotive industry, such as surface hardening treatment of titanium automobile engine valves for the purpose of high power, low fuel consumption, and quietness.
3. Vacuum ion nitriding process and equipment
Ion nitriding is a high-precision chemical heat treatment based on vacuum processing. The process has low processing temperature, small deformation of parts, no oxidation and chemical pollution, no unnecessary components and structures of nitriding layer, high surface hardness, high fatigue strength, short processing time, no need to grind after treatment to remove traditional nitriding. The brittle "white bright layer" has low process cost. Therefore, the process almost completely overcomes the shortcomings of conventional nitriding treatment. It is now used for heat treatment of various automotive parts, including crankshafts, camshafts, steering pivots, gears, bushings, valves, piston rods, synchronizer rings, timer gears and sprockets, etc. Heat treatment.
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