Thoughts On Heat Treatment Industry

1. Heat treatment is the key technology to improve the life and reliability of equipment manufacturing products

  Heat treatment is a key technology to improve product life and reliability in equipment manufacturing industry. The shape of the product depends on forming manufacturing, but its performance completely depends on the blank manufacturing process.Heat treatment does not change the size and shape of the workpiece but changes the internal structure of the material by heating and cooling, so as to control the internal performance. Therefore, it is a key technology in the equipment manufacturing industry to improve the service life and reliability of products.

  Heat treatment can greatly improve the strength of metal materials. For example, structural steel, many of which are tempered (tempered at high temperature after quenching) in industry, has a strength of about 600 ~ 1000MPa.During the second world war had a great leap forward, the aircraft landing gear in the former Soviet union by conditioning treatment after quenching temperature tempering, make it to the tensile strength of 1600 mpa, the former Soviet aircraft after installing a new landing gear, reduce weight, flexibility, technically leading the German air force, with ultra-high-strength steel heat treatment was born from now on. After continuous research, the strength of structural steel reached 1800MPa.In recent years, Chinese academician xu zhuyao led his team to study q-p-t treatment (quenching, quenching, tempering, and strengthening), which has increased the strength of structural steel to 2100MPa, three times that of the original tempered treatment. The latest news, Beijing Steel Research Institute is studying 2600MPa types of steel, the strength of the increase not only depends on the composition of the steel but also depends on the heat treatment process, from this you can see the key role of heat treatment.

  With the increased strength, the product can be made light.For example, a high-power hydraulic coupler, a pump wheel in the rotation, driven by hydraulic oil driven from the wheel rotation, the original use of tempered steel, then switch to ultra high strength steel heat treatment scheme, the product deadweight reduced twice, the volume reduced to the original 1/4.

  As another example, through heat treatment can improve the reliability of products, feed water pump of 300000 coal-fired power plants of large power unit pump, power up to 4.6 million megawatts, gear at high speed, the growth speed of 6000 rotations per minute (RPM), the original is easy to damage when using, uncertain, and the damage gear must be imported from abroad, then through cooperation, the gas carburizing process is improved and it can overcome the original abnormal damage as a result, all the way to the relics, 300000 kw this unit run 20 years without an accident.

Damaged gear in the gearbox

  Heat treatment output value only accounts for a few thousandths of the total output value of equipment manufacturing industry, which is not valued. Four two dial one thousand jins, however, the level of heat treatment, can make the machine service life by dozens of times, even hundreds, so with famous brand products in the world, all with unique heat treatment technology and strictly confidential, the key technology of heat treatment have become the market competitiveness of core essential factor, others can copy the function, the appearance of similar products, service life and reliability is difficult to achieve. Heat treatment can not get the attention it deserves in our country, and the world advanced level, there is a huge gap in our country a large number of low-end products, heavy environmental resources cost, can only get a small profit, high-end equipment or the key parts in the high-end equipment have to rely on imports, a serious threat to China’s economic security and national security, heat treatment has become a bottleneck restricting the development of manufacturing industry in our country.

  For example, the production of bearings in our country has accounted for more than 20% of the world’s bearing production. However, the high-end bearings that our country needs account for more than 10% of our bearing demand, but we have to rely on imports. For example, precision bearings with speeds above 2,500 RPM, aero-engine bearings, and wind turbine bearings are imported. High-speed railway bearings above 200 km are also imported, and many weapons such as submarines, aircraft carriers, missiles, and other bearings are imported.GGr15 steel bearing standard in our country and abroad, used in the steel grade, from 1901 to today has 114, ingredients without modification, the more than one hundred years of trial and error, heat treatment developed dozens of times of bearing life, while China’s low-end bearing according to the unit price than imported bearing the size of the same price differs a few times, so the profit is very low.

  Shanghai Turbine Works produces 100 kW ultra-supercritical generating units. The rotor of the generating units is imported. The price of a rotor is about 75 million yuan, which is equal to half of the cost of the whole turbine. Shanghai jujube made a great determination, the high – pressure rotor forging to attack down, very hard. A total of 14 root, performance qualified. And when the first rotor with qualified performance produced in China was delivered, the foreign import price immediately dropped from 75 million to 30 million, so that advanced heat treatment technology can not be bought, can not be taken, only independent research and development.

2. Heat treatment research and development is difficult, long cycle

  Is a detail decides success or failure of the technology, heat treatment hardening, how long heating, heat preservation, which place go down, after which place first, and so on are exquisite, and the same grade of steel, the use of different requirements, different quenching heating temperature, the heating temperature of tempering, heat treatment process window is very narrow, slightly almost reach the best effect. The averager & D cycle of materials and their processing technology is 20 years, and the averager & D cycle of a product is two years. In foreign countries, the basic research of materials is done first and then the product is done. However, after the introduction of products, we explored the process and followed others all the time. We did not realize the key role of heat treatment and did not take the first step in the layout.

  Heat treatment research and development is difficult, master heat treatment is to master the core elements of market competitiveness. For example, our team has studied high-pressure rotors for several years, and different situations may occur after heat treatment. One rotor is very strange, with only one position with extremely low strength, while the other positions are very good and low. After analysis, it turns out to be local forging, heating and overburning (see Figure 3). And time, heat treatment after the organization of intermetallic compounds (see figure 4), because the rotor material can be used to 600 ℃, by adding alloying elements, but sometimes ran to the intermetallic alloy, only after proper heat treatment the intermetallic compound, solid solution to heat resistance, alloy elements into the. Sometimes on round according to the process, performance is good, now a washed-up, after our long time analysis, accidentally discovered a black spot, the spots are non-metallic inclusions, probe, from here find it particularly high content of niobium, near-poverty niobium, beside a big circle heat intensity is reduced, at 620 ℃ tensile, appear empty. We also notice that the number of holes is inversely proportional to the time of fracture. Therefore, only when the oxygen content and non-metallic inclusion are controlled and the correct heat treatment is carried out, can qualified products be obtained.

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