Large-acting car body bolt thermal integration technology containment strategy
For the Changan company, which is based on the automobile industry, the scale of the automobile L involves the production of large-scale automobile bolts, and the quality of the automobile is the most, which is related to the improvement of the quality of the automobile bolts. For the heat treatment car, Detian has dozens of car bolts in and out of the workshop, the number is thousands of tens of thousands, so it is responsible for ensuring the quality of the car, that is, through heat treatment to improve and lift, the inner part of the car bolt Analysis of technical reasons.
Reasons for non-conforming products In the heat treatment process of automobile bolts, a major quality problem is that the hardness caused by various factors does not meet the requirements of process data, such as uneven hardness (mixed and unqualified); high hardness Or low, oxidative decarburization, excessive thread size, raw material mixing and other issues.
The reason for the failure of hardness is the main reason for the failure of heat treatment of automobile bolts. The main reason for the failure of heat treatment is the heat treatment. The multiple pickling causes the thread ruler and j-tolerance; the protection performance of the mesh belt furnace is small; the temperature of the furnace is not allowed; During the heat treatment, the Ningqi car snails piled up too much and were too dense, and the raw materials had problems in technical research and measures.
Standardize the quenching process conditions of the bolts. The quenching temperature of the automobile bolts is generally selected according to the actual production, 890 ° C (35 steel), 870 ° C (40 steel), 860 ° C (45 steel), 850 ° C (50 steel). In order to ensure that the bolts of different types can be uniformly heated and ensure the full transformation of the structure, the quenching heating time is very important. Especially for bolts of 35 steel material whose quenching quality is not stable and difficult to control, the quenching time is generally controlled at 35-45 min, not less than 35 min, so as to avoid uneven or low hardness after quenching oil cooling. The hardenability requirement is not achieved.
The tempering temperature varies according to the hardness requirements. For the 35 steel and 45 steel materials that are frequently used, the hardness requirements are HR bar 1 - 33, HRC 22 - 32 bolts. We generally choose tempering temperatures of 480 to 50 ° C respectively. 540-560 ° C, the time is 6Omin, not less than 4Omin, if the tempering time is not enough, the hardness value is uneven or high. Standard pickling process. For reworked heat-treated car bolts, including re-quenching and re-tempering, we stipulate that we will not send pickling after re-heat treatment, and then send pickling after the inspection is passed (production process is as follows) to avoid multiple repairs. In the pickling process, the thread size is too bad.
Mesh belt furnace grinding group painting wash group 1 car screw du retreat heat treatment flow A: retired qualified flow sequence: 12345H: retired unqualified flow order: 12364. Adjusting the protective atmosphere to make the bolts do not decarburize and strengthen the protection performance of the mesh belt furnace from the equipment and technically.
Firstly, the method of enriching gas into the mesh belt furnace is adopted to enhance its protective effect. Based on experience and several times of process tests, we have determined the flow rate of the enriched gas, which is 0. 2 0. Preferably, in this case, on the one hand, the carbon potential of the furnace atmosphere is increased, and the oxidative decarburization tendency of the parts is reduced, and on the other hand, since the temperature and pressure in the furnace are not high, the carburization conditions are not reached, and no The surface of the part is carbonized, that is, the carbon potential in the furnace atmosphere and the carbon potential on the surface of the part are in a dynamic equilibrium state, which plays a protective role.
Secondly, the water mark line in the water tank should be kept at about 120m away from the slot. It is not allowed to be higher than 130. The oil in the quenching oil tank should be about 130mm away from the slot. It is not allowed to be higher than 150mm every half an hour. Check once to prevent air from entering the person; at the same time, always pay attention to the protective atmosphere displayed by the rotameter and whether the rich gas flow is normal to ensure the positive pressure inside.
Regular temperature measurement of the furnace In order to solve the problem of large temperature error of the mesh belt furnace, it is required that after the overhaul or long-term deactivation of the furnace, the furnace temperature detection must be carried out before each furnace opening to check the true error of the equipment furnace temperature. To ensure the actual process temperature for quenching and tempering. The meter periodically verifies the meter and the meter regularly checks the temperature control meter once a week to ensure that the meter displays the temperature accurately. Strengthen on-site supervision and batch management technology cadres to strengthen on-site supervision. The squad leader and the squad leader carefully review their responsibilities, strengthen quality control, and the operators work hard to place the car bolts densely and evenly on the transmission belt, and strictly control the speed of the conveyor belt. Ensure uniform and constant speed transfer bolts.
Persuading the education operators to adhere to the principle of quality first, we must not neglect the quality of the products due to the progress of the work. In addition, we also issued a notice requesting that regardless of the batch size, we will adhere to the batch transfer system, that is, stipulate a batch of 2,000 pieces, quenching, tempering, pickling, polishing and inspection in batches to strengthen the management of intermediate circulation links. .
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