straight seam steel pipe preheating, straight seam steel pipe deformation, straight seam steel pipe annealing

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Methods and annealing steps for preheating deformation of straight seam steel pipes

Date:2025-01-09
First, methods for preheating deformation of straight seam steel pipes:
1. Reasonable material selection. For precision and messy molds, micro-deformation mold steels with good quality should be selected. For mold steels with serious carbide segregation, reasonable casting quenching and tempering heat treatment should be carried out. For larger and uncast mold steels, solid solution double refinement heat treatment can be carried out. Reasonable selection of heating temperature and control of heating speed. For precision and messy molds, slow heating, preheating, and other balanced heating methods can be used to reduce mold heat treatment deformation.
2. Correct heat treatment process operation and reasonable tempering heat treatment process are also effective methods to reduce the deformation of precision and messy molds. The causes of deformation of precision and messy molds are often messy, but as long as the deformation rules are mastered and the causes of occurrence are analyzed, the deformation of the mold can be reduced and controlled by using special methods.
3. Precision and messy molds should be preheated to eliminate the residual stress generated during machining. For precision and messy molds, if conditions permit, try to use vacuum heating quenching and deep cooling treatment after quenching. Under the premise of ensuring the hardness of the mold, try to use pre-cooling, graded cooling quenching, or warm quenching process.
4. The mold design should be reasonable, the thickness should not be too different, the shape should be symmetrical, and the deformation rules should be mastered for molds with large deformation, and processing allowances should be reserved. For large, precise, and messy molds, a combined design can be used. For some precision and messy molds, pre-heat treatment, aging heat treatment, and tempering nitriding heat treatment can be used to control the accuracy of the mold. When repairing defects such as mold sand holes, pores, and wear, use equipment with low heat impact such as cold welding machines to avoid deformation during the repair process.

Second, straight seam steel pipe annealing steps:
Straight seam steel pipe annealing is heating the steel pipe to a temperature that keeps it warm at this temperature, and then slowly cools it to room temperature. There are several types of annealing, such as annealing, spheroidizing annealing, and stress relief annealing.
1. Heating the steel pipe to a predetermined temperature, keeping it warm for some time, and then slowly cooling it with the furnace is called annealing. The purpose is to reduce the hardness of steel and eliminate uneven structure and internal stress in steel.
2. Heat the steel pipe to 750 degrees, keep it warm for some time, slowly cool it to below 500 degrees, and then cool it in the air. This is called spheroidizing annealing. The purpose is to reduce the hardness and cutting performance of steel, and it is mainly used for high-carbon steel.
3. Stress annealing of steel pipes is also called low-temperature annealing. Heat the steel to 500-600 degrees, keep it warm for some time, slowly cool it to below 300 degrees with the furnace, and then cool it to room temperature. The structure does not change during annealing, and the internal stress of the metal is mainly eliminated.
4. Normalizing The heat treatment process of heating the steel pipe to 30-50℃ above the critical temperature, keeping it warm for an appropriate period, and cooling it in still air is called normalizing. The main purpose of normalizing is to refine the structure, and the performance of steel, and obtain a structure close to the equilibrium state. Compared with the annealing process, the main difference between normalizing and annealing is that the cooling rate of normalizing is slightly faster, so the production cycle of normalizing heat treatment is short. Therefore, when annealing and normalizing can also meet the performance requirements of parts, normalizing should be used as much as possible.
5. Quenching: The heat treatment process of heating the steel pipe to a certain temperature above the critical point (the quenching temperature of 45 steel is 840-860℃, and the quenching temperature of carbon tool steel is 760-780℃), holding it for a certain time, and then cooling it in water (oil) at an appropriate speed to obtain martensite or bainite structure is called quenching. The main difference between quenching and annealing and normalizing in the process is the fast cooling speed, the purpose is to obtain martensite structure. Martensite structure is an unbalanced structure obtained after the quenching of steel. It has high hardness, but poor plasticity and toughness. The hardness of martensite increases with the increase in the carbon content of steel.
6. Tempering: After the steel pipe is hardened, it is heated to a certain temperature below the critical temperature, kept warm for a certain time, and then cooled to room temperature. The heat treatment process is called tempering. Steel parts after quenching cannot generally be used directly, and can only be used after tempering. Because the hardness and brittleness of quenched steel are high, brittle fracture often occurs when used directly. Tempering can eliminate or reduce internal stress, reduce brittleness, and improve toughness; on the other hand, it can adjust the mechanical properties of quenched steel to achieve the performance of steel. According to the tempering temperature, tempering can be divided into three types: low-temperature tempering, medium-temperature tempering, and high-temperature tempering.
1) Low-temperature tempering 150-250; reduce internal stress, and brittleness, and maintain high hardness and wear resistance after quenching.
2) Medium-temperature tempering 350-500; improve elasticity and strength.
3) High-temperature tempering 500-650; tempering of quenched steel parts above 500°C is called high-temperature tempering. After high-temperature quenching, quenched steel parts have comprehensive mechanical properties (both strength and hardness and good plasticity and toughness). Therefore, medium-carbon steel and medium-carbon alloy steel are generally treated with high-temperature tempering after quenching. Shaft parts are widely used. Quenching + high-temperature tempering is called quenching and tempering treatment.
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straight seam steel pipe preheating, straight seam steel pipe deformation, straight seam steel pipe annealing
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