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The inspection method can be smeared with soapy water at the joints of the annealing furnace to see if gas escapes. The places where the gas is easy to escape are the places where the annealing furnace enters the pipe and the place where the pipe comes out. The sealing ring in this place is particularly easy to wear and tear. Check frequently and change frequently.

A process plan for pretreatment of Wuxi precision steel pipes before cold bending is proposed, and the influence of normalizing temperature, holding time and cooling method on the microstructure and mechanical properties of raw material pipes is studied and analyzed, and the conventional normalizing process of Wuxi precision steel pipes is determined: heating temperature (890±10) ℃, keep it for 6min and then let it cool in air.

The conventional normalizing process can completely eliminate the Widmanstler structure of the Wuxi precision steel pipe, making the matching of yield strength and tensile strength more reasonable, the yield strength ratio σS/bσ≤0.78, the elongation 5δ≥30%, and the cold forming performance is greatly improved. And avoid cold bending cracking phenomenon.

The expansion coefficient can be expressed in volume or length, usually expressed in length.

Density The density of a substance is the mass of the substance per unit volume, in kg/m3 or 1b/in3.

The residual tensile stress mainly comes from the residual tensile stress generated by the equipment during the welding process. At present, annealing after welding cooling is used in engineering to eliminate residual stress, and post-weld cooling is an important process for generating residual stress, which wastes energy and is prone to large welding residual stress. Post-weld heat treatment is a new technique for relieving residual stress. The Wuxi precision steel pipe is preheated to the post-heat treatment temperature before welding, and the weldment is continuously heated to maintain this temperature during the welding process. Quenching can increase the strength and hardness of the steel pipe, but reduce its plasticity. Quenching agents commonly used in quenching include water, oil, alkaline water and salt solutions. Tempering of Wuxi precision steel pipe Reheating the quenched Wuxi precision steel pipe to a certain temperature, and then cooling it by a certain method is called tempering. Its purpose is to eliminate the internal stress generated by quenching, reduce hardness and brittleness, and achieve the expected mechanical properties. Tempering is divided into three types: high temperature tempering, medium temperature tempering and low temperature tempering. Tempering is often used in conjunction with quenching and normalizing. The heat treatment method of high temperature tempering after quenching and tempering treatment is called quenching and tempering treatment.