Quenching process of cs seamless pipe

Quenching refers to transforming the structure of cs seamless pipe from austenite to martensite or bainite, and heating cs seamless steel pipe to above AC3 or AC1 temperature. Then keep warm until all or part of the internal structure of the seamless steel pipe is austenitized, and then rapidly cool at a temperature greater than the critical cooling temperature until the MS transforms into a heat treatment process of martensite.

Quenching and tempering of cs seamless steel pipe are very important and widely used processes in the heat treatment process. Quenching can significantly increase the strength and hardness of steel. If combined with tempering at different temperatures, the internal stress of quenching can be eliminated (or reduced), and the combination of strength, hardness and toughness can be obtained to meet different requirements. Therefore, quenching and tempering are two inseparable heat treatment processes.

Process: Heat the CS seamless pipe to the quenching temperature, keep it warm for a period of time, and then rapidly cool it in water, brine or oil (individual materials are in the air).

Purpose:

1) Make cs seamless pipe obtain higher hardness and wear resistance;

2) Make the cs seamless pipe obtain certain special properties after tempering, such as higher strength, elasticity and toughness.

Common problems during quenching of cs seamless pipes include deformation, cracking, air oxidation, carburization, insufficient or uneven strength, surface corrosion, coarse grain, over-temperature, and alloy composition not qualified according to quality inspection standards. In actual production, corresponding preventive measures should be taken according to the causes of quenching deformation and quenching cracks, so as to ensure uniform heating and proper heating of seamless pipes as much as possible.

Precaution:

1) Use a cooling medium with good hardenability, formulate reasonable heat treatment and quenching process parameters and select a reasonable cooling medium or control operation method;

2) Improve the heat treatment process, adopt vacuum heating, protective atmosphere heating, fully deoxidized salt bath furnace heating, graded quenching, and isothermal quenching;

3) Sufficient tempering to obtain stable microstructure and properties; multiple tempering to fully transform retained austenite and eliminate new stress

4) Improve the forging process or perform correct spheroidizing annealing and normalizing treatment to prevent local overheating or overburning, and take protective measures or pre-cooling measures;

5) Properly adjust the composition of the steel grade, reduce the content of C element, refine the grain, and improve the resistance to crack growth. The mass fraction of C and Mnv> should be strictly controlled for water-quenched steel grades. When w ( C ) + w ( M n ) / 3 ≥ 0.9%, there is a risk of cracking in the water-quenching process, and the oil-quenching process should be used. For high C and high Mn steel grades, reducing the quenching temperature and cooling rate is beneficial to prevent the occurrence of quenching cracks in steel pipes.

CS seamless steel pipe is a long strip of steel with a hollow section. A large number of pipelines are used to transport fluids, such as pipelines for transporting oil, natural gas, gas, water and certain solid materials. Compared with welded steel tubes, steel pipes have the same flexural and torsional strength, but are lighter in weight, and are economical section steels.

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