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304 stainless steel thick-walled tube heat treatment after normalizing and tempering mechanical properties

304 stainless steel thick-walled tube heat treatment after normalizing and tempering mechanical properties

Time:2022-03-18 Source:China Wuxi JiaNuo Special Steel Co.

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304 stainless steel thick-walled tube is a commonly used niobium-reinforced low-alloy medium-temperature pressure vessel steel, whose yield strength is greater than 50 kg / mm2. Metallurgical standards (YB) 182-69 “manufacturing boilers with carbon steel and ordinary low-alloy steel plate technical conditions” specifies the chemical composition and mechanical properties of 304 stainless steel thick-walled tube. Stainless steel tube manufacturer thickness less than 40 mm thick thick steel pipe is usually supplied in the hot-rolled condition. 40-115 mm thick steel pipe is supplied in the annealed condition (5908-9 hours, furnace cooling); however, the product should be used in the normalized tempered or quenched and tempered condition.

The critical point temperatures of 304 stainless steel thick-walled tubes are listed in the table. After normalizing and tempering treatment, thick-walled stainless steel pipe can obtain good overall mechanical properties. However, if the normalizing temperature is lower than 930, the strength is low. Normalizing temperature higher than 1000, strength increases and toughness begins to decline. When the tempering temperature is higher than 700, the strength of the steel pipe will be greatly reduced, but the toughness will not be significantly improved. Therefore, the recommended heat treatment specifications for 304 stainless steel thick-walled tubes are as follows.

Normalizing: at 950-980 insulation 1.5-2 minutes/mm.

Tempering: 600-650 insulation for 5-7 minutes / mm

The mechanical properties of thick-walled stainless steel tubes with different heat treatments (including normalizing, normalizing and tempering, repeated heat treatment and quenching and tempering, etc.) are listed in the table). . The low, medium and high temperature properties of different heat treated steel tubes show that the heat treated 304 stainless steel thick-walled tubes have good medium and low temperature properties. Through the impact measurement of the May (U-notch), the steel Wenzhou stainless steel pipe tube tough-brittle transition temperature of about -400. The instantaneous tensile strength does not change much below 400. Therefore, this steel is currently the ideal steel for pressure vessels with higher strength. Hot-rolled state 304 stainless steel thick-walled pipe organization is pearlite, containing a small amount of soxhite ten and a small amount of ferrite. Soxhlet 950 normalizing and 650 tempering produce a small amount of pearlite and ferrite, soxhlet ten 950 water quenching and 650 tempering produce little ferrite.

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