Heat treatment standard of 4140 forged steel

    One, the steps and conditions in the heat treatment of 4140 forged steel:
A, normalizing:
Normalizing temperature at 858 °C ~ 912 °C, and maintain the temperature within the specified time. Cooling in air.
B, quenching:
1, temperature Requirements: heated to 816 °C ~ 871 °C, and maintain the temperature within the specified time.
2, the cooling medium requirements: generally uses oil cooling.
C, tempering:
Tempering temperature is not lower than 552 °C, and maintain the temperature within the specified time. The holding time according to the following method to calculate.
1. If the material size less than 2 inches: heat preservation time is not lower than 60 minutes.
2. The material of size greater than two inches: at least 30 minutes per inch (or at least 12 minutes per centimeter) to calculate the holding time. (Material size according to the maximum cross-sectional dimension calculation)
To record the detailed process of heat treatment of 4140 steel (including heating time, heating rate, graphs and charts, furnace type, heat preservation time, cooling mode and other related information), and written the heat treatment report, furnace No. of heat treatment should also be recorded in the material identification certificate.
    Two, ultrasonic testing:
After heat treatment of 4140 forged steel, the removal of the epidermis by mechanical processing way, and then subjected to ultrasonic testing, ultrasonic testing surface roughness of the surface is not more than Ra6.3. Ultrasonic testing equipment, personnel and detection methods, refer to ASTM SA 388-2004 edition, a single defect is less than Φ3.2mm, multiple defects is less than Φ1.6mm. Defects allowed in a non-machined surface, machined surfaces must not have any flaws.
    Three, hardness test:
1, the hardness testing methods and requirements in accordance with ASTM E10 and ASTM E18 requirements.
2, hardness test results must be recorded in the test report, and noted in the material identification certificate.

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