Standard Quenching & Tempering Process Specially for Drill Pipes

Complete technological process flow

Loading and positioning → High-pressure descaling → Austenitizing and heat preservation in walking beam quenching furnace → Internal and external spray quenching cooling → Intermediate buffer transportation → High-temperature tempering and holding in walking beam tempering furnace → Air slow cooling and blanking

1. Quenching process parameters

Heating temperature: 880~930℃ (standard temperature 900℃ for S135 steel grade); holding time ranges from 40 to 60 minutes and will be extended according to the wall thickness of upset ends. The drill pipe enters the quenching cooling section within 15 seconds after discharging from the furnace, with a rotation speed of 70~100 r/min. The spray water pressure is adjustable between 0.5~10 MPa, and the water flow rate at the upset sections can be regulated independently.

2. Tempering process parameters

Tempering temperature: 540~675℃ (560~590℃ for high-strength S135 drill pipes); holding time: 60~85 minutes. Slow forced air cooling is carried out within the temperature range of 350~480℃ after tempering to guarantee the low-temperature impact energy index.

3. Mechanical property requirements after heat treatment (Compliant with API 5DP standard)

For S135 drill pipes: minimum yield strength ≥931MPa, minimum tensile strength ≥1034MPa, longitudinal impact energy ≥100J at -20℃, free from temper brittleness, and capable of resisting hydrogen sulfide stress corrosion.