Identification of tempering temperature in heat treatment of seamless steel pipe

To accurately identify the tempering temperature during the heat treatment of seamless steel pipes, the tempering temperature can be determined by observing the tempering color. The tempering color changes with temperature, and these variations differ based on the material being treated. Below is a breakdown provided by experts.

1. Tempering Colors for Carbon Steel Seamless Pipes:

Light yellow: 200°C

Brown: 240°C

Purple: 260°C

Blue-purple: 280°C

Blue: 300°C

Blue-gray: 350°C

Gray: 400°C

2. Tempering Colors for Stainless Steel Seamless Pipes:

Light wheat yellow: 290°C

Wheat yellow: 340°C

Light reddish brown: 390°C

Light red: 450°C

Light blue: 530°C

Dark blue: 600°C

3. Tempering Colors for Low Alloy Seamless Pipes:

Light wheat yellow: 225°C

Wheat yellow: 235°C

Light reddish brown: 265°C

Light red: 280°C

Light blue: 290°C

Dark blue: 315°C

These color changes are closely related to temperature. As long as the tempering colors are distinct, one can determine the corresponding heat treatment temperature. However, it’s important to note that the duration of tempering can also influence the color, although this guide focuses primarily on temperature.