ASME Boiler and Pressure Vessel Code(BPVC) Section II Part D has listed the thermal expansion coefficients at elevated temperatures for ASTM A420 WPL6 material which pertains to Group 1. These coefficients include the instantaneous coefficient of thermal expansion, the mean coefficient of thermal expansion, and the linear thermal expansion coefficient. ASTM A420 Gr. WPL6 is a typical carbon steel used for low-temperature service.

1. Instantaneous Coefficient of Thermal Expansion for ASTM A420 WPL6

Temp. °F	70	100	150	200	250	300	350	400	450
Coefficient A	6.4	6.6	6.8	7.0	7.2	7.3	7.5	7.7	7.8
Temp. °F	500	550	600	650	700	750	800	850	900
Coefficient A	8.0	8.2	8.3	8.5	8.7	8.8	9.0	9.1	9.2
Temp. °F	950	1000	1050	1100	1150	1200	1250	1300	-
Coefficient A	9.3	9.4	9.4	9.5	9.5	9.5	9.5	9.5	-

*Coefficient A: the instantaneous coefficient of thermal expansion, Unit: ×10⁻⁶(inch/in./°F).

2. Mean Coefficient of Thermal Expansion for ASTM A420 WPL6

Temp. °F	70	100	150	200	250	300	350	400	450
Coefficient B	6.4	6.5	6.6	6.7	6.8	6.9	7.0	7.1	7.2
Temp. °F	500	550	600	650	700	750	800	850	900
Coefficient B	7.3	7.3	7.4	7.5	7.6	7.7	7.8	7.9	7.9
Temp. °F	950	1000	1050	1100	1150	1200	1250	1300	-
Coefficient B	8.0	8.1	8.1	8.2	8.3	8.3	8.4	8.4	-

*Coefficient B: the mean coefficient of thermal expansion in going from 70°F to indicated temperature. Unit: ×10⁻⁶(inch/inch/°F).

3. Linear Thermal Expansion Coefficient for ASTM A420 WPL6

Temp. °F	70	100	150	200	250	300	350	400	450
Coefficient C
Temp. °F	500	550	600	650	700	750	800	850	900
Coefficient C
Temp. °F	950	1000	1050	1100	1150	1200	1250	1300	-
Coefficient C									-

*Coefficient C: the linear thermal expansion in going from 70°F to indicated temperature. Unit: inch/100 ft.