Creep-resistant and high-temperature steels to EN 10269

Creep-resistant steels retain their strength at elevated temperatures at which ordinary quenched and tempered steels lose strength. They are alloyed with chromium, molybdenum and vanadium; the carbides of these elements remain stable even at 400 to 550 °C and keep the yield strength high. For fasteners, they are standardised in EN 10269, together with the test values at room temperature and at elevated temperature. Historically, many drawings still refer to the VdTÜV material data sheets.

The grades in the RS Randack range

• 21CrMoV5-7 (1.7709): The classic turbine and steam boiler material for reduced-shank bolts, studs and nuts up to about 500 °C.
• 40CrMoV4-6 (1.7711): Higher strength than 21CrMoV5-7 with comparable elevated-temperature strength, for highly loaded flanged joints.
• X22CrMoV12-1 (1.4923) and X19CrMoVNbN11-1 (1.4913): Martensitic high-temperature steels with 11 to 12% chromium for temperatures above 500 °C, for example on steam turbines and high-temperature valves; they are cooled slowly after forging and require precisely controlled heat treatment.
• Nickel-based alloys take over above the range of martensitic steels.

What is different in production

In the quenched and tempered condition, creep-resistant steels are harder to machine and harder to roll than 42CrMo4; RS Randack nevertheless rolls the threads, including in the quenched and tempered condition, using rolling dies designed for these materials. In addition to the tensile test and hardness, the elevated-temperature yield strength can be verified on request through a partner laboratory, and the impact energy in our own laboratory.

What you should specify

Service temperature and duration, material number or standard, required elevated-temperature yield strength, property class or minimum values, certificate type.