Based on research of 12%Cr-steel high-temprature bolt in different service conditions,accelerated creep rupture test is used to evaluate safe reliability of bolts which has serviced for 350000 hours.

The test and research result of the 1Cr-1/5Mo steel showed that by means of adjusting the chemical compositions and the heat treatment parameters of the material,the high temperature bolt which meets various kinds of mechanical property targets and technical requirements could be produced.

In the course of execution of this guideline, however, the author finds out some problems in it, which seriously affects the normal operation and the supervision work of the high temperature bolts, thus, an a.

A new high temperature bolting steel containing boron has been developed successfully.

The material mainly used for high-temperature bolts on large-capacity thermal power units is 12% Cr steel,but it has been discovered in application that the said steel had problems,such as the hardness value decreasing rapidly,the impact value being lower,and the impact index of C-422 bolts of 12% Cr steel hasn\'t standard can be based on,etc.

Research progress on Type IV cracking of 9%～12%Cr high-grade heat-resisting steel;