The influence of different tempering temperature on stainless steel with a capillary

Alloy contains nearly 9% 1% of chromium and molybdenum, according to its composition, they are also referred to as the 9 Cr Mo steel 1. Stainless steel capillary in hot rolling have banded under the condition of martensitic phase, high hardness, therefore tempering treatment will be necessary to reduce the hardness in order to obtain good machinability. Stainless steel capillary recrystallization temperature greater than 790 ℃. Low temperature on the microstructure and mechanical properties of stainless steel with a capillary almost has no effect, and the higher tempering temperature can make the recrystallization organization in ferrite phase and uneven. Recently, a Chinese engineer by observing the metallographic and scanning electron microscope and microhardness test, studied the different tempering temperature ( 300~780℃） And tempering hardness of stainless steel belt capillary structure under the influence of cooling rate. Results show that the hardness of 300 ~ 400 ℃ changed little; Under the 500 ~ 600 ℃, for carbide precipitation sensitive area, in which a large number of dispersed carbides in the matrix precipitation, in the area, high hardness, is on the rise; When the temperature from 600 ℃ to 780 ℃, the carbide along the grain boundary precipitation adequately, lower hardness. Gradually reduce with the increase of tempering cooling rate, hardness, at 5 ℃ / min speed within the range of 500 ~ 600 ℃, slow cooling and scattered carbide precipitation and the high matrix hardness; 780 ℃ tempering heat preservation after cooling, cooling speed, 50℃/分钟) Fast, carbide precipitation sensitive range, less precipitation carbides in the matrix, and the hardness is low, processing performance is good. Stainless steel capillary used in engineering components, superheater coil, manifold and steam pipe, the thickness is smaller. Compared with other steel T series, which helps to improve the thermal fatigue life of several times. This allows them to increase the operating temperature to a higher level, so as to improve the efficiency of the power plant. T91 tube belongs to ASTM A213, it do ferrite and austenite boiler superheater and seamless steel tube heat exchanger.