Heating of stainless-steel pipes in dissociated ammonia

Conclusions

• 1. Heat treatment of pipes in conveyor furnaces with an atmosphere of dissociated ammonia leads to slight decarburizing and considerable saturation with nitrogen.

• 2. Saturation with nitrogen is intensified with increasing temperatures and holding times. When the temperature is raised 100° the saturation of steels 08Kh18N10T and 12Kh18N10T with nitrogen increases by a factor of 3–4, and that of steels 09Kh16N15M3B and 03Kh16N15M3B by a factor of 1.5–2. When the holding time is increased from 1 to 10 min at 1080° the saturation with nitrogen increases by a factor of more than ten.

• 3. Saturation with nitrogen induces susceptibility to ICC after heating to 1080° and higher and holding for 5 min.

• 4. Heat treatment of thin-walled pipes of corrosion-resistant steels in dissociated ammonia increases the susceptibility to ICC, and therefore heating should be conducted in air.