Views:6 Author:Site Editor Publish Time: 2017-10-25 Origin:Site
Seamless steel pipe has five technical delivered conditions. They are BK , BKW , BKS, GBK and NBK. Another expression is +C, +LC, +SR,+A, +N.
l BK or +C temperature service means Cold Finished (Hard). There is no need heat temperature treatment for the last process of cold drawn or cold rolled craft.
l BKW or +LC temperature service means cold finished (soft). The seamless steel pipes will get slight and low temperature treatment in the last process either cold drawn or cold rolled craft.
l BKS or +SR temperature service means cold finished and stress-relived. Get one temperature below Ac1, keep this temperature in certain time period. Let the steel pipes recovery its condition and release the internal stress.
l GBK and +A temperature service means annealed heat treatment. The organization will get recrystallization after treatment. The temperature will be up to Ac3, And keep warm and let it is cooling slowly in oven. After less than 500℃ let it is cooling in the air.
l NBK or +N temperature service means normalized heat treatment. The temperature should be higher 30℃ to 50℃ while it attaches to Ac3 or Accm temperature. It will be cooling in the air or by ban and cold water. So it is cooling faster than GBK heat temperature treatment.
Different temperature services of seamless steel tubes have different function. Pls check the mechanical properties of tubes under the different delivery conditions.