The essence of the precision cold drawn steel tube of high temperature tempering brittleness, generally regarded as phosphorus, tin, antimony, arsenic and other impurity elements in the original austenite grain boundary partial poly, lead to the result of grain boundary embrittlement. And alloy elements such as manganese, nickel, chromium and the impurity elements in grain boundary occur together, promote the impurity element enrichment and aggravate embrittlement. And molybdenum, on the other hand, with impurity elements such as phosphorus has side impact beams strong interaction, can make the intracrystalline phase precipitation and prevents the grain boundary of phosphorus together, can reduce the high temperature tempering brittleness of rare earth elements also has a role similar to that of the molybdenum. Impurities such as titanium more effectively promote the phosphorus element in the intracrystalline precipitation, impurities and decreases the grain boundary of partial poly slows down the high temperature tempering brittleness.
The original organization for precision cold drawn steel tempering steel beam impact tubes high temperature tempering brittleness of significant differences in the sensitivity. Martensite high temperature tempering organization for high temperature tempering brittleness sensitivity is the largest, bainite high temperature tempering times, pearlitic structure is minimal.
Reduce the cold drawn seamless steel tube of high temperature tempering brittleness measures are:
(1) the cold oil or water fast cooling after high temperature tempering to suppress impurity elements in grain boundary together;
(2) using molybdenum precision cold drawn tubes light tube, when the content of molybdenum in steel up to 0. 7%, the high temperature tempering embrittlement tendency is greatly reduced, more than the limit of 20 # precision steel pipe in formation of molybdenum carbide special rich, molybdenum content in the matrix is reduced, precision tube embrittlement tendency but increases;
(3) the lower the content of impurity elements in the 20 # precision steel tube;
(4) components in the high temperature temper embrittlement area for a long term, single and molybdenum can also be difficult to prevent embrittlement, only lower content of impurity elements in the 20 # precision steel tube, improve the purity of precision tube, and supplemented by aluminum and composite alloying of rare earth elements, can effectively prevent the high temperature tempering brittleness.
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