The original organization for precision cold drawn steel tempering steel high temperature tempering brittleness of significant differences in the sensitivity. Martensite high temperature tempering organization for high temperature cold drawn tubes tempering brittleness sensitivity is the largest, bainite high temperature tempering times, pearlitic structure is minimal.
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 strong interaction, can make the intracrystalline phase precipitation and prevents the grain boundary of phosphorus together, can reduce the high temperature beam impact tubes 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.
Large diameter cold drawn seamless steel tube production process: the tube billet - heat - punch to heading, annealing and pickling - oil - multi-channel time cold drawn to billet tube - heat treatment - straightening, hydrostatic test - tag to put in storage. Cold drawn seamless steel tube rolling method of the hot rolled complex, their production process first three steps are basically the same. The difference from the fourth step, circular tube billet after punch, heading, annealing. After annealing to use special acid pickling liquid. After acid pickling, oil. And then followed by cold drawn through multi-channel time. After heat treatment, will be straightening. Steel pipe after straightening the internal inspection by the conveyor belt to the metal detection machine, if steel pipe internal crack, air bubble equivalent problem will also be singled out.
From her appearance, cold drawn seamless tube length is shorter in hot rolled seamless steel tube. Wall thickness in cold drawn seamless tube than the uniform hot-rolled seamless steel pipe, hot-rolled tube of low accuracy, surface roughness, and high precision cold drawn pipe, the surface roughness or some.
Pure cold drawn steel tube main use: automobile, machinery, motorcycles, refrigeration equipment, pneumatic cylinder, hydraulic parts, bearings, and other mechanical properties of steel precision, smoothness, cleanliness, have side impact beams high requirements of the customers. Precision cold drawn pipe (finishing) is to use cold drawn pipe seamless pipe as a raw material processing control the tolerance and surface brightness and the high precision of steel tube material. Precision cold drawn pipe has high precision, high finish, good internal cleanliness, steel pipe under high pressure without leakage, cold bending deformation, flaring, flattening without cracks and other characteristics, can make all kinds of complex deformation and mechanical processing. The chemical composition of the precision cold drawn pipe with carbon sulfur C, Si, Si, Mn, Mn, S, P, P, chromium Cr.