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Seamless steel pipe in the drawing process of the reasons for cracking

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In the production process of seamless pipe, there are cold hardening and hydrogen embrittlement phenomenon, they are caused by cold drawn seamless pipe cracking the main reason. In this paper, two phenomena were analyzed and some measures to prevent cracking of small caliber seamless steel tubes were proposed. Analysis of the phenomenon of burst Cold drawn seamless pipe is the smaller diameter of the seamless steel pipe through the drawing die to reduce the diameter of the cold formed, the process is generally annealing, pickling, drawing. Cold-drawn small-caliber seamless steel pipe in the drawing process, sometimes from beginning to end like a bamboo crack as quickly split phenomenon, we call this phenomenon unified cracking. The reasons for cracking include:

(1) work hardening.

(2) hydrogen embrittlement phenomenon. 1.1 The impact of work-hardening Steel in the drawing of a large number of plastic deformation, causing significant lattice distortion, so that lattice energy increased, the metal can increase, leading to internal stress uneven metal, resulting in residual stress. This will increase the hardness of metal, toughness decreased. The higher the hardness of the metal, the greater the residual stress during cold drawing, the more obvious the phenomenon of hardening. When the residual stress reaches a certain value, the metal will tear along the grain boundary of a row, the formation of steel pipe cracking. 1.2 hydrogen embrittlement phenomenon In addition to the use of acid in the process of descaling, sulfuric acid and iron precipitation reaction of hydrogen. Hydrogen in the form of atoms or ions into the steel, the formation of solid solution. The effect of hydrogen on the mechanical properties of steel is typical of the phenomenon of hydrogen embrittlement.




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