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The Reason For The Cold Drawn Tube Burst
Apr 21, 2018

The cold-drawn tube is formed by reducing the diameter of the seamless steel tube through a drawing die, and the process route is generally annealed, pickled, and drawn. In the process of drawing cold-drawn small-caliber seamless steel tubes, cracks may begin to crack as much as the bamboo ridges from head to tail. We call this phenomenon collectively cracking.

The reasons for the cracking are:

(1) Work hardening

The effect of work hardening on the steel pipe during cold drawing produces a large number of plastic deformations, causing significant lattice distortion, thereby increasing the lattice energy and increasing the internal energy of the metal, resulting in nonuniform metal internal stress and residual internal stress. This increases the hardness of the metal and decreases its toughness. The higher the metal hardness, the greater the residual internal stress during cold drawing, and the more obvious the work hardening phenomenon. When the residual stress reaches a certain value, the metal will tear along a certain column of grain boundaries, forming a crack in the steel pipe.

(2) hydrogen embrittlement

Effect of Hydrogen Embrittlement Phosphoric acid reacts with iron to evolve hydrogen during descaling with acid. Hydrogen penetrates into the steel as atoms or ions to form a solid solution. The effect of hydrogen on the mechanical properties of steel is typically manifested in hydrogen embrittlement. Cold-drawn steel pipe is a kind of steel pipe, that is, it is classified according to different production processes, and is different from hot-rolled (expanded) pipe. In the process of expanding the capillary blank or raw material tube, it is made by multi-pass cold drawing process, and is usually performed on a single-chain or double-chain cold-drawing machine of 0.5-100 T. Cold-rolled (dial) steel pipe in addition to general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, oil cracking pipe, machining pipe, thick-walled pipe, small-caliber plus inner mold cold-drawn pipe other It also includes carbon thin-walled steel pipes, alloy thin-walled steel pipes, stainless thin-walled steel pipes, and special-shaped steel pipes. The cold-drawn steel pipe can have an outer diameter of 6mm, a wall thickness of 0.25mm, a thin-walled pipe outer diameter of up to 5mm, a wall thickness of less than 0.25mm, and an accuracy and surface quality that is significantly better than that of a hot-rolled (expanded) pipe, but is subject to a process. Constraints, their caliber and length are subject to certain restrictions.