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Why does seamless steel pipe crack during production?

The reasons for the hazards are:
(1) Cold work hardening;
(2) Hydrogen embrittlement status.
The content of this article analyzes these two situations and clearly puts forward some countermeasures to avoid the cracking of cold-drawn seamless steel pipes. Analysis of cracking conditions: Cold-drawn seamless steel pipes are produced by cold-drawing precision steel pipes with smaller diameters according to drawing abrasive tools. The processing process lines are generally quenching, pickling passivation, and drawing. In the whole process of drawing and drawing, cold-drawn seamless steel pipes sometimes crack as quickly as a bamboo rod from beginning to end. Everyone refers to this kind of situation as cracking.

The hazards of cold work hardening

The cold-drawn seamless steel tube causes a lot of plastic deformation, resulting in significant lattice constant turbulence, which in turn increases the kinetic energy of the lattice constant, and the metal material can increase, resulting in uneven internal stress of the metal material and residual thermal stress. That will increase the hardness of the metal and decrease the ductility. The higher the metal hardness, the greater the residual thermal stress during cold drawing, and the more significant the cold work hardening. When the internal stress reaches a certain standard value, the metal material will tear along a certain column of crystal pages, resulting in the cracking of the seamless steel pipe.

The hazards of hydrogen embrittlement

In the whole process of removing the oxide scale with acid solution, the generation of hydrochloric acid and iron reflects the dissolved radon gas. Hydrogen penetrates into steel in the form of molecules or positive ions to produce a solid solution. The typical hazard of hydrogen to the physical properties of steel is mainly manifested in hydrogen embrittlement.
The raw material of the thick-walled cold-drawn seamless steel pipe is a round finish-rolled pipe. The round steel pipe blanks are processed by laser cutting by an automatic cutting machine to produce blanks with a length of about one meter, and are sent to the melting furnace for heating via a conveyor belt. The slab is sent into the melting furnace for heating, the temperature is about 1200°C. However, the material is radon or acetylene gas. The temperature control in the furnace is a crucial problem. After the announcement of the round finish rolling tube, it will go through the working pressure piercing machine to carry out the hollow. Generally, the more common piercing machine is the tapered roller piercing machine. This type of piercing machine has high production efficiency, good product quality, large diameter expansion of broken holes, and can wear a variety of steel grades. After the hole is broken, the round finish rolling tube is sequentially formed by three-roll cross rolling, continuous rolling or extrusion. After extrusion, the die should be removed. The die machine runs at a high speed according to the cone-shaped twist drill to enter the steel blank to make holes to produce seamless steel pipes. The inner diameter of the seamless steel pipe is determined by the diameter of the twist drill of the die machine. After the seamless steel pipe is sizing, it enters the glass fiber reinforced plastic cooling tower. According to the water spray cooling, the seamless steel pipe needs to be straightened after being cooled. After straightening, the seamless steel pipe is sent by the conveyor belt to the metal material flaw detector (or pressure test) for internal flaw detection. If the seamless steel pipe has cracks, bubbles and other problems, it will be detected. After the quality inspection of seamless steel pipes, the selection should be based on strict hand-made. After the quality inspection of seamless steel pipes, paint the serial number, specification model, production date, etc. with paint. It is hoisted into the warehouse by a crane.


Tips:Seamless steel pipes for structural use include GB/T8162-2008, ISO2937, ASTMA53, ASTMA106, JISG3441, BSEN10210-1
Structural seamless steel pipes are used for general structures and mechanical equipment structures, and many are used for various structural seamless steel pipes in engineering construction, mechanical equipment, transportation, airlines, oil exploration and other manufacturing industries.
Structural seamless steel pipe model specification diameter 10.0Mm-168.2mm thin thickness 1.0Mm-20.0Mm
 

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