Heat treatment of ms seamless pipe

When the steel is cooled from high temperature, the carbon and nitrogen in the ferrite are supersaturated, and the carbon and nitrogen in the iron can be slowly formed at normal temperature, so that the strength and hardness of the steel are improved, and the ductility and toughness are lowered. This phenomenon is called quenching aging. Low carbon steel tubing with seamless will have an aging effect even if it is not quenched. The deformation of low carbon steel tubing with seamless produces a large number of dislocations. The carbon and nitrogen atoms in the ferrite interact elastically with dislocations, and carbon and nitrogen atoms gather around the dislocation lines. This combination of carbon and nitrogen atoms and dislocation lines is called the Cochrane gas mass (Kelly gas mass). It increases the strength and hardness of steel and reduces the ductility and toughness. This phenomenon is called deformation aging. Deformation aging is more harmful to the ductility and toughness of low carbon steel than quenching aging.

There are obvious upper and lower yield points on the tensile curve of low carbon steel. From the upper yield point until the end of the yield extension, a surface wrinkle band formed on the surface of the sample due to uneven deformation is called the Rydes belt. Many stamping parts are often scrapped. There are two ways to prevent it. A high pre-deformation method, the pre-deformed steel is placed for a period of time and the Rudes belt is also produced when stamping, so the pre-deformed steel should not be placed too long before stamping. The other is to add aluminum or titanium to the steel to form a stable compound with nitrogen to prevent deformation aging caused by the formation of Kodak air mass.

Manufacturing process of ms seamless pipe

The raw material of the seamless mild steel pipe is a round tube blank. The round tube blank is cut by a cutting machine into a billet with a length of about 1 meter, and is sent to the furnace for heating via a conveyor belt. The billet is fed into the furnace and heated at a temperature of approximately 1200 degrees Celsius. The fuel is hydrogen or acetylene. The temperature control in the furnace is a key issue.

After the round tube billet comes out of the furnace, it is pierced by a pressure piercing machine. 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 perforation diameter expansion, and can wear a variety of steel types.

After piercing, the round tube billet is successively cross-rolled, continuous rolled or extruded by three rolls. After squeezing, take off the tube and calibrate. The sizing machine uses a tapered drill bit to rotate at a high speed into the steel blank to punch holes to form a steel pipe. The inner diameter of the steel pipe is determined by the length of the outer diameter of the drill bit of the sizing machine.

After the steel pipe is sized, it enters the cooling tower and is cooled by spraying water. After the steel pipe is cooled, it will be straightened. After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by the conveyor belt for internal flaw detection. If there are cracks, bubbles, etc. inside the steel pipe, it will be detected.

After the quality inspection of steel pipes, strict manual selection is required. After the quality inspection of the steel pipe, paint the serial number, specification, production batch number, etc. with paint. It is hoisted into the warehouse by a crane.

Cold treatment method of ms seamless pipe

If the cold treatment method of the ms seamless steel pipe is not correct, its performance will be affected to a certain extent. Therefore, precautions must be taken when cold processing, but most people do not know how to do this. In fact, the main content lies in the following points.

The ms seamless steel pipe should be boiled in boiling water for 30 seconds before cold treatment, which can effectively eliminate about 15% of the internal stress, and the retained austenite can achieve a stable effect. Then, cold treatment can be carried out in a conventional manner. Of course, the second suggestion is to choose a regular treatment of minus 60 degrees, and then go deep cold at minus 120 degrees.

The lower the treatment temperature, the faster the retained austenite will be transformed into martensite, but not completely. Through experiments, it can be found that there will be about 2% retained austenite. At this time, it is necessary to retain retained austenite to achieve a certain buffering effect.

After cold treatment, the mild steel seamless steel pipe needs to be taken out and heated in hot water, which can effectively eliminate about 40% of the cold treatment stress. After gradual heating, tempering and cold treatment should be carried out as soon as possible, most of which can be eliminated as soon as possible to avoid cracks and obtain stability. The performance of the product ensures that the product will not be deformed in the later use process, which is convenient for daily storage.