How do seamless pipes perform redox reactions?

How do seamless pipes perform redox reactions?

The spark identification method for cesium seamless pipe materials is a method that uses the physical and chemical phenomena produced during the grinding process of steel to determine its chemical composition. When the steel sample is ground on the grinding wheel, the abrasive grains are ejected along the tangential direction of the grinding wheel rotation. The abrasive grains are in a high temperature state and the surface is strongly oxidized, forming a layer of Fe0 film. The carbon in the CS seamless pipe reacts easily with oxygen at high temperatures, Fe0+C→Fe+C0, reducing Fe0; the reduced Fe will be oxidized again and then reduced again.

This oxidation-reduction reaction circulates and continuously produces CO gas. When the iron oxide film on the surface of the particles cannot control the generated CO gas, explosions will occur and sparks will form. If there are still unreacted Fe and C remaining in the exploded particles, the reaction will continue to occur and secondary, tertiary or multiple explosion sparks will occur.

The carbon in CS seamless pipe is the basic element that forms sparks. When steel contains elements such as manganese, silicon tungsten, chromium, and molybdenum, their oxides will affect the lines, color, and state of sparks. Based on the characteristics of the sparks, the carbon content and other element content of the steel can be roughly judged.

The structure and properties of CS seamless pipes after cold drawing are uneven.

Due to the uneven deformation of seamless steel pipes during the cold drawing process, the degree of deformation from the outer surface layer to the inner surface layer is different. The additional bending deformation and additional shear deformation near the outer layer are larger, so the total deformation degree of the outer layer is larger. It is larger than the inner layer, so the outer layer has finer grains and higher hardness, while the inner layer is the opposite. If the tube wall is thicker, the friction coefficient is large, the die taper angle is large, the total deformation degree of the inner and outer layers is also greatly different, and the non-uniformity of the structure and performance increases. After deformation, the inner and outer tissue properties are inconsistent.

Seamless tube cold drawn inner hole finish

The smoothness of the inner hole of cold-drawn seamless pipes will bring a lot of trouble to customers, which will not only affect the customer's yield, but also affect the quality of the finished product. So what is the inner hole finish of cold drawn seamless pipes? This is mainly based on the customer's product requirements. In the field of hydraulic steel pipes, the inner hole finish requirement of cold-drawn seamless pipes can reach Rz2.0mm/M.

What impact does it have on the inner hole finish of cold drawn seamless pipes?

1) Perforation

Many times, due to immature piercing experience, uncontrollable piercing temperature, short piercing equipment, uneven heating of round steel, etc., the temperature deviation between the inside and outside of the steel pipe is large, forming pits, pits, etc. The piercing furnace should be lengthened to allow the steel pipe to be heated evenly.

2) Cold drawing

Due to the defects of the cold drawing mold itself, the internal finish of the finished seamless pipe is not good. Professional customized precision molds should be used. The higher the precision, the better the quality of the internal and external surface finish of the finished product after cold drawing.

3) Pickling

Due to strict environmental protection requirements in recent years, many manufacturers do not have pickling processes or professional experience and can only process outdoors. The impurities inside the cold-drawn seamless pipe cannot be completely cleaned, or there may be too much acid to form pits, pitting corrosion and other problems. Different pickling methods and times should be used for different steel types to ensure the smoothness of the inner hole.

4) Production process

Another important reason that affects the inner hole finish of cold-drawn seamless pipes is the deformation of seamless steel pipes during the cold-drawing process. The amount of deformation mainly depends on the number of cold drawing passes. The smaller the deformation, the better the finish, but the cost will also increase. We take quality as the basis and produce according to the actual needs of our customers.