The service life of thick-walled steel pipes is related to the surface decarburization of precision tubes. If the surface is decarburized, the strength and wear resistance of the spiral tube will be reduced, which will directly affect the service life of the spiral tube. If the decarburized layer on the spiral tube is not cleaned, the surface hardness and wear resistance of the spiral tube will be reduced accordingly, and during the quenching process, the change in the volume of the inner and outer layers will cause cracks to form on the surface of the workpiece.

To solve the problem of surface decarburization, it is mainly necessary to deal with the heat treatment process. Because decarburization and oxidation of the spiral tube are carried out at the same time, during the heat treatment process, the thick-walled steel pipe should be kept away from air as much as possible, which can improve the decarburization phenomenon. The media that cause decarburization on the surface of thick-walled steel pipes are mainly oxidizing gases such as oxygen, water vapor and carbon dioxide. When these gases come into contact with the heated spiral tube, they will cause oxidation and decarburization of the spiral tube. Therefore, it is also very important to control the ratio of carbon dioxide and carbon monoxide in the furnace. In fact, adding protective gas nitrogen into the thick-walled steel pipe forging furnace is also very effective. Nitrogen can disperse certain oxidizing gases and reduce the decarburization of the spiral tube.

Precision tube is a high-precision, high-brightness seamless steel tube produced by cold drawing or cold rolling. The inner and outer diameters can be accurate to within 0.2mm or even higher. The surface finish is high and suitable for occasions with high requirements for surface quality. It is light in weight and has excellent mechanical properties and processing properties while ensuring bending and torsional strength. Its mechanical properties and processing properties can be further improved by heat treatment processes such as normalizing, quenching, and tempering.

The precision rolled tube is a seamless steel tube that uses a fine rolling process to ensure the surface smoothness and dimensional accuracy of the inner and outer walls of the tube meet international standard requirements. The outer diameter tolerance of conventional products can be controlled within ±0.05mm, and the wall thickness tolerance is within ±0.1mm; and special industries have higher requirements. It has excellent comprehensive performance, can withstand high pressure, and does not crack or wrinkle during deformation processes such as cold bending, flaring, and flattening. It can perform various complex deformations and mechanical processing, which improves production efficiency and product quality.

Precision drawn tube is formed into a tube by mechanical force and drawing force. Specifically, precision-drawn tube is formed into tube by heating the billet from round to manufacturing temperature and then using multiple drawing machines in the pipeline. In this process, the billet is stretched and forged into tube. During the processing of precision drawn tube, the minimum diameter can reach 0.1 mm. The surface of precision drawn tube is smooth, without an oxide layer, and the shape and size of inner and outer walls are controlled very accurately.

Precision rolled tube is made of tube by mechanical rolling. Specifically, the precision rolled tube is first rolled into a mother tube with billet in cooling state and then continuously rolled by multi-pass rolling mill to form it into tube with specified size and shape. Compared with cold drawing method, rolling method has faster processing speed and higher production efficiency.
The surface of a precision rolled tube is relatively rough, but the inner and outer diameter size accuracy is easier to control, and the minimum diameter can reach 0.8 mm. Compared with precision drawn tube, precision rolled tube has lower production cost, but its product strength and dimensional accuracy are relatively low.

1. Different composition: High carbon steel refers to steel with a carbon content between 0.6% and 1.5%. It has higher strength and hardness and also improves the wear resistance and heat resistance of the material. However, due to the high carbon content, it is prone to problems such as cracks and deformation and requires appropriate heat treatment.
Alloy steel refers to the addition of alloy elements such as chromium, molybdenum, nickel, etc., to ordinary steel to improve certain properties of steel. Alloy steel not only has high strength, corrosion resistance, and heat resistance but also has good toughness and plasticity.

2. Different performance: Due to the addition of alloy elements, alloy steel has better corrosion resistance, thermal strength, and toughness, while high carbon steel has higher strength and wear resistance;

3. Different applications: High carbon steel is suitable for manufacturing knives, springs, auto parts, etc., while alloy steel can be used to manufacture aviation parts, motors, electrical parts, etc.

1. High carbon steel has poor hardenability
After water quenching, the critical quenching diameter of carbon steel is 15~20mm. For parts with a diameter greater than 20mm, it is impossible to quench even with water quenching, and it cannot be guaranteed that the entire cross section will obtain consistent comprehensive mechanical properties. Therefore, for large parts with high requirements, carbon steel is definitely not suitable. Alloy steel has high hardenability and can be used to manufacture parts with large cross-sections and complex shapes.

2. High carbon steel has low high temperature strength and poor red hardness
When carbon steel is used at temperatures above 200℃, its strength and hardness will decrease rapidly. Alloy steel has good stability after tempering. Good red hardness and can work at higher temperatures.

3. High carbon steel cannot obtain good comprehensive performance
For example, when using quenching and tempering treatment to try to obtain good comprehensive performance, if you want to ensure higher strength, the toughness is low, and if you want to ensure better toughness, the strength is low. This is due to the poor tempering stability of carbon steel. Therefore, the comprehensive performance obtained by carbon steel is far worse than that of alloy steel; that is, alloy steel has very good strength and toughness.

4. High carbon steel does not have special properties
For example, high temperature hardness or tensile strength, oxidation resistance, corrosion resistance, special electrical and magnetic properties, etc., cannot be obtained with carbon steel, and only alloy steel can be used to meet the above requirements. Carbon steel also has some advantages. For example, by changing its carbon content and performing appropriate heat treatment, many properties required in industrial production can be obtained. Because carbon steel is low in price, easy to produce, and has good processing performance, it is still a very widely used steel material in industry, accounting for more than 80% of the total steel consumption.