What are the main aspects where the processing of duplex stainless steel pipes is particularly chall

The processing of duplex stainless steel pipes is difficult mainly due to the following aspects: 

High tendency of work hardening

During the processing of duplex stainless steel tubes, due to their unique organizational structure, a rapid work hardening phenomenon occurs. This means that as the processing progresses, the surface hardness of the material significantly increases, making further processing more difficult. Greater cutting force and higher processing energy are required, and at the same time, the wear of the cutting tool is accelerated. 

Poor cutting performance

Fast tool wear: The high strength and high hardness of duplex stainless steel impose extremely high requirements on the wear resistance of the tools. During the cutting process, the friction between the tool and the workpiece is intense, and the tool is prone to wear, chipping, etc., resulting in shortened tool life, increased processing costs and tool changes, and reduced processing efficiency. 

Chips are difficult to control: The chips generated during the processing of duplex stainless steel tubes have high strength and good toughness. They are not prone to breaking or curling, but tend to wrap around the cutting tools and workpieces, which affects the processing accuracy and surface quality, and may also cause safety issues. Special chip-breaking measures need to be taken to control the shape of the chips. 

Processing accuracy is difficult to guarantee: During the processing, due to the large cutting force, the workpiece is prone to deformation, especially for thin-walled parts or parts with high precision requirements, it is more difficult to ensure the processing accuracy. At the same time, the elastic modulus of duplex stainless steel is relatively low, and after processing, it is prone to springback, which further affects the dimensional accuracy and shape accuracy of the parts. 

The forming process is very difficult.

Cold bending is challenging: During the cold bending process, duplex stainless steel pipes require a considerable amount of bending force. Moreover, due to work hardening, cracks are prone to occur during the bending process. There are also higher requirements for the bending radius. A too small bending radius will cause the outer layer of the pipe to be subjected to excessive tensile stress and rupture, while the inner layer will be subjected to excessive compressive stress and wrinkle. 

The control of hot processing is complex: Although hot processing can reduce the deformation resistance of materials, duplex stainless steel tubes require extremely strict temperature control during the hot processing process. If the temperature is too high, it will cause grain growth, affecting the mechanical properties and corrosion resistance of the material; if the temperature is too low, the expected processing effect cannot be achieved, and there is still a considerable processing difficulty. In addition, the cooling speed after hot processing will also have an impact on the microstructure and properties of the material, and precise control is required. 

Welding processing has high requirements.

Welding thermal influence zone issue: During the welding process, the thermal influence zone of duplex stainless steel pipes is prone to undergo organizational changes, such as grain growth and change in composition ratio, which will lead to a decline in the corrosion resistance and mechanical properties of the thermal influence zone. To reduce these adverse effects, it is necessary to strictly control the welding heat input and adopt appropriate welding process parameters, such as a smaller welding current and a faster welding speed, which requires high requirements for welding operation techniques. 

Welding material selection: It is necessary to choose welding materials that match the chemical composition of the duplex stainless steel pipe to ensure that the corrosion resistance and mechanical properties of the weld seam are similar to those of the base material. At the same time, the quality of the welding material has a significant impact on the welding quality. Therefore, it is necessary to strictly control the composition and performance of the welding material, which increases the difficulty of welding material selection and management. 

Post-welding treatment: After welding, in order to eliminate welding stress and improve the microstructure and properties of the welded joint, appropriate heat treatment is often required. However, the heat treatment process for duplex stainless steel tubes is rather complex. The suitable heat treatment parameters need to be determined based on the specific material composition and welding process; otherwise, it may lead to deterioration of the material properties.