In mechanical processing, it is common to encounter seamless steel pipes with high hardness that are difficult to machine. This not only affects processing efficiency but also leads to increased tool wear and reduced product surface quality. Through scientific stress relief annealing treatment, this challenge can be effectively addressed, enhancing the machinability of seamless steel pipes.

Analysis of Causes of High Hardness

High hardness in seamless steel pipes usually stems from work hardening generated during cold processing. During plastic deformation processes like cold drawing and cold rolling, the internal grains of the steel pipe become distorted, and dislocation density increases, leading to a rise in the material's strength and hardness, and a decrease in plasticity. Additionally, the presence of residual stress also affects machining performance, making the processing difficult.

Changzhou Tenjan Steel Pipe Co., Ltd. found in its production that the hardness of cold-processed seamless steel pipes without proper heat treatment is often 20-30% higher than in the annealed state. This not only increases cutting resistance but also easily causes tool chipping and rough machined surfaces.

Principle of Stress Relief Annealing Process

Stress relief annealing is a heat treatment process that involves heating the seamless steel pipe to an appropriate temperature (typically below the Ac1 point), holding it for a certain time, and then cooling it slowly. This process allows recovery within the metal, eliminating lattice distortion and reducing dislocation density, thereby softening the material and improving machinability.

Changzhou Tenjan Steel Pipe Co., Ltd. employs advanced stress relief annealing processes, precisely controlling heating temperature and holding time. Typically, seamless steel pipes are heated to 500-650°C, held for 2-4 hours, and then cooled with the furnace. This treatment effectively reduces material hardness, increases plasticity, and simultaneously relieves residual stress.

Key Influence of Process Parameters

The effectiveness of stress relief annealing depends on three key parameters: heating temperature, holding time, and cooling rate. If the temperature is too low, stress cannot be fully relieved; if too high, it may cause microstructural changes. Insufficient holding time leads to incomplete treatment, while excessive time increases production costs. Too rapid cooling may introduce new stresses.

Through numerous process trials, Changzhou Tenjan Steel Pipe Co., Ltd. has established a comprehensive database of heat treatment parameters. They develop customized annealing processes for seamless steel pipes of different materials and specifications, ensuring each batch of products achieves the ideal hardness for machining.

Significant Improvement in Post-Treatment Results

The machinability of seamless steel pipes after stress relief annealing is significantly improved. Specific manifestations include: cutting force reduced by 30%-50%, tool life extended by 2-3 times, machined surface roughness improved by 1-2 grades, and production efficiency increased by over 25%. These improvements directly reduce machining costs and enhance product quality.

Feedback from customers of Changzhou Tenjan Steel Pipe Co., Ltd. indicates that seamless steel pipes treated with optimized annealing show significantly improved processing efficiency on automatic lathes and a marked increase in product qualification rates.

Professional Advice on Material Selection and Treatment

When selecting seamless steel pipes, Changzhou Tenjan Steel Pipe Co., Ltd. recommends that customers choose the appropriate delivery condition based on machining requirements. For components requiring extensive turning, priority should be given to soft (annealed) seamless steel pipes that have undergone stress relief annealing; for structural parts requiring higher strength, hard state pipes can be selected.

The company can also provide customized heat treatment services according to specific customer needs, ensuring that the hardness, strength, and other indicators of the seamless steel pipes fully meet usage requirements.

Conclusion

Through scientific stress relief annealing treatment, the challenges in machining seamless steel pipes can be effectively resolved. Relying on professional heat treatment technology and strict quality control, Changzhou Tenjan Steel Pipe Co., Ltd. provides customers with seamless steel pipe products offering excellent machinability. Choosing Tenjan makes machining more efficient and production smoother. Please feel free to contact us for the most professional technical support and service.