Production status of titanium alloy seamless tube in China

The production technology of titanium alloy seamless tube is mainly extrusion and rolling. Extrusion technology is characterized by high efficiency, high quality, low energy consumption and less/no cutting process. Titanium alloy extrusion technology is developing slowly because of its high resistance to deformation, large tonnage, poor thermal conductivity and easy pollution in air. The rolling technology is mainly divided into two-roll (LG Type) rolling and multi-roll (LD Type) rolling, two-roll rolling is used for cogging, multi-roll rolling is used for sizing and finishing. The types of pipe mill widely used in China are LG-30, LG-90, LG-180, LD-90, LD-180, etc. .

The seamless tube of titanium alloy produced by domestic enterprises is mainly used in four aspects. First, the transportation of offshore oil platform, the application of titanium alloy can reduce the platform weight, reduce the cost, increase the service life; Third, as a lightweight structural material, it is used in the pipeline system of aerospace equipment, and fourth, it is used in the fields of biomedicine and orthopaedics implantation.

The factors affecting the quality of titanium tube and the control measures in the production process of domestic enterprises.

Influencing factors: alloy quality

Problem description: the formation of high-density inclusions, segregation or brittle-hard phase, resulting in uneven tube formation, tube preparation cracks and even cracking. 

Control measures: 1. Using multiple vacuum consumable smelting; 2. Reduce the melting current, slow down the melting speed; 3. Use advanced electron beam cold bed furnace melting.

Influencing factors: tube blank quality

Problem description: The extruded tube blank has fine microstructure and good plasticity, but the equipment is complex and the investment is large. 

Control measures: 1. The extrusion process is suitable for the production of titanium tube blank with low strength and high dimensional accuracy. 2. The cross-rolling piercing process is suitable for the production of titanium tube blank with high strength, fixed specification and large batch.

Influencing factors: heat treatment

Problem description: too high temperature will lead to coarse tissue, too low will lead to under-annealing, residual stress and work hardening can not be eliminated, affect the subsequent processing and finished product performance. 

Control measures: 1. The alloy transformation point should be determined accurately for each batch of materials. 2. The reasonable heat treatment process should be established according to the pipe processing route and the mechanical properties of the alloy. 3. Strict control of heat treatment atmosphere.

Influence factor: deformation

Problem description: too much deformation will lead to poor surface quality, cracks, cracks, etc. . Small deformation can not be broken coarse original grain, low mechanical properties, low production efficiency. 

Control measures: 1. The machining passes should be arranged reasonably according to the allowable pass deformation and the maximum accumulative deformation of the alloy. 2. Attention should be paid to the matching of Q value and deformation so as to produce favorable texture orientation.

Influencing factors: lubrication process

Problem description: high efficient lubricant can reduce plastic forming resistance, ensure the surface quality of pipe, prevent local overheating, reduce tool and die loss. 

Control measures: 1. Consider the forming process, according to the characteristics of each alloy selection of appropriate lubricants; 2. Analyze the dissection process and design the composite lubricant accurately.