About the processing and application of titanium welded pipe

Titanium and titanium alloy straight seam welded pipes (referred to as “titanium welded pipes”) are obtained by welding titanium and titanium alloy coiled strips or wide sheets by crimping into tubular shapes. The titanium alloy grades in the United States mainly include Gr.1, Gr.2, and Gr.12.

The production process of titanium welded pipe is as follows: titanium strip unwinding → shear butt welding → loop sleeve storage → titanium strip cleaning → tube forming type → welding → weld eddy current flaw detection → predetermined diameter → on-line annealing → fine sizing / straightening → Eddy current testing → laser caliper → online coding → fixed length cutting → ultrasonic flaw detection → fine ruler / flat head → air tightness test → finished product inspection → packaging and storage.

In the past ten years, the rapid development of China’s titanium welded pipe industry is mainly due to the domestic breakthrough in the production technology of titanium welded pipe raw material–titanium coil, the technical performance index and quality stability of domestic cold-rolled titanium coil. Can meet the requirements of titanium welded pipe.

The field of application of titanium welded pipes is expanding. Titanium welded pipes have become the preferred pipe for many industries to replace stainless steel pipes, copper-nickel alloy pipes and titanium seamless pipes. After several years of development, titanium welded pipe has broken through a series of key process and technical bottlenecks, and has been widely used in electric power, air conditioning, seawater desalination, water treatment equipment and other fields. In addition, domestic titanium welded pipes have also achieved bulk export. It can be seen that the production process and quality level of domestic titanium welded pipes have been greatly improved.

Comprehensive advantages of titanium welded pipe

In China, the production technology of low-strength and low-alloy titanium seamless pipes is relatively mature. In some pipes requiring high pressure resistance and structural stress, thick-walled titanium seamless pipes are generally used. However, due to the low yield of titanium seamless tubes and long lead times, the development of titanium welded pipes has become a trend in the titanium tube industry. Compared with titanium seamless pipes, the comprehensive advantages of titanium welded pipes are becoming more and more obvious. In Japan, the United States, Europe and other countries and regions, titanium welded pipes are gradually replacing titanium rolled pipes.

The mechanical properties of titanium welded pipe and titanium seamless pipe are basically the same.

Taking titanium and titanium alloy tubes for heat exchangers and condensers as an example, the national standard is GB/T 3625-2007, the American standard is ASTMB338, and the difference between chemical composition, mechanical properties and process performance of titanium welded pipe and titanium seamless pipe is different. Not big, even the same. With the advancement of titanium welded pipe welding and heat treatment technology, domestic thin-walled titanium welded pipe generally adopts single-gun or multi-gun TIG/PAW self-welding welding. After welding, it adopts online heat treatment process to optimize the welding and annealing process to make the base metal and weld bead. The microstructure of the heat-affected zone is substantially close, and the welding stress is eliminated, and the weld bead is homogenized. Through comparison, it is found that the weld composition of the titanium welded pipe is basically the same as that of the base metal, and the mechanical properties and corrosion resistance of the weld are the same as those of the base metal.

The appearance and quality of titanium welded pipe is better than titanium seamless pipe

The titanium welded pipe is welded by cold rolling coil, the wall thickness is uniform, the concentricity is good, the smoothness is good, and the pipe is not easy to scale. Especially for thin-walled titanium tubes, production by seamless rolling process cannot meet its technical requirements. Titanium seamless pipes are difficult to achieve a wall thickness of less than 1 mm by rolling or drawing processes; while titanium welded pipes can achieve wall thicknesses of 0.5 mm or less, saving a lot of materials and costs. At the same time, due to the thin wall thickness of the titanium welded pipe, a higher heat transfer coefficient can be obtained, and a better heat transfer effect can be obtained.

Titanium welded pipe costs and environmental advantages stand out

The production process of titanium seamless pipe is complicated. Conventionally, a three-roll or multi-roll mill and a drawing machine are used to roll or draw a certain size of the pipe blank through multiple passes, and finally a seamless pipe is produced after reducing the diameter and reducing the wall. The process has low production efficiency and low yield. Titanium seamless pipe from titanium sponge to pipe, through rolling or drawing, material waste is large, the finished product rate is only about 50%, and large-scale mass production cannot be achieved, and the production cycle is relatively long.

The titanium welded pipe is produced by an automatic continuous production line, which is formed by cold-bending forming, welding, on-line heat treatment, sizing straightening, non-destructive testing and air tightness testing using a titanium strip with uniform wall thickness. From titanium sponge to welded pipe, the material utilization rate is usually about 80%. If the titanium tape is used as the raw material, the material utilization rate is above 95%. With the rapid development of the domestic titanium industry and the maturing of welding technology, the production efficiency of titanium welded pipe will be greatly improved, the quality stability, consistency and production efficiency will be higher, and can be cut to the required length according to customer requirements. The delivery time is short, the material utilization rate is high, and the unit cost will be lower than that of the seamless pipe.

Titanium seamless pipes are usually produced by processes such as rolling or drawing. A large amount of rolling oil, drawing oil, etc. will be used in the production process, and the production site is seriously polluted. After the titanium tube is rolled and drawn, the grease and dirt on the inner and outer surfaces of the pipe need to be degreased and pickled, and the pickling process is highly polluting to the environment. In order to ensure the health of the operators and protect the environment, it is necessary to increase the protective equipment and protective measures, thus increasing the capital investment and the production cost of the products. The titanium welded pipe is continuously mass-produced through an automated production line, with stable quality and high production efficiency. In addition to certain energy consumption such as water and electricity, there is almost no pollution to the environment.

With the deepening of the understanding of titanium welded pipes, the use of titanium welded pipes in the petrochemical industry will be recognized by the market, the scope of use will become wider and wider, and the market share will become larger and larger. Although titanium welded pipe has higher investment cost than common fluid conveying pipe, its cost is lower than that of titanium seamless pipe, and the investment cost of titanium welded pipe can be compensated in use from the life and maintenance cycle of titanium welded pipe. The use of titanium welded pipes in piping systems can reduce production costs by reducing the number of periodic maintenance, reducing downtime, improving product quality, and increasing pipeline life. In particular, in recent years, the global titanium industry is not very prosperous, and the competition is very fierce. The price of titanium welded pipe has been at a relatively low level. The enterprises in the petrochemical industry have lower investment costs in the early stage of selecting titanium welded pipes.

Although China’s titanium welded pipe industry has achieved rapid development, production technology and quality level have been greatly improved, titanium welded pipe has been widely used in electric power, seawater desalination, water treatment equipment, air conditioning equipment and other industries, but in the petrochemical industry, the use of titanium welded pipe Still in the promotion.