Development of titanium and titanium alloy longitudinal welded pipe in China
In this paper, the development history, application, production technology and product standards of titanium and titanium alloy longitudinal welded pipe in China are introduced and commented in detail, and the future development trend is predicted. This paper introduces the current production process of a single 6 meter long titanium and titanium alloy longitudinal welded pipe. The titanium welded pipe produced by this process can not only ensure uniform wall thickness, but also reduce the splicing girth weld in the pipeline installation. It fills the domestic blank in the production of large diameter single 6m long titanium and titanium alloy longitudinal welded pipe. It is pointed out that the product standard of large diameter titanium and titanium alloy welded pipe has not been formulated and published so far, which has a certain impact on the development of large diameter titanium and titanium alloy welded pipe industry.
Table of Contents
- 1 Introduction
Development of titanium welded pipe in China
- 2.1 Working condition of titanium welded pipe
- 2.2 Development process of titanium welded pipe
- 2.3 Brief introduction of production process of small diameter titanium longitudinal welded pipe
- 2.4 Brief introduction of production process of large diameter titanium longitudinal welded pipe
- 2.5 Application of titanium welded pipe
- 3 Brief introduction of Chinese titanium welded pipe standards and specifications
- 4 Prospect of titanium welded pipe
With the development of China’s industrial technology and the introduction of new technologies, pipeline corrosion is an extremely serious damage factor affecting the development of modern industry. The pipeline corrosion of industrial, mining and chemical enterprises, such as running, emitting, dripping and leakage, not only affects the normal production, but also reduces the product quality, pollutes the environment, wastes energy and increases the probability of potential safety hazards The long-term existence has seriously hindered the progress of China’s industrialization. Therefore, a kind of pipeline with the characteristics of corrosion resistance, high strength, wear resistance, low cost, low pollution and easy maintenance is imperative.
Titanium and titanium alloy straight seam welded pipe (hereinafter referred to as “titanium welded pipe”) has high strength, light weight, good heat transfer and corrosion resistance. As a substitute for steel and stainless steel pipe, the use of large diameter titanium welded pipe in industrial pipeline has also been recognized by the market. Although the investment cost of titanium welded pipe is higher than that of common fluid transportation pipeline, its cost is about 15% – 25% lower than that of titanium seamless pipe. From the analysis of service life and maintenance cycle of titanium welded pipe, the investment cost of titanium welded pipe can be compensated in use. The use of titanium welded pipe in pipeline system can reduce the number of regular maintenance, reduce the shutdown time, improve product quality and improve product quality Pipe life to reduce production costs.
Up to now, titanium has been widely used in chemical, petroleum, petrochemical, vacuum salt making, pharmaceutical, seawater desalination, electric power and other industries. In particular, titanium can better resist the erosion of chloride ions, so titanium materials are used more in the medium related to chlorine, such as the production of ion-exchange membrane caustic soda, a large number of titanium materials have been used in manufacturing equipment, pipes and pipe fittings. There are also formic acid, acetic acid, propylene oxide and other chemical projects are using titanium pipeline transportation medium to solve the pipeline corrosion problem and prolong the service life of the pipeline. In titanium pipeline, the chemical composition, mechanical properties and process performance of titanium welded pipe and titanium seamless pipe are basically the same. However, titanium welded pipe has the advantages that titanium seamless pipe does not have in practical application: titanium welded pipe can realize the transportation of large diameter and super large diameter flow, and the economy and applicability of titanium welded pipe are easier to be popularized and used.
As a relatively unique form of titanium pipe products, titanium welded pipe is a kind of product which is formed by rolling titanium plate or titanium strip into tube shape and welding gap by tungsten inert gas welding. Due to its excellent corrosion resistance and high specific strength, it has attracted wide attention and application in the industrial field since it was developed. At present, small diameter titanium welded pipe (nominal size DN 100 and below) has been used in various condensers and heat exchangers, gradually replacing titanium seamless pipe as the preferred material for heat exchange pipe, and large diameter titanium welded pipe (nominal size above DN 100) is also widely used as industrial pipeline in chemical, petroleum, petrochemical, salt making, pharmaceutical and marine engineering industries.
In the early days of the founding of the People’s Republic of China, titanium was only used in the military industry, belonging to the national strategic control materials. It was not used in the chemical industry of civil industry until the 1970s. Up to now, it has a history of more than 40 years. As an excellent corrosion-resistant structural material, titanium has established its irreplaceable position. As an ideal material for chemical transportation of corrosive medium pipeline, titanium welding More and more attention has been paid to the design of equipment and pipeline.
Working condition of titanium welded pipe
As we all know, titanium welded pipe is often used in corrosive environment because of its excellent characteristics. When the liquid with corrosive medium flows through the titanium welded pipe, the corrosion medium will slightly erode the inner wall of the welded pipe. The corrosion degree of titanium welded pipe is different with the medium and its concentration. In general, the corrosion rate of high concentration medium is higher than that of low concentration medium in the same medium, the corrosion rate of medium containing halogen is higher than that of other salt solution under boiling condition, and the corrosion rate of titanium material with high inner wall bearing pressure under the same wall thickness and medium is higher than that of titanium material with low inner wall bearing pressure.
Therefore, the service life of titanium welded pipe mainly depends on the corrosive medium, service environment and bearing pressure.
Development process of titanium welded pipe
Due to the constraints of raw materials and processing technology, the production technology of titanium welded pipe has been in the hands of a few professional manufacturers in Japan, the United States, France, Russia and other countries for many years. Therefore, compared with other titanium processing products, China’s titanium welded pipe started late, and its early development was relatively slow, which directly affected the formation of titanium welded pipe product standardization. So far, the national standard of titanium welded pipe is not perfect.
Baoji Titanium Pipe Co., Ltd. can not produce complete titanium pipe from China since 1985. However, at that time, it was not possible to produce titanium strip coil, which is the raw material of titanium welded pipe. Due to the multiple influences of technology introduction and digestion and raw material procurement difficulties, the production line did not really have production capacity until the end of 1990s, with an annual production capacity of only about 200 tons.
In the mid-1990s, China’s Changzhou and France’s valtimet (France, titanium and the United States) Co., Ltd. jointly established Farino Great Wall Welded Pipe Co., Ltd., and introduced three small-diameter welded pipe production lines to produce titanium welded pipe. However, due to the factors that domestic titanium coil production technology is not up to standard, most of the raw materials are imported from Japan and the United States. Due to the limitation of quality and production, the domestic titanium welded pipe market was not really formed at that time.
With the breakthrough of domestic titanium strip production technology, Yaang Pipe Industry Co., Limited has successfully realized batch production by adopting cold-rolled sheet and strip produced. The thick wall titanium welded pipe welding technology developed by the company fills in the blank of domestic welded pipe production technology. At the same time, the use of titanium strip coil in Yaang Pipe Industry Co., Limited also fills the blank of producing titanium welded pipe with domestic titanium strip.
At the beginning of this century, with the emergence of the problems of running, emitting, dripping and leaking caused by corrosion in industrial pipeline system, the demand for corrosion-resistant large-diameter titanium welded pipe is increasing day by day. Some titanium equipment manufacturers use rolling method to produce short and large diameter titanium welded pipe (single pipe length is no more than 3m). However, due to the immature production technology, there are some problems such as small production capacity, low productivity, unstable product quality and unfavorable installation.
Brief introduction of production process of small diameter titanium longitudinal welded pipe
The processing of small-diameter titanium welded pipe is based on titanium strip as raw material, which is extruded on a special roller continuous forming machine after uncoiling, and the final product is completed on the overall production line. This method is continuous production, which has the advantages of large production capacity, high productivity, good molding quality and labor saving. Among them, there are many forming methods of roller continuous forming machine, and W bending forming method is mostly used for titanium welded pipe.
Brief introduction of production process of large diameter titanium longitudinal welded pipe
The production of large diameter titanium welded pipe in China is limited by the technical level and small market demand, and the intermittent production process is often used. The raw material is titanium coil or titanium wide plate, which is pressed by special equipment.
There are also several forming methods for large diameter titanium welded pipe forming equipment. For titanium welded pipe, single radius bending deformation method and multi radius bending deformation method are commonly used. Compared with single radius bending deformation method, the diameter of multi radius bending deformation method is not limited. Single radius bending method is only applicable to the outer diameter of standard pipe, but not to the production of non-standard pipe. At present, China’s demand for large-diameter titanium welded pipe is still relatively low, which is related to the production cost, production technology and product standardization.
Application of titanium welded pipe
Titanium welded pipe was first used in the field of aerospace because of its high specific strength. It can reduce the weight of aircraft, and at the same time, it can also prolong the service life and reduce the maintenance time.
At the beginning of this century, the civil market of titanium materials and products has been formed. Titanium welded pipe is widely used in petrochemical, salt making, pharmaceutical and other industries because of its excellent corrosion resistance and thermal conductivity.
With the rapid development of modern industry, the natural environment and water resources are greatly polluted, which makes the copper and copper alloy pipes and stainless steel pipes which have excellent performance in pure water and clean sea water easily suffer from serious corrosion leakage. Therefore, titanium welded pipe, as a substitute for other metal materials, is also used in seawater desalination equipment.
Although the price of titanium welded pipe is slightly higher, the service life of the whole titanium pipe is greatly improved, the maintenance cost is reduced, and the environmental pollution is small, which is in line with the overall requirements of building an economical and environmental friendly society.
Brief introduction of Chinese titanium welded pipe standards and specifications
The production technology of titanium welded pipe in China develops slowly and starts late, so the standards and specifications of titanium welded pipe are still in development and improvement.
In 1984, China was compiled by Baoji Nonferrous Metal processing plant and approved by the State Bureau of technical supervision. The national standards GB4367-84 “welding and welding rolling titanium tubes” and GB4368-84 “welding rolled titanium tubes for heat exchangers and condensers” were issued in China. This standard has been implemented for nearly 11 years, guiding and standardizing the production and manufacturing of small-diameter titanium welded pipe at that time. The promulgation of these two standards represents the beginning of standardization of small-diameter titanium welded pipe in China, and is the main reference document for the production, distribution, design and construction of titanium welded pipe in China.
With the development and maturity of titanium welded pipe manufacturing technology, in order to make the standard better guide the production and manufacturing of titanium welded pipe in China, the national standard GB / T3624-1995 “titanium and titanium alloy pipe” (replacing GB 4367-84) and GB / T “titanium and titanium alloy tube for heat exchanger and condenser” (replacing GB4368-84) were revised and issued in October 1995. These two standards effectively combine titanium seamless pipe and titanium welded pipe into one standard, which represents that the production and manufacturing of small diameter titanium seamless pipe and titanium welded pipe has entered the normal development level in China.
Prospect of titanium welded pipe
At present, the application of titanium materials in civil industry accounts for more than 80% of the total amount of titanium materials in China. In the 12th Five Year Plan, the state has increased the investment and reconstruction of energy, chemical industry, marine engineering and other projects. It is planned that China’s petroleum, chemical industry, synthetic fiber, salt making, alkali making, offshore engineering and other industries are in a new period of development, renewal and transformation. In the past, petroleum and chemical equipment mostly use ordinary steel or stainless steel, and the equipment structure is obsolete, which affects the quality of products. Most of the anticorrosive materials used in the new modern equipment are required to have strong corrosion resistance. For example, the sodium ions and chloride ions in the ion-exchange membrane caustic soda plant are highly acidic and alkaline after being separated by the ion-exchange membrane method or the membrane method. The temperature is about 80 ℃. It is difficult to resist the corrosive effect of medium when the pipeline is made of ordinary steel and stainless steel materials. Therefore, titanium materials are widely used to replace steel or stainless steel materials to make electrolyzers, separators, containers, pipes, pipe fittings and pump valves at home and abroad. Good use value and economic benefits are obtained. About 300-500 tons of titanium materials are used in the annual output of 1 million tons of caustic soda plant, among which 60-100 tons of titanium pipes and fittings are used. The application scope of titanium welded pipe will be gradually expanded, such as offshore platform, seawater desalination device and salt water cooling device in power plant.
Due to the high cost of titanium, there are certain restrictions on the wide application of titanium welded pipe. In order to reduce the cost of titanium pipe, some domestic manufacturers have successfully developed titanium / steel composite pipe (base pipe material is steel, lining or inner cover material is titanium material) referring to SY6623-2005 bimetallic composite pipe. When the process is mature, the cost of titanium / steel composite pipe is lower than that of titanium pipe The composite pipe will be the development direction of anti-corrosion pipeline in the future.
Source: Network Arrangement – China Titanium Alloy Welded Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.epowermetals.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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