The manufacture of metal bellows begins with the selection of raw materials and passes through the main process links such as tube blank manufacturing, bellows forming, shaping, heat treatment, surface treatment, quality inspection, etc. to produce bellows that meet the design requirements.

Corrugated pipe is a thin shell component with complex shape and high performance requirements. It has many manufacturing processes and complicated processes. Therefore, in the manufacture of bellows, the correct process design and implementation is crucial.

制造 Corrugated pipe billet manufacturing process: Metal bellows pipe billet is divided into two types: seamless pipe billet and seam pipe billet.

The manufacture of seamless pipe blanks depends on different raw materials. Manufactured by different processes. Materials plus the factory can provide long stainless steel thin-walled seamless pipes with a wall thickness of 0.1 ~ 0.3mm and an outer diameter of φ10 ~ 60mm. This seamless pipe has a high surface finish and a large wall thickness tolerance (+/- 0.03mm). It is generally used to manufacture spiral bellows and ring bellows with low performance requirements. Metal bellows production plants can use 0.8 ~ 1mm thick metal sheet (strip) material or standard thin-walled pipes with wall thickness of 0.5 ~ 1mm. After various deep drawing or spinning drawing processes, various specifications of corrugated pipe blanks are manufactured. This process can produce tube blanks with high surface finish, small wall thickness tolerances (<= + /-0.005mm), and shorter lengths, which are used to make highly demanding corrugated pipes. The manufacture of seam tube blanks is generally made by selecting the required thickness of plate or strip, and using special welding after the reel. The quality of seam tube blanks depends directly on the quality of the plate (strip) material and welding quality. Generally, its wall thickness tolerance is easier to control. 1. Multiple thinning and deep drawing manufacturing process The multiple thinning and deep drawing manufacturing process is suitable for manufacturing corrugated pipe blanks with a length of less than 300 mm. The process mainly includes blanking, multiple deep drawing, multiple heat treatment and multiple thinning. Deepen. 2. Steel ball spinning thinning and stretching manufacturing process and equipment Steel ball spinning thinning and deep drawing is a process in which the blank is drawn and thinned by rolling between the convex mold, the concave mold and the steel ball under high speed rotation. method. The high-speed rotation of the punch (or die) drives the steel ball itself to rotate and rotate at high speed along the circumference of the blank. When the blank is fed axially on the punch, the material is affected by positive and tangential forces. Deformation. 3． Welded pipe blank manufacturing process The manufacture of corrugated pipe blank by welding method is a process method with high production efficiency, low cost, easy control of wall thickness and strong adaptability. At present, it is mostly used for manufacturing large diameter corrugated pipe blanks for expansion joints and pipe blanks for hoses. The welding of corrugated pipe blanks currently uses mainly gas-shielded DC argon arc welding, micro-arc plasma welding, and laser welding. The welding thickness is 0.1mm ~ 1mm, and the materials are 1Cr18Ni9Ti, 0Cr18Ni9, 00Cr17Ni14Mo2 and GH169. 4． Manufacturing of multi-layer bellows tube blanks Multi-layer bellows have higher pressure resistance, smaller stiffness and larger displacement, and are often used to manufacture metal expansion joints and bellows for leak-free valves. Multi-layer bellows used for expansion joints generally have an inner diameter of more than φ80mm. Most of its tube blanks are reserved for the casing gap when welding the tube blanks, and after welding into the corresponding layer of tube blanks, the casing can be sequenced. Most of the multi-layer bellows for valves have an inner diameter less than φ60mm, and their multi-layer pipes are broken, and there are different manufacturing methods. One method is to manufacture the corresponding layers of tube blanks by rolling or spinning according to the reserved casing gaps, and the tubes are sequentially sleeved into multilayer tube blanks. Another method is to select a basic tube blank, and then use a reduction or expansion process to change the tube blank into the corresponding layer. It is then sequentially jacketed into multilayer tube blanks. Because this modification is less accurate than the diameter tolerances of rolled and spin-rolled pipes, the casing clearance is slightly larger. According to the different requirements of the interlayer quality of the corrugated pipe products for the casing of the multilayer pipe blank, two methods can be used: the hard casing and the soft casing. After the manufactured hard pipe blank is cleaned, the inner and outer surfaces are directly sleeved, and then solid solution or annealing heat treatment is performed. This method requires heat treatment and pickling after the casing, which makes it difficult to ensure the smooth surface of the interlayer and no excess between the layers. The hard tube blank is first heat treated and pickled. After obtaining the smooth surface quality, it is softened Under the state of the casing, the interlayer quality of the bellows product can be reliably guaranteed. Corrugated tube forming process and equipment Corrugated tube corrugated forming is the key process of manufacturing corrugated tube. The commonly used forming methods are: hydraulic forming, mechanical forming, rubber forming, welding forming, electrochemical forming, etc. Hydroforming and mechanical forming are common processes in the metal bellows manufacturing industry. It is suitable for manufacturing U-shaped, S-shaped, Ω-shaped corrugated pipes with good plasticity of copper alloy, stainless steel, elastic alloy and high-temperature alloy, etc. It has wide adaptability and good processability.

  1. Hydroforming process Hydroforming is the most widely used and most common forming method for metal bellows. It is mainly used to make annular bellows. It can form bellows with wall thickness of 0.08 ~ 4mm. Corrugated pipe hydroforming is a process in which a pipe blank is formed into a corrugated pipe in a special mold when the stress exceeds the yield strength under the liquid pressure of the inner wall.

  2. Mechanical forming process The mechanical forming of bellows includes spinning, rolling and mechanical expansion. Generally speaking, mechanical forming has the advantages of simple process, easy tool manufacturing, and high production efficiency. At the same time, there are disadvantages such as rough manufacturing and low performance. It is mostly used in the manufacture of spiral bellows, bellows expansion joints, and large-diameter thick-wall bellows.

3. Rubber forming process Rubber forming process is a kind of bulging process. It uses rubber as a forming convex die, which deforms like a rubber convex die under pressure. The tube blank is formed into a corrugated tube according to a concave cavity. The forming method is usually a single-wave continuous forming.

4. Mechanical hydraulic forming Mechanical hydraulic forming is a method in which a pipe blank is first rolled inward by a rolling method, and then expanded outward by a hydraulic method to form a corrugated pipe. The corrugated pipe formed by mechanical hydraulic pressure has strengthened due to the wave crest and trough, which have played a good role in improving the elasticity of the corrugated pipe. It is an effective process method for manufacturing deep wave corrugated pipes.

 

Heat treatment of bellows

Heat treatment is an essential and important process in the manufacturing process of bellows and in obtaining elastic properties of bellows. Manufacture of bellows materials can be divided into work hardening type and dispersion strengthening type according to the strengthening method. Commonly used hardening materials include H80, QSn6.5-0.1, NiCu28-2.5-1.5, 1Cr18Ni9Ti and 00Cr17Ni14Mo2. After recrystallization annealing or quenching and solid solution treatment, they form a single α solid solution or a single austenite. They have excellent plastic deformation properties, can meet the requirements of diameter reduction, thinning, and forming processes, and cold deformation during corrugated tube forming. In the process, the material is work hardened, such as GH4132, GH4169 and so on. They form a single supersaturated solid solution in the quenched solid solution state, have excellent plasticity, and can meet the plastic deformation properties of cold working. During the aging heat treatment after the bellows are formed, the dispersed strengthening phase precipitates to strengthen the material, thereby making the bellows Get excellent bullet ratio performance. The purpose of the heat treatment of the corrugated pipe is twofold: first, to eliminate work hardening and restore plasticity during the manufacturing process of the corrugated pipe; and second, to strengthen the material and obtain elasticity. Corrugated tube heat treatment has internal and external quality requirements. Intrinsic quality is the material's certain microstructure, grain size and mechanical properties after heat treatment; external quality is mainly the degree of surface oxidation after heat treatment.

 

Surface treatment of bellows

  1. Surface treatment process of copper alloy The surface treatment process of copper alloy bellows includes oil removal, loose oxide scale, weak pickling, bright pickling and passivation.

  2. Surface treatment process of stainless steel The surface treatment process of stainless steel bellows is mainly degreasing, loosening oxide scale and pickling.

 

Shaping process of bellows

After the bellows is formed, the wave length and wave shape of the bellows are different from the requirements of the pipette due to the elastic rebound, and it must be shaped. For corrugated pipes made of work-hardened materials, manual and mechanical shaping are generally used. For the corrugated tube of dispersion hardened material, it is put into the aging fixture for aging, so that the corrugated tube is shaped to achieve the shaping effect. Stable treatment process of the corrugated pipe During the processing of the corrugated pipe, internal stress will be generated, which will cause it to spring and the geometric dimension to be unstable. The purpose of the stable treatment of the bellows is to eliminate stress, stable performance and stable geometric size. The stabilization treatment of the bellows includes a thermal stabilization treatment process and a mechanical stabilization treatment process. Under normal circumstances, only thermal stabilization is required, and mechanical stabilization is required only when there are special requirements.