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.

A bellows is a thin shell component with complex shapes 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.

 

Corrugated pipe blank manufacturing process:

 

Metal bellows pipe blanks are divided into two types: seamless pipe blanks and seam pipe blanks.

 

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 tube has a high finish,

However, the wall thickness tolerance is relatively large (+/- 0.03mm), which is generally used to manufacture spiral bellows and annular bellows with low performance requirements. Metal bellows production plants can use 0.8 ~ 1mm thick metal plate (strip) material or standard thin-walled pipes with wall thickness of 0.5 ~ 1mm.

After several 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 pipe blanks is generally made by selecting the required thickness of plate or strip, and using special welding butt welding after the roll. The quality of seam tube blanks depends directly on the quality of the plate (strip) material and welding quality. Generally speaking, its wall thickness tolerance

Easier to control.

 

1. Multiple thinning and drawing manufacturing process

 

Multiple thinning and drawing manufacturing process is suitable for making corrugated pipe blanks with tube length less than 300mm. The process mainly includes blanking, multiple drawing, multiple heat treatment and multiple thinning and drawing.

 

2. Spin ball thinning and stretching manufacturing process and equipment

 

The spinning and thinning of the steel ball is a process method in which the blank is drawn and thinned by rolling between the punch, the die and the steel ball under high speed rotation. The high-speed rotation of the male die (or female die) drives the steel ball itself to rotate along the periphery of the blank.

High-speed rotation, when the blank is subjected to axial feed on the punch, the material is deformed by the forward and tangential forces.

 

3． Welded pipe blank manufacturing process

 

制造 The manufacture of corrugated pipe blanks by welding 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． Manufacture of multilayer corrugated pipe blanks

 

Multilayer bellows have higher pressure resistance, but also have less rigidity and larger displacement. They are commonly used to manufacture metal expansion joints and bellows for leak-free valves.

 

The multi-layer bellows for expansion joints generally has 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 of less than φ60mm. The multi-layer pipe is 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.

 

(2) The casing of multi-layer pipe blanks can be used in two ways: hard casing and soft casing according to the requirements of the interlayer quality of the corrugated tube products. 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. State of the casing, can make bellows production

The quality between layers is reliably guaranteed.

 

Bellows forming process and equipment

 

的 Corrugated forming of corrugated pipe is the key process of manufacturing corrugated pipe. The commonly used forming methods are: hydraulic forming, mechanical forming, rubber forming, welding forming, electrochemical forming, etc.

 

Hydraulic forming 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. It has a wide range of

Adaptability and good workability.

 

1. Hydroforming process

 

Hydraulic forming 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 subjected to liquid pressure on the inner wall when the stress exceeds the yield

After strength, it is formed into a corrugated tube in a special mold.

 

2. Mechanical forming process

 

Mechanical forming of bellows, including spin forming, roll forming and mechanical expansion.

 

Generally speaking, mechanical forming has the advantages of simple process, easy tooling 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 hydroforming

 

Mechanical hydroforming is a method of rolling the tube blank inwardly by rolling method, and then expanding outward to form a corrugated tube by hydraulic method. The corrugated pipe formed by mechanical hydraulics has been strengthened due to the wave crests and troughs participating in the deformation.

It plays a good role in improving the elasticity of the bellows, and is an effective process method for manufacturing deep wave bellows.

 

 

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 corrugated pipe heat treatment is twofold: one is to eliminate work hardening and restore plasticity during the manufacturing process of the corrugated pipe; the other is to strengthen the material and obtain elasticity.

 

Corrugated pipe 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

 

Stainless steel bellows surface treatment process 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 bellows 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 bellows:

 

In the process of 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 stable treatment of corrugated pipe includes thermal stabilization process and mechanical stabilization process. Under normal circumstances, only thermal stabilization is required, and mechanical stabilization is required only when there are special requirements.