The manufacture of metal bellows is based on the selection of raw materials, through the main process steps of tube blank manufacturing, bellows forming, shaping, heat treatment, surface treatment, quality inspection, etc., to produce bellows that meet the design requirements.
The 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, proper process design and implementation are critical.
Corrugated tube blank manufacturing process
Metal bellows tube blanks are divided into two types: seamless tube blanks and seamed tube blanks.
The manufacture of seamless tube blanks is based on different raw materials. Made using different processes. The material plus 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, but a large wall thickness tolerance (+/- 0.03 mm), which is commonly used to make spiral bellows and ring bellows with less demanding performance. The metal bellows production plant can use various metal plate (belt) materials with a thickness of 0.8~1mm or standard thin-walled pipes with a wall thickness of 0.5~1mm to manufacture corrugated pipe blanks of various specifications through multiple deep drawing or spinning and drawing processes. This process can produce tube blanks with high surface finish, small wall thickness tolerance (<= +/- 0.005 mm) and short length for the manufacture of high requirements bellows.
The manufacture of the seamed blank is generally carried out by using a plate or strip of the required thickness, and after the reel is welded by special welding. The quality of the seamed tube blank depends directly on the quality of the sheet (tape) and the quality of the weld. In general, the 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 the manufacture of bellows blanks with a tube blank length of less than 300 mm. The process mainly includes blanking, multiple drawing, multiple heat treatment and multiple thinning and drawing.
2. Steel ball spinning and thinning stretching manufacturing process and equipment
The spinning and thinning of the steel ball is a process in which the blank is deepened and thinned by pressing between the punch, the die and the steel ball under high-speed rotation. The high-speed rotation of the punch (or the die) drives the steel ball itself to rotate and rotates at a high speed along the circumference of the blank. When the blank is axially fed on the punch, the material is subjected to positive and tangential forces. Deformation.
3. Welding tube blank manufacturing process
The method of manufacturing a bellows tube by welding is a process method with high production efficiency, low cost, easy wall thickness control and strong adaptability. At present, it is widely used for manufacturing large-diameter bellows tube blanks for expansion joints and for manufacturing tube blanks for hoses. The welding of bellows tube blanks is mainly carried out by gas-protected 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 multi-layer bellows tube blank
Multi-layer bellows have high pressure resistance, small rigidity and large displacement, and are commonly used to manufacture metal expansion joints and bellows for leak-free valves.
Multi-layer bellows for expansion joints generally have an inner diameter of more than φ80mm. Most of the tube blanks are reserved for the tube blanks. After the tube blanks are respectively welded into the corresponding layers, the casings can be sequentially ordered.
Most of the multi-layer corrugated tubes for valves have an inner diameter of less than φ60 mm, and the multi-layer tubes are broken, and there are different manufacturing methods. One is to separately manufacture the corresponding layer tube blanks by rolling or spinning process according to the reserved casing gap, and sequentially order the casing into a multilayer tube blank. Another method is to select a basic tube blank, and then use the process of reducing or expanding diameter to change the tube blank of the corresponding layer. The sleeves are then sequentially ordered into a multilayer tube blank. Since this modification is less accurate than the diameter tolerance of the rolling and spinning tubes, the reserved sleeve gap is slightly larger.
The casing of the multi-layer tube blank can be made according to the requirements of the corrugated tube product for the quality of the interlayer, and the two methods of the hard casing and the soft casing can be adopted. After the finished hard tube blank is cleaned, the inner and outer surfaces are cleaned, and then directly sleeved, and then subjected to solid solution or annealing heat treatment. This method is difficult to ensure that the interlayer surface is smooth and there is no excess between the layers due to the heat treatment and pickling process. The hard tube blank is first subjected to heat treatment and pickling, and then softened after obtaining a smooth surface quality. The casing under the state can ensure the quality of the interlayer of the bellows product.
Bellows forming process and equipment
Corrugation of bellows is a key process in the manufacture of bellows. At present, the commonly used forming methods are: hydroforming, mechanical forming, rubber forming, welding forming, electrochemical forming, and the like.
Hydroforming and mechanical forming are common processes in the metal bellows manufacturing industry. It is suitable for the manufacture of U-shaped, S-shaped and Ω-shaped corrugated pipes of copper alloy, stainless steel, elastic alloy and high-temperature alloy with good plasticity, and has wide adaptability and good processability.
1. Hydroforming process
Hydroforming is one of the most widely used and most common forming methods for metal bellows. It is mainly used to manufacture annular bellows, and can form bellows with wall thickness of 0.08~4mm. The hydroforming of the bellows is that the tube blank is formed into a bellows in a special mold after being subjected to the liquid pressure of the inner wall and when the stress exceeds the yield strength.
2. Mechanical forming process
Mechanical forming of bellows, including spin forming, roll forming, and mechanical expansion.
Generally, mechanical forming has the advantages of simple process, easy tooling manufacturing, and high production efficiency. At the same time, there are also shortcomings such as rough manufacturing and low performance. It is widely used in the manufacture of spiral bellows, corrugated expansion joints, and large diameter thick wall corrugated pipes.
3. Rubber forming process
The rubber forming process is one of the bulging processes. The utility model adopts rubber as a forming punch, deforms like a plastic punch under pressure, and forms a bellows according to a concave mold cavity, and the forming method is usually a single wave continuous forming.
4. Mechanical hydroforming
Mechanical hydroforming is a forming method in which a tube blank is first rolled inward by a rolling method, and then a bellows is formed by a hydraulic method. The mechanically hydraulically formed bellows has been strengthened due to the participation of the peaks and troughs, and has played a good role in improving the elasticity of the bellows. It is an effective process for manufacturing deep wave bellows.
Heat treatment of bellows
Heat treatment is an indispensable and important process in the manufacturing process of the bellows and in obtaining the elastic properties of the bellows.
The corrugated pipe material can be divided into two types: work hardening type and dispersion strengthening type according to the strengthening method. Commonly used hardening materials are H80, QSn6.5-0.1, NiCu28-2.5-1.5, 1Cr18Ni9Ti and 00Cr17Ni14Mo2. After recrystallization annealing or quenching solution treatment, they form a single α solid solution or single austenite, which has excellent plastic deformation properties, can meet the requirements of variable diameter, thinning and forming process, and cold deformation during bellows forming. During the process, the material is work hardened, GH 4132, GH 4169, and the like. In the quenching and solid solution state, they form a single supersaturated solid solution, which has excellent plasticity and can satisfy the plastic deformation property of cold working. When the aging heat treatment after bellows forming, the dispersed strengthening phase is precipitated to strengthen the material, thereby making the bellows Get excellent ratio performance.
The purpose of heat treatment of bellows is twofold: one is to eliminate work hardening and restore plasticity during the manufacturing process of bellows; the other is to strengthen the material and obtain elasticity.
Corrugated tube heat treatment has both intrinsic and extrinsic quality requirements. The intrinsic quality is obtained by heat treatment to obtain a certain state of the structure, grain size and mechanical properties of the material; the external quality is mainly the degree of surface oxidation after heat treatment.
Surface treatment of bellows
1. Copper alloy surface treatment process
The surface treatment process of copper alloy bellows includes processes such as degreasing, loose scale, weak pickling, bright pickling and passivation.
2. Stainless steel surface treatment process
The surface treatment process of stainless steel bellows is mainly degreasing, loosening and oxidizing scale and pickling.
Bellows shaping process
After the bellows is formed, the bellows and the wave shape of the bellows are different from the requirements of the suction meter due to the elastic rebound, and shaping must be performed.
For bellows made of work hardened materials, both manual and mechanical shaping methods are generally used. For the bellows of the dispersion hardened material, it is placed in the aging fixture to set the bellows to shape the corrugated tube to achieve the shaping effect.
Stable processing of bellows
During the processing of the bellows, internal stresses are generated, making it elastic and unstable in geometry. The purpose of stabilizing the bellows is to eliminate stress, stability, and stable geometry.
The stable treatment of the bellows includes a heat stabilization treatment process and a mechanical stabilization treatment process. Under normal circumstances, only heat stabilization treatment is required, and mechanical stabilization is required only when there are special requirements.
Hospital Furniture,Medical Equipment,Surgical Equipment
Pukang Medical Instruments Co., Ltd. , http://www.xs-medicalbeds.com