Introduction to common pressure welding
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Welding generally refers to the welding of metals. It is a forming method that uses heating or pressure, or both at the same time, to create inter-atomic bonding forces between two separate objects and connect them into one body. Depending on the degree of heating and process characteristics during the welding process, welding methods can be divided into three major categories. They are fusion welding, pressure welding, and brazing, which are the three main welding methods. Today’s article mainly introduces pressure welding:
1.What is pressure welding?
Pressure welding is a metal welding process that heats the contact surfaces of metal workpieces to the welding temperature by applying a certain amount of pressure, and then maintaining pressure on them for a certain period of time to achieve welding. Pressure welding usually requires auxiliary heating sources, such as resistance heating, friction heating, arc heating, etc., to heat the joint surface to the welding temperature. During the welding process, pressure not only helps ensure the fit of the joint surfaces, but also helps promote the diffusion of metal atoms, resulting in a strong welded joint.
Pressure welding is a common metal welding method that is widely used in various industrial fields, such as automobile manufacturing, aerospace, electronic equipment manufacturing, etc. It has the advantages of fast welding speed, high welding quality and high production efficiency, so it has been widely used in mass production.
2.Classification of pressure welding
Whether heated or not during the welding process, a pressurized welding method is required. Common pressure welding includes spot welding, seam welding, cladding welding, resistance welding, friction welding, cold pressure welding, diffusion welding, explosion welding, etc. Different pressure welding techniques are different. Let’s briefly introduce these pressure welding methods respectively:
(1) Spot welding
Spot welding is a common metal welding process, also known as resistance spot welding, mainly used to join thin metal workpieces. In spot welding, the welding electrode applies a certain amount of pressure to heat the contact points of two or more metal workpieces to the melting temperature, and then cuts off the current, allowing the metal to rapidly cool and solidify under the pressure to form a welding point. In this way, a spot weld can be completed in a very short time.
Features of spot welding include:
Fast: The welding time of spot welding is usually very short, generally tens to hundreds of milliseconds, so the welding speed is very fast.
Efficient: Due to the short welding time, spot welding is suitable for mass production and can improve production efficiency.
Suitable for thin sheet metal: Spot welding is often used to join thin sheet metal, such as automobile bodies, home appliance casings, etc.
Simple operation: The operation of spot welding equipment is relatively simple and does not require complex process control.
Small welding area: The heat generated by spot welding is localized around the welding electrode contact point, so it has less impact on the surrounding workpiece
Applicable materials include:
Thin sheet metal: Spot welding is mainly used to connect thin sheet metal, such as steel plates, aluminum plates, etc., usually with a thickness between 0.5mm and 3mm.
Stainless steel: Stainless steel is a common spot welding material used in automobile manufacturing, kitchenware manufacturing and other fields.
Aluminum alloy: Aluminum alloy is also often used for spot welding, especially in the field of automobile manufacturing, for joining body parts, etc.
Galvanized steel sheet: In the manufacturing of home appliances, such as washing machines, refrigerators, etc., galvanized steel sheets are commonly used for spot welding.
(2) Seam welding
Seam welding is a common metal welding process. It is mainly used to weld the seam of two metal workpieces into a continuous weld. Unlike spot welding, seam welding is generally suitable for welding longer welding lines and the welding seam is wider.
Seam welding is usually used to join the seams of metal sheets, such as manufacturing metal tanks, pipes, frames and other workpieces that require sealing and strength. Its advantages include fast welding speed and high production efficiency, so it is widely used in many industrial fields.
Seam welding characteristics
Continuous welding: Seam welding is continuous welding at the seams of metal workpieces to form a continuous weld. This continuous welding method ensures the strength and sealing of the welded joint.
Suitable for long welding lines: Seam welding is suitable for situations where welding needs to be carried out along long seams, such as pipes, metal tanks, etc.
Larger welding area: Since the welding is performed along the seam, the welding area is relatively large and can provide high welding strength.
High production efficiency: Seam welding usually uses automated equipment for continuous welding, so it can achieve high-efficiency production and is suitable for large-scale production lines.
Less deformation: The welding area is locally heated during seam welding. Deformations are usually smaller than other methods, helping to maintain the geometry of the workpiece.
Suitable for a variety of metal materials: Seam welding is suitable for joining a variety of metal materials, including stainless steel, aluminum alloy, carbon steel, etc.
Stable welding quality: Due to the continuous welding method, seam welding can provide more stable welding quality and consistency, which is beneficial to ensuring product quality.
(3) Cladding welding
Cladding is a welding technology that is usually used to coat the base metal surface with a layer of corrosion-resistant or special-performance materials to improve the performance of the base metal or protect the base metal. Cladding typically involves covering the surface of a base metal with one or more alloy materials, forming a protective layer that is sealed and has the desired properties. The specific process of cladding welding usually includes steps such as selecting appropriate cladding materials, preparing the base metal surface, controlling welding parameters, performing cladding welding, and performing subsequent processing.
Cladding welding features:
Protection: Cladding welding forms a protective alloy layer on the surface of the base metal, which can effectively protect the base metal from corrosion, wear, high temperature and other external environments, thus extending the service life of metal components.
Customizability: Appropriate coating materials can be selected according to specific needs to have specific properties, such as corrosion resistance, high temperature resistance, wear resistance, etc., to meet the requirements of different engineering projects.
Material saving: Cladding welding can coat a layer of alloy material on the surface of the base metal without having to make the entire component into alloy material, thus saving the use of expensive alloy materials.
Wide applicability: Cladding welding is suitable for metal parts of various shapes and sizes. It can be applied to various metal materials such as steel, aluminum, copper, etc., and is suitable for different industries and fields.
Repair and restoration: Cladding welding can be used to repair the surface of damaged metal parts, such as repairing corroded, worn or damaged parts, to extend their service life.
Process flexibility: The cladding welding process is relatively flexible and can adapt to different production environments and process requirements. It is easy to operate and easy to control.
Improved surface quality: After cladding welding, the base metal surface usually has a better finish and flatness, which helps to improve the overall surface quality and aesthetics.
Environmentally friendly: Compared with other surface treatment methods, cladding welding usually does not require the use of chemicals or solvents, produces less pollution, and meets environmental protection requirements.
(4) Resistance welding
Resistance welding presses the parts to be welded between two electrodes and passes current. The resistance heat generated by the current flowing through the contact surface and adjacent areas of the parts is used to process them into a molten or plastic state, forming a metal bond under pressure. A welding method. The basic principle of resistance welding is to use resistance heating to melt metal, pressurize it and combine it.
Resistance welding features:
High efficiency: fast welding speed, suitable for mass production.
The welding area is locally heated to reduce deformation.
Suitable for various metal materials.
High degree of automation and easy to operate.
(5) Friction welding
Friction welding is a solid-state welding method that uses the heat and pressure generated by friction on the contact surface of the workpiece to plasticize and flow the material, and achieve connection through interface molecular diffusion and recrystallization. The heat of friction welding is concentrated on the joint surface, the heat affected zone is narrow, and the joint surface generally does not melt. There are many methods of friction welding. According to the friction action trajectory and process characteristics, there are continuous drive friction welding, energy storage friction welding, phase control friction welding, inertial friction welding, orbital friction welding and friction stir welding.
Friction welding characteristics
Solid state welding: No additional welding materials are required during the welding process, the welding is done in solid state conditions between the workpieces.
No melting: The welding process does not involve the melting of metal, so there are no problems such as pores and cracks caused by molten metal.
High efficiency: Friction welding is fast, the welding time is usually between a few seconds and tens of seconds, and is suitable for mass production.
Wide applicability: Friction welding is suitable for welding various metals and alloy materials, including aluminum, titanium, nickel, steel, etc.
Low heat input: Since no metal is melted during the welding process, the heat input of friction welding is relatively low, which can reduce workpiece deformation and welding residual stress.
Environmentally friendly: There is no welding smoke and harmful gas emissions during the friction welding process, and there is less environmental pollution.
(6) Cold pressure welding
Cold pressure welding is a method that uses pressure to plastically deform the metal to be welded at room temperature to achieve solid-state welding. During pressure deformation, the oxide film on the contact surface of the workpiece is destroyed and extruded, allowing pure metal contact to achieve intergranular bonding, which can purify the welded joint. The applied pressure is generally higher than the yield strength of the material to produce 60 to 90% deformation. The pressurization method can be slow extrusion, rolling or impact force, or it can be pressurized several times to achieve the required deformation.
Cold pressure welding characteristics
No heating required: There is no need to heat the workpiece to the melting temperature, saving energy and time.
The welding process is pollution-free: no welding materials are required, and no welding slag, gas and smoke are produced during the welding process.
Lower cost: Compared with traditional thermal welding methods, the cost of cold pressure welding equipment is lower.
Wide applicability: suitable for welding of a variety of metal materials and shapes.
High welding strength: The welding connection strength is equivalent to the base material, and the weld surface is smooth and beautiful.
However, the disadvantages of cold pressure welding also include: slower welding speed, higher welding pressure control requirements, higher requirements for workpiece surface quality, etc.
(7) Diffusion welding
Diffusion welding is a commonly used welding technology that uses high-temperature heating and pressure to melt the metal surface and form a strong connection at the joint. Diffusion welding is widely used in the connection and repair of metal materials in many fields of industrial manufacturing. It has the advantages of high strength, corrosion resistance, and no need for additional filling materials, making it one of the indispensable welding methods in industrial production.
Diffusion welding characteristics
No melting: The diffusion welding process does not involve the melting of metal, but is performed under solid-state conditions. Therefore, no by-products such as molten metal, gas and smoke are produced during the welding process, and the welding area remains clean.
Interatomic Diffusion: Diffusion welding is achieved by diffusion between metal atoms at the welding interface. This interatomic diffusion makes the welded joint join more uniformly, and the strength of the welded joint is usually higher than other welding methods.
Uniformity: Because welding is performed under solid-state conditions and the diffusion of metal atoms during the welding process is uniform, diffusion welding can usually produce a uniform and stable welded joint without pores and inclusions in the welding area.
Wide applicability: Diffusion welding is suitable for welding of various metals and alloy materials, including high-temperature alloys, connections between different metals, etc. It is usually used for welding high-demand components, such as aerospace, nuclear energy, electronic devices and other fields.
High strength: Because the diffusion of metal atoms during the welding process makes the connection of the welded joint tighter and more uniform, diffusion welding can usually produce welded joints with higher strength.
No oxidation: Since there is no melting of metal involved in the welding process, the welding area is not susceptible to oxidation, helping to maintain the quality and performance of the welded joint.
Environmentally friendly: There is no emission of smoke, gas and harmful substances during the diffusion welding process, which has little impact on the environment and meets environmental protection requirements.
(8) Explosion welding
Explosive welding refers to a method that uses the impact force generated by the explosion of explosives to cause rapid collision of workpieces to achieve welding. Explosive welding is a method of welding between metals using explosives as energy. This kind of welding uses the shock wave when the explosive explodes, causing the metal to be impacted at high speed and combined in a very short metallurgical process.
Explosive welding characteristics
Rapidity: Explosion welding is an instantaneous welding process, and the welding time is usually only a few milliseconds to tens of milliseconds. Due to its extremely fast welding speed, it is suitable for welding large or thick workpieces, which can effectively reduce welding time and improve production efficiency.
High strength: Because the metal is instantly melted and fully mixed during the welding process, forming a uniform weld joint, it usually produces high welding quality and strength. Welded joints are generally stronger than traditional welding methods.
Small deformation: Because the welding time is extremely short, explosion welding can usually reduce the deformation and residual stress of the workpiece and keep the shape and size of the workpiece stable.
No external heating required: Explosion welding uses high temperature and high pressure generated by the explosive shock wave of metal to achieve welding, and does not require additional heating equipment or fuel. Therefore, there is no need to preheat the workpiece or the welding area, saving energy and time.
Large welding area: Explosion welding is usually able to weld a larger area of joints in one welding process, and is suitable for welding large or complex-shaped workpieces.
Wide applicability: Explosion welding is suitable for welding a variety of metals and alloy materials, including iron, aluminum, copper, titanium, etc. It is usually used for welding high-demand components, such as aerospace, nuclear energy, electronic devices and other fields.
Although explosion welding has many advantages, there are also some limitations, such as the need for subsequent processing of the workpiece after welding to remove oxides and residual impurities in the welding area, as well as safety hazards during the welding process, and the need to strictly control the size and size of the explosion energy. Location etc. In addition, the equipment and processes of explosive welding are usually complex and the cost is relatively high.
3. Precautions for pressure welding
(1) Safety equipment and operations:
Wear appropriate personal protective equipment, including safety glasses, earplugs (if needed), protective gloves and protective clothing.
Make sure the operating area is well ventilated to prevent the build-up of harmful gases and fumes.
Avoid wearing loose clothing, jewelry, long hair, etc. while working to prevent them from getting caught in or coming into contact with moving machine parts.
(2) Equipment inspection and preparation:
Make sure the welding equipment is in good working order, inspect the equipment regularly and perform maintenance.
Select the appropriate electrode and welding head according to the size and requirements of the welding workpiece.
Check the power and cooling systems of your welding equipment to ensure they are functioning properly.
(3) Workpiece preparation:
Before welding, clean the workpiece surface to remove grease, oxides and other contaminants to ensure welding quality.
Make sure the workpiece is clamped and positioned correctly to prevent movement or tilting during the welding process.
(4) Welding parameter settings:
Set appropriate welding parameters such as pressure, current, welding time and cooling time according to the workpiece material, thickness and welding requirements.
Before starting welding, preheat to reach the desired welding temperature.
(5) Welding process monitoring:
During the welding process, closely monitor the welding parameters and temperature changes in the welding area.
Ensure the welding process is stable and avoid excessively high or low welding temperature and pressure.
(6) Safety measures:
Stay vigilant during welding to prevent accidents.
Place visible safety warning signs near welding equipment to alert others to their attention.
(7) Treatment after welding:
After welding is completed, turn off the welding equipment and clean up residues such as welding slag and oxides in the welding area in time.
Inspect welded joints to ensure their quality meets requirements.
(8) Record and evaluate:
Record the welding parameters and any abnormalities during the welding process.
Regularly evaluate welding quality and equipment performance, and make necessary adjustments and improvements in a timely manner.
In this article, we introduce and discuss various welding methods, including spot welding, seam welding, cladding welding, resistance welding, friction welding, cold pressure welding, explosion welding, etc. Each welding method has its unique characteristics, advantages and disadvantages, and applicable environments. The appropriate method can be selected according to specific needs and application scenarios.
Spot welding is a commonly used welding method, suitable for welding thin plate metal materials, and has the advantages of fast welding speed and high production efficiency. Seam welding is suitable for welding thick plate metal materials and can achieve larger area welding connections. Cladding welding uses a coating agent to protect the welding area, which can improve welding quality and efficiency. Resistance welding uses electric current to generate heat through the workpiece to achieve welding connections, and is suitable for welding various metal materials. Friction welding generates heat by applying mechanical friction between workpieces to achieve welding connections, and is suitable for welding between different metal materials. Cold pressure welding connects workpieces by applying pressure at room temperature, avoiding the influence of heat, and is suitable for materials that are sensitive to the influence of welding. Explosive welding uses the high temperature and high pressure generated by the explosion shock wave of metal to achieve welding connections, and is suitable for welding large or thick workpieces.
No matter which welding method is chosen, it is necessary to strictly follow the corresponding operating procedures and precautions to ensure that the welding process is safe and efficient, and that good welding quality is obtained. At the same time, for different welding tasks and environments, it is necessary to select suitable welding equipment and materials, as well as appropriate operating techniques and parameters, so as to achieve the ideal welding effect.
To sum up, welding technology plays a vital role in various industries and application fields. Through continuous research and development, we can further improve welding quality, efficiency and reliability to meet changing needs and challenges. I hope this article will shed some light on welding technology and be helpful to your work and study.
