Introduction to common non fusion welding technologies
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Non fusion welding, as an ancient but constantly evolving metal joining process, carries endless creativity and innovation in the field of human engineering. In this field full of integration of technology and art, welding technology is not only a technology, but also a superb craftsman’s art, turning metal materials into links to connect components. Whether it is heavy industrial projects in the manufacturing industry or precision machining of tiny parts, non-fusion welding technology plays an indispensable role. This article will deeply explore the nature, application and significance of non-fusion welding in modern engineering, with a view to unveiling the mystery of this technical field for readers.
1.what is fusion welding
Non-fusion welding is a common metal joining process that heats metal above its melting point so that it melts and forms a connection on the contact surface. During the welding process, metal is heated to a sufficient temperature to melt it using a suitable heat source (such as arc, flame, laser, etc.). In the molten state of the metal, the metal parts to be connected are brought into contact with each other through appropriate technical means and a connection is formed. Subsequently, it cools and solidifies to form a welded joint.
The basic principle of non-fusion welding is to use heat energy to bring metals to their melting point and join them together in the molten state. This connection method can produce good contact, making the welded joint have good strength and sealing. Non fusion welding is widely used in metal fabrication, construction, the automotive industry, and pipeline and shipbuilding.
Non fusion welding can be achieved through different methods, such as arc welding, gas welding, laser welding, plasma welding, etc. Each method has its applicable scenarios and characteristics. Factors such as welding parameters, equipment and material selection, quality control, etc. need to be considered during the welding process to ensure that the quality of the welded joint meets the design requirements and standards.
2.Fusion welding welding method
Fusion welding is mainly divided into arc welding, gas welding, laser welding, plasma welding, electron beam welding and other methods. Each method has its applicable scenarios and characteristics.
(1) Arc welding
Rod arc welding is the most widely used welding method in industrial production. The metal to be welded is used as one pole, and the electrode is used as the other pole. When the two poles are close to each other, an arc is generated. The heat generated by arc discharge (commonly known as arc combustion) is used to connect the electrode and the workpiece. The welding process of melting each other and forming a weld after condensation, thereby obtaining a strong joint.
Common arc welding methods mainly include electrode arc welding (SMAW), submerged arc welding (SAW), gas tungsten arc welding (GTAW or TIG welding), plasma arc welding (PAW) and gas metal arc welding (GMAW or MIG). welding, MAG welding), etc.
①Welding rod arc welding
Welding rod arc welding uses the welding rod and the workpiece as two electrodes. During welding, the heat and blowing force of the arc are used to locally melt the workpiece. At the same time, under the action of arc heat, the end of the welding rod melts to form droplets, and the workpiece is partially melted to form an oval-shaped pit filled with liquid metal. The melted liquid metal of the workpiece and the droplets form a molten pool. During the welding process, the coating and non-metallic materials The inclusions melt with each other and undergo chemical changes to form a non-metallic substance called slag covering the surface of the weld. As the arc moves, the molten pool cools and solidifies to form a weld.
②Submerged arc welding
Submerged arc welding is a method of welding where the arc burns under a layer of flux. The metal electrode used in submerged arc welding is a bare welding wire that is fed automatically without interruption. During the welding process, a welding trolley or other mechanical and electrical devices are generally used to realize automatic movement of the arc. The arc of submerged arc welding is buried under the granular flux and burns. The arc heat causes the part of the workpiece where the arc directly acts, the end of the welding wire and the flux to melt and evaporate. The gases evaporated by the metal and flux form a closed cavity around the arc. Burns in this cavity. The cavity is surrounded by a slag film composed of slag produced by melting the flux. This slag film not only well isolates the air from contact with the arc and molten pool, but also prevents arc light from radiating out. The welding wire heated and melted by the arc falls in the form of molten droplets and mixes with the molten workpiece metal to form a molten pool. The less dense slag floats on the molten pool. In addition to mechanical isolation and protection of the molten pool metal, the slag also undergoes a metallurgical reaction with the molten pool metal during the welding process, thus affecting the chemical composition of the weld metal. As the arc moves forward, the molten pool metal gradually cools and crystallizes to form a weld. After the molten slag floating on the upper part of the molten pool cools, a slag shell is formed to continue to protect the weld at high temperatures and prevent it from being oxidized.
③Tungsten arc welding
Tungsten argon arc welding refers to an arc welding method that uses tungsten or tungsten alloy (thorium tungsten, cerium tungsten, etc.) as the electrode and argon gas as the protective gas. It is referred to as TIG welding or GTAW welding. During welding, filler metal may or may not be added depending on the groove form of the weld and the performance of the weld metal. Filler metal is usually added from the front of the arc. Due to the special characteristics of aluminum, magnesium and its alloy materials, AC tungsten arc welding is required for welding, while DC tungsten arc welding is used for other metal materials. In order to control the heat input, pulsed tungsten arc welding is increasingly used.
④Plasma arc welding
Plasma arc is a special form of arc. This arc also uses tungsten or tungsten alloy (thorium tungsten, cerium tungsten, etc.) as the electrode of the arc, and uses argon as the protective gas. However, the tungsten electrode does not extend out of the nozzle, but retracts in. Inside the nozzle, the nozzle is water-cooled, also known as water-cooled nozzle. The inert gas is divided into two parts. One part is the gas ejected between the tungsten electrode and the water-cooling nozzle, which is called ion gas; the other part is the gas ejected between the water-cooling nozzle and the protective gas cover, which is called the ion gas. Shielding gas, using plasma arc as a heat source, can be used for welding, cutting, spraying and surfacing, etc.
⑤Gas metal arc welding
Gas metal arc welding means that the welding wire replaces the tungsten electrode. The welding wire itself is one pole of the arc, which plays the role of conduction and arc burning. At the same time, it serves as a filling material, which is continuously melted and filled into the weld under the action of the arc. The commonly used protective gas around the arc can be the inert gas Ar, the active gas CO2, or the Ar+CO2 mixed gas, etc. Gas metal arc welding using Ar as the shielding gas is called MIG welding; gas metal arc welding using CO2 as the shielding gas is called CO2 welding.
(2) Gas welding
Gas welding is also called air welding. PMA plasma brazing machine completely replaces traditional brazing equipment. It is a new generation of brazing equipment that does not require oxygen, acetylene, liquefied gas, alcohol, and gasoline combustible gases. Adopting the IGBT inverter control principle, the flame is very stable during welding. The entire equipment is lightweight and convenient, suitable for outdoor welding. The welding machine is simple to operate and requires only those who have some basic knowledge of welding. No special training is required. This product does not require flammable and explosive gases such as acetylene, and its safety performance is greatly improved. It only requires electricity, and the advantages of using plasma brazing machines in some underdeveloped areas (without oxygen, acetylene, gasoline, etc.) are very obvious. During the welding process, gas flux can be used directly instead of the traditional manual addition of borax to improve the wettability and fluidity of the brazing and reduce the formation of pores. Improve the tensile strength of the weld, and there will be no oxidation or blackening on the surface during the welding process. No pickling is required, which greatly improves welding efficiency.
Advantages: It has good adaptability to the welding of cast iron and some non-ferrous metals; gas welding can play a greater role when welding is needed in areas with insufficient power supply.
Disadvantages: low production efficiency; large deformation and heat-affected zone of workpiece after welding; difficult to achieve automation.
(3) Laser welding
Laser welding is an efficient and precise welding method that uses high-energy-density laser beams as heat sources. Laser welding is one of the important aspects of the application of laser material processing technology. In the 1970s, it was mainly used for welding thin-walled materials and low-speed welding. The welding process is of the heat conduction type, that is, the laser radiation heats the surface of the workpiece, and the surface heat diffuses to the interior through heat conduction. By controlling the width, energy, peak power and repetition frequency of the laser pulse and other parameters to melt the workpiece and form a specific molten pool. Due to its unique advantages, it has been successfully used in precision welding of micro and small parts.
(4) Plasma welding
Plasma arc welding refers to the fusion welding method that uses the high energy density beam of plasma arc as the welding heat source. Plasma arc welding has the characteristics of concentrated energy, high productivity, fast welding speed, small stress deformation, stable arc and suitable for welding thin plates and boxes. It is especially suitable for various refractory, easily oxidized and heat-sensitive metal materials ( Such as tungsten, molybdenum, copper, nickel, titanium, etc.) welding.
Features: Micro-beam plasma arc welding can weld foils and thin plates; it has a small hole effect and can better realize single-sided welding and double-sided free forming; the plasma arc energy density is high, the arc column temperature is high, and the penetration ability is strong, achieving 10~ 12mm thick steel can be welded without grooves and can be formed on both sides at one time. The welding speed is fast, the productivity is high, and the stress deformation is small. ; The equipment is relatively complex, consumes a lot of gas, has strict assembly clearance and clean requirements for workpieces, and is only suitable for indoor welding.
(5) Electron beam welding
Electron beam welding is widely used in many industries such as aerospace, atomic energy, national defense and military industry, automobiles, and electrical and electrical instrumentation due to its advantages of not requiring welding rods, not easily oxidized, good process repeatability, and small thermal deformation. The basic principle of electron beam welding is that the cathode in the electron gun emits electrons due to direct or indirect heating. The electrons are accelerated by the high-voltage electrostatic field and then focused by the electromagnetic field to form an electron beam with extremely high energy density. This electron beam is used to After bombarding the workpiece, the huge kinetic energy is converted into heat energy, which melts the workpiece at the welding point and forms a molten pool, thereby achieving welding of the workpiece.
3.Equipment and welding materials used in fusion welding
(1) Arc Welding:
Welding equipment:
Welding Machine: Arc welding requires a welding machine that can provide the required current and voltage to create an arc.
Welding Torch: A welding torch is used to direct the electrical current and welding material, and to control the welding process. It may be handheld or automated.
Welding power supply: Provides the power required during the welding process.
Electrode Clamp: Used to connect the electrode or welding wire to the power supply of the welding machine.
Welding materials:
Welding Rod: A welding rod is a metal core covered with flux and used for manual arc welding.
Welding wire: Welding wire is a metal wire that is heated and melted by the current and voltage provided by the welding machine and used to fill the weld.
(2) Gas Shielded Welding:
Welding equipment:
Welding Machine: Gas shielded welding requires a welding machine to provide power to create the arc.
Gas protection equipment: includes gas bottles (usually argon or carbon dioxide), gas flow regulators and gas protection guns.
Gas flow meter: used to regulate and control the flow of gas.
Welding materials:
Welding Wire: Welding wire is a filler metal material used to fill the weld and provide the required alloy composition.
(3) Oxy-Fuel Welding:
Welding equipment:
Gas welding equipment: including acetylene and oxygen welding machines, gas cylinders (acetylene cylinders and oxygen cylinders) and welding guns.
Air pressure regulator: used to regulate the flow and pressure of acetylene and oxygen.
Flame nozzle: produces a controllable flame for heating metal workpieces.
Welding materials:
Acetylene and oxygen: mixed together to create a high-temperature flame used to heat metal workpieces.
(4) Laser Welding:
Welding equipment:
Laser welding machine: including laser, optical system and welding workbench.
Laser cooling system: used to cool the laser to maintain its operating temperature.
Laser beam delivery system: delivers the laser beam to the welding area.
Welding materials:
Welding wire or rod: fills the weld and provides the required alloy composition.
4.Precautions for non fusion welding
(1) Safety measures:
Wear appropriate personal protective equipment, including welding helmet, gloves, goggles, earplugs and heat-resistant clothing.
Make sure the work area is well ventilated and away from flammable materials and combustible gases.
When performing high-power welding, flame shields or heat shields should be used to protect surrounding equipment and personnel.
(2) Material preparation:
Clean the workpiece surface to remove grease, coating or dirt to ensure good welding quality.
For thicker materials, preheating the workpiece can reduce thermal stress during welding.
(3) Select appropriate welding parameters:
Select the appropriate welding current, voltage, welding speed and welding angle according to the type, thickness and welding position of the welding material.
For different welding materials and thicknesses, the power and current of the welding machine may need to be adjusted.
(4) Welding technology:
Use correct welding techniques such as arc stabilization technology, uniform welding speed and appropriate welding angle.
When manual welding, maintain a stable holding posture and an appropriate welding angle to ensure smooth welding lines.
(5) Control the welding area:
Make sure the welding arc fully covers the welding area to avoid offset or gaps during welding.
For parts where the welding angle and position are difficult to control, appropriate welding auxiliary tools or supporting equipment can be used.
(6) Post-welding treatment:
After welding is completed, shut down the welding equipment in time and cool the welding area to avoid thermal stress and deformation.
Remove welding residue and slag, and perform necessary grinding or cleaning to improve the surface quality of the welded joint.
(7) Quality inspection and evaluation:
Use appropriate inspection methods, such as visual inspection, penetrant inspection, X-ray inspection, etc., to inspect and evaluate the quality of welded joints.
Ensure that welded joints meet design requirements and relevant standards, such as welding quality, size and tightness.
(8) Continuous improvement and learning:
Continuously learn new welding techniques and best practices, communicate and share experiences with peers.
Regularly conduct welding operation training and skill improvement to improve welding skills and process levels.
In the final stage of welding work, what we witness is not only the connection of metals, but also the inheritance and sublimation of the craftsmanship spirit. Non fusion welding, as an ancient and constantly evolving craft, carries humankind’s control over materials and unremitting pursuit of technology. The completion of every welding is a reflection of respect for craftsmanship and strict requirements for quality.
However, the world of non-fusion welding will never stop moving forward. In the ever-changing industrial environment, we need to maintain humility, constantly learn new knowledge and master new technologies to cope with increasingly complex welding tasks. Only by constantly improving yourself can you remain invincible in the fierce competition.
Therefore, let us continue to explore and pursue excellence with our love and awe for non fusion welding skills. Let us use our wisdom and sweat to write a glorious chapter of non fusion welding technology and contribute our share to the progress and development of mankind. May we always dream and pursue the light of the beauty of non fusion welding!
