Compare the characteristics and uses of manual arc welding and gas welding, and give welding example

Manual arc welding: An arc welding that relies on manual manipulation of the electrode for welding, is the most commonly used method in engineering welding. In manual arc welding, the arc heat generated between the coated electrode and the workpiece is used to melt the electrode and the workpiece, form a molten pool and carry out a series of complex physical metallurgical reactions, and form a weld after cooling to connect the workpiece into a whole.

The equipment used in manual arc welding is simple, the method is simple and flexible, and it is suitable for welding in any space position, but the operation technology requirements for welders are high, the labor intensity is high, the labor conditions are poor, and the production efficiency is low. The guarantee of welding quality depends to a large extent on the technical level of the welder.

Manual arc welding is suitable for the welding of carbon steel, low alloy steel, stainless steel, copper and copper alloy, aluminum and aluminum alloy and other metal materials, as well as cast iron welding and surfacing welding of various metal materials.

For active and refractory metal materials such as titanium, niobium, zirconium, molybdenum and other materials, manual arc welding is generally not used due to the unsatisfactory protection effect and the quality does not meet the requirements; For low melting point metal materials such as lead, tin, zinc, etc., due to the high arc temperature, manual arc welding is not used.

Gas welding: A welding method that relies on the flame energy generated by the violent combustion reaction of gas and oxygen to heat and melt the base metal. Commonly used gases include acetylene, liquefied petroleum gas and hydrogen.

Gas welding does not require a power supply, making it especially suitable for field construction in areas where there is no power supply. However, the temperature of the gas welding flame is low, and the heat is relatively dispersed; low production efficiency; large welding deformation; Poor joint performance. Gas welding is often used for the welding of thin plates and small-diameter pipes that are not very demanding.

The gas welding flame is a heat source for thermal cutting, and can also be used as a heat source for on-site copper tube brazing; The lead lining of the equipment is also commonly used for hydrogen-oxygen flame welding.

Welding examples of manual arc welding: steel structure, steel grid, steel truss steel structure layers: super high-rise steel structure construction parts: main body, steel columns, steel beams, steel support steel structure adopts manual arc welding.

Manual arc welding, now generally called manual electrode arc welding.

Manual electrode arc welding, a more common welding method, is characterized by manual, electrode welding. Generally, steel structures and boilers are used;

Gas welding, a welding method that uses oxyacetylene flame as a heat source, is now less used, and when the turning tool is welded on the saddle, it can also be used, gas welding copper brazing.

Arc welding is a fusion welding method that uses arc heat energy as a heat source, such as electrode arc welding, tungsten inert gas shielded welding, MIG/MAG welding, etc., while gas welding is a welding method that uses gas flame as a heat source, such as oxyacetylene welding.

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According to the different welding processes, arc welding can be divided into automatic welding, semi-automatic welding, argon arc welding and manual welding.

According to the different degrees of automation, arc welding can be divided into automatic welding, semi-automatic welding, and manual welding. According to different welding methods, it can be divided into argon bucket arc welding, electrode welding, submerged arc trembling welding and so on. I hope my write-off defeat will help you and I wish you a happy life!

First of all, the two poles of the output end of the electric welding machine are connected with the weldment and welding tong respectively. Then use the welding tongs to clamp the electrode. During welding, an arc is drawn between the electrode and the weldment, and the high-temperature arc partially melts the end of the electrode and the weldment to form a molten pool.

The molten pool then cools and solidifies to form a weld, so that the two separate weldments are firmly joined as a whole. After the coating of the welding rod is melted, slag is formed to cover the molten pool, and the slag is cooled to form a slag shell to protect the weld. Finally, the slag shell is removed and the welding of the joint is completed.

Welding core: The welding core is a metal wire coated with a coating inside the electrode. What it does is:

Plays the role of an electrode. That is, conducts an electric current, creating an arc.

Weld metal is formed. After the weld core is melted, its droplets transition into the molten pool as filler metal, and after fusing with the molten base metal, it is condensed into the weld metal. Peel:

The coating is a coating layer that is pressed onto the solder core. It is prepared by a variety of raw materials such as ore powder, organic powder, ferroalloy powder and binder in a certain proportion. Due to the presence of arc stabilizers, gas-making agents and slag-forming agents in the coating as shown in Table 5-3, the main functions of the coating are:

Stabilize the arc. Some components in the coating can ionize gas particles, which can make the arc easy to ignite, stabilize combustion and reduce melt droplet splashing, etc. Protect the melt pool.

Under the action of high-temperature arc, the decomposition of the coating produces a large amount of gas and slag, which prevents the molten droplets and molten pool metal from coming into contact with the air. After the slag solidifies, a slag shell is formed to cover the surface of the weld, which prevents the oxidation of the high-temperature weld metal and slows down the cooling rate of the weld metal.

Improve weld quality.

Deoxidation, desulfurization, phosphorus, dehydrogenation and other harmful impurities are carried out through metallurgical reactions in the molten pool, and the beneficial alloying elements that have been burned are supplemented.

The basic methods of fusion welding are: gas welding, arc welding, thermite welding, gas rolling protection welding, plasma welding, electron beam welding, laser welding, etc. Arc welding is under the action of arc temperature regulation, the welding rod and the welded metal (base metal) are melted, and a metal molten pool is formed at the welding place of the base metal; The surface of the electrode has a coating, and the electrode is melted into the molten pool as a filler metal as an electrode on the one hand.

The coating decomposes and melts at a controlled temperature to produce a large amount of protective gas, which protects the powder pool and weld from the harmful effects of air.

Gas welding is a method of welding by using the heat of mixed combustion of olemine gas and oxygen. Combustible gases are mainly acetylene, hydrogen, and natural gas. The most commonly used is oxy-acetylene welding (generally referred to as gas welding).

According to the different mixing ratios of oxygen and acetylene, the flame can be divided into three categories: oxidation flame, which is used for yellow negative and galvanized sheet welding; Neutral flame has a wide range of uses, mainly used for medium and large nuclear pants, low carbon steel, low alloy steel, stainless steel, copper, bronze, aluminum and aluminum alloy, lead, tin, magnesium alloy and gray cast iron welding; Carbonization flame is mostly used for welding of high-carbon steel, various cast iron, high-speed steel, cemented carbide, Monel alloy, tungsten carbide and aluminum bronze.

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2021 textbook p74

Knowledge point: welding. Compared with other fusion welding methods, gas-electric welding has the following characteristics:

1) The visibility of the arc and the molten pool is good, and the welding parameters can be adjusted according to the molten pool during the welding process.

2) The welding process is easy to operate, there is no slag or very little slag, and there is basically no need to clean slag after welding.

4) It can weld magnesium, aluminum, titanium and their alloys with strong chemical activity and easy to form high melting point oxide films.

5) It is conducive to the mechanization and automation of the welding process of the bureau, especially the mechanized welding of the spatial position.

6) When working in the outdoor tung cover, it is necessary to set up a wind shield, otherwise the gas rapid protection effect is not good, or even very poor.

7) The light radiation of the arc is very strong.

8) The welding equipment is more complex and higher than the electrode arc welding equipment.

Advantages: 1) Flexible process and strong adaptability;

2) Good quality and quantity;

3) It is easy to return to Zheng to control deformation and improve stress through process adjustment;

4) The equipment is simple and easy to operate.

Missing Celebration Points:

1) The requirements for welders are high, and the operation technology and experience of welders directly affect the quality of products.

2) poor working conditions;

3) Low productivity.