Gas type of welding by using a filler wire or rod is a process in which the combustion of gasoline with gaseous fuel and sometimes oxygen creates a flame at the end of the welding torch, and the resulting heat melts the base metal and filler metal. The flame consists of two parts, an inner cone, and a protective cover. If acetylene is used as the gas fuel, then this is called oxyfuel welding. The flux can be used to deoxidize and clean the surfaces of metals used to weld them. Features of the gas welding process:
- The flame temperature is determined by the gaseous fuel.
- Gaseous acetylene gives the highest flame temperature (3087 °C).
- The combustion of hydrogen gas raises the flame temperature to 2660°C.
- The heat content of the reaction includes the heat of combustion of the first and second stages.
- The minimum reaction of the flame with the base metal and filler metal when using a flame is neutral.
- Air is not normally used for the reaction. Because the nitrogen contained in it absorbs heat and reduces the heat contained in the process.
Disadvantages and limitations:
- Due to the power limitation of this process, the welding speed is low.
- The total heat input per unit length of the metal is large. Thus, a large area of thermal influence is formed.
- The deformation of the welded metal occurs due to the large area of exposure to strong heat.
- This method is not used for welding active metals such as titanium and zirconium due to process capacity limitations.
Welding torch There are devices that have the function of regulating the mixing and direction of the gas mixture. On the handle of the burner, there are two valves for independent regulation of the supply of gases (acetylene and oxygen), and the head of the burner is selected according to the thickness of the connecting parts and is attached to the handle. 
The mechanism for mixing gases in welding torches is usually based on the absorption of gaseous acetylene by oxygen and the implementation of the mixing process in a mixing tube. These most commonly used types of burners are called injection burners and have low fuel gas pressure and oxygen pressure set at 3-5 bar. These torches are used for welding with acetylene. Another similar type of gas pressure welding torch is known as a pressure torch and is commonly used in hydrogen gas welding, which consists of three white conical parts known as the neutral (normal) flame. Blue and purple halos are formed. This gas has a maximum combustion temperature of about 3200 °C and is a white cone in the range of 2 to 5 mm from the sickle. With a mixture ratio of oxygen and acetylene of 1 to 1, the conical part of the flame is bright white and has a certain range. This type of flame is called neutral flame and is used when welding steel. If the selected oxygen content is high, the cone of the burner head becomes smaller and leans more towards blue. The extra oxygen in the flame binds to the melt and makes the weld brittle. In addition to burning around and around the weld, it causes oxygen to enter the weld area. This type of flame is also used for welding brass parts, as well as hot parts for electroplating, smoothing, etc., so the amount of acetylene is higher than the amount of oxygen. 
The cone of the burner head has no special access and is painted yellow. In this case, due to a lack of oxygen, a certain amount of carbon monoxide continues to burn, which, due to the pressure of the flame, enters the melt and increases its carbon content and thereby increasing the hardness of the work piece in the welding zone. This type of flame is called a regenerative flame and is used when welding cast iron and aluminum parts. Gas-shielded metal arc welding (MIG) and (MAG) use the heat generated by a DC electric arc between a consumable metal electrode and the work piece to form a weld pool. Slowly welds metals. In the United States, MIG and MAG welding is known as metal arc welding (GMAW). MIG/MAG is similar to MMA in that the heat needed for welding is generated by creating an arc between a consumable metal electrode and the work piece. The electrode melts, forming a weld. The main difference is that the metal electrode is a smaller-diameter welding wire that is fed through the contact tip of the wire spool while the shielding gas is fed through the welding torch. Because the wire is fed continuously, the manual process is sometimes referred to as semi-automatic welding. Gas cylinders are used in both MIG and MAG welding to supply shielding gas and compatible filler consumables. For example, when welding aluminum, you need to use an aluminum wire, while when welding steel, MIG requires a suitable steel filler wire. The difference between MIG welding and MAG welding: MIG (metal inert gas) welding is a welding process in which an arc is created between a consumable wire electrode and the workpiece. Inert gases or gas mixtures are used as shielding gases. Argon and helium are commonly used for MIG welding of non-ferrous metals such as aluminium. 
MAG (Metal Active Gas) welding is an arc welding process in which an arc is created between a consumable wire electrode and the material to be joined. Active shielding gases are used in MAG welding, mainly for welding steels. These protective gases are a mixture of carbon dioxide, argon and oxygen. From this, it can be concluded that the only difference between these two welds is the type of shielding gas used. In this section, we will introduce you to the most common and well-known MIG welding electrodes. These electrodes are used for carbon steel, stainless steel, and aluminum. The most common MIG welding electrodes are solid wire electrodes. Thickness A varies from 0.023 to 0.045. Some of them are rough and are used for heavy industrial work. The most popular MIG electrode sizes used by welders are:
- 023
- 030
- 035
- 045
Size 035 is commonly used for many construction jobs. If you want to choose electrodes for home welding, then it is better to use electrodes with a smaller diameter. The smaller the electrode, the less energy it needs to do work. Just remember that single electrode MIG welding time allows you to weld metals of different thicknesses. Stainless steel MIG welding uses a variety of electrodes because it is used in a wide variety of projects requiring different grades of stainless steel. It is also commonly welded in the same industries as carbon steel. For example, a stainless steel brace welded to a building consists of stainless steel pipes. Here are the different types of stainless steel electrodes. Stainless steel is usually welded using sections of electrodes and is:
- ER308L
- ER309L
- ER 316L
Filler welding rod
Filler metal or rod in the welding process refers to any material used to join two pieces of metal during welding or brazing. When two objects come together, the filler metal melts between them, forming a bridge. After the filler dries, it fuses with objects on both sides, forming a strong bond. The filler material used in joining metals comes in a variety of forms to meet the needs of different projects. Coated electrodes consist of solid metal rods coated with alloys or protective coatings. These metals are used in electrode welding or submerged arc welding, which is one of the main welding methods. During this process, a filler metal rod is placed in the weld zone. When heat is applied to this area, the metal rod melts, filling the gap between them. Coated electrodes are usually made from carbon or chromium steel, which are used to improve the corrosion resistance of the final product. Bare electrode filler is another form of metal and is commonly used in gas shielded arc welding. The wire feed mechanism consists of metal wire wound into metal. When welding, the user runs a wire through a shielded welder to connect two metal objects. Bare electrode wires often contain metals such as copper, tin, lead, or nickel. Welders looking for a filler metal can also choose a flux that is used in submerged arc welding. During this process, the flux covers the entire arc when joining the two materials. By masking the welding arc, flux fillers protect the user from sparks, flames, and other welding hazards. When selecting a filler metal, workers must decide how to compare the tensile strength of the filler metal with the tensile strength of the metal. When the strength of each is relatively equal, the filler is said to match the metal. Fillers weaker than the surrounding metal are considered insufficient, which can help reduce the risk of cracking or breaking of high-strength materials. Fillers that are stronger than the surrounding metal are considered overfitted. 
Superior filler metal provides higher strength in some applications, but comes at a higher cost and may not be suitable for all projects. In addition to matching the strength of the material, workers must consider several other factors when selecting filler metal. The choice of filler can be influenced by the size of metal objects, as well as the material from which they are made. This decision can also be influenced by the fire or corrosion resistance of the metal, as well as the type of welding technology used. Filler metals are alloys or non-alloys that melt and melt when heated to flow through the space between two closely adjacent parts to form a brazed or brazed joint. The filler metal has suitable melting and flow properties that allow capillary distribution over properly prepared welds. Welding consumables provide joints that meet performance requirements such as strength and corrosion resistance. They also conform to the American Welding Society (AWS), American Society for Testing and Materials (ASTM), and ISO standards in almost every respect. Standard fill metals include tin, lead, silver, lead-free and non-cadmium silver, copper, aluminum, nickel, and gem gold. 
Welding consumables are available in solid form (such as rings and wires, billets, washers, and powder) and pastes. Low-melting filler metals are sprayed as a powder and mixed with the flux to form a paste structure. Welding processes operate at the melting temperature of the parent metal and require the parent metal itself to begin to melt. They usually require more precise heat distribution than a small burner because melting of the entire work piece can be avoided by controlling the distribution of heat throughout the room rather than limiting the maximum amount of heat. If a filler material is used, it will have the same alloy and melting point as the base metal. Not all welding processes require filler metal. In oxyfuel welding, only a portion of the existing base metal needs to be melted, which is sufficient for mechanical degreasing prior to welding. Forge or hammer welding uses a hammer blow to close a hot seam and also locally increase its heat. Many gas welding processes, e.g. b Start wires are usually autogenous and a separate wire rod of the same metal is only added if there is a gap that needs to be filled. For some metals, such as lead or aluminum alloys, cut strips of the same metal are used as filler. Steel is usually welded with a filler metal specially made for this purpose. To prevent rust during storage, these wires are often lightly copper plated. In arc welding, the filler rod is mainly used as a consumable electrode, which also generates heat in the work piece. The electrical discharge from this electrode provides heat that melts both electrodes and heats the base metal. TIG welding is an electric welding process that uses an unused tungsten electrode to provide heat, to which a filler rod is manually added. This is a process similar to gas welding, but with a different heat source. 
Use of filler rods and metals:
- Coated electrodes
Coated electrodes are commonly used in shielded metal arc welding and are a major factor in the popularity of this method.
- Bare wire electrode
Bare electrode wire is used in gas-shielded metal arc welding, and bare electrode rods are used in gas-shielded metal arc welding.
- Tubular electrode wire
Tubular electrode wire is used in spiral wire arc welding.
- Welding flux
Welding flux used in submerged arc welding