Gas shielded welding process and joint microstructure and properties of cast steel for coal machinery and medium plate w

    
    Welding is an important part of many metal and steel processing operations. Shielded metal arc welding (SMAW), also known as Manual Metal Arc welding (MMAW), is a welding process that uses a consumable electrode, usually made of flux-coated metal, with a flux-coated outer shield to protect the weld pool from atmospheric contamination. There are various types of shielding gases commonly used with these processes, such as argon, helium and carbon dioxide. SMAW is an economical and easy to use process, making it one of the most popular welding processes, especially for fabricating cast steel.
    
    Cast steel is a versatile and cost-effective material used to fabricate applications ranging from structural members to coal machinery, and is especially useful for wear-resistant applications, due to its good hardness and abrasion resistance. Manufacturers increasingly rely on SMAW welding to produce wear-resistant cast steel components for use in mining, construction, and other industries that require tough wear-resistant materials.
    
    Cast steel welding with shielded metal arc welding is typically achieved through a preheating process where the steel is heated to a temperature between 800-900°C, followed by welding the components with a voltage of 18-32 volts and current of 80-250 amps. The welding procedures consist of melting the base material, depositing the weld metal on the workpiece, followed by providing a filler material between the two components in a form of a joint. The quality of the weld joints depend on various parameters such as the type of electrode, welding current, and shielding gas flow.
    
    Most commonly SMAW welded cast steel components are post weld heat treated (PWHT) to ensure the quality of the joint. PWHT is done at a temperature range of 700-750°C and the components are held for two hours to create the desired microstructure. The other techniques used for the PWHT are furnace postweld heat treatments, where the components are exposed to 950-1150°C for five minutes to improve their properties.
    
    The combination of PWHT and SMAW welding techniques enables the production of cast steel components for coal machinery and medium plate wear-resistant steel applications with improved mechanical properties. The combination of welding parameters used to join the components together, including the shielding gas and the preheating temperature, enable the production of higher strength and ductility welds of the finished product.
    
    The microstructures of cast steels welded with the SMAW process are varied and depend on the welding parameters used. The weld microstructures generally consist of small ferrite grains with large austenite grains. The ferrite content appears to increase with increased preheating temperatures and increased welding current. The presence of micro-cracks in the welds has been observed due to the presence of hydrogen in the weld metal, which can be reduced by using low-hydrogen electrodes and the proper selection of welding parameters.
    
    The chemical composition of the welds is usually similar to that of the base material and the weld deposit, but slightly different from the parent metal. The chemical composition can vary due to the atmosphere, which is affected by the shielding gas used during welding.
    
    The properties of the weldments depend on the mechanical properties of the parent material and the welding parameters used. The mechanical properties of the weldments are improved by postweld heat treatments and the chemical composition of the weld deposits. The overall strength of the weldment is greater than that of the parent material, but slightly lower than that of the base material. The ductility of the weldment also improves with postweld heat treatment.
    
    SMAW welding of cast steel is a widely used welding technique for applications such as mining, construction, and other wear-resistant applications. This process produces weldments that are strong and durable and are capable of withstanding the harsh operating conditions of these applications. The welds produced by this process meet the stringent quality requirements that the industry is facing today. The welds also have good corrosion and fatigue resistance, making them suitable for use in many industrial applications.

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