Welding thermoplastic is very similar to welding glass. The weld quality is high, similar to that of electron beam welding. Automation is used in different processes of manufacturing such as machining and welding. Welded aluminium needed heat treating to restore strength lost in welding. ERW pipes are manufactured from the longitudinal welding of steel. Argon is commonly used as a shielding gas for DCEN welding of aluminum. Thoriated electrodes are suitable for use in DCEN welding of aluminum. The hoses are designed for use in welding and cutting metal. Exposure to powdered aluminium or aluminium welding fumes can cause pulmonary fibrosis. The development and manufacture of spot welding equipment began in 1936. Propylene is used in production welding and cutting. Submerged arc welding (SAW) is a common arc welding process. This method of welding and cutting metal later became common. The neutral flame is the flame most generally used when welding or cutting. It is used as a shielding gas in welding methods such as atomic hydrogen welding.