(1) Welding the chemically active metals and alloys. Inert gases argon or helium do not chemically react with chemically active aluminum, titanium, magnesium, copper, nickel and their alloys, nor are they soluble in liquid metals, even at elevated temperatures. It is difficult to weld these materials with slag-protected welding methods such as hand or submerged arc welding, or they can not be welded at all. (2) Physically available welded joints. Weld metal obtained by this welding method has high purity, less gas and gas inclusions, and less welding defects. Low-carbon steel, low-alloy steel, and stainless steel, which require high weld metal quality, are commonly used for this type of welding. (3) Solderable thin pieces, small pieces. (4) Single-sided welding and double-sided forming and welding all-position. (5) Low welding productivity. The welding current used by TIG welding is limited by the tungsten current carrying capacity, the arc power is small, the arc penetration is small, the welding depth is shallow and the welding speed is low, and the tungsten electrode needs to be replaced frequently during the welding process.

Large diameter cold drawn seamless steel pipe is more than 1000MM diameter steel pipe, large diameter seamless steel pipe is made of ingot or solid tube perforation made of capillary, and then by hot-rolled, cold-rolled or cold dial made. The large-diameter thick-walled steel pipe we purchase is either long or short or short and can be welded. If it is long, we need to remove the extra part, that is, cut it, and its length is suitable for the length required for construction of the steel pipe. Cutting of large diameter seamless steel pipe are many ways. Here are three common large diameter cutting method. 1, The use of sawing machine. Sawing machine is characterized by a complete incision and construction of the welding convenience, the disadvantage is that the efficiency is too low, that is too slow.  2, The use of artificial gas cutting. Features are fast, high efficiency, the disadvantage is that the surface of the incision at the sawtooth shape, hinder and construction. 3, The use of pipe self-propelled automatic cutting machine. The use of pipe self-propelled automatic cutting machine is characterized by low cost, cutting mouth at the smooth and neat, after the use of pipe self-propelled automatic cutting machine after cutting a large diameter cold drawn seamless steel pipe and cut the use of sawing machine is not too large the difference.

Straight seam welded steel pipe finished product is completed, the appearance of the weld to be checked, the weld surface to be smooth, there is no crack phenomenon. But also on the weld fusion status check to see whether the weld  porosity, slag inclusions and so on. In the production of straight seam steel pipe, weld defects caused by the following reasons: 1. Welding seams are not soldered, there are impurities on the surface or too large openings. 2. Welding speed should not be too fast. 3. Welding strictly control the speed and current size, or easily form a stoma.

Precision pipe is a kind of high precision steel pipe material after cold drawing or hot rolling. Because the inner and outer wall of the precision steel tube are free of oxide layer, high pressure without leakage, high precision, high smoothness, cold bending is not deformed, flaring, flattening crack-free and so a little, so mainly used to produce pneumatic or hydraulic components of products such as cylinder, can be seamless, but also welded pipe. The chemical composition of precision steel carbon C, silicon Si, manganese Mn, sulfur S, phosphorus P, chromium Cr. The difference between precision steel pipe and seamless steel pipe 1, The main feature of seamless steel pipe without welding seam, can withstand greater pressure. Products can be very rough cast or cold dial. 2, Precision steel tube is the product of recent years, mainly in the hole, the outer wall size has strict tolerances and roughness.

Large-scale seamless tube forming technology are: hot spinning method, hot extrusion method, hot piercing rolling method, hot push expansion method. details as follows: 1, Hot spinning method It is the flat blank or pre-shaped blank fixed to the rotating mandrel, with the wheel pressure on the rough, while the wheel for axial feed, after one or more processing, to obtain a variety of thin-walled hollow rotary system product of the process. The advantage is the product of high precision, good mechanical properties, a wide range of sizes. Tool mold is simple, easy to replace, production costs lower than other methods. The main disadvantage is the long production hours, low output, the processing of the pipe by the device length restrictions, short size. 2, Hot extrusion method Before extrusion, it is necessary to pretreat the billet by machining. When the pipe with a diameter of less than 100mm is squeezed, the equipment will be put into small parts with less material waste and the technology is more mature. However, once the pipe diameter size increases, the use of hot extrusion method requires large tonnage and high-power equipment, the corresponding control system should be upgraded. 3, Hot piercing rolling method Hot perforation rolling to the longitudinal extension of the rolling and oblique-based extension. Longitudinal rolling extension of the main limited rolling mandrel rolling mill, mandrel less limited mandrel rolling, three mandrel rolling and floating mandrel rolling. These methods have the advantages of high production efficiency, low metal consumption, good product quality, advanced control system and wide application. Slant rolling extension rolling method with a small investment, the process is short, suitable for small quantities, more varieties, specifications and high precision medium-thickness seamless pipe production has also been widely used. 4, Hot push expansion method Push to expand the diameter of the device is simple, low cost, easy maintenance, economical and durable, flexible product specifications change, such as the need to prepare large-diameter elbow and similar products, just add some accessories. Suitable for the production of thin-walled large-diameter seamless steel pipe, can produce no more than the capacity of thick-walled tubes.