T91 is high temperature (<625 °C) high-pressure heat-resistant steel, metallographic structure is martensite, mainly used in small-caliber pipe systems of thermal power plants and other high-pressure heat-resistant occasions. Previously, it was mainly imported from American AMSE standard products, and now domestically produced 10Cr9Mo1VNb basically reached At the American standard level, the application of this material is becoming more common, but welding does have some difficulty. The welding method adopts manual tungsten argon arc. In general, the small specification welding is used, that is, the welding speed is improved, the thickness of the welding layer is reduced, the heat affected zone is reduced, and the heat treatment zone is reduced while ensuring good fusion. Second, pre-weld preparation 1. There is a vertical butt joint P91 pipe, the specification is 60×5mm, the interface is opened V-groove, the gap is 2~3mm, the single-side slope angle is 30~35°, and the blunt edge is 2~3mm. Grind the 30~50mm around the groove. Note that there should be no defects such as cracks in the groove and nearby (usually using a low magnification magnifying glass). 2, welding consumables: ER90S-B9, 2.4mm. 3, welding machine: WS315, positive connection, tungsten pole 2.5mm. Third, the welding operation 1. Position the vertical pipe docking assembly to minimize the amount of misalignment. 2, the back (inside the tube) is filled with argon. If the tube is too long, use a soluble paper to form a fluffy ball at a certain distance from the welding joint to block, and the flow rate of argon gas is about 10L/min. 3, pre-heating before welding, can be heated by common oxygen-acetylene flame, control preheating temperature 200~300 °C, can use far infrared thermometer or temperature pen. 4, the bottom welding, to wait for a certain period of time after filling the argon, can be welded to prevent oxidation; the bottom arc swing amplitude should not be too large; when welding to the two slopes, a little pause to prevent poor fusion at the edge of the groove. If there is an obstacle and cannot be welded properly, the inner lining can be used for argon arc welding, and the arc welding is first performed on the most difficult side of the opposite side, and the arc is closed on the side of the front easy welding. The bottom welding process parameters: current 90~95A, welding gas 8~10L/min, back gas 12~15L/min. 5, filler welding, must wait until the temperature of the bottom weld is reduced to below 200 °C, in order to start argon arc filling welding; filling welding process parameters: current 95 ~ 100A, welding gas 8 ~ 10L / min, back gas 8 ~ 10L / Min; the thickness of the filling layer is about 2~3mm. Generally, it is preferably 1~1.5mm from the edge of the outer slope. 6, cover welding, in order to avoid defects such as poor fusion, slag inclusion, undercut, etc., the cover layer should be welded thinner and welded in two steps, the first weld accounts for 2/3 of the weld bead. The crescent-shaped small swing must fuse the downslope well and keep it as neat as possible. The second weld accounts for 1/2 of the weld bead. When operating, pay attention to the arc and the wire to the up-slope edge. The arc length is short, but it cannot be clipped. Tungsten, the wire is melted and the arc is immediately moved down to prevent undercut. Cover welding process parameters: current 90~95A, welding gas 8~10L/min. Fourth, post-weld treatment 1. Immediately after welding the cover, wrap the weld with asbestos cloth to reduce the cooling rate. 2, post-weld heat treatment, usually by rope-shaped far-infrared heater for heating, that is, the same number of rope heaters around the weld, the temperature rise and fall speed ≤150 °C / h, heating width ≥ 60mm, insulation width ≥ 100mm, The constant temperature is 760±10°C, and the constant temperature is ≥30min. Zysen offer Radius Bend Waveguide and Miter Bend Waveguide, 90degree bend, E-bend and
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Technical points of small tube T91 argon arc welding butt joint
I. Overview