Sealing welding technique of low-alloy steel pipe plate and stainless steel pipe of low-pressure heat exchanger

Abstract

The invention discloses a sealing welding technique of a low-alloy steel pipe plate and a stainless steel pipe of a low-pressure heat exchanger, comprising the following steps: the stainless steel pipe is arranged in a pipe hole in the low-alloy steel pipe plate, the pipe exceeds the end part of the pipe plate by 0 to 1.0mm, the pipe plate is not provided with a bevel edge, and manual argon arc welding or automatic argon arc welding is carried out to the stainless steel pipe and the low-alloy steel pipe plate; the technological parameters thereof when the argon arc welding is carried out are as follows: the voltage is 10 to 16V, the current is 50 to 110A and the welding speed is 0.6 to 1.2mm / s; as a further improvement, welding wires containing more than or equal to 19.5 percent of chromium and more than or equal to 9 percent of nickel by weight percentage are also used when in argon arc welding, and the wire feeding speed is 2.5 to 3.15mm / s. The sealing welding technique has the advantages of having less procedure and simple processing and being time-saving, improves production efficiency, reduces production cost, has no crack for the welding seam, and can meet the long-term and stable operation of the low-pressure heat exchanger.

Description

technical field [0001] The invention relates to a sealing welding process for a low-alloy steel pipe plate and a stainless steel pipe of a low-pressure heat exchanger. Background technique [0002] At present, for the sealing welding process of low-alloy steel pipe plates and stainless steel pipes of low-pressure heat exchangers, since the tube plates are mostly low-alloy steels such as SA350LF2, and the pipes are austenitic stainless steels such as SA213TP304, in order to make the combination of the two better after welding, such as figure 1 As shown, the following methods are commonly used: 1) preheating before welding of tube sheet 5; 2) surfacing transition layer 7 and surface layer 6 on the plane of tube sheet 5, the stainless steel material for the first surfacing welding is ER309L, and the second surfacing welding The stainless steel material to be welded is ER347; 3) Post-welding heat and heat treatment of the tube plate; 4) Two vertical lathes (rough lathe and fine ...

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Problems solved by technology

[0002] At present, for the sealing welding process of low-alloy steel pipe plates and stainless steel pipes of low-pressure heat exchangers, since the tube plates are mostly low-alloy steels such as SA350LF2, and the pipes are austenitic stainless steels such as SA213TP304, in order to make the combination of the two better after welding, such as figure 1 As shown, the following methods are commonly used: 1) preheating before welding of tube sheet 5; 2) surfacing transition layer 7 and surface layer 6 on the plane of tube sheet 5, the stainless steel material for the first surfacing welding is ER309L, and the second surfacing welding The stainless steel material to be welded is ER347; 3) Post-welding heat and heat treatment of the tube plate; 4) Two vertical lathes (rough lathe and fine lathe), and the surfacing layer 6 is turned flat; 5) 100% UT of the surfacing layer 6 +100% PT flaw detection, and then finish turning the surfacing layer 6 to the drawing size; 6) Drill some pipe holes in the surfacing layer 6 and the tube sheet 5; 7) Pass the stainless steel pipe 4 through the low alloy steel pipe plate 5 and the surfacing layer 6 tube holes, manual argon arc welding or automatic argon arc welding is performed on the stainless steel tube 4 and the surfacing layer 6; through this method, the tube plate 5 and the tube 4 can be firmly combined, and cracks are not easy to occur during use, but due to many processes , the processing is cumbersome, time-consuming, low production efficiency and high cost

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