Discussion on welding of p91t91 steel I

2022-08-12
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Talking about the welding of p91/t91 steel (I)

1 Unit overview

the third phase 2660mw unit project of Huaneng Dezhou Power Plant is designed by Shandong Electric Power Consulting Institute. If the indicator light flashes or other lights are on, the main equipment is supplied by means of island international bidding. Among them, the boiler island is designed and manufactured by German Babcock company (D.B company); The gas turbine island equipment is designed and manufactured by General Electric Company (GE). The #2 bid (#6 unit) of the installation project is undertaken by Shandong Electric Power Construction Second Company

p91/t91 steel is widely used in main gas, high pressure superheater, high pressure reheater and other projects in this project. The main applications are shown in the following table: 2 Introduction to welding procedure qualification

the p91/t91 steel equipment of phase III 6 unit of Huade power plant is supplied by D.B company and trained at the same time. Welding materials and pipes for construction. The project requires that the welding procedure qualification adopts ASME standard, but the supplier has not provided relevant qualification data; Therefore, at the beginning of the project, our company carried out the welding procedure qualification of sa33591 steel and SA213T91 steel in time

the contents of the P91 steel welding process plan used in the evaluation are as follows: groove type: Double V-shaped, butt gap: mm

welding rod/wire brand: e9015-b9/er90s-b9 (welding materials are supplied by the foreign party)

preheating method/temperature: tracking electric heating/℃ (GTAW), ℃ (SMAW)

shielding gas: argon, purity ≥ 99.99%, argon flow: front l/min, back first pass lmin, The second time lmin

interlayer temperature: <300 ℃ (controlled by far-infrared detector), post heat treatment: raise the temperature to ℃ after welding, keep the temperature for 2h

heat treatment: temperature 750 ℃ -770 ℃, keep the temperature for 5min/mm, and not less than 3H; The rise and fall temperature of post welding heat treatment is less than 150 ℃/h

one vertically fixed and one horizontally fixed ∮ 219 is welded according to the above process × 30 test pieces, after inspection and inspection, meet the requirements: 3 Welding construction process

on the basis of qualified process evaluation, relevant welding operation instructions have been prepared in time. The contents of p91/t91 steel welding operation instructions are as follows: 3.1 selection of welding materials

welding wire er90s-b9

welding rod e9015-b9 3.2 butt joint

3.2.1. The butt joint equipment of reducing hull friction resistance coating 1 should adopt this experimental machine, which is a reliable experimental instrument special for "friction" teaching and scientific research in Colleges and universities

3.2.2 SA335P91 large diameter pipe: butt joint clearance mm; Small diameter pipe: butt gap mm

3.3 back argon filling scheme

3.3.1 adopt back argon filling protection process to avoid oxidation of weld root. Argon filling protection is required not only for the first priming, but also for the second arc welding and the first electric welding. (no root oxidation occurred during construction)

3.3.2 argon filling method of large diameter pipe: generally, special tools can be made; When it is impossible to adopt special loosening devices, high-temperature resistant pressboard and temperature resistant adhesive tape can be used to form a closed gas chamber near the welded junction. Argon filling of small-diameter pipe: both ends of the pipe orifice can be blocked with water-soluble paper

3.3.3 argon filling position:

① fill argon from the flaw detection hole

② use the butt gap to flatten the slender copper pipe or stainless steel pipe and stretch it into the welding area through the groove for inflatable protection

③ from the open end of the pipe, use the argon filling tool made to fill argon. 3.4 welding preheating br 3

4.1 preheat before welding according to the following temperature:

ws: Welding preheat ℃,

d: Welding preheat ℃

3.4.2 SA335P91 large diameter pipe:

computer temperature control equipment is used to track and preheat the welded junction. Thermocouples are symmetrically arranged. Thermocouples and pipe fittings should be in good contact and qualified by measurement. SA213T91 small diameter pipe is preheated by flame, and the temperature is measured with a temperature measuring pen

3.4.3 preheating width: not less than 3 times the pipe wall thickness from each side of the groove center

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