CN103143850A - Process for preventing cold cracking of ASTM (American society for testing material) standard high-strength, low-alloy and atmospheric-corrosion-resistance structural steel - Google Patents
Process for preventing cold cracking of ASTM (American society for testing material) standard high-strength, low-alloy and atmospheric-corrosion-resistance structural steel Download PDFInfo
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Abstract
The invention provides a process for preventing cold cracking of ASTM standard high-strength, low-alloy and atmospheric-corrosion-resistance structural steel in nuclear power stations of more than million kilowatt grades. The process is characterized by comprising the steps that a preheating temperature is increased before welding, a root part is welded, dehydrogenation treatment is performed at an interrupt interval in a welding processing, after-welding stress relieving heat treatment is performed after welding, and finally nondestructive testing is performed on weld joints. The process can be applied to welding of ASTM standard high-strength, low-alloy and atmospheric-corrosion-resistance structural steel in nuclear power stations of follow-up AP1000 and major special projects CAP1400 and welding of other standard nuclear-grade materials with identical chemical compositions.
Description
Technical field
The present invention relates to a kind of technique that prevents welding cold cracking, being applied to material is in the gigawatt power nuclear power station of air corrosion resisting high strength low alloy structural steel.
Background technology
China does not have systematic technical regulation of welding for nuclear power plant specially at present, and every kind of new American Standard trade mark material is used in the welding of nuclear power station, is all new problem and challenge.Thickness surpasses the high-strength low alloy steel of 100mm is forcing the welding difficulty under restrained situation larger, and can be for reference without corresponding mature experience.
But Nuclear Power Station level device support material therefor is ASTM standard High-Strength Low-Alloy structural steel resisting atmosphere corrosion, contain a certain amount of P in chemical composition, although P can have certain positive role to improving atmospheric corrosion resistance, P can cause crack sensitivity to increase, and implosion occurs; P also can worsen the toughness of steel, and particularly restriction reduces the impact flexibility of steel, and therefore for the hyper-thick pipe welding of this type of steel grade, existing welding procedure is difficult to guarantee to avoid welding process to produce cold crack.
Summary of the invention
But the purpose of this invention is to provide a kind of ASTM standard High-Strength Low-Alloy structural steel resisting atmosphere corrosion of can avoiding and produce the method for cold crack in welding process.
In order to achieve the above object, technical scheme of the present invention has been to provide a kind of technique of the ASTM of preventing standard high-strength low-alloy structural steel resisting atmosphere corrosion cold crack, it is characterized in that, step is:
The first step, preheating: preheat temperature is increased to 160 ℃～180 ℃, and the preheating width is increased to 120mm～150mm, and at weld seam both sides increase insulation thickness;
Second step, welding: adopt the computer temperature control Equipment for Heating Processing to carry out electrical heating in whole welding process and follow the tracks of constant temperature, guarantee that interlayer temperature all is not less than preheat temperature, its concrete steps are: butt welded seam carries out root weld, after completing, immediately the commissure is warming up to 200 ℃～400 ℃, constant temperature at least 4 hours carries out root and interlayer Liquid Penetrant again and detects after slowly cooling to room temperature, carry out subsequently multi-layer multi-pass welding;
The 3rd step, post weld heat treatment and Non-Destructive Testing: butt welded seam carries out local post weld heat treatment immediately after welding job is completed, and is to be cooled to room temperature, then butt welded seam carries out Non-Destructive Testing.
Preferably, when carrying out electrical heating tracking constant temperature, arrange at least 4 points for measuring temperature, the temperature gap between any two points for measuring temperature is no more than 50 ℃.
Preferably, completed multi-layer multi-pass welding in many days if divide, or after completing welding the same day, carry out immediately weld seam is warming up to 280 ℃～320 ℃, constant temperature at least 4 hours slowly cools to the preheating that re-starts the described first step before room temperature is treated to begin next day to weld, after perhaps completing welding the same day, computer temperature control type Equipment for Heating Processing keeps the interlayer temperature of weld seam to be not less than preheat temperature, until restart welding next day.
The present invention has following advantage:
1, when preheating with preheat temperature to bringing up to 160 ℃～180 ℃ from original 121 ℃, the preheating width is brought up to 120mm～150mm from original 80mm, and at weld seam both sides increase insulation thickness, the welding overall process adopts the computer temperature control Equipment for Heating Processing to carry out electrical heating and follows the tracks of constant temperature, prevent the too fast loss of heat and be beneficial to the effusion of diffusible hydrogen, to guarantee that in whole welding process, the interlayer temperature all is not less than preheat temperature, prevent preheat temperature weld seam and the too fast crackle that occurs of mother metal heat radiation of causing on the low side.
2, increased the hydrogen measure that disappears: after root weld is completed, welding job interrupts the gap, be warming up to immediately 200 ℃～400 ℃, constant temperature at least 4 hours, carrying out root and interlayer Liquid Penetrant after slowly cooling to room temperature detects again, fundamentally eliminate the impact of diffusible hydrogen, prevent that weld crack from appearring in root and interlayer.
3, change post weld heat treatment opportunity: former technique is that post weld heat treatment is carried out at the qualified rear of butt welded seam Non-Destructive Testing after welding is completed, after improving after welding job is completed butt welded seam carry out immediately local post weld heat treatment, reduce the peak value of welding stress, make stress distribution milder, play part and eliminate the purpose of welding stress, prevent that weld seam from producing delayed crack because of internal stress.
In sum, the invention provides a kind of welding procedure of air corrosion resisting high strength low alloy structural steel, can realize preventing that the improved technology of crackle from appearring in the welding of core level hyper-thick pipe supporting member, but can be applicable to the core level ASTM High-Strength Low-Alloy structural steel resisting atmosphere corrosion welding of follow-up AP1000 and great special CAP1400 nuclear power station, also can be applicable to the welding of other identical standard core level material of chemical composition, effectively prevent cold crack.
The specific embodiment
For the present invention is become apparent, hereby be described in detail below with preferred embodiment.
The welding of the applied AP1000 nuclear power station steam generator of this example cross-brace body of wall carriage, weld crack post analysis, improvement appearred in early stage, remedy technology is not enough, provides to be applicable to the technique that the above nuclear power station of million kilowatt core level of the same race American Standard material can prevent weld crack.
The case technology background: steam generator cross-brace body of wall carriage mother metal design material is ASTM A588 Gr.A or Gr.B, and carrier frame plate is the thickest is 101.8mm, but belongs to the High-Strength Low-Alloy structural steel resisting atmosphere corrosion.Limited by on-the-spot installation site, slope type can only be processed into monolateral V-arrangement, and the deposited metal loading is large, and the weld job cycle is long, and the welding process difficult quality is controlled, is prone to crackle.
The former welding procedure of example has problems: wherein one overlaps steam generator body of wall carriage welding process intermediate survey and have crackle in Non-Destructive Testing report demonstration weld seam when final the examination, proves that there is technical deficiency in former technique.
Process implementing step after improving is as follows:
Step 1, improve actual preheat temperature to from 110 ℃ to 160 ℃～180 ℃, increase the preheating width from 80mm to 120mm～150mm, and at steam generator carrier frame plate centre position filling insulation material, the mother metal both sides increase insulation thickness, the welding overall process adopts the computer temperature control Equipment for Heating Processing to carry out electrical heating and follows the tracks of constant temperature, prevent the too fast loss of heat and be conducive to the effusion of diffusible hydrogen, to guarantee that in whole welding process, the interlayer temperature all is not less than preheat temperature, prevent preheat temperature weld seam and the too fast crackle that occurs of mother metal heat radiation of causing on the low side.
In above-mentioned steps, insulation material should be laid two-layer on heater, and insulation material outside is fixed with waffle slab, the overlap joint gap must not be arranged, to prevent thermal loss between insulation material.
Step 2, the hydrogen treatment measures that disappear that increase.
Step 2.1, after root weld is completed, the mother metal surface that checks that weld seam and resistance heater cover without chip, grease, metal splash after, immediately weld seam is warming up to 280 ℃～320 ℃, constant temperature at least 4 hours carries out root PT again and detects after slowly cooling to room temperature.
Step 2.2, in the time of can't completing welding job continuously within a working day, applicable computer temperature control type Equipment for Heating Processing keeps the interlayer temperature of weld seam to be not less than preheat temperature, until restart welding; Or the same day carry out immediately weld seam is warming up to 280 ℃～320 ℃ after completing welding, constant temperature at least 4 hours slowly cools to room temperature and treats to begin next day to re-start preheating before welding.
Step 2.3, complete welding after, the mother metal surface that checks that weld seam and resistance heater cover without chip, grease, metal splash after, immediately weld seam is warming up to 280 ℃～320 ℃, constant temperature at least 4 hours carries out Liquid Penetrant to final weld seam and detects after slowly cooling to room temperature.
In above-mentioned steps, the layout of point for measuring temperature must not be less than 4, and namely thermocouple all will be arranged in four positions of weld seam, heat affected area, weld seam back, mother metal, and guarantees that the temperature gap of any two points is no more than 50 ℃, and the hydrogen treatment temperature that guarantees to disappear can reach.
Step 3, change post weld heat treatment opportunity.After final welding is completed, first do not carry out final Non-Destructive Testing, carry out post weld heat treatment according to improving technique, first heating up immediately, to eliminate welding stress remaining in weld seam, after being cooled to room temperature, butt welded seam carries out final Non-Destructive Testing.
Claims (3)
1. a technique that prevents ASTM standard high-strength low-alloy structural steel resisting atmosphere corrosion cold crack, is characterized in that, step is:
The first step, preheating: preheat temperature is increased to 160 ℃～180 ℃, and the preheating width is increased to 120mm～150mm, and at weld seam both sides increase insulation thickness;
Second step, welding: adopt the computer temperature control Equipment for Heating Processing to carry out electrical heating in whole welding process and follow the tracks of constant temperature, guarantee that interlayer temperature all is not less than preheat temperature, its concrete steps are: butt welded seam carries out root weld, after completing, immediately the commissure is warming up to 200 ℃～400 ℃, constant temperature at least 4 hours carries out root and interlayer Liquid Penetrant again and detects after slowly cooling to room temperature, carry out subsequently multi-layer multi-pass welding;
The 3rd step, post weld heat treatment and Non-Destructive Testing: butt welded seam carries out local post weld heat treatment immediately after welding job is completed, and is to be cooled to room temperature, then butt welded seam carries out Non-Destructive Testing.
2. a kind of technique that prevents ASTM standard high-strength low-alloy structural steel resisting atmosphere corrosion cold crack as claimed in claim 1, it is characterized in that, when carrying out electrical heating tracking constant temperature, arrange at least 4 points for measuring temperature, the temperature gap between any two points for measuring temperature is no more than 50 ℃.
3. a kind of technique that prevents ASTM standard high-strength low-alloy structural steel resisting atmosphere corrosion cold crack as claimed in claim 1, it is characterized in that, completed multi-layer multi-pass welding in many days if divide, or after completing welding the same day, carry out immediately weld seam is warming up to 280 ℃～320 ℃, constant temperature at least 4 hours, slowly cool to the preheating that re-starts the described first step before room temperature is treated to begin next day to weld, after perhaps completing welding the same day, computer temperature control type Equipment for Heating Processing keeps the interlayer temperature of weld seam to be not less than preheat temperature, until restart welding next day.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114147248A (en) * | 2021-11-16 | 2022-03-08 | 常熟市常盛重工钢结构有限公司 | Welding process of low-alloy high-strength structural steel |
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Patent Citations (4)
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| JPH06320278A (en) * | 1993-04-12 | 1994-11-22 | Nippon Steel Corp | Manufacture of slab for air-hardened seamless steel tube |
| JPH07241692A (en) * | 1994-03-03 | 1995-09-19 | Hitachi Ltd | Fusion repair method of crack |
| CN1814387A (en) * | 2006-02-24 | 2006-08-09 | 中国有色金属工业第六冶金建设公司金属结构厂 | 12Cr1MoV alloy steel pipe welding method |
| CN102756235A (en) * | 2012-07-23 | 2012-10-31 | 苏州热工研究院有限公司 | Field welding repair method especially for larger and penetrating defects in steel casting with heavy wall thickness |
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| 周旭: ""AP1000蒸汽发生器管板锻件焊接质量问题分析及预防措施"", 《中国核科学技术进展报告（第二卷）――中国核学会2011年学术年会论文集第2册（铀矿冶分卷、核能动力分卷（上））》 * |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114147248A (en) * | 2021-11-16 | 2022-03-08 | 常熟市常盛重工钢结构有限公司 | Welding process of low-alloy high-strength structural steel |
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Application publication date: 20130612 |