JPS5943828A - Method for relieving residual stress in piping - Google Patents

Abstract

PURPOSE:To relieve the residual stress in stainless steel piping and to prevent stress corrosion cracking by heating the parts of the piping close to both sides of the weld zone from the outsides and by cooling them. CONSTITUTION:Heating and cooling devices 3 are placed at the outsides of the parts of austenitic stainless steel piping 1 close to both sides of the welded joint 2. The parts close to the joint 2 are heated to a prescribed temp. with the devices 3 from the outsides to the insides, and the outsides are rapidly cooled. Compressive stress parts formed in the piping 1 by heating and cooling can be allowed to coincide with the tensile stress part of the joint 2 by controlling the heating and cooling positions, the heating temp., etc. in accordance with the thickness and diameter of the piping 1. Thus, the tensile stress in the joint 2 can be relieved.

Description

【発明の詳細な説明】 本発明はオーステナイトステンレス鋼配管の溶接部の残
留応力軽減方法に係る。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing residual stress in welds of austenitic stainless steel piping.

鋼管の溶接継手部には第１図に示すように．管内面に引
張の残留応力が存在する。オーステナイトステンレス鋼
の場合この残留応力と溶接熱影響部の鋭敏化の共存によ
って．腐食環境Ｆでは応力腐食割．Ｉ′Ｌを発生する恐
れがある。As shown in Figure 1, welded joints of steel pipes are There is tensile residual stress on the inner surface of the tube. In the case of austenitic stainless steel, this residual stress coexists with the sensitization of the weld heat affected zone. Stress corrosion occurs in corrosive environment F. There is a possibility that I'L will occur.

この残留応力を除去するため種々方法が開発されており
，高周波加熱による改序方法等がある。しかし欠点とし
ては内面を水冷却するために大容量の加熱装置を必要と
することである。Various methods have been developed to remove this residual stress, including a reforming method using high-frequency heating. However, the disadvantage is that a large capacity heating device is required to cool the inner surface with water.

本発明は大容量の加熱装置を必要としない制御容易な応
力改善方法を提供するべく，ステ／レス配管溶接部の両
側近傍を外面から加熱した後，冷却することを特徴とす
る配管の残留応力軽減方法を提案する。In order to provide an easy-to-control stress improvement method that does not require a large-capacity heating device, the present invention aims to reduce the residual stress in piping by heating the vicinity of both sides of a stainless steel piping weld from the outside and then cooling it. Suggest mitigation methods.

本発明方法の一実施例を第２図について説明する。配管
ｌの溶接継手部２の近傍の両側における管外面に，加熱
及び冷却用装置３を設置する。加熱方法は高周波，ガス
等の曲々の方法が適用１可能である。また冷却は水冷風
等の冷媒を用いる。An embodiment of the method of the invention will be described with reference to FIG. Heating and cooling devices 3 are installed on the outer surface of the pipe 1 on both sides near the welded joint 2. As the heating method, various methods such as high frequency, gas, etc. can be applied. For cooling, a refrigerant such as water-cooled air is used.

溶接部２の近傍に設置した加熱及び冷却用装置３によっ
て所定の温度に管肉厚全体を昇温し，次に外面を急冷す
ると，第３図に示す如く，ある時間，肉厚方向に温度勾
配をつけることができる。その後，室温にまで冷却する
と第４図に示すように，管外面側の加熱冷却部には圧縮
応力が発生し，反対に管内面には引張応力が発生し，そ
の近傍には圧縮応力が発生する。When the entire wall thickness of the pipe is heated to a predetermined temperature using a heating and cooling device 3 installed near the welded part 2, and then the outer surface is rapidly cooled, the temperature increases in the thickness direction for a certain period of time as shown in Fig. 3. You can create a slope. After that, when the tube is cooled to room temperature, as shown in Figure 4, compressive stress is generated in the heated and cooled part on the outer surface of the tube, while tensile stress is generated on the inner surface of the tube, and compressive stress is generated in the vicinity. do.

従って、管の肉厚、直径に応じ、加熱冷却を行う位置、
加熱温度等を側脚することによって。Therefore, depending on the wall thickness and diameter of the pipe, the position where heating and cooling is performed,
By adjusting the heating temperature etc.

加熱冷却による管内面圧縮応力部を溶接継手部の引張応
力部に合致させることができる。かくして溶接継手部の
引張応力を低減させることができる。The compressive stress portion on the inner surface of the tube due to heating and cooling can be made to match the tensile stress portion of the welded joint. In this way, the tensile stress in the welded joint can be reduced.

このようにして、オーステナイトステンレス鋼配管溶接
継手部の内面引張応力を低減させることによって、管内
面が腐食環境にさらされる場合でも、応力腐食割れの発
生を防止できる。By reducing the inner surface tensile stress of the austenitic stainless steel pipe weld joint in this manner, stress corrosion cracking can be prevented from occurring even when the inner surface of the pipe is exposed to a corrosive environment.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は配管淫ｆ１と部の残留応力の説明図、第２図は
水元明方７人の一実施例の要領図、第３図及び第４図は
同上における温度勾配図及び応力状態図である。 第１図 第２図Figure 1 is an explanatory diagram of residual stress in piping f1 and part, Figure 2 is a schematic diagram of an example of Mizumoto Akikata 7, and Figures 3 and 4 are temperature gradient diagrams and stress states in the same case. It is a diagram. Figure 1 Figure 2

Claims (1)

【特許請求の範囲】[Claims] オーステナイトステンレス鋼配管溶接部の両側近傍を外
面から加熱した後，冷却することを特徴とする配管の残
留応力軽減方法。A method for reducing residual stress in piping that is characterized by heating the vicinity of both sides of a welded part of austenitic stainless steel piping from the outside and then cooling it.