JP4599957B2 - High frequency induction heating residual stress improvement method - Google Patents

Description

The present invention relates to a high-frequency induction heating residual stress improving method for improving the residual stress of the inner surface of the welded joint portion of the austenitic stainless steel pipe.

  The PLR piping in the nuclear power plant is made of austenitic stainless steel. In welding a pipe joint made of austenitic stainless steel, residual tensile stress may remain on the inner surface of the joint, and stress corrosion cracking (hereinafter referred to as SCC) may occur.

  Therefore, in a nuclear power plant, in order to prevent SCC, a high frequency induction heating residual stress improvement method (Induction Heating Stress Improvement-IHSI) is used. This high frequency induction heating residual stress improvement method is to dispose the residual tensile stress generated on the inner surface of the pipe of the welded joint part, by placing a high frequency induction coil on the outer periphery of the welded joint part and flowing cooling water through the pipe, A high-frequency current is passed through the high-frequency induction coil to heat the welded joint and its vicinity, generate a temperature difference between the inner and outer surfaces necessary for stress improvement, and then return the welded joint to room temperature, thereby remaining residual tension on the pipe inner surface. The stress is reduced.

  In this high frequency induction heating residual stress improvement method, as shown in Non-Patent Document 1, it has been conventionally required to improve the residual tensile stress on the inner surface in the vicinity of the welded part (depot part) to 98 MPa or less. ing.

  In order to satisfy this requirement, if the coil width of the high frequency induction coil to be arranged is L (mm) and the temperature difference between the inner and outer surfaces of the pipe is ΔT, the conditions of the following equations (5) and (6) can be satisfied. Non-Patent Document 1 defines what is necessary.

  Conventionally, austenitic stainless steel used for piping is, for example, SUS304, and the maximum heating temperature is uniformly set to 550 ° C. or less in order to prevent sensitization.

Iida et al., “Guidelines on Stress Relieving Method by High Frequency Induction Heating (SCC Countermeasure Method) TNS-G2804-1985”, Japan Thermal Power Technology Association, Nuclear Power Technology Committee, p. 5-26

  However, as a countermeasure against SCC, it has been found that even if the residual stress is improved under the above conditions, the occurrence of SCC cannot be completely eliminated. That is, in the conventional high frequency induction heating residual stress improvement method, the residual stress on the inner surface in the vicinity of the deposit portion should be 98 MPa or less, but actually, the welding material portion (depot portion), the base material portion, It has been found that tensile stress acts on the boundary of this, which may cause SCC.

  Therefore, the present inventors pay attention to the residual stress remaining at the boundary between the deposit part and the base material part and the coil cover allowance which is the distance from the coil end of the high frequency induction coil to the center of the joint part, and the residual stress at the boundary. However, at least a compressive stress is generated instead of a tensile stress, that is, a high-frequency induction heating residual stress improving method and a high-frequency induction coil capable of reducing the residual tensile stress to 0 MPa or less at the boundary between the deposit portion and the base material portion are manufactured. I came to do it.

  On the other hand, when the weld joint is in the vicinity of the bent portion of the pipe or the portion where the plug is formed, the center position of the high-frequency induction coil may not be matched with the center position of the weld joint. In this case, it has been found that the effect of improving the residual stress is slightly weakened because the heating conditions are different from those when the high-frequency induction coil is arranged around the weld joint. Therefore, in addition to the conditions for the coil covering allowance, which is the distance from the coil end of the high-frequency induction coil to the center of the joint in this case, the construction conditions are defined such that the residual tensile stress is 0 MPa or less.

上記（１）式中のΔＴを求めておき、その内外面温度差ΔＴに基づいて定数Ａが１．０〜１．９の範囲の条件で、且つＫが２．０〜４．０の範囲の条件で、溶接材部と母材部との境界の残留応力を解析して各定数Ａにおける定数Ｋと残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる定数Ｋの範囲（３．０〜４．０）を求めておき、
次いで、コイル幅Ｌがその定数Ｋの範囲（３．０〜４．０）のコイルについて、上記（１）式中のΔＴ₀を変化させ、溶接材部と母材部との境界の残留応力を解析して各定数ＫにおけるΔＴ ₀ と残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる内外面温度差ΔＴ₀の範囲を求めると共に上記（１）式から定数Ａの範囲を決定しておき、
これら解析結果から残留引張応力が０ＭＰａ以下となる定数Ｋと定数Ａの組み合わせを決定し、その決定した定数Ｋと定数Ａに基づいて、配管の内外面に温度差ΔＴ₀を与え、且つコイル幅Ｌを設定して高周波誘導加熱するに際して、
定数Ｋを３．０以上としたとき定数Ａを１．７以上とし、
定数Ｋを３．５以上としたとき定数Ａを１．６以上とし、
定数Ｋを４．０以上としたとき定数Ａを１．５以上とすることを特徴とする高周波誘導加熱残留応力改善法である。 In order to improve the residual stress of the inner surface of the welded joint portion of the austenitic stainless steel pipe, the high frequency induction coil is arranged with a predetermined width around the joint portion on the outer periphery of the welded joint portion. In the high-frequency induction heating residual stress improvement method in which a high-frequency current is passed through the high-frequency induction coil and the weld joint is heated while flowing cooling water through the pipe, the residual tensile stress at the boundary between the welded part and the base material is set to 0 MPa. In order to make the following, the actual inner and outer surface temperature difference of the welded joint portion of the pipe is ΔT ₀ , the coil width in which the high frequency induction coil is disposed is L, and the residual tensile stress at a position 10 mm from the welding center is 98 MPa or less. Assuming that the temperature difference between the inner and outer surfaces is ΔT, ΔT ₀ and ΔT are defined by Equation 1 and L is defined by Equation 2,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to the coil having a coil width L in the range of the constant K ( _3.0 to _4.0 ), ΔT ₀ in the equation (1) is changed, and the residual stress at the boundary between the welded material portion and the base material portion is changed. The relationship between ΔT ₀ and the residual stress at each constant K is obtained and graphed, and the range of the inner and outer surface temperature difference ΔT ₀ where the residual tensile stress is 0 MPa or less is obtained based on the graph and (1) in advance to determine the range of the constant a from the equation,
From these analysis results, a combination of constant K and constant A at which the residual tensile stress is 0 MPa or less is determined, and based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width When setting L and performing high frequency induction heating ,
When the constant K is 3.0 or more, the constant A is 1.7 or more,
When the constant K is 3.5 or more, the constant A is 1.6 or more,
This is a high frequency induction heating residual stress improvement method characterized in that the constant A is 1.5 or more when the constant K is 4.0 or more .

上記（１）式中のΔＴを求めておき、その内外面温度差ΔＴに基づいて定数Ａが１．０〜１．９の範囲の条件で、且つＫが２．０〜４．０の範囲の条件で、溶接材部と母材部との境界の残留応力を解析して各定数Ａにおける定数Ｋと残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる定数Ｋの範囲（３．０〜４．０）を求めておき、
次いで、コイル幅Ｌがその定数Ｋの範囲（３．０〜４．０）のコイルについて、定数Ｋ’が１．０、定数Ｂが１．０の条件で、上記（１）式中のΔＴ₀を変化させ、溶接材部と母材部との境界の残留応力を解析して各定数ＫにおけるΔＴ ₀ と残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる内外面温度差ΔＴ₀の範囲を求めると共に上記（１）式から定数Ａの範囲を決定しておき、
これら解析結果から残留引張応力が０ＭＰａ以下となる定数Ｋと定数Ａの組み合わせを決定し、定数Ｂが１．０、定数Ｋ’が１．０以上となるようにコイルかぶり代ｄを設定した場合に、その決定した定数Ｋと定数Ａに基づいて、配管の内外面に温度差ΔＴ₀を与え、且つコイル幅Ｌを設定して高周波誘導加熱するに際して、
定数Ｋを３．０以上とし、定数Ａを１．８以上とすることを特徴とする高周波誘導加熱残留応力改善法である。 In the invention of claim 2 , in order to improve the residual stress of the inner surface of the welded joint portion of the austenitic stainless steel pipe, a high frequency induction coil is short on the outer periphery of the welded joint portion of the distance from the coil end to the joint center. The high frequency induction heating residual stress is arranged so that the coil cover allowance, which is the distance, is shifted so as to be d, and the welding joint is heated by supplying a high frequency current to the high frequency induction coil while flowing cooling water in the pipe. In the improvement method, the boundary between the welded material part and the base material part when the thickness of the welded joint part of one of the pipes is t and the thickness of the welded joint part of the other pipe is a constant B × t in order to residual tensile stress less the 0 MPa, residual actual inner and outer surfaces the temperature difference [Delta] T _0, the coil width to place the high-frequency induction coil is L, and 10mm positions from the welding center of the welded joint portion of the pipe Pull When the temperature difference between the inner and outer surfaces where the tensile stress is 98 MPa or less is ΔT, ΔT ₀ and ΔT are defined by Equation 3, L is Equation 4, and d is Equation 5,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to the coil whose coil width L is in the range of the constant K (3.0 to 4.0), ΔT in the above equation (1) under the condition that the constant K ′ is 1.0 and the constant B is 1.0. By changing ₀ , the residual stress at the boundary between the welded material part and the base material part is analyzed to obtain the relationship between ΔT ₀ and the residual stress at each constant K and graphed , and the residual tension based on the graph stress leave determining the scope of the constant a from the equation (1) with determining the range of the inner and outer surface temperature difference [Delta] T ₀ equal to or less than 0 MPa,
When the combination of the constant K and the constant A at which the residual tensile stress is 0 MPa or less is determined from these analysis results, and the coil cover allowance d is set so that the constant B is 1.0 and the constant K ′ is 1.0 or more Further, based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width L is set to perform high frequency induction heating .
This is a high frequency induction heating residual stress improving method characterized in that the constant K is 3.0 or more and the constant A is 1.8 or more .

上記（１）式中のΔＴを求めておき、その内外面温度差ΔＴに基づいて定数Ａが１．０〜１．９の範囲の条件で、且つＫが２．０〜４．０の範囲の条件で、溶接材部と母材部との境界の残留応力を解析して各定数Ａにおける定数Ｋと残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる定数Ｋの範囲（３．０〜４．０）を求めておき、
次いで、コイル幅Ｌがその定数Ｋの範囲（３．０〜４．０）のコイルについて、定数Ｋ’が１．０、定数Ｂが１．５の条件で、上記（１）式中のΔＴ₀を変化させ、溶接材部と母材部との境界の残留応力を解析して各定数ＫにおけるΔＴ ₀ と残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる内外面温度差ΔＴ₀の範囲を求めると共に上記（１）式から定数Ａの範囲を決定しておき、
これら解析結果から残留引張応力が０ＭＰａ以下となる定数Ｋと定数Ａの組み合わせを決定し、定数Ｂが１．５、定数Ｋ’が１．０以上となるようにコイルかぶり代ｄを設定した場合に、その決定した定数Ｋと定数Ａに基づいて、配管の内外面に温度差ΔＴ₀を与え、且つコイル幅Ｌを設定して高周波誘導加熱するに際して、
定数Ｋを３．０以上とし、定数Ａを１．４以上とすることを特徴とする高周波誘導加熱残留応力改善法である。 The invention according to claim 3, to improve the residual stress of the inner surface of the welded joint portion of the austenitic stainless steel pipe, short of the distance the high-frequency induction coil to the welded joint from the outer periphery thereof a coil end to joint center The high frequency induction heating residual stress is arranged so that the coil cover allowance, which is the distance, is shifted so as to be d, and the welding joint is heated by supplying a high frequency current to the high frequency induction coil while flowing cooling water in the pipe. In the improvement method, the boundary between the welded material part and the base material part when the thickness of the welded joint part of one of the pipes is t and the thickness of the welded joint part of the other pipe is a constant B × t In order to make the residual tensile stress of 0 MPa or less, the actual temperature difference between the inner and outer surfaces of the welded joint of the pipe is ΔT ₀ , the coil width in which the high frequency induction coil is arranged is L, and the residual at a position 10 mm from the welding center. Pull When the temperature difference between the inner and outer surfaces where the tensile stress is 98 MPa or less is ΔT, ΔT ₀ and ΔT are defined by Equation 6, L is Equation 7, and d is Equation 8,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to the coil having a coil width L in the range of the constant K (3.0 to 4.0), ΔT in the above equation (1) under the condition that the constant K ′ is 1.0 and the constant B is 1.5. By changing ₀ , the residual stress at the boundary between the welded material part and the base material part is analyzed to obtain the relationship between ΔT ₀ and the residual stress at each constant K and graphed , and the residual tension based on the graph stress leave determining the scope of the constant a from the equation (1) with determining the range of the inner and outer surface temperature difference [Delta] T ₀ equal to or less than 0 MPa,
When the combination of the constant K and the constant A at which the residual tensile stress is 0 MPa or less is determined from these analysis results, and the coil cover allowance d is set so that the constant B is 1.5 and the constant K ′ is 1.0 or more Further, based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width L is set to perform high frequency induction heating .
This is a high frequency induction heating residual stress improving method characterized in that the constant K is 3.0 or more and the constant A is 1.4 or more .

上記（１）式中のΔＴを求めておき、その内外面温度差ΔＴに基づいて定数Ａが１．０〜１．９の範囲の条件で、且つＫが２．０〜４．０の範囲の条件で、溶接材部と母材部との境界の残留応力を解析して各定数Ａにおける定数Ｋと残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる定数Ｋの範囲（３．０〜４．０）を求めておき、
次いで、コイル幅Ｌがその定数Ｋの範囲（３．０〜４．０）のコイルについて、定数Ｋ’が０．５、定数Ｂが１．０の条件で、上記（１）式中のΔＴ₀を変化させ、溶接材部と母材部との境界の残留応力を解析して各定数ＫにおけるΔＴ ₀ と残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる内外面温度差ΔＴ₀の範囲を求めると共に上記（１）式から定数Ａの範囲を決定しておき、
これら解析結果から残留引張応力が０ＭＰａ以下となる定数Ｋと定数Ａの組み合わせを決定し、定数Ｂが１．０、定数Ｋ’が０．５以上となるようにコイルかぶり代ｄを設定した場合に、その決定した定数Ｋと定数Ａに基づいて、配管の内外面に温度差ΔＴ₀を与え、且つコイル幅Ｌを設定して高周波誘導加熱するに際して、
定数Ｋを３．０以上とし、定数Ａを２．０以上とすることを特徴とする高周波誘導加熱残留応力改善法である。 The invention according to claim 4, to improve the residual stress of the inner surface of the welded joint portion of the austenitic stainless steel pipe, short of the distance the high-frequency induction coil to the welded joint from the outer periphery thereof a coil end to joint center The high frequency induction heating residual stress is arranged so that the coil cover allowance, which is the distance, is shifted so as to be d, and the welding joint is heated by supplying a high frequency current to the high frequency induction coil while flowing cooling water in the pipe. In the improvement method, the boundary between the welded material part and the base material part when the thickness of the welded joint part of one of the pipes is t and the thickness of the welded joint part of the other pipe is a constant B × t In order to make the residual tensile stress of 0 MPa or less, the actual temperature difference between the inner and outer surfaces of the welded joint of the pipe is ΔT ₀ , the coil width in which the high frequency induction coil is arranged is L, and the residual at a position 10 mm from the welding center. Pull When the temperature difference between the inner and outer surfaces where the tensile stress is 98 MPa or less is ΔT, ΔT ₀ and ΔT are defined by Equation 9, L is defined by Equation 10, and d is defined by Equation 11,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to the coil having a coil width L in the range of the constant K (3.0 to 4.0), ΔT in the above equation (1) under the condition that the constant K ′ is 0.5 and the constant B is 1.0. By changing ₀ , the residual stress at the boundary between the welded material part and the base material part is analyzed to obtain the relationship between ΔT ₀ and the residual stress at each constant K and graphed , and the residual tension based on the graph stress leave determining the scope of the constant a from the equation (1) with determining the range of the inner and outer surface temperature difference [Delta] T ₀ equal to or less than 0 MPa,
When the combination of the constant K and the constant A at which the residual tensile stress is 0 MPa or less is determined from these analysis results, and the coil cover allowance d is set so that the constant B is 1.0 and the constant K ′ is 0.5 or more Further, based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width L is set to perform high frequency induction heating .
This is a high frequency induction heating residual stress improving method characterized in that the constant K is set to 3.0 or more and the constant A is set to 2.0 or more .

上記（１）式中のΔＴを求めておき、その内外面温度差ΔＴに基づいて定数Ａが１．０〜１．９の範囲の条件で、且つＫが２．０〜４．０の範囲の条件で、溶接材部と母材部との境界の残留応力を解析して各定数Ａにおける定数Ｋと残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる定数Ｋの範囲（３．０〜４．０）を求めておき、
次いで、コイル幅Ｌがその定数Ｋの範囲（３．０〜４．０）のコイルについて、定数Ｋ’が０．５、定数Ｂが２．０の条件で、上記（１）式中のΔＴ₀を変化させ、溶接材部と母材部との境界の残留応力を解析して各定数ＫにおけるΔＴ ₀ と残留応力の関係を求めておくと共にグラフ化しておき、そのグラフに基づいて残留引張応力が０ＭＰａ以下となる内外面温度差ΔＴ₀の範囲を求めると共に上記（１）式から定数Ａの範囲を決定しておき、
これら解析結果から残留引張応力が０ＭＰａ以下となる定数Ｋと定数Ａの組み合わせを決定し、定数Ｂが２．０、定数Ｋ’が０．５以上となるようにコイルかぶり代ｄを設定した場合に、その決定した定数Ｋと定数Ａに基づいて、配管の内外面に温度差ΔＴ₀を与え、且つコイル幅Ｌを設定して高周波誘導加熱するに際して、
定数Ｋを３．０以上とし、定数Ａを１．６以上とすることを特徴とする高周波誘導加熱残留応力改善法である。 The invention of claim 5, to improve the residual stress of the inner surface of the welded joint portion of the austenitic stainless steel pipe, short of the distance the high-frequency induction coil to the welded joint from the outer periphery thereof a coil end to joint center The high frequency induction heating residual stress is arranged so that the coil cover allowance, which is the distance, is shifted so as to be d, and the welding joint is heated by supplying a high frequency current to the high frequency induction coil while flowing cooling water in the pipe. In the improvement method, the boundary between the welded material part and the base material part when the thickness of the welded joint part of one of the pipes is t and the thickness of the welded joint part of the other pipe is a constant B × t In order to make the residual tensile stress of 0 MPa or less, the actual temperature difference between the inner and outer surfaces of the welded joint of the pipe is ΔT ₀ , the coil width in which the high frequency induction coil is arranged is L, and the residual at a position 10 mm from the welding center. Pull When the temperature difference between the inner and outer surfaces where the tensile stress is 98 MPa or less is ΔT, ΔT ₀ and ΔT are defined by Equation 12, L is Equation 13, and d is Equation 14,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to a coil having a coil width L in the range of the constant K (3.0 to 4.0), ΔT in the above equation (1) under the condition that the constant K ′ is 0.5 and the constant B is 2.0. By changing ₀ , the residual stress at the boundary between the welded material part and the base material part is analyzed to obtain the relationship between ΔT ₀ and the residual stress at each constant K and graphed , and the residual tension based on the graph stress leave determining the scope of the constant a from the equation (1) with determining the range of the inner and outer surface temperature difference [Delta] T ₀ equal to or less than 0 MPa,
When the combination of the constant K and the constant A at which the residual tensile stress is 0 MPa or less is determined from these analysis results, and the coil cover allowance d is set so that the constant B is 2.0 and the constant K ′ is 0.5 or more Further, based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width L is set to perform high frequency induction heating .
This is a high frequency induction heating residual stress improving method characterized in that the constant K is 3.0 or more and the constant A is 1.6 or more .

配管に鋭敏化が発生する鋭敏化温度と鋭敏化時間τの関係を示した鋭敏化線図に基づいて、鋭敏化が発生しない加熱温度及び加熱時間で加熱される請求項１から５いずれかに記載の高周波誘導加熱残留応力改善法である。 In the invention of claim 6, the welded joint heated by the high-frequency induction coil has a sensitization time τ in which the sensitization occurs in the pipe defined by Equation 15,

Based on the sensitized diagram sensitization is showing the relationship between the sensitization temperature and sensitization time generated τ to the pipe, from claim 1, the sensitization is heated at a heating temperature and the heating time does not occur to 5 or It is the described high frequency induction heating residual stress improvement method.

A seventh aspect of the present invention is the high frequency induction according to any one of the first to sixth aspects, wherein the arrangement pitch of the conductive wires of the coil at both ends of the high frequency induction coil is shorter than the arrangement pitch of the conductive wires at the coil width center side. It is a heating residual stress improvement method.

  According to the present invention, even when the center position of the high-frequency induction coil cannot be matched with the center position of the weld joint, the residual tensile stress is set to 0 MPa or less at the boundary between the weld material part (depot part) and the base material part. Exhibits excellent effects such as

  High Frequency Induction Heating Residual Stress Improvement Method (IHSI) has been developed as one of the SCC countermeasures for austenitic stainless steel pipes in existing nuclear power plants, and improves residual tensile stress in the heat affected zone near the weld line. It is a construction method.

  In the high frequency induction heating residual stress improving method according to the present invention, as shown in FIG. 1, a high frequency induction coil 3 is arranged on the outer periphery of a welded joint portion 2 of a pipe 1 with a predetermined width around the joint portion 2. Alternatively, when a projection such as a plug (not shown) is formed on the surface of the pipe 1 in the vicinity of the weld joint 2, the high frequency induction coil 3 is connected to the weld joint 2 of the pipe 1 as shown in FIG. 2. On the outer periphery, the coil cover allowance d, which is the distance from the coil end to the center of the joint portion 2, is offset so as to have a predetermined value.

  Then, while flowing cooling water through the pipe 1, a high-frequency current is supplied from the high-frequency heating power source 4 to the high-frequency induction coil 3 to heat the joint portion 2, thereby generating a large temperature difference in the thickness direction of the pipe 1. At this time, compression yield occurs on the outer surface 5 of the heating section of the pipe 1, and tensile yield occurs on the inner surface 6. 1 and 2, the high-frequency induction coil 3 is shown as an integral schematic diagram, but as shown in FIGS. 8 to 10, the high-frequency induction coil 3 is configured by winding a plurality of conductive wires 10, 11, and 12. Yes.

  Next, when the heating is stopped, the temperature difference between the inner and outer surfaces 5 and 6 of the pipe 1 disappears, the tensile residual stress remains in the place where the outer surface 5 of the pipe 1 is compression yielded, and Compressive residual stress occurs.

  The high frequency induction heating residual stress improvement method applies the above principle to the welded joint portion 2 to reduce or compress the residual tensile stress on the inner surface of the pipe 1.

  As described above, the conventional improvement demand is that the residual tensile stress is 98 MPa or less at a position 10 mm from the welding center.

  As basic conditions in this case, if the coil width L (mm) in which the high-frequency induction coil is arranged and the temperature difference ΔT (° C.) between the inside and outside of the pipe, the conditions of the following expressions (5) and (6) can be satisfied. Non-patent document 1 stipulates that this should be done. In addition, the high frequency induction coil in this case is arrange | positioned centering on the welded joint part.

  Here, 2.0√ (Rt), 2 for each of the four types of 1.0ΔT, 1.3ΔT, 1.6ΔT, and 1.9ΔT, based on the inner and outer surface temperature difference ΔT obtained by the equation (5). .5√ (Rt), 3.0√ (Rt), 3.5√ (Rt), 4.0√ (Rt) and analyzing the residual tensile stress at a position 10 mm from the weld center of the pipe inner surface. Thus, the coil width (coil length) capable of satisfying the above requirements and the temperature difference between the inner and outer surfaces of the pipe were calculated. As a result, as shown in FIG. 3, it is derived that the standard for satisfying the conventional requirement is that the temperature difference between the inner and outer surfaces is 1.0 ΔT or more and the coil width is 2.7√ (Rt) or more. The pipe welding in this analysis is performed using a normal groove having a groove angle of approximately 30 °.

  However, even if the residual stress is improved under the above conditions, the residual stress can be improved to 98 MPa or less at a position 10 mm from the center of welding, but at this value, there is a possibility that tensile stress remains in the welded joint. For this reason, it has been found that tensile stress acts on the boundary between the weld material part (depot part) and the base material part, and the degree of residual stress reduction may be low.

  In addition, in the SCC countermeasure material such as SUS316LC (low carbon), for example, knowledge that SCC is generated in the vicinity of the welded portion was obtained. It has been found that this is because the residual stress due to welding becomes high at the boundary between the welded material portion and the base material portion.

  Therefore, the inventors set the evaluation point for stress improvement as the boundary between the weld material part and the base material part, and set the residual stress to be at least compressive stress instead of tensile stress, that is, 0 MPa or less.

  First, the case where the high frequency induction coil 3 is arranged around the weld joint 2 with a normal groove having a groove angle of approximately 30 ° will be analyzed.

  Based on the pipe inner / outer surface temperature difference ΔT obtained by the equation (5), 2.0√ (Rt), 2.5 for each of four types of 1.0ΔT, 1.3ΔT, 1.6ΔT, and 1.9ΔT. √ (Rt), 3.0√ (Rt), 3.5√ (Rt), 4.0√ (Rt), remaining boundary of weld material portion (depot portion) 7 and base material portion 8 under the conditions of The stress was analyzed and calculated (see FIG. 4).

On the other hand, for the four types of coils having coil widths L of 3.0√ (Rt), 3.2√ (Rt), 3.5√ (Rt), and 4.0√ (Rt), the inner / outer surface temperature difference ΔT. ₀ and was analyzed the relationship between the residual stress of the boundary between the weld material portion (deposition unit) 7 and the base material portion 8 (see FIG. 5).

  Pipe welding in these analyzes is performed in the normal groove shape shown in FIG. As shown in the drawing, a 2 mm square lip is formed on the inner surface 6 side of the pipe 1, and the groove angle is approximately 30 ° from the inner surface 6 to a position of 19 mm. At a position 19 mm or more away from the inner surface 6, the groove angle is approximately 10 °. An insert ring (not shown) is provided between lips of adjacent pipes 1. The high frequency induction coil 3 is arranged with a predetermined width around the weld joint 2.

From the analysis results of FIG. 4 and FIG. 5, the residual stress of the tension the higher the inner and outer surfaces the temperature difference [Delta] T ₀ of the pipe 1 is small, the operation proceeds to the compression side, coil width (coil length) as L is longer, No tensile It was found that the residual stress was reduced.

From the graph of FIG. 5, the inner and outer surface temperature difference ΔT _{0 at} which the tensile residual stress is 0 MPa or less is 445 ° C. (= 1.63ΔT (ΔT = 273 ° C. )) or more at 3.0√ (Rt). Yes, it was found to be 415 ° C. (= 1.52ΔT) or more when 3.5√ (Rt) and 400 ° C. (= 1.47ΔT) or more when 4.0√ (Rt).

From these results and the graph of FIG. 4, (1) the inner and outer surface temperature difference ΔT ₀ of the welded joint portion 2 of the pipe 1 is 1.7 ΔT or more and the coil width L is 3.0√ (Rt) or more.
(2) The inner / outer surface temperature difference ΔT ₀ is 1.6ΔT or more and the coil width L is 3.5√ (Rt) or more.
(3) The inner / outer surface temperature difference ΔT ₀ is 1.5ΔT or more and the coil width L is 4.0√ (Rt) or more.
Was set as a new standard for satisfying the above condition when the coil was arranged in the center with a normal groove shape.

That is, in the present invention, in order to improve the residual stress of the inner surface of the welded joint portion 2 of the austenitic stainless steel pipe 1, the high frequency induction coil 3 is arranged on the outer periphery of the welded joint portion 2 with a predetermined width around the welded joint portion 2. In the high-frequency induction heating residual stress improvement method in which the welding joint portion 2 is heated by flowing a high-frequency current through the high-frequency induction coil 3 while flowing cooling water in the pipe 1, the welding material portion (depot portion) 7 and the mother In order to set the residual tensile stress at the boundary with the material part 8 to 0 MPa or less, the temperature difference between the inner and outer surfaces of the welded joint part 2 of the pipe 1 is ΔT ₀ , and the coil width in which the high-frequency induction coil is arranged is L,

, The temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe so that the constant A becomes 1.7 or more, and the coil width is set so that the constant K becomes 3.0 or more and high frequency induction heating is performed. It is characterized by.

Further, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe so that the constant A is 1.6 or more, and the coil width is set so that the constant K is 3.5 or more so that high frequency induction heating is performed. It may be.

Further, the temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe so that the constant A becomes 1.5 or more, and the coil width is set so that the constant K becomes 4.0 or more so that high frequency induction heating is performed. It may be.

By the way, the maximum heating temperature of the pipe 1 is set to a temperature not exceeding the temperature at which the pipe 1 is sensitized. The maximum heating temperature is determined according to the type of stainless steel material. For example, in SUS304, although it is 550 degreeC, (DELTA) T is 273 degreeC from the following (5) formula ((nu) = 0.3, E = 195000, (alpha) = 15.14 * 10 < ^-6 >, (sigma) _y = 288). And 1.7ΔT is 464.1 ° C. Since the cooling water is approximately 50 ° C., the heating temperature may be 514.1 ° C. and does not exceed the maximum heating temperature. Therefore, the heating temperature does not exceed the maximum heating temperature for 1.6 ΔT and 1.5 ΔT.

  Note that the maximum heating temperature varies according to the heating time. As an example, FIG. 6 is a sensitization diagram showing the relationship between sensitization temperature (heating temperature) at which sensitization occurs in SUS304 and SUS304LC and sensitization time (heating time), and FIG. 7 shows SUS316 and SUS316L (SUS316LC). ) Shows a sensitization diagram showing the relationship between the sensitization temperature (heating temperature) at which sensitization occurs and the sensitization time (heating time). Here, the heating time τ is calculated by the following equation (7).

  According to the equation (7), for example, in a pipe made of SUS304 having a thickness of 40 mm, the heating time τ is 311 sec (t = 40, a = 3.59), and even in SUS316, the heating time τ is long. Both are 10 minutes or less. Therefore, in SUS304, SUS304LC, SUS316, and SUS316LC (SUS316L), the maximum heating temperature can be set to 650 ° C.

As a result, the temperature difference ΔT ₀ between the inner and outer surfaces of the pipe 1 can be secured larger, and even when it is difficult to secure the coil width L, the residual tensile stress at the boundary between the welded material portion (depot portion) 7 and the base material portion 8. Can be set to 0 MPa or less.

  Next, in the case where the high frequency induction coil 3 is disposed with a predetermined width around the weld joint 2 having a normal groove, the coil according to the present embodiment having a coil width L of 3.0√ (Rt), The temperature distribution of each part of the pipe 1 when the outer surface temperature of the pipe 1 is heated to the maximum heating temperature is compared with a conventional coil having a coil width L of 2.7√ (Rt). FIG. 8 shows the temperature distribution of the pipe 1 when heated by the coil according to the present embodiment, and FIG. 9 shows the temperature distribution of the pipe 1 when heated by the conventional coil.

The coil conductor 10 according to this embodiment having a coil width L of 3.0√ (Rt) has 14 turns at an equal pitch, and the conventional coil conductor 10 having a coil width L of 2.7√ (Rt) has an equal pitch. It was 12 turns.

  As shown in FIGS. 8 and 9, when the coil width is 3.0√ (Rt), the outer surface temperature of the pipe 1 is equal to or higher than 1.7ΔT + the inner surface temperature than when the coil width is 2.7√ (Rt). Since the area (area having a stress improvement effect) is wide and the portions heated on both sides of the welded joint portion 2 become longer, the inner and outer surface temperature difference 1.7 ΔT can be reliably ensured in the welded joint portion 2. Therefore, the compressive residual stress generated in the inner surface 6 of the pipe 1 when the heating is stopped can be further increased, and the stress improvement effect is enhanced.

  Therefore, it can be ensured that the residual tensile stress at the boundary between the weld material part (depot part) 7 and the base material part 8 is 0 MPa or less, and the occurrence of SCC in the weld joint part 2 can be reliably prevented.

  In addition, the high-frequency induction coil 3 according to the present embodiment has a sufficiently wide range in which the inner / outer surface temperature difference 1.7 ΔT can be ensured as compared with the welded joint portion 2, so that the heating temperature can be lowered.

Furthermore, since the inner / outer surface temperature difference ΔT ₀ is set for a plurality of types of coil widths L, when it is difficult to secure the coil width L, the inner / outer surface temperature difference ΔT ₀ corresponding to the coil width L is set. If applied, it can be ensured that the residual tensile stress at the boundary between the weld material part (depot part) 7 and the base material part 8 is 0 MPa or less, and the occurrence of SCC in the weld joint part 2 can be reliably prevented. If the predetermined inner / outer surface temperature difference ΔT ₀ cannot be applied, the coil width L may be increased.

  FIG. 10 shows another embodiment of the high-frequency induction coil 3 according to the present invention.

  In such an embodiment, in the coil width direction, the arrangement pitch of the conducting wires 11 of the coils at both ends is made shorter than the arrangement pitch of the conducting wires 12 at the coil width center side, and further, the conducting wires 11 at both ends are connected to the center side. It arrange | positions so that it may be near the outer surface 5 of the piping 1 rather than the conducting wire 12.

According to the present embodiment, the temperature at both end portions in the coil width direction can be increased as compared with the case of the equal pitch arrangement, so that the region where the inner / outer surface temperature difference ΔT ₀ is equal to or greater than 1.7ΔT + inner surface temperature (stress improvement) A region having an effect) can be ensured widely compared to the coil in the case of FIG. 8, and the stress improving effect when cooling after heating is further enhanced.

  Next, the case where the center of the high frequency induction coil 3 and the center of the welded joint portion 2 cannot be matched with each other in the normal groove (offset arrangement) will be analyzed.

For three types of coils having coil widths L of 3.0√ (Rt), 3.5√ (Rt), 4.0√ (Rt), the inner / outer surface temperature difference ΔT ₀ and the welding material portion (depot portion) 7 And the residual stress at the boundary between the base material portion 8 were analyzed (see FIG. 11).

  Pipe welding in this analysis is performed in the normal groove shape shown in FIG. The high frequency induction coil 3 is arranged such that a coil cover allowance, which is a distance from the coil end to the center of the joint 2, is d. The fog allowance d is expressed by the following equation (3).

  In FIG. 11, the constant K ′ is set to 1.0 and the fog allowance d is set for analysis.

  Furthermore, in this analysis, attention was also paid to the thickness of the pipe 1 to be connected. The thickness in the vicinity of the welded joint part 2 of one pipe 1 is t, the thickness in the vicinity of the welded joint part 2 of the other pipe 1 is a constant B × t, and a constant B = 1.0 (the thickness t of the pipe 1). In addition to the welded part 2 that is equal), analysis was also performed on the welded part 2 ′ (see FIG. 11) where the constant B = 1.5.

  From the analysis result of FIG. 11, in the case of both constant B = 1.0 and constant B = 1.5, the higher the temperature difference between the inner and outer surfaces of the pipe 1, the smaller the residual stress of tension, and the shift to the compression side may occur. understood.

From the graph of FIG. 11, the inner / outer surface temperature difference ΔT _{0 at} which the tensile residual stress becomes 0 MPa or less is 3.0√ (Rt), 3.5√ (Rt) when the constant B = 1.0. ) It was found that all the coils of 4.0√ (Rt) were 470 ° (= 1.72 ΔT) or more. On the other hand, when the constant B = 1.5, it was found that the inner / outer surface temperature difference ΔT _{0 at which} the tensile residual stress becomes 0 MPa or less is 380 ° (= 1.39ΔT) or more.

  Here, when the thickness in the vicinity of the joint portion 2 of the other pipe 1 is thicker than the thickness in the vicinity of the joint portion 2 of the other pipe 1 as in the connection between the elbow pipe and the straight pipe, the thickness is By increasing the rigidity, the rigidity changes (increases) at the side of the joint, which is considered to increase the residual stress improvement effect.

based on the above results,
(1) When the constant B = 1.0 (when the thickness in the vicinity of the joint portion 2 of the pipe 1 to be connected is equal), the welding of the pipe 1 with the coil cover allowance d = 1.0√ (Rt) or more The inner and outer surface temperature difference ΔT ₀ of the joint portion 2 is 1.8 ΔT or more, and the coil width L is 3.0√ (Rt) or more.
(2) When the constant B = 1.5, the coil cover allowance d = 1.0√ (Rt) or more, and the inner / outer surface temperature difference ΔT ₀ of the welded joint portion 2 of the pipe 1 is 1.4ΔT or more, The coil width L is 3.0√ (Rt) or more.
This is a new standard for satisfying the above conditions when the coil is offset in a normal groove shape.

  By the way, the maximum heating temperature of the pipe 1 is, for example, 550 ° C. in SUS304. In this case, ΔT is 273 ° C. according to the equation (3), and 1.8ΔT is 491.4 ° C. Since the cooling water is approximately 50 ° C., the heating temperature may be 541.4 ° C. and does not exceed the maximum heating temperature. Similarly, for 1.4ΔT, the heating temperature does not exceed the maximum heating temperature.

  Next, the constant K ′ was set to 0.5, and the fogging allowance d was set for analysis. Analysis is performed on the welded portion 2 where the thickness of the pipe 1 is constant B = 1.0 (the thickness t of the pipe 1 is equal) and the welded portion 2 ″ where the constant B = 2.0 (see FIG. 12). Went.

The other conditions are the same as in FIG. 11, and the inner and outer surface temperature differences ΔT for three types of coils having coil widths L of 3.0√ (Rt), 3.5√ (Rt), and 4.0√ (Rt). The relationship between ₀ and the residual stress at the boundary between the weld material part (depot part) 7 and the base material part 8 was analyzed.

  From the analysis result of FIG. 12, in both the case where the constant B = 1.0 and the constant B = 2.0, the higher the temperature difference between the inner and outer surfaces of the pipe 1, the smaller the residual stress of the tensile force, and it can shift to the compression side. understood.

From the graph of FIG. 12, the inner and outer surface temperature difference ΔT _{0 at} which the tensile residual stress becomes 0 MPa or less is 3.0√ (Rt), 3.5√ (Rt) when the constant B = 1.0. ) It was found that all the coils of 4.0√ (Rt) were 525 ° (= 1.92ΔT) or more. This value is calculated (extrapolated) based on the measured value of the graph. On the other hand, when the constant B = 2.0, it was found that the inner / outer surface temperature difference ΔT _{0 at which} the tensile residual stress becomes 0 MPa or less is 435 ° (= 1.59ΔT) or more.

based on the above results,
(1) When the constant B = 1.0 (when the thickness in the vicinity of the joint portion 2 of the pipe 1 to be connected is equal), the welding of the pipe 1 with the coil cover allowance d = 0.5√ (Rt) or more The inner and outer surface temperature difference ΔT ₀ of the joint portion 2 is 2.0ΔT or more, and the coil width L is 3.0√ (Rt) or more.
(2) When the constant B = 2.0, the coil cover allowance d = 0.5√ (Rt) or more, and the inner / outer surface temperature difference ΔT ₀ of the welded joint portion 2 of the pipe 1 is 1.6ΔT or more, The coil width L is 3.0√ (Rt) or more.
This is a new standard for satisfying the above conditions when the coil is offset in a normal groove shape.

That is, in the present invention, in order to improve the residual stress of the inner surface of the welded joint portion 2 of the austenitic stainless steel pipe 1, the high-frequency induction coil 3 is placed on the outer periphery of the welded joint portion 2 from the coil end to the center of the joint portion 2. The coil cover is shifted so that the shorter one of the distances is d, and the welding joint portion 2 is heated by flowing a high-frequency current through the high-frequency induction coil 3 while flowing cooling water through the pipe 1. In the high-frequency induction heating residual stress improvement method, the weld material portion when the thickness of the welded joint portion 2 of one pipe 1 is t and the thickness of the welded joint portion 2 of the other pipe 1 is a constant B × t. In order to set the residual tensile stress at the boundary between 7 and the base metal part 8 to 0 MPa or less, the temperature difference between the inner and outer surfaces of the welded joint part 2 of the pipe 1 is ΔT ₀ , the coil width in which the high frequency induction coil 3 is arranged is L, and 10mm from the welding center And ΔT ₀ and ΔT are defined as Equation 31, L as Equation 32, and d as Equation 33, where ΔT is the inner and outer surface temperature difference at which the residual tensile stress at 98 MPa or less is defined as

When the constant B is 1.0, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe 1 so that the constant A becomes 1.8 or more, and the coil width L is made so that the constant K becomes 3.0 or more. This is characterized in that high frequency induction heating is performed by setting the coil cover margin d so that the constant K ′ is 1.0 or more.

When the constant B is 1.5, giving a temperature difference [Delta] T ₀ on the inner and outer surfaces of the pipe 1 so that the constant A is 1.4 or more, and such that the constant K is 3.0 or more Alternatively, the coil width L may be set, and the coil cover allowance d may be set so that the constant K ′ is 1.0 or more, so that high frequency induction heating may be performed.

Further, when the constant B is 1.0, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe so that the constant A becomes 2.0 or more, and the constant K becomes 3.0 or more. High frequency induction heating may be performed by setting the coil width L and setting the coil cover allowance d so that the constant K ′ is 0.5 or more.

Further, when the constant B is 2.0, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe so that the constant A is 1.6 or more, and the constant K is 3.0 or more. High frequency induction heating may be performed by setting the coil width L and setting the coil cover allowance d so that the constant K ′ is 0.5 or more.

  By the way, the maximum heating temperature of the pipe 1 is, for example, 550 ° C. in SUS304. In this case, ΔT is 273 ° C. from the equation (3), and 2.0ΔT is 546 ° C. Since the cooling water is approximately 50 ° C., the heating temperature is 596 ° C. and exceeds 550 ° C. As described above, the maximum heating temperature is 650 ° C. as verified from the graphs of FIG. 6 and FIG. Therefore, there is no problem even at 2.0ΔT. Also about 1.6 ΔT, the heating temperature does not exceed the maximum heating temperature.

  Next, in the case where the high frequency induction coil 3 is a normal groove and the center of the high frequency induction coil 3 and the center of the welded joint portion 2 are not aligned with each other (offset with a constant K ′ = 1.0). The high-frequency induction coil 3 of this embodiment (see FIG. 13) with a coil width L of 3.0√ (Rt) and a conventional coil with a coil width L of 2.7√ (Rt) (see FIG. 14). The temperature distribution of each part of the pipe when the outer surface temperature of the pipe 1 is the maximum heating temperature is compared. In addition, the conducting wires 11 and 12 of the coil having a coil width L of 3.0√ (Rt) have the arrangement pitch of the conducting wires 11 of the coils at both ends shorter than the arrangement pitch of the conducting wires 12 on the coil width center side. Coil wires 10 having a coil width L of 2.7√ (Rt) are arranged at an equal pitch.

  As shown in FIGS. 13 and 14, when the coil width is 3.0√ (Rt), the outer surface temperature of the pipe 1 is equal to or higher than 1.8ΔT + the inner surface temperature than when the coil width is 2.7√ (Rt). Since the area (area having a stress improvement effect) is wide and the portions heated on both sides of the welded joint portion 2 become longer, the inner and outer surface temperature difference 1.8 ΔT can be reliably ensured in the welded joint portion 2. Therefore, the compressive residual stress generated in the inner surface 6 of the pipe 1 when the heating is stopped can be further increased, and the stress improvement effect is enhanced.

  Therefore, it can be ensured that the residual tensile stress at the boundary between the weld material part (depot part) 7 and the base material part 8 is 0 MPa or less, and the occurrence of SCC in the weld joint part 2 can be reliably prevented.

  In addition, the high-frequency induction coil 3 according to the present embodiment has a sufficiently wide range in which the inner / outer surface temperature difference of 1.8 ΔT can be ensured as compared with the welded joint portion 2, so that the heating temperature can be lowered.

  Further, when the coil width L is 3.0√ (Rt), the arrangement pitch of the conducting wires 11 at both ends is made smaller, so the inner and outer surface temperature difference is 1. A region (region having a stress improvement effect) of 8ΔT or more is wide, and a portion heated on both sides of the welded joint portion 2 becomes long. Therefore, the compressive residual stress generated in the inner surface 6 of the pipe 1 when the heating is stopped can be further increased, and the stress improvement effect is enhanced.

As described above, according to the high-frequency induction heating residual-stress improving method according to the present invention, by setting the coil head margin d, the coil width L of the inner and outer surfaces temperature difference [Delta] T ₀ of the pipe 1, the weld joint portion 2 parts Can be reliably included in a region having a stress improving effect. Therefore, it can be ensured that the residual tensile stress at the boundary between the weld material part (depot part) 7 and the base material part 8 is 0 MPa or less, and the occurrence of SCC in the welded joint part 2 can be reliably prevented.

  Further, according to the present embodiment, the arrangement pitch of the conducting wires 11 of the coils at both ends is made shorter than the arrangement pitch of the conducting wires 12 at the coil width center side, so that the temperature at both end portions in the coil width can be increased. It is possible to expand the region where the temperature difference between the inner and outer surfaces is 1.8 ΔT or more (the region having a stress improvement effect).

In the above embodiment, the pipe 1 is described as an example in which straight pipes are connected in series. However, the present invention can be applied even when the pipes are connected in a predetermined angle instead of in series. It is. In this case, as shown in FIG. 15, the coil width is such that the distance l ₁ between the end portion of the heating portion 17 of one pipe 15 and the central portion in the thickness direction of the other pipe 16, and the heating portion of the other pipe 16. A length obtained by adding a distance l ₂ between the end of 18 and the central portion in the thickness direction of one pipe 15 is set. According to this, the same effect as the above-mentioned embodiment can be obtained.

It is a partially broken perspective view of piping and a high frequency induction coil for explaining a high frequency induction heating residual stress improving method according to the present invention. It is a partially broken perspective view of piping and a high frequency induction coil for explaining a high frequency induction heating residual stress improving method according to the present invention. It is the graph which showed the relationship between the residual stress of the position of 10 mm from a welding center, and a coil width. It is the graph which showed the relationship between the residual stress and the coil width L of the boundary of a deposit part and a base material part at the time of arrange | positioning a coil centering on the weld joint part of a normal groove | channel. It is a graph showing the relationship between the inner and outer surfaces the temperature difference [Delta] T ₀ of the residual stress and the pipe of the boundary between depots portion and the base material portion when the center is disposed a coil welded joint portion of the normal groove. (A) is a graph showing the relationship between sensitization temperature and sensitization time of stainless steel (SUS304), (b) is a graph showing the relationship between sensitization temperature and sensitization time of stainless steel (SUS304LC). is there. (A) is a graph showing the relationship between the sensitization temperature and sensitization time of stainless steel (SUS316), (b) is a graph showing the relationship between the sensitization temperature and sensitization time of stainless steel (SUS316L). is there. It is the figure which showed the temperature distribution of piping which arrange | positioned the high frequency induction coil which concerns on this invention in the center of the welded joint part, and was heated. It is the figure which showed the temperature distribution of the piping which arrange | positioned the conventional high frequency induction coil in the center of the welded joint part, and was heated. It is the figure which showed the temperature distribution of the piping heated by arrange | positioning the high frequency induction coil which concerns on other embodiment of this invention in the center of a welded joint part. This is a graph showing the relationship between the residual stress at the boundary between the deposit and the base metal part and the temperature difference ΔT ₀ between the inside and outside of the pipe when the coil is offset at the weld joint of the normal groove with a predetermined coil cover allowance. is there. This is a graph showing the relationship between the residual stress at the boundary between the deposit and the base metal part and the temperature difference ΔT ₀ between the inside and outside of the pipe when the coil is offset at the weld joint of the normal groove with a predetermined coil cover allowance. is there. It is the figure which showed the temperature distribution of the piping which carried out the offset arrangement | positioning of the high frequency induction coil which concerns on this invention in the welded joint part, and was heated. It is the figure which showed the temperature distribution of the piping which carried out the offset arrangement | positioning of the conventional high frequency induction coil in the welded joint part, and was heated. It is sectional drawing which showed the case where piping is connected orthogonally. It is the side view which showed the groove | channel normally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piping 2 Welded joint part 3 Frequency induction coil 5 Outer surface 6 Inner surface 7 Welding material part (depot part)
8 Base material part 10 Conductor 11 Conductor 12 Conductor 15 Piping 16 Piping

Claims (7)

In order to improve the residual stress of the inner surface of the welded joint of the austenitic stainless steel pipe, a high-frequency induction coil is arranged on the outer periphery of the welded joint with a predetermined width around the joint, and cooling water is poured into the pipe. In the high-frequency induction heating residual stress improvement method in which a high-frequency current is passed through the high-frequency induction coil while heating and the weld joint is heated, the pipe is adjusted so that the residual tensile stress at the boundary between the weld material and the base material is 0 MPa or less. ΔT ₀ is the actual inner / outer surface temperature difference of the welded joint portion, L is the coil width in which the high-frequency induction coil is disposed, and ΔT ₀ is the inner / outer surface temperature difference at which the residual tensile stress at a position 10 mm from the welding center is 98 MPa or less. Where ΔT ₀ and ΔT are defined by Equation 1 and L is defined by Equation 2,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to the coil having a coil width L in the range of the constant K ( _3.0 to _4.0 ), ΔT ₀ in the equation (1) is changed, and the residual stress at the boundary between the welded material portion and the base material portion is changed. The relationship between ΔT ₀ and the residual stress at each constant K is obtained and graphed, and the range of the inner and outer surface temperature difference ΔT ₀ where the residual tensile stress is 0 MPa or less is obtained based on the graph and (1) in advance to determine the range of the constant a from the equation,
From these analysis results, a combination of constant K and constant A at which the residual tensile stress is 0 MPa or less is determined, and based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width When setting L and performing high frequency induction heating ,
When the constant K is 3.0 or more, the constant A is 1.7 or more,
When the constant K is 3.5 or more, the constant A is 1.6 or more,
A method for improving high frequency induction heating residual stress, wherein constant A is 1.5 or more when constant K is 4.0 or more . In order to improve the residual stress of the inner surface of the welded joint of austenitic stainless steel piping, a high frequency induction coil is placed on the outer periphery of the welded joint, and the coil cover that is the shorter of the distance from the coil end to the joint center In the high-frequency induction heating residual stress improvement method in which the welding joint portion is heated by flowing a high-frequency current through the high-frequency induction coil while flowing cooling water in the pipe while allowing the cost to be shifted to d, The residual tensile stress at the boundary between the welded material part and the base material part is 0 MPa or less when the thickness in the vicinity of the welded joint part of the pipe is t and the thickness of the welded joint part of the other pipe is a constant B × t. Accordingly, ΔT ₀ is the actual temperature difference between the inner and outer surfaces of the weld joint of the pipe, L is the coil width in which the high-frequency induction coil is disposed, and the residual tensile stress at a position 10 mm from the welding center is 98 MPa. When the temperature difference between the inner and outer surfaces is ΔT, ΔT ₀ and ΔT are defined by Equation 3, L is defined by Equation 4, and d is defined by Equation 5,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to the coil whose coil width L is in the range of the constant K (3.0 to 4.0), ΔT in the above equation (1) under the condition that the constant K ′ is 1.0 and the constant B is 1.0. By changing ₀ , the residual stress at the boundary between the welded material part and the base material part is analyzed to obtain the relationship between ΔT ₀ and the residual stress at each constant K and graphed , and the residual tension based on the graph stress leave determining the scope of the constant a from the equation (1) with determining the range of the inner and outer surface temperature difference [Delta] T ₀ equal to or less than 0 MPa,
When the combination of the constant K and the constant A at which the residual tensile stress is 0 MPa or less is determined from these analysis results, and the coil cover allowance d is set so that the constant B is 1.0 and the constant K ′ is 1.0 or more Further, based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width L is set to perform high frequency induction heating .
A method of improving high frequency induction heating residual stress, wherein the constant K is 3.0 or more and the constant A is 1.8 or more . In order to improve the residual stress of the inner surface of the welded joint of austenitic stainless steel piping, a high frequency induction coil is placed on the outer periphery of the welded joint, and the coil cover that is the shorter of the distance from the coil end to the joint center In the high-frequency induction heating residual stress improvement method in which the welding joint portion is heated by flowing a high-frequency current through the high-frequency induction coil while flowing cooling water in the pipe while allowing the cost to be shifted to d, The residual tensile stress at the boundary between the welded material part and the base material part is 0 MPa or less when the thickness in the vicinity of the welded joint part of the pipe is t and the thickness of the welded joint part of the other pipe is a constant B × t. Accordingly, ΔT ₀ is the actual temperature difference between the inner and outer surfaces of the weld joint of the pipe, L is the coil width in which the high-frequency induction coil is disposed, and the residual tensile stress at a position 10 mm from the welding center is 98 MPa. When the temperature difference between the inner and outer surfaces is ΔT, ΔT ₀ and ΔT are defined by Equation 6, L is defined by Equation 7, and d is defined by Equation 8,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to the coil having a coil width L in the range of the constant K (3.0 to 4.0), ΔT in the above equation (1) under the condition that the constant K ′ is 1.0 and the constant B is 1.5. By changing ₀ , the residual stress at the boundary between the welded material part and the base material part is analyzed to obtain the relationship between ΔT ₀ and the residual stress at each constant K and graphed , and the residual tension based on the graph stress leave determining the scope of the constant a from the equation (1) with determining the range of the inner and outer surface temperature difference [Delta] T ₀ equal to or less than 0 MPa,
When the combination of the constant K and the constant A at which the residual tensile stress is 0 MPa or less is determined from these analysis results, and the coil cover allowance d is set so that the constant B is 1.5 and the constant K ′ is 1.0 or more Further, based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width L is set to perform high frequency induction heating .
A method of improving high frequency induction heating residual stress, wherein the constant K is set to 3.0 or more and the constant A is set to 1.4 or more . In order to improve the residual stress of the inner surface of the welded joint of austenitic stainless steel piping, a high frequency induction coil is placed on the outer periphery of the welded joint, and the coil cover that is the shorter of the distance from the coil end to the joint center In the high-frequency induction heating residual stress improvement method in which the welding joint portion is heated by flowing a high-frequency current through the high-frequency induction coil while flowing cooling water in the pipe while allowing the cost to be shifted to d, The residual tensile stress at the boundary between the welded material part and the base material part is 0 MPa or less when the thickness in the vicinity of the welded joint part of the pipe is t and the thickness of the welded joint part of the other pipe is a constant B × t. Therefore, the actual inner and outer surface temperature difference of the welded joint portion of the pipe is ΔT ₀ , the coil width in which the high frequency induction coil is disposed is L, and the residual tensile stress at a position 10 mm from the welding center is 98 MPa. When the temperature difference between the inner and outer surfaces is ΔT, ΔT ₀ and ΔT are defined by Equation 9, L is defined by Equation 10, and d is defined by Equation 11,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to the coil having a coil width L in the range of the constant K (3.0 to 4.0), ΔT in the above equation (1) under the condition that the constant K ′ is 0.5 and the constant B is 1.0. By changing ₀ , the residual stress at the boundary between the welded material part and the base material part is analyzed to obtain the relationship between ΔT ₀ and the residual stress at each constant K and graphed , and the residual tension based on the graph stress leave determining the scope of the constant a from the equation (1) with determining the range of the inner and outer surface temperature difference [Delta] T ₀ equal to or less than 0 MPa,
When the combination of the constant K and the constant A at which the residual tensile stress is 0 MPa or less is determined from these analysis results, and the coil cover allowance d is set so that the constant B is 1.0 and the constant K ′ is 0.5 or more Further, based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width L is set to perform high frequency induction heating .
A method of improving high frequency induction heating residual stress, wherein the constant K is 3.0 or more and the constant A is 2.0 or more . In order to improve the residual stress of the inner surface of the welded joint of austenitic stainless steel piping, a high frequency induction coil is placed on the outer periphery of the welded joint, and the coil cover that is the shorter of the distance from the coil end to the joint center In the high-frequency induction heating residual stress improvement method in which the welding joint portion is heated by flowing a high-frequency current through the high-frequency induction coil while flowing cooling water in the pipe while allowing the cost to be shifted to d, The residual tensile stress at the boundary between the welded material part and the base material part is 0 MPa or less when the thickness in the vicinity of the welded joint part of the pipe is t and the thickness of the welded joint part of the other pipe is a constant B × t. Accordingly, ΔT ₀ is the actual temperature difference between the inner and outer surfaces of the weld joint of the pipe, L is the coil width in which the high-frequency induction coil is disposed, and the residual tensile stress at a position 10 mm from the welding center is 98 MPa. When the temperature difference between the inner and outer surfaces is ΔT, ΔT ₀ and ΔT are defined by Equation 12, L is defined by Equation 13, and d is defined by Equation 14,

ΔT in the above equation (1) is obtained, the constant A is in the range of 1.0 to 1.9 based on the inner and outer surface temperature difference ΔT, and K is in the range of 2.0 to 4.0. The residual stress at the boundary between the welded material part and the base metal part is analyzed under the conditions described above, and the relationship between the constant K and the residual stress in each constant A is obtained and graphed , and the residual tensile stress is based on the graph. The range of the constant K (3.0 to 4.0) in which is 0 MPa or less is obtained,
Next, with respect to a coil having a coil width L in the range of the constant K (3.0 to 4.0), ΔT in the above equation (1) under the condition that the constant K ′ is 0.5 and the constant B is 2.0. By changing ₀ , the residual stress at the boundary between the welded material part and the base material part is analyzed to obtain the relationship between ΔT ₀ and the residual stress at each constant K and graphed , and the residual tension based on the graph stress leave determining the scope of the constant a from the equation (1) with determining the range of the inner and outer surface temperature difference [Delta] T ₀ equal to or less than 0 MPa,
When the combination of the constant K and the constant A at which the residual tensile stress is 0 MPa or less is determined from these analysis results, and the coil cover allowance d is set so that the constant B is 2.0 and the constant K ′ is 0.5 or more Further, based on the determined constant K and constant A, a temperature difference ΔT ₀ is given to the inner and outer surfaces of the pipe, and the coil width L is set to perform high frequency induction heating .
A method of improving high frequency induction heating residual stress, characterized in that the constant K is 3.0 or more and the constant A is 1.6 or more . The weld joint heated by the high-frequency induction coil has a sensitization time τ in which sensitization occurs in the pipe defined by Equation 15,

Based on the sensitized diagram sensitization is showing the relationship between the sensitization temperature and sensitization time generated τ to the pipe, from claim 1, the sensitization is heated at a heating temperature and the heating time does not occur to 5 or The described high frequency induction heating residual stress improvement method. The high frequency induction heating residual stress improving method according to any one of claims 1 to 6 , wherein the arrangement pitch of the conductive wires of the coil at both ends of the high frequency induction coil is shorter than the arrangement pitch of the conductive wires at the coil width center side.

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