JP2022015256A - METHOD FOR MANUFACTURING WELDED JOINT USING Ni STEEL FOR LOW TEMPERATURE - Google Patents
METHOD FOR MANUFACTURING WELDED JOINT USING Ni STEEL FOR LOW TEMPERATURE Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 76
- 239000010959 steel Substances 0.000 title claims abstract description 76
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000003466 welding Methods 0.000 claims abstract description 95
- 239000002131 composite material Substances 0.000 claims abstract description 18
- 230000005389 magnetism Effects 0.000 claims abstract description 18
- 239000012535 impurity Substances 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 7
- 230000001678 irradiating effect Effects 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 230000005347 demagnetization Effects 0.000 abstract description 8
- 238000007796 conventional method Methods 0.000 abstract 1
- 238000005485 electric heating Methods 0.000 abstract 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 55
- 239000000463 material Substances 0.000 description 23
- 230000000694 effects Effects 0.000 description 14
- 239000010953 base metal Substances 0.000 description 11
- 239000002184 metal Substances 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000003949 liquefied natural gas Substances 0.000 description 9
- 230000006866 deterioration Effects 0.000 description 8
- 229910000990 Ni alloy Inorganic materials 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 238000007664 blowing Methods 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 238000005096 rolling process Methods 0.000 description 5
- 238000003860 storage Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000005469 granulation Methods 0.000 description 3
- 230000003179 granulation Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000003915 liquefied petroleum gas Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 238000009863 impact test Methods 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
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- 230000000052 comparative effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
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- 238000011156 evaluation Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
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- 230000004927 fusion Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
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Abstract
Description
本発明は、低温用Ni鋼を用いて溶接継手を製造する方法に関する。 The present invention relates to a method for manufacturing a welded joint using Ni steel for low temperature.
液化温度が-162℃である液化天然ガス(LNG)は、クリーンなエネルギーとして知られており、環境問題への取り組みなどから、その需要は益々増加する傾向にある。このようなLNGを蓄える貯蔵タンクには、一般に、極低温での靱性を確保するために、6~9%程度のNiが添加された低温用Ni鋼が用いられる。同様に、LNG燃料のタンクや、エタン、エチレン、液化石油ガス(LPG)を輸送する船舶においても低温用Ni鋼が使用されている。 Liquefied natural gas (LNG), which has a liquefaction temperature of -162 ° C, is known as clean energy, and its demand tends to increase more and more due to efforts to tackle environmental problems. In the storage tank for storing such LNG, low-temperature Ni steel to which about 6 to 9% of Ni is added is generally used in order to secure toughness at extremely low temperatures. Similarly, low temperature Ni steel is also used in LNG fuel tanks and ships transporting ethane, ethylene and liquefied petroleum gas (LPG).
この低温用Ni鋼の溶接では、溶接継手を構成する溶接金属の極低温での強度と靱性確保のために、溶接材料としては、Niを50%以上含有したNi基合金(高Ni合金)が用いられており、また、溶接方法としては、ティグ(TIG)溶接やサブマージアーク溶接(SAW)やシールドメタルアーク溶接(SMAW)が一般に採用されている(例えば特許文献1参照)。ちなみに、このような溶接材料の使用については、Ni量が高いNi基合金はオーステナイト組織を有して、これが極低温において安定であり、脆性破壊を起こし難いためである。 In the welding of this low-temperature Ni steel, a Ni-based alloy (high Ni alloy) containing 50% or more of Ni is used as the welding material in order to ensure the strength and toughness of the weld metal constituting the welded joint at extremely low temperatures. It is used, and as a welding method, TIG welding, submerged arc welding (SAW), and shield metal arc welding (SMAW) are generally adopted (see, for example, Patent Document 1). Incidentally, regarding the use of such a welding material, a Ni-based alloy having a high Ni content has an austenite structure, which is stable at an extremely low temperature and is unlikely to cause brittle fracture.
そして、低温用Ni鋼を溶接するにあたっては、低温用Ni鋼が磁性を帯びやすく、溶接継手を形成する母材の溶接実施部での残留磁気が高いと磁気吹きを生じてしまうことから、十分な配慮が必要となる。すなわち、低温用Ni鋼は、保磁力、透磁率が高いため容易に残留磁気が形成され、この残留磁気の影響により溶接アークが乱れて溶接が困難となってしまい、また、溶接金属の品質劣化を招いてしまう。そのため、低温用Ni鋼では、鋼材の出荷時等に残留磁気を取るための脱磁処理を実施する必要がある。 When welding low-temperature Ni steel, low-temperature Ni steel tends to be magnetized, and if the residual magnetism at the welded portion of the base metal forming the welded joint is high, magnetic blowing will occur. Consideration is required. That is, since nickel steel for low temperature has high coercive force and magnetic permeability, residual magnetism is easily formed, and the influence of this residual magnetism disturbs the welding arc and makes welding difficult, and the quality of the weld metal deteriorates. Will be invited. Therefore, for low-temperature Ni steel, it is necessary to carry out demagnetization treatment to remove residual magnetism at the time of shipment of the steel material.
この脱磁処理とは、一般に、鋼板をコイル内に通して、コイルに交番電流を流しつつ、徐々にその磁界を弱めることで残留磁気を低減させる方法が採用されている(例えば特許文献1参照)。このような方法は古くから用いられており、鋼材の残留磁気を一定水準まで(通常は30ガウス程度まで)低減した上で出荷しなければならない。 As the demagnetization treatment, a method is generally adopted in which a steel plate is passed through a coil, an alternating current is passed through the coil, and the magnetic field is gradually weakened to reduce residual magnetism (see, for example, Patent Document 1). ). Such a method has been used for a long time and must be shipped after reducing the residual magnetism of the steel material to a certain level (usually to about 30 gauss).
ところが、LNGのような貯蔵タンクを製造するためには、膨大な量の鋼材が使用される。特に、近年ではタンクの大型化が進み、それに伴って低温用Ni鋼の使用量も増加することから、脱磁処理だけでも多大なコストと労力が費やされることになる。加えて、低温用Ni鋼は、脱磁処理が済んだ後であっても、建造場所への運搬のほか、タンク製造現場での加工や組み立て時などでも着磁するおそれがある。そのため、例えば運搬時においては、他の鋼材で用いられるマグネットリフト等は使用することができず、運搬や加工、組み立てを経て貯蔵タンクを製造するまで、低温用Ni鋼を着磁させないための管理だけでも大きな負担になっている。 However, a huge amount of steel is used to manufacture a storage tank such as LNG. In particular, in recent years, the size of tanks has increased, and the amount of Ni steel for low temperature used has increased accordingly, so that demagnetization processing alone consumes a great deal of cost and labor. In addition, low-temperature Ni steel may be magnetized not only after being transported to the construction site but also during processing and assembly at the tank manufacturing site, even after the demagnetization treatment is completed. Therefore, for example, during transportation, magnet lifts and the like used for other steel materials cannot be used, and control is performed so that low-temperature Ni steel is not magnetized until the storage tank is manufactured through transportation, processing, and assembly. It is a big burden just by itself.
LNG貯蔵タンク等を製造するにあたり、残留磁気の問題によりこれまで多くの負担を要していた低温用Ni鋼の溶接について、本発明者らはこれを改善する方法について鋭意検討した結果、レーザビームを照射して溶融させながら通電加熱した溶接ワイヤを供給するホットワイヤ・レーザ複合溶接を採用することで、低温用Ni鋼が残留磁気を有した状態であっても磁気吹き等の影響を受けずに溶接継手を製造することができ、しかも、信頼性に優れた高品質の溶接継手が得られるようになることを見出し、本発明を完成させた。 As a result of diligent studies on a method for improving the welding of low-temperature Ni steel, which has been burdensome due to the problem of residual magnetism in manufacturing LNG storage tanks, etc., the laser beam. By adopting hot wire / laser composite welding that supplies welding wire that has been energized and heated while irradiating and melting, it is not affected by magnetic blowing even if the low temperature Ni steel has residual magnetism. The present invention has been completed by finding that a welded joint can be manufactured and a high-quality welded joint having excellent reliability can be obtained.
したがって、本発明の目的は、従来のように脱磁処理を行わなくても、低温用Ni鋼が残留磁気を有した状態で、高品質の溶接継手を製造することができる低温用Ni鋼を用いた溶接継手の製造方法を提供することにある。 Therefore, an object of the present invention is to provide a low-temperature Ni steel capable of producing a high-quality welded joint in a state where the low-temperature Ni steel has residual magnetism without performing a demagnetization treatment as in the conventional case. It is an object of the present invention to provide the manufacturing method of the welded joint used.
すなわち、本発明の要旨は次のとおりである。
(1)低温用Ni鋼を用いて溶接継手を製造する方法であって、
該低温用Ni鋼が30ガウス以上の残留磁気を有した状態で、レーザビームを照射して溶融させながら通電加熱した溶接ワイヤを供給するホットワイヤ・レーザ複合溶接により溶接継手を得ることを特徴とする、低温用Ni鋼を用いた溶接継手の製造方法。
(2)前記低温用Ni鋼の板厚が4~60mmである、(1)に記載の低温用Ni鋼を用いた溶接継手の製造方法。
(3)前記低温用Ni鋼は、化学組成が、質量%で、
C:0.03~0.10%、
Si:0.01~0.5%、
Mn:0.3~1.5%、
Ni:5~10%、
P:0.015%以下、
S:0.003%以下、
Al:0.005~0.08%、
B:0.001%以下、
Ti:0.010%以下、
Nb:0.010%以下、
V:0.010%以下、
N:0.010%以下、
O:0.005%以下、
Cu:1.0%以下、
Cr:1.0%以下、
Mo:1.0%以下、
残部:Fe及び不純物、
である、(1)又は(2)に記載の低温用Ni鋼を用いた溶接継手の製造方法。
That is, the gist of the present invention is as follows.
(1) A method of manufacturing a welded joint using Ni steel for low temperature.
It is characterized in that a welded joint is obtained by hot wire / laser composite welding in which the low temperature Ni steel has a residual magnetism of 30 gauss or more and supplies a welded wire heated by energization while being melted by irradiating a laser beam. A method for manufacturing a welded joint using Ni steel for low temperature.
(2) The method for manufacturing a welded joint using the low temperature Ni steel according to (1), wherein the low temperature Ni steel has a plate thickness of 4 to 60 mm.
(3) The low temperature Ni steel has a chemical composition of% by mass.
C: 0.03 to 0.10%,
Si: 0.01-0.5%,
Mn: 0.3-1.5%,
Ni: 5-10%,
P: 0.015% or less,
S: 0.003% or less,
Al: 0.005 to 0.08%,
B: 0.001% or less,
Ti: 0.010% or less,
Nb: 0.010% or less,
V: 0.010% or less,
N: 0.010% or less,
O: 0.005% or less,
Cu: 1.0% or less,
Cr: 1.0% or less,
Mo: 1.0% or less,
Remaining: Fe and impurities,
The method for manufacturing a welded joint using the Ni steel for low temperature according to (1) or (2).
本発明によれば、着磁しやすい低温用Ni鋼について、従来のように脱磁処理を行わなくても、磁気吹き等の影響を受けずに溶接継手を製造することができるようになり、しかも、信頼性に優れた高品質の溶接継手を得ることができる。 According to the present invention, it becomes possible to manufacture a welded joint of Ni steel for low temperature, which is easily magnetized, without being affected by magnetic blowing or the like without performing demagnetization treatment as in the conventional case. Moreover, it is possible to obtain a high-quality welded joint with excellent reliability.
以下、本発明について詳しく説明する。
先ず、本発明における溶接継手の製造方法では、溶接手段として、レーザビームを照射して母材を溶融させながら、通電加熱した溶接ワイヤを供給して溶接継手を得るホットワイヤ・レーザ複合溶接を採用する。このホットワイヤ・レーザ複合溶接は、溶接ワイヤを溶融温度付近まで加熱して挿入するホットワイヤシステムとレーザ熱源を組み合わせた溶接法であり、レーザ熱源をホットワイヤシステムと併用することで、開先精度に対する裕度が小さく、しかも、継手の特性に対する母材成分の影響が大きいといったレーザ熱源を利用したレーザ溶接の短所を補いつつ、ホットワイヤから供給される溶着金属が融点直下まで加熱されることから、エネルギー密度の低いレーザビームの照射でも、十分な溶融金属を形成することができる。
Hereinafter, the present invention will be described in detail.
First, in the method for manufacturing a welded joint in the present invention, hot wire / laser composite welding is adopted as a welding means to obtain a welded joint by supplying a welded wire heated by energization while irradiating a laser beam to melt the base metal. do. This hot wire / laser composite welding is a welding method that combines a hot wire system that heats and inserts the weld wire to near the melting temperature and a laser heat source. By using the laser heat source together with the hot wire system, the groove accuracy Because the weld metal supplied from the hot wire is heated to just below the melting point, while compensating for the disadvantages of laser welding using a laser heat source, such as a small margin for welding and a large effect of the base metal component on the characteristics of the joint. Sufficient molten metal can be formed even by irradiation with a laser beam having a low energy density.
このようなホットワイヤ・レーザ複合溶接であれば、レーザビームを照射して母材を溶融させるため、磁力によって溶接アークが偏向するような磁気吹きの発生を抑えることができ、特に脱磁処理を行わなくても低温用Ni鋼の溶接を安定して行うことができる。つまり、低温用Ni鋼が30ガウス以上の残留磁気を有した状態であっても、品質の良い溶接継手を安定して得ることができる。ただし、残留磁気が300ガウスを超えるような極端に着磁した状態であると溶接金属の健全性に影響を及ぼすおそれがあることから、好ましくは低温用Ni鋼が30ガウス以上300ガウス以下の状態でホットワイヤ・レーザ複合溶接により溶接継手を得るようにするのがよい。なお、低温用Ni鋼の残留磁気は、溶接時の影響を考慮するために、溶接継手を形成する母材(低温用Ni鋼)の溶接実施部での値を言うものとする。例えば、突合せ溶接の場合には、突合せ溶接向けに形成する開先での値であり、また、すみ肉溶接の場合には、溶接を実施する鋼板の角部における値とする。 In such hot wire / laser composite welding, since the base metal is melted by irradiating the laser beam, it is possible to suppress the generation of magnetic blow that causes the welding arc to be deflected by magnetic force, and in particular, demagnetization treatment is performed. Welding of low temperature Ni steel can be performed stably even if it is not performed. That is, even if the low-temperature Ni steel has a residual magnetism of 30 gauss or more, a high-quality welded joint can be stably obtained. However, if the residual magnetism is extremely magnetized to exceed 300 gauss, the soundness of the weld metal may be affected. Therefore, the Ni steel for low temperature is preferably 30 gauss or more and 300 gauss or less. It is better to obtain a welded joint by hot wire / laser composite welding. The residual magnetism of Ni steel for low temperature refers to the value at the welded portion of the base metal (Ni steel for low temperature) forming the welded joint in order to consider the influence during welding. For example, in the case of butt welding, it is the value at the groove formed for butt welding, and in the case of fillet welding, it is the value at the corner of the steel plate to be welded.
また、このようなホットワイヤ・レーザ複合溶接の特徴が、高Ni合金からなる溶接材料を用いた低温用Ni鋼の溶接において有利に作用するため、溶接時の入熱をある程度制御しながらも、溶接パス数を減らして溶接継手を得ることができる。すなわち、高Ni合金の溶接材料では多量のNi添加に伴う高温割れの発生や、溶接熱影響部(HAZ)の靱性の劣化を抑制するために、一般に溶接時の入熱を制御する必要がある。一方で、溶接入熱を低減すると、所定の溶接継手を得るための溶接回数(溶接パス数)が必然的に増えてしまうために溶接効率が低下する。これに対して、ホットワイヤ・レーザ複合溶接では、エレクトロガスアーク溶接等の高効率溶接法に比べて溶接入熱を低減しながら、エネルギー密度の低いレーザビームの照射でも、十分な溶融金属を形成することができることから、好適には1パス溶接も可能であり、溶接効率を確保しつつ、高温割れの発生やHAZにおける靱性の低下を抑制することができる。 Further, since such a feature of hot wire / laser composite welding has an advantageous effect in welding low-temperature Ni steel using a welding material made of a high Ni alloy, the heat input during welding is controlled to some extent, while controlling the heat input during welding. Welded joints can be obtained by reducing the number of welding passes. That is, in a high Ni alloy welding material, it is generally necessary to control the heat input during welding in order to suppress the occurrence of high temperature cracking due to the addition of a large amount of Ni and the deterioration of the toughness of the weld heat affected zone (HAZ). .. On the other hand, if the welding heat input is reduced, the number of weldings (the number of welding passes) for obtaining a predetermined welded joint is inevitably increased, so that the welding efficiency is lowered. On the other hand, in hot wire / laser composite welding, a sufficient molten metal is formed even by irradiation with a laser beam having a low energy density while reducing welding heat input as compared with a high efficiency welding method such as electrogas arc welding. Therefore, one-pass welding is also preferably possible, and it is possible to suppress the occurrence of high-temperature cracking and the decrease in toughness in HAZ while ensuring welding efficiency.
このホットワイヤ・レーザ複合溶接については、レーザビームを照射して母材を溶融すると共に、母材との間で溶接ワイヤに通電してホットワイヤとし、この通電加熱した溶接ワイヤを母材の溶融部分に供給して、溶融した母材と溶接ワイヤからなる溶融プールを形成しながらレーザビームを移動させて、溶接継手を得るようにすればよく、公知の方法と同様にすることができる。また、溶接継手の種類としては特に制限はなく、例えば、突合せ溶接やすみ肉溶接のほか、角継手、重ね継手、T字継手、十字継手等を挙げることができる。その際、融合不良や高温割れ等の溶接欠陥の抑制を考慮すると、好ましくは、ホットワイヤ・レーザ複合溶接における溶接条件について、エネルギー密度を300W/mm2以下に制御するのがよい。ここで、エネルギー密度とはレーザ溶接における出力(kW)を溶接時のスポット面積(mm2)で割った値である。スポットの形状は円形、矩形等が一般に用いられるが、形状によらずエネルギー密度にて制御可能である。エネルギー密度の制御は、溶接変形の抑制、溶接継手靱性の低減に有効である。 In this hot wire / laser composite welding, a laser beam is irradiated to melt the base metal, and the welding wire is energized with the base metal to form a hot wire, and the energized and heated welding wire is used to melt the base metal. The laser beam may be moved while supplying to the portion to form a molten pool composed of the molten base metal and the weld wire to obtain a welded joint, and the same method as a known method can be used. The type of welded joint is not particularly limited, and examples thereof include butt welding and fillet welding, as well as square joints, lap joints, T-shaped joints, and cross joints. At that time, considering the suppression of welding defects such as fusion defects and high temperature cracks, it is preferable to control the energy density to 300 W / mm 2 or less for the welding conditions in the hot wire / laser composite welding. Here, the energy density is a value obtained by dividing the output (kW) in laser welding by the spot area (mm 2 ) at the time of welding. The shape of the spot is generally circular, rectangular, or the like, but it can be controlled by the energy density regardless of the shape. Controlling the energy density is effective in suppressing welding deformation and reducing weld joint toughness.
また、本発明においては、例えば、LNGやLPGを蓄える貯蔵タンクやこれらを輸送するタンカー等のように、極低温での靱性を確保するために6~9%程度のNiが添加された低温用Ni鋼を母材として用いて溶接継手を得るようにする。この低温用Ni鋼については、所定の化学組成を有するものを用いるようにするのがよい。その化学組成を特定する理由については、以下に説明するとおりである。なお、これらの説明における「%」は、特に断りがない限り「質量%」を表す。 Further, in the present invention, for low temperature use to which about 6 to 9% Ni is added in order to secure toughness at extremely low temperature, for example, a storage tank for storing LNG and LPG, a tanker for transporting these, and the like. A welded joint is obtained by using Ni steel as a base material. As for this Ni steel for low temperature, it is preferable to use one having a predetermined chemical composition. The reason for specifying the chemical composition is as described below. In addition, "%" in these explanations represents "mass%" unless otherwise specified.
(C:0.03~0.10%)
Cは、強度確保の観点から0.03%以上含有させる必要がある。しかしながら、含有量が多くなり過ぎると靱性の低下をきたすことから、その上限は0.10%とする。好ましくは、Cの含有量は0.04%以上0.07%以下であるのがよい。
(C: 0.03 to 0.10%)
C needs to be contained in an amount of 0.03% or more from the viewpoint of ensuring strength. However, if the content is too large, the toughness will decrease, so the upper limit is set to 0.10%. Preferably, the C content is 0.04% or more and 0.07% or less.
(Si:0.01~0.5%)
Siは脱酸作用を有するほか、強度を向上させる元素であり0.01%以上の含有量が必要である。しかしながら、その含有量が多過ぎると溶接継手靱性などの低下をきたすため、その上限は0.50%であり、好ましくは0.03~0.4%である。
(Si: 0.01-0.5%)
Si has a deoxidizing effect and is an element that improves strength, and a content of 0.01% or more is required. However, if the content is too large, the toughness of the welded joint will decrease, so the upper limit is 0.50%, preferably 0.03 to 0.4%.
(Mn:0.3~1.5%)
Mnは、強度及び靱性を向上させる元素であり、0.3%以上含有させる必要がある。しかしながら、その含有量が多過ぎると母材及びHAZの靱性劣化をきたすことから、その上限は1.5%である。好ましくは0.4~1.2%である。
(Mn: 0.3-1.5%)
Mn is an element that improves strength and toughness, and needs to be contained in an amount of 0.3% or more. However, if the content is too large, the toughness of the base metal and HAZ deteriorates, so the upper limit is 1.5%. It is preferably 0.4 to 1.2%.
(Ni:5.0~10.0%)
Niは、強度及び靱性を同時に向上させる作用を有し、低温の液体を貯蔵するためのタンク、なかでも-165℃という極低温のLNGを貯蔵するLNGタンクを製造するための母材に欠かせない元素であり、5.0%以上の含有量が必要である。しかしながら、10.0%を超えて含有させても、その効果は飽和してコストが嵩むばかりである。好ましくは5.5~9.5%である。
(Ni: 5.0 to 10.0%)
Ni has the effect of improving strength and toughness at the same time, and is indispensable as a base material for manufacturing tanks for storing low-temperature liquids, especially LNG tanks for storing cryogenic LNG at -165 ° C. It is a non-elemental element and requires a content of 5.0% or more. However, even if it is contained in excess of 10.0%, the effect is saturated and the cost is increased. It is preferably 5.5 to 9.5%.
(P:0.015%以下)
Pは、鋼に不可避的に含有される不純物元素であり、粒界偏析元素であるためにHAZにおける粒界割れの原因となる。母材及びHAZの靱性を向上させるために、Pの含有量は0.015%以下にする。好ましくは0.010%以下である。Pの含有量は0であってもよいが、過度な低減はコストの増加を招くことなどから、0.003%以上とするのが好ましい。なお、Pは鉄鋼材料の製造において不可避的に混入される点で、後述する残部としての不純物と同じであるが、Pは、上記のとおりHAZの靭性向上の観点から、その含有量を別途規定している。
(P: 0.015% or less)
P is an impurity element inevitably contained in steel, and since it is a grain boundary segregation element, it causes grain boundary cracking in HAZ. In order to improve the toughness of the base metal and HAZ, the content of P should be 0.015% or less. It is preferably 0.010% or less. The content of P may be 0, but it is preferably 0.003% or more because excessive reduction causes an increase in cost. It should be noted that P is the same as the impurities as the balance described later in that it is inevitably mixed in the production of steel materials, but the content of P is separately specified from the viewpoint of improving the toughness of HAZ as described above. is doing.
(S:0.003%以下)
Sは、多量に存在する場合、溶接割れ起点となるMnS単体の析出物を生成する。そのため、Sの含有量は0.003%以下にする必要がある。好ましくは0.002%以下である。Sの含有量は0であってもよいが、過度な低減はコストの増加を招くことなどから、0.0002%以上とするのが好ましい。なお、Sは鉄鋼材料の製造において不可避的に混入される点で、後述する残部としての不純物と同じであるが、Sは、上記のとおり溶接割れ抑制の観点から、その含有量を別途規定している。
(S: 0.003% or less)
When S is present in a large amount, it produces a precipitate of MnS alone, which is the starting point of welding cracks. Therefore, the content of S needs to be 0.003% or less. It is preferably 0.002% or less. The content of S may be 0, but it is preferably 0.0002% or more because excessive reduction causes an increase in cost. It should be noted that S is the same as impurities as a balance described later in that it is inevitably mixed in the production of steel materials, but S has a separately specified content from the viewpoint of suppressing welding cracks as described above. ing.
(Al:0.005~0.08%)
Alは脱酸元素であり、鋼の清浄性を確保するために0.005%以上含有させる必要がある。しかしながら、その含有量が多過ぎると、粗大なAl2O3を生成したり、溶接継手の靱性が低下するため、その上限は0.08%である。好ましくは0.01~0.05%である。
(Al: 0.005 to 0.08%)
Al is a deoxidizing element and needs to be contained in an amount of 0.005% or more in order to ensure the cleanliness of steel. However, if the content is too large, coarse Al 2 O 3 is generated and the toughness of the welded joint is lowered, so that the upper limit is 0.08%. It is preferably 0.01 to 0.05%.
(B:0.001%以下)
Bは、強度を高める作用を有する。すなわち、Bは粒界に偏析して強度改善効果を有する。しかしながら、Bの含有量が0.001%を超えると、靱性が損なわれる。好ましくは0.0005%以下である。Bの含有量は0であってもよいが、上記の作用を発現させるためには0.0003%以上とするのがよい。
(B: 0.001% or less)
B has an effect of increasing strength. That is, B segregates at the grain boundaries and has a strength improving effect. However, if the B content exceeds 0.001%, the toughness is impaired. It is preferably 0.0005% or less. The content of B may be 0, but it is preferably 0.0003% or more in order to exhibit the above-mentioned action.
(Ti:0.010%以下)
Tiは、炭窒化物の形成を通じて破壊の起点増加による靱性劣化を招くため、0.010%以下に抑制する必要がある。好ましくは0.005%以下である。Tiの含有量は0であってもよいが、Tiは炭窒化物を形成し組織細粒化に寄与することから、このような作用を発現させるためには0.003%以上とするのがよい。
(Ti: 0.010% or less)
Since Ti causes toughness deterioration due to an increase in the starting point of fracture through the formation of carbonitride, it is necessary to suppress it to 0.010% or less. It is preferably 0.005% or less. The content of Ti may be 0, but since Ti forms carbonitride and contributes to microstructural granulation, it should be 0.003% or more in order to exhibit such an effect. good.
(Nb:0.010%以下)
Nbは、炭窒化物の形成を通じて破壊の起点増加による靱性劣化を招くため、0.010%以下に抑制する必要がある。好ましくは0.005%以下である。Nbの含有量は0であってもよいが、Nbは炭窒化物を形成し組織細粒化に寄与することから、このような作用を発現させるためには0.003%以上とするのがよい。
(Nb: 0.010% or less)
Since Nb causes deterioration of toughness due to an increase in the starting point of fracture through the formation of carbonitride, it is necessary to suppress it to 0.010% or less. It is preferably 0.005% or less. The content of Nb may be 0, but since Nb forms a carbonitride and contributes to microstructural granulation, it should be 0.003% or more in order to exhibit such an effect. good.
(V:0.010%以下)
Vは、炭窒化物の形成を通じて破壊の起点増加による靱性劣化を招くため、0.010%以下に抑制する必要がある。好ましくは0.005%以下である。Vの含有量は0であってもよいが、Vは炭窒化物を形成し組織細粒化に寄与することから、このような作用を発現させるためには0.005%以上とするのがよい。
(V: 0.010% or less)
V causes toughness deterioration due to an increase in the starting point of fracture through the formation of carbonitride, and therefore needs to be suppressed to 0.010% or less. It is preferably 0.005% or less. The content of V may be 0, but since V forms carbonitride and contributes to microstructural granulation, it should be 0.005% or more in order to exhibit such an effect. good.
(N:0.010%以下)
Nは不可避的不純物として混入する元素であり、靱性劣化を招く場合があるため0.010%以下に低減する。好ましくは0.006%以下である。Nの含有量は0であってもよいが、過度な低減はコストの増加を招くことなどから、0.002%以上とするのが好ましい。なお、Nは鉄鋼材料の製造において不可避的に混入される点で、後述する残部としての不純物と同じであるが、Nは、上記のとおり靱性劣化抑制の観点から、その含有量を別途規定している。
(N: 0.010% or less)
N is an element mixed as an unavoidable impurity and may cause deterioration of toughness, so it is reduced to 0.010% or less. It is preferably 0.006% or less. The content of N may be 0, but it is preferably 0.002% or more because excessive reduction causes an increase in cost. It should be noted that N is the same as impurities as a balance described later in that it is inevitably mixed in the production of steel materials, but N has a separately specified content from the viewpoint of suppressing toughness deterioration as described above. ing.
(O:0.005%以下)
Oは、酸化物の形成を通じて靱性劣化を招くため、0.005%以下とする必要がある。好ましくは0.003%以下である。Oの含有量は0であってもよいが、過度な低減はコストの増加を招くことなどから、0.001%以上とするのが好ましい。なお、Oは鉄鋼材料の製造において不可避的に混入される点で、後述する残部としての不純物と同じであるが、Oは、上記のとおり靱性劣化抑制の観点から、その含有量を別途規定している。
(O: 0.005% or less)
O must be 0.005% or less because it causes toughness deterioration through the formation of oxides. It is preferably 0.003% or less. The content of O may be 0, but it is preferably 0.001% or more because excessive reduction causes an increase in cost. It should be noted that O is the same as the impurities as the balance described later in that it is inevitably mixed in the production of steel materials, but O is separately defined for its content from the viewpoint of suppressing toughness deterioration as described above. ing.
(Cu:1.0%以下)
Cuは、強度を高める作用を有する。しかしながら、その含有量が1.0%を超えるとHAZの靱性低下を招く。好ましくは0.5%以下である。Cuの含有量は0であってもよいが、上記の作用を発現させるためには0.02%以上とするのがよい。
(Cu: 1.0% or less)
Cu has the effect of increasing the strength. However, if the content exceeds 1.0%, the toughness of HAZ is lowered. It is preferably 0.5% or less. The content of Cu may be 0, but it is preferably 0.02% or more in order to exhibit the above-mentioned action.
(Cr:1.0%以下)
Crは、強度を高める作用を有する。しかしながら、その含有量が1.0%を超えるとHAZの靱性低下を招く。好ましくは0.8%以下である。Crの含有量は0であってもよいが、上記の作用を発現させるためには0.02%以上とするのがよい。
(Cr: 1.0% or less)
Cr has the effect of increasing the strength. However, if the content exceeds 1.0%, the toughness of HAZ is lowered. It is preferably 0.8% or less. The Cr content may be 0, but it is preferably 0.02% or more in order to exhibit the above-mentioned action.
(Mo:1.0%以下)
Moは、強度を高める作用を有する。しかしながら、その含有量が1.0%を超えるとHAZの靱性低下を招く。好ましくは0.5%以下である。Moの含有量は0であってもよいが、上記の作用を発現させるためには0.02%以上とするのがよい。
(Mo: 1.0% or less)
Mo has the effect of increasing the strength. However, if the content exceeds 1.0%, the toughness of HAZ is lowered. It is preferably 0.5% or less. The Mo content may be 0, but it is preferably 0.02% or more in order to exhibit the above-mentioned action.
上記成分の残部は、鉄(Fe)及び不純物である。ここで、「不純物」とは、鋼を工業的に製造する際に、鉱石やスクラップ等のような原料を始めとして、製造工程の種々の要因によって混入する成分であって、本発明に悪影響を与えない範囲で許容されるものを意味する。 The rest of the above components are iron (Fe) and impurities. Here, the "impurity" is a component mixed by various factors in the manufacturing process, including raw materials such as ore and scrap, when steel is industrially manufactured, and has an adverse effect on the present invention. It means what is allowed within the range not given.
本発明においては、ホットワイヤ・レーザ複合溶接を採用することで、エネルギー密度の低いレーザビームの照射でも、十分な溶融金属を形成することができることから、板厚Tが4~60mm、好ましくは10~50mmの低温用Ni鋼に対して、溶接継手を得るようにするのが望ましい。 In the present invention, by adopting hot wire / laser composite welding, a sufficient molten metal can be formed even by irradiation with a laser beam having a low energy density. Therefore, the plate thickness T is 4 to 60 mm, preferably 10. It is desirable to obtain a welded joint for low temperature Ni steel of ~ 50 mm.
また、溶接継手を得る際に用いる溶接材料については、ホットワイヤ・レーザ複合溶接において通電加熱しながら供給する溶接ワイヤとして用いることができるものであればよく、好ましくは、一般に、低温用Ni鋼の溶接で用いられるような高Ni合金の溶接材料であるのがよい。すなわち、Ni量が高いNi合金はオーステナイト組織を有して、これが極低温において安定であり、脆性破壊を起こし難い。そのため、例えば、質量割合でNiを50%以上、好ましくは55~75%含有するオーステナイト構造を有したNi基合金(高Ni合金)を用いるようにするのがよい。このような高Ni合金の溶接材料について、市販品の例としては、NITTETSU FILLER196(以上、日鉄溶接工業社製商品名)、TG-S709S(以上、神戸製鋼社製商品名)等を挙げることができる。 Further, the welding material used for obtaining the welded joint may be any material as long as it can be used as a welding wire to be supplied while energizing and heating in hot wire / laser composite welding, and generally, Ni steel for low temperature is preferable. It is preferable to use a high Ni alloy welding material as used in welding. That is, a Ni alloy having a high Ni content has an austenite structure, which is stable at extremely low temperatures and is unlikely to cause brittle fracture. Therefore, for example, it is preferable to use a Ni-based alloy (high Ni alloy) having an austenite structure containing 50% or more, preferably 55 to 75% of Ni in terms of mass ratio. Examples of commercially available products for such high Ni alloy welding materials include NITTETSU FILLER 196 (above, product name manufactured by Nippon Steel Welding & Co., Ltd.), TG-S709S (above, product name manufactured by Kobe Steel), and the like. Can be done.
次に、実施例に基づいて本発明について説明するが、本発明はこれらの内容に制限されるものではない。 Next, the present invention will be described based on examples, but the present invention is not limited to these contents.
(試験例1)
表1に示す化学成分及び機械特性等を有した発明例1~10、比較例1~19に係る鋼板(低温用Ni鋼)を母材(被溶接材)として使用した。鋼板は焼入焼戻し(QT)若しくは熱加工制御圧延後焼戻し(TMCT)で製造した。このうち、QTは、鋳片を1000~1200℃に加熱した後、所定の寸法に圧延して冷却後、更に800~900℃に加熱して焼き入れした後に、更にまた560~600℃に加熱して焼戻しを行った。TMCTについては900~1200℃に加熱した後、700℃以上の温度で制御圧延を完了して冷却後、560~600℃に加熱して焼戻しを行った。QT、TMCTともに、必要に応じて焼き入れ前に605~750℃の中間熱処理を行った。なお、表1に示した各鋼板の化学組成は、それぞれの化学成分の残部がFe及び不純物である。
(Test Example 1)
The steel plates (Ni steel for low temperature) according to Invention Examples 1 to 10 and Comparative Examples 1 to 19 having the chemical components and mechanical properties shown in Table 1 were used as the base material (welded material). Steel sheets were manufactured by quenching tempering (QT) or thermal machining controlled rolling and then tempering (TMCT). Of these, QT heats the slab to 1000 to 1200 ° C, rolls it to a predetermined size, cools it, heats it to 800 to 900 ° C, quenches it, and then heats it to 560 to 600 ° C. And then tempered. The TMCT was heated to 900 to 1200 ° C., then controlled rolling was completed at a temperature of 700 ° C. or higher, cooled, and then heated to 560 to 600 ° C. for tempering. Both QT and TMCT were subjected to an intermediate heat treatment at 605 to 750 ° C. before quenching, if necessary. In the chemical composition of each steel sheet shown in Table 1, the balance of each chemical component is Fe and impurities.
また、これらの鋼板の機械特性として、鋼板の引張特性については、板厚(T)が16mm以下の鋼板ではJIS Z2241:2011-5号試験片を全厚にて圧延方向と垂直方向に採取し、板厚(T)が16mmを超える鋼板ではJIS Z2241:2011-4号試験片を板厚1/4の位置(1/4t)から圧延方向と垂直方向に採取して、それぞれ室温にて試験して引張強さ(TS)を求めた。鋼板の衝撃特性については、全ての鋼板において板厚1/4の位置(1/4t)の位置、及び、圧延方向と並行に、JIS Z2242:2018に規定された2mmVノッチシャルピー試験片を採取し、-196℃の温度でシャルピー衝撃試験を実施して、吸収エネルギー値(svE-196℃)を求めた。 As for the mechanical properties of these steel sheets, regarding the tensile properties of the steel sheet, for steel sheets with a plate thickness (T) of 16 mm or less, JIS Z2241: 2011-5 test pieces were sampled at the total thickness in the direction perpendicular to the rolling direction. For steel sheets with a plate thickness (T) of more than 16 mm, JIS Z2241: 2011-4 test pieces are sampled from the position of 1/4 of the plate thickness (1 / 4t) in the direction perpendicular to the rolling direction and tested at room temperature. The tensile strength (TS) was obtained. Regarding the impact characteristics of steel sheets, 2 mm V notch Charpy test pieces specified in JIS Z2242: 2018 were taken in parallel with the position of 1/4 of the plate thickness (1 / 4t) and the rolling direction in all steel sheets. , -A Charpy impact test was carried out at a temperature of 196 ° C to determine the absorbed energy value (svE-196 ° C).
この試験例1では、表1に示した各鋼板について、それぞれ2枚並べて20°のV字(V形)開先を形成する突合せ溶接により溶接継手を得るようにし、その際にV字を形成して溶接実施部となる各鋼板の対向面(開先面)から溶接開始位置および任意の5箇所をそれぞれ選び出し、残留磁気をガウスメーターで測定して、これらのなかで最も大きな値(最大値)をその鋼板の溶接実施部における残留磁気として表1に示した。なお、溶接の際の裏当金には、母材である鋼板と同じものをそれぞれ使用した。なお、溶接継手の種類としては特に制限はなく、例えば、開先溶接やすみ肉溶接のほか、せん溶接やスロット溶接等を挙げることができる。 In this test example 1, two steel plates shown in Table 1 are arranged side by side to form a 20 ° V-shaped (V-shaped) groove, and a welded joint is obtained by butt welding, and a V-shape is formed at that time. Then, the welding start position and any five points are selected from the facing surface (groove surface) of each steel sheet to be the welding execution part, and the residual magnetism is measured with a Gauss meter, and the largest value (maximum value) among these is measured. ) Is shown in Table 1 as the residual magnetism in the welded portion of the steel sheet. For the backing metal at the time of welding, the same steel plate as the base material was used. The type of welded joint is not particularly limited, and examples thereof include groove welding, fillet welding, wire welding, and slot welding.
また、溶接材料としては、JIS Z3332:2007に規定されるYGT9NI-2相当のニッケル(Ni)基合金ワイヤ(φ1.2mm)を使用し、ホットワイヤ・レーザ複合溶接で通電加熱する溶接ワイヤとして、表2に示す溶接条件で溶接継手を作製した。ここで、ホットワイヤ・レーザ複合溶接(HWL)では、レーザ溶接機とホットワーヤ用溶接電源を使用した。そして、表1に示した鋼板と上記のNi基合金ワイヤを用いて、ホットワイヤ・レーザ複合溶接方法により、溶接長500mmの溶接継手を作製した。その際、ホットワイヤ溶接はワイヤ加熱電流100~400A、ワイヤ供給速度は2~30m/min.とした。レーザ溶接におけるパラメータとして溶接速度1~5m/min.、レーザ出力3~20kWとし、溶接スポット径を調整することでエネルギー密度の制御を行った。また、シールドガスはAr(流量30L/min.)を用いた。
一方で、比較として、ガスタングステンアーク溶接(GTAW)による継手作成も行った。溶接材料はホットワイヤ・レーザ複合溶接と同じニッケル基合金とArシールドガスを用い、電流値280A、電圧値10V、目標入熱量18kJ/cmとした。
Further, as the welding material, a nickel (Ni) -based alloy wire (φ1.2 mm) equivalent to YGT9NI-2 specified in JIS Z3332: 2007 is used, and as a welding wire to be energized and heated by hot wire / laser composite welding. Welded joints were manufactured under the welding conditions shown in Table 2. Here, in hot wire laser composite welding (HWL), a laser welder and a welding power supply for hot wire were used. Then, using the steel plate shown in Table 1 and the above-mentioned Ni-based alloy wire, a welded joint having a welding length of 500 mm was produced by a hot wire / laser composite welding method. At that time, the wire heating current was 100 to 400 A for hot wire welding, and the wire supply speed was 2 to 30 m / min. The energy density was controlled by adjusting the welding spot diameter with a welding speed of 1 to 5 m / min. And a laser output of 3 to 20 kW as parameters in laser welding. The shield gas used was Ar (flow rate 30 L / min.).
On the other hand, as a comparison, we also made joints by gas tungsten arc welding (GTAW). As the welding material, the same nickel-based alloy and Ar shield gas as in the hot wire / laser composite welding were used, and the current value was 280 A, the voltage value was 10 V, and the target heat input amount was 18 kJ / cm.
このような試験例1について、表2には、表1に示した鋼板と溶接条件の組み合わせを示している。このうちの各評価について、先ず、磁気吹きの判定としては、溶接途中で溶融ビードが偏ったり蛇行する現象が発生した場合に×、それ以外を○と評価した。また、得られた溶接継手の衝撃特性を評価するために、母材である鋼板の板厚1/4の位置(1/4t)でのボンド部(溶接金属とHAZの厚みの比率が1:1)をノッチ位置としてJIS Z2242:2018に規定された2mmVノッチシャルピー試験片を採取し、-196℃の温度でシャルピー衝撃試験を実施し、吸収エネルギー値(継手シャルピー)を求めた。更にまた、得られた溶接継手について、放射線透過試験法により溶接欠陥の有無を調べた。JIS Z 3106:2001に準じて試験を行い、2種以上の欠陥が確認されたものを×、それ以外を○として判定した。 For such Test Example 1, Table 2 shows the combination of the steel sheet and the welding conditions shown in Table 1. Regarding each of these evaluations, first, as the determination of magnetic blowing, x was evaluated when the molten bead was biased or meandering during welding, and ○ was evaluated otherwise. Further, in order to evaluate the impact characteristics of the obtained welded joint, the bond portion (the ratio of the thickness of the weld metal and the HAZ is 1: 1) at the position (1 / 4t) of the plate thickness of the steel plate which is the base material is 1: A 2 mm V notch Charpy test piece specified in JIS Z2242: 2018 was taken with 1) as the notch position, and a Charpy impact test was performed at a temperature of -196 ° C. to obtain an absorbed energy value (joint charpy). Furthermore, the obtained welded joints were examined for welding defects by a radiation transmission test method. The test was conducted according to JIS Z 3106: 2001, and those in which two or more types of defects were confirmed were judged as x, and those in which other defects were judged as ◯.
以上の結果から分かるように、本発明によれば、着磁しやすい低温用Ni鋼について、従来のように脱磁処理を行わなくても、磁気吹き等の影響を受けずに溶接継手を製造することができるようになり、しかも、信頼性に優れた高品質の溶接継手を得ることができる。
As can be seen from the above results, according to the present invention, a welded joint is manufactured for low-temperature Ni steel, which is easily magnetized, without being affected by magnetic blowing, etc., without being demagnetized as in the conventional case. It is possible to obtain a high-quality welded joint with excellent reliability.
Claims (3)
該低温用Ni鋼が30ガウス以上の残留磁気を有した状態で、レーザビームを照射して溶融させながら通電加熱した溶接ワイヤを供給するホットワイヤ・レーザ複合溶接により溶接継手を得ることを特徴とする、低温用Ni鋼を用いた溶接継手の製造方法。 It is a method of manufacturing welded joints using Ni steel for low temperature.
It is characterized in that a welded joint is obtained by hot wire / laser composite welding in which the low temperature Ni steel has a residual magnetism of 30 gauss or more and supplies a welded wire heated by energization while being melted by irradiating a laser beam. A method for manufacturing a welded joint using Ni steel for low temperature.
C:0.03~0.10%、
Si:0.01~0.5%、
Mn:0.3~1.5%、
Ni:5~10%、
P:0.015%以下、
S:0.003%以下、
Al:0.005~0.08%、
B:0.001%以下、
Ti:0.010%以下、
Nb:0.010%以下、
V:0.010%以下、
N:0.010%以下、
O:0.005%以下、
Cu:1.0%以下、
Cr:1.0%以下、
Mo:1.0%以下、
残部:Fe及び不純物、
である、請求項1又は2に記載の低温用Ni鋼を用いた溶接継手の製造方法。
The low temperature Ni steel has a chemical composition of% by mass.
C: 0.03 to 0.10%,
Si: 0.01-0.5%,
Mn: 0.3-1.5%,
Ni: 5-10%,
P: 0.015% or less,
S: 0.003% or less,
Al: 0.005 to 0.08%,
B: 0.001% or less,
Ti: 0.010% or less,
Nb: 0.010% or less,
V: 0.010% or less,
N: 0.010% or less,
O: 0.005% or less,
Cu: 1.0% or less,
Cr: 1.0% or less,
Mo: 1.0% or less,
Remaining: Fe and impurities,
The method for manufacturing a welded joint using the low temperature Ni steel according to claim 1 or 2.
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