JP4822733B2 - Welded joints for steel structures - Google Patents
Welded joints for steel structures Download PDFInfo
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- JP4822733B2 JP4822733B2 JP2005113027A JP2005113027A JP4822733B2 JP 4822733 B2 JP4822733 B2 JP 4822733B2 JP 2005113027 A JP2005113027 A JP 2005113027A JP 2005113027 A JP2005113027 A JP 2005113027A JP 4822733 B2 JP4822733 B2 JP 4822733B2
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- 229910000831 Steel Inorganic materials 0.000 title claims description 42
- 239000010959 steel Substances 0.000 title claims description 42
- 238000003466 welding Methods 0.000 claims description 103
- 229910052751 metal Inorganic materials 0.000 claims description 41
- 239000002184 metal Substances 0.000 claims description 41
- 239000000203 mixture Substances 0.000 claims description 37
- 230000009466 transformation Effects 0.000 claims description 29
- 229910000734 martensite Inorganic materials 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 24
- 238000001816 cooling Methods 0.000 claims description 13
- 229910000851 Alloy steel Inorganic materials 0.000 claims description 10
- 230000008569 process Effects 0.000 claims description 7
- 229910052804 chromium Inorganic materials 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 5
- 230000008602 contraction Effects 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 4
- 239000000463 material Substances 0.000 description 58
- 239000000126 substance Substances 0.000 description 7
- 238000010276 construction Methods 0.000 description 6
- 230000002829 reductive effect Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 238000010792 warming Methods 0.000 description 3
- 229910000640 Fe alloy Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010790 dilution Methods 0.000 description 2
- 239000012895 dilution Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- -1 C: 0.20 wt% or less Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000002737 fuel gas Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 230000000452 restraining effect Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
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- Butt Welding And Welding Of Specific Article (AREA)
Description
本発明は、船舶、橋梁、貯槽、建設機械等の鋼構造物に用いて好適な溶接継手に係り、特に、溶接中に発生する溶接継手の変形を抑制するものである。 The present invention relates to a welded joint suitable for use in steel structures such as ships, bridges, storage tanks, construction machines, and the like, and particularly suppresses deformation of a welded joint that occurs during welding.
船舶，橋梁，貯槽等の建造物や建設機械等の大型機械においては、低合金鋼材（Cr，Ni，Mo等を添加した引張強度レベル400〜590MPaの鋼材）が用いられており、その鋼材からなる各部材の接合には溶接が多用されている。そのため鋼構造物（たとえば建造物，大型機械等）は、構築する際の溶接施工によって、溶接金属（すなわち溶接材料と鋼材が溶融し、さらに冷却されてできた鋼）の熱収縮が発生し、溶接継手が変形する。 Low-alloy steel materials (steel materials with a tensile strength level of 400 to 590 MPa added with Cr, Ni, Mo, etc.) are used in large machinery such as ships, bridges, storage tanks, and construction machinery. Welding is often used for joining the respective members. For this reason, steel structures (for example, buildings, large machines, etc.) undergo thermal contraction of the weld metal (ie, the steel that is made by melting the weld material and the steel material and then cooling it) due to the welding work during construction, The weld joint is deformed.
その変形量の許容範囲は、鋼構造物の用途に応じて規定されており、たとえば道路橋では道路橋示方書，船舶では日本鋼船工作精度標準に規定されている。変形量が許容範囲を超える場合には、溶接継手を加熱して変形を矯正する。変形した溶接継手の加熱には燃料用ガスが大量に消費されており、その燃焼によって多量のＣＯ2 が大気中に放散されている。 The allowable range of the deformation amount is defined according to the use of the steel structure. For example, it is defined in the road bridge specifications for road bridges and the Japanese steel ship working accuracy standard for ships. If the amount of deformation exceeds the allowable range, the weld joint is heated to correct the deformation. A large amount of fuel gas is consumed for heating the deformed welded joint, and a large amount of CO 2 is diffused into the atmosphere by the combustion.
一方、地球温暖化の問題は、環境に与える影響の大きさや深刻さから、緊急に対応すべき課題である。温暖化を防止するためには、温暖化を招く要因となるガス（いわゆる温室効果ガス，特にその大部分を占めるＣＯ2 ）の排出を抑制する必要がある。
そのため鋼構造物を構築する際の溶接施工において、溶接継手の変形を減少させて、溶接した後の加熱による矯正を不要にする溶接技術（すなわち溶接精度の向上およびエネルギー消費量の低減を達成する技術）が種々検討されている。
On the other hand, the problem of global warming is an issue that should be addressed urgently because of the magnitude and seriousness of its impact on the environment. In order to prevent global warming, it is necessary to suppress emissions of gases that cause global warming (so-called greenhouse gases, particularly CO 2 occupying most of them).
Therefore, in welding construction when constructing steel structures, welding technology that reduces the deformation of welded joints and eliminates the need for correction by heating after welding (ie, improving welding accuracy and reducing energy consumption) Various techniques have been studied.
一般に、鋼材同士を溶接により接合して溶接継手を製作すると、溶接時の加熱および溶接後の冷却によって、溶接継手の変形が生じる。特に、薄い鋼材を溶接する場合には、溶接継手の変形量が大きくなることが知られている。
溶接継手が変形する原因は、溶接入熱により融点以上に加熱され溶融した溶接金属が、溶接の後で冷却されて凝固、収縮することによって応力が発生し、その応力によって溶接継手が変形することにある。溶接継手の変形量は、通常、溶接変形量と呼ばれる指標で評価する。溶接変形量は、溶接前の母材に沿う長さａに対する、溶接方向に直交する断面での溶接後に生じた変形量ｂの比（すなわちｂ／ａ）で表わされることが多い。
Generally, when steel products are joined together by welding to produce a welded joint, the welded joint is deformed by heating during welding and cooling after welding. In particular, when a thin steel material is welded, it is known that the amount of deformation of the weld joint increases.
The cause of the deformation of the welded joint is that the weld metal that has been heated and melted above the melting point by welding heat input is cooled and solidified and contracted after welding, and stress is generated, and the welded joint is deformed by the stress. It is in. The deformation amount of a welded joint is usually evaluated by an index called a welding deformation amount. The welding deformation amount is often represented by the ratio of the deformation amount b generated after welding in a cross section perpendicular to the welding direction to the length a along the base material before welding (that is, b / a).
このような溶接継手の変形を低減する方法として、溶接継手を加熱して矯正する前記した方法の他に、鋼材を拘束して溶接する等の方法が広く採用されている。しかしながら、これらの方法は、多大な作業時間を要するので、その作業中に消費される燃料が増大する。しかも溶接作業コストの高騰や溶接作業能率の低下を招くという問題もあった。
特許文献１に開示された溶接方法では、溶接に供される鋼板の化学組成も限定されるため、汎用の鋼板を用いる場合には十分な効果が得られないという問題もあった。
As a method for reducing the deformation of such a welded joint, in addition to the above-described method for correcting the welded joint by heating, a method of restraining and welding the steel material is widely adopted. However, these methods require a large amount of work time, and the fuel consumed during the work increases. In addition, there has been a problem that the welding work cost increases and the welding work efficiency decreases.
In the welding method disclosed in Patent Document 1, since the chemical composition of the steel sheet used for welding is also limited, there is a problem that a sufficient effect cannot be obtained when a general-purpose steel sheet is used.
また特許文献２には、ワイヤ中に占める化学成分により規定される相変態温度を620℃以下としているが、実施例によると規定範囲内でも変形量が異なっており、必ずしも溶接継手の変形の抑制に効果的な範囲とは言い難い。
一方、特許文献３には、溶接により生成する溶接金属を、溶接後の冷却過程でマルテンサイト変態を起こさせ、室温においてマルテンサイト変態の開始時よりも膨張している状態とする溶接方法が提案されている。この方法によれば、溶接継手の疲労強度が向上するとしている。しかしながら特許文献３に記載された技術を薄肉鋼材の溶接に適用すると、溶接金属の膨張によって、かえって溶接変形が大きくなるという問題が残されていた。
In
On the other hand, Patent Document 3 proposes a welding method in which a weld metal produced by welding undergoes martensitic transformation in the cooling process after welding, and is in a state of expanding more than at the start of martensitic transformation at room temperature. Has been. According to this method, the fatigue strength of the welded joint is improved. However, when the technique described in Patent Document 3 is applied to welding of thin-walled steel materials, there remains a problem that welding deformation becomes rather large due to expansion of the weld metal.
さらに特許文献４では、溶接金属の化学組成およびマルテンサイト変態開始温度を限定することにより耐溶接変形性に優れた溶接継手を提唱している。しかしながら特許文献４に開示された溶接材料では、溶接継手の耐変形性能は向上するものの、溶接金属の靭性が劣るため、伸びがほとんどないという問題があった。また溶接材料の作業性にも問題があり、溶接金属の形状もよくなかった。
本発明は上記のような問題を解消するためになされたものであり、その目的は溶接継手の耐溶接変形能を向上させ、かつ通常の溶接が可能な鋼構造物用溶接継手を提供することにある。
The present invention has been made to solve the above problems, and its object is to improve the resistance welding deformability of the welded joint, and normal welding to provide a steel structure for welding joint hand possible There is.
本発明者らは、溶接材料を用いて接合した25mm厚以下の低合金鋼材の溶接継手に発生する変形を抑制する方法について鋭意研究した。その結果、溶接継手の変形を抑制するためには、溶接金属の組成を、溶接後の冷却過程でマルテンサイト変態を起し、かつ室温まで冷却したのちにマルテンサイト変態開始時に比較して大きな膨張あるいは収縮を生じない状態となる組成とすることが肝要であることに想到した。好ましくは溶接金属の組成を、室温まで冷却したのちにマルテンサイト変態開始時とほぼ同じ程度の伸び量あるいはやや収縮状態となる、温度−伸び曲線（熱膨張曲線）を有するような組成とすることである。 The present inventors diligently studied a method for suppressing deformation generated in a welded joint of a low alloy steel material having a thickness of 25 mm or less joined using a welding material. As a result, in order to suppress the deformation of the welded joint, the composition of the weld metal undergoes a martensitic transformation in the cooling process after welding, and after cooling to room temperature, the expansion is greater than that at the start of the martensitic transformation. Or it came to mind that it is important to make it the composition which does not produce shrinkage. Preferably, the composition of the weld metal is such that it has a temperature-elongation curve (thermal expansion curve) that, after being cooled to room temperature, becomes almost the same amount of elongation as the start of martensite transformation or slightly contracted. It is.
そして本発明者らは、上記したような組成の溶接金属とするためには，溶接材料の組成以外に、溶接に供される鋼材からの希釈を考慮する必要があり、鋼材（すなわち低合金鋼）の組成に応じて溶接材料の組成および溶接入熱等の溶接条件を調整して、溶接することが肝要であることを知見した。本発明は、上記した知見に基づいて、さらに検討を加え完成されたものである。 In order to obtain a weld metal having the above composition, the present inventors need to consider dilution from the steel material used for welding in addition to the composition of the welding material. It was found that welding is important by adjusting the welding conditions such as the composition of the welding material and the welding heat input in accordance with the composition of). The present invention has been completed with further studies based on the above findings.
この溶接方法は、溶接により生成する溶接金属を、溶接後の冷却過程でマルテンサイト変態を起こさせ、室温においてマルテンサイト変態の開始時よりも膨張している状態とするようにしている。そして、この溶接方法に使用される溶接材料（すなわち溶接ワイヤ）としては、マルテンサイト変態開始温度を400℃未満150℃以上と低温化させた溶接材料を用いて、溶接により発生した溶接金属のマルテンサイト変態開始温度を550℃未満360℃以上とするものである。そして、このような溶接方法および溶接材料を用いることにより、溶接継手に発生する熱歪みを緩和させ、溶接施工後の変形の矯正などの処理も緩和できる効果を有するものである。
In this welding method, the weld metal produced by welding undergoes martensitic transformation in the cooling process after welding, and is in a state of expanding at room temperature as compared with the start of martensitic transformation. As a welding material (that is, a welding wire) used in this welding method, a martensite transformation start temperature is reduced to a temperature lower than 400 ° C. and 150 ° C. or higher, and martensite of weld metal generated by welding is used. The site transformation start temperature is less than 550 ° C and 360 ° C or more. And by using such a welding method and welding material, it has the effect that the thermal distortion which generate | occur | produces in a welded joint is relieve | moderated, and the process of correction of the deformation | transformation after welding construction, etc. can also be relieve | moderated.
上記問題を解決するために本発明者らが検討した結果、次のような知見を得た。すなわち、溶接材料にCr、Niを添加させることにより促進されたマルテンサイト変態を、ある温度で開始、終了させ、マルテンサイト変態の膨張現象を限定することにより、溶接継手の変形の防止に効果があることを実証したのである。
なおかつ化学組成をある特定の範囲とすることにより、溶接継手の変形量の緩和を達成できることを見出したのである。すなわち継手の総合的な性能を高めることができる。
As a result of studies conducted by the present inventors in order to solve the above problems, the following knowledge was obtained. In other words, the martensitic transformation promoted by adding Cr and Ni to the welding material is started and terminated at a certain temperature, and the expansion phenomenon of the martensitic transformation is limited, thereby preventing the deformation of the welded joint. It proved that there was.
In addition, it has been found that the amount of deformation of the welded joint can be reduced by setting the chemical composition within a certain range. That is, the overall performance of the joint can be enhanced.
本発明はこの知見に基づいて、さらに検討を加え完成されたものである。
すなわち本発明は、低合金鋼材を溶接して製造する鋼構造物用溶接継手において、溶接金属がＣ：0.20質量％以下、Cr： 4.0〜7.34 質量％、Ni： 0.3〜7.0 質量％、Si： 1.0質量％以下、Mn： 2.0質量％以下、Ｐ： 0.020質量％以下、Ｓ： 0.010質量％以下を含み残部Feおよび不可避的不純物からなる組成を有し、溶接金属のマルテンサイト変態開始温度を 373〜550 ℃の範囲とする鋼構造物溶接継手である。
The present invention has been completed with further studies based on this finding.
That is, the present invention provides a steel structures for welded joint prepared by welding a low alloy steel weld metal C: 0.20 wt% or less, Cr: 4.0 to 7.34 mass%, Ni: 0.3 to 7.0 wt%, Si: 1.0% by mass or less, Mn: 2.0% by mass or less, P: 0.020% by mass or less, S: 0.010% by mass or less and the balance Fe and inevitable impurities, and the martensitic transformation start temperature of the weld metal is 373 a steel structures welded joint hands in the range of to 550 ° C..
溶接金属は、上記した組成に加えて、Moを 2.0質量％以下およびNbを 1.0質量％以下のうちの１種または２種を含有することが好ましい。
Weld metal, in addition to the above-described composition preferably contains one or two of 1.0% by mass or less of 2.0 mass% or less and Nb and Mo.
本発明によれば、通常の溶接技術を採用して溶接を行なっても、溶接継手の変形を抑制できる。 According to the present invention, even when welding is performed using a normal welding technique, deformation of the welded joint can be suppressed.
本発明の溶接継手は、溶接材料（すなわち溶接ワイヤ）を用い、溶接に供される鋼材同士を溶接することにより作製される。本発明の溶接継手では、板厚25mm以下の低合金鋼材を用いる。低合金鋼材としては、 300〜590MPa級、特に490MPa級、590MPa級薄肉高張力鋼材が好適であるが、本発明に用いられるこれら低合金鋼材の組成については、特に限定する必要はなく、通常公知の鋼材いずれもが適用可能である。 The weld joint of the present invention is produced by welding steel materials to be welded to each other using a welding material (that is, a welding wire). In the welded joint of the present invention, a low alloy steel material having a plate thickness of 25 mm or less is used. As the low alloy steel material, 300 to 590 MPa class, particularly 490 MPa class, 590 MPa class thin-walled high-tensile steel material is suitable, but the composition of these low alloy steel materials used in the present invention is not particularly limited and is generally known. Any of these steel materials can be applied.
また、用いられる溶接材料は、溶接に供される鋼材に適合した溶接条件で、後述する組成の溶接金属を形成できる組成を有するものであれば、通常公知の溶接材料いずれもが適用可能である。後述する組成の溶接金属が形成できるように、溶接条件により鋼材からの希釈等を考慮して適宜選択すればよいのである。
本発明では、鋼材に応じて溶接材料の組成および溶接方法、溶接条件を調整して、適正な組成の溶接金属を形成する。本発明の溶接継手の溶接方法は、被覆アーク溶接、ガスメタルアーク溶接、サブマージアーク溶接、ＦＣＷ(フラックス コアド ワイヤ)など各種溶接法がいずれも好適に適用できる。また継手形状は、荷重非伝達型十字溶接継手、角回し溶接などの隅肉溶接継手、突き合わせ溶接継手など、船舶、海洋構造物、ペンストック、橋梁、貯槽、建設機械等の大型鋼構造物に用いられる継手形状がいずれも好適である。
Moreover, as long as the welding material used has the composition which can form the weld metal of the composition mentioned later on the welding conditions suitable for the steel materials with which welding is used, all the well-known welding materials are applicable. . What is necessary is just to select suitably considering the dilution from steel materials etc. with welding conditions so that the weld metal of the composition mentioned later can be formed.
In the present invention, a weld metal having an appropriate composition is formed by adjusting the composition of the welding material, the welding method, and the welding conditions according to the steel material. As the welding method for the welded joint of the present invention, any of various welding methods such as covered arc welding, gas metal arc welding, submerged arc welding, and FCW (flux cored wire) can be suitably applied. In addition, the shape of the joint can be applied to large steel structures such as ships, offshore structures, penstocks, bridges, storage tanks, construction machinery, such as load non-transmission type cross welded joints, fillet welded joints such as corner turning welds, and butt welded joints. Any joint shape used is suitable.
次に、本発明の溶接継手における溶接金属について説明する。本発明の溶接継手における溶接金属は、溶接後の冷却過程でマルテンサイト変態を起し、かつ室温まで冷却したのちにマルテンサイト変態開始時に比較して、大きな膨張あるいは収縮を生じない状態，好ましくは室温まで冷却したのちにマルテンサイト変態開始時とほぼ同じ程度の伸び量あるいはやや収縮状態を示す組成に調整される。 Next, the weld metal in the weld joint of the present invention will be described. The weld metal in the welded joint of the present invention undergoes martensitic transformation in the cooling process after welding, and after cooling to room temperature, does not cause large expansion or contraction compared to the beginning of martensitic transformation, preferably After cooling to room temperature, the composition is adjusted to a composition that exhibits an elongation amount or a slightly contracted state that is almost the same as that at the start of the martensitic transformation.
このような状態を有する本発明の溶接金属とするためには、溶接材料ではなく、鋼材、溶接材料および溶接条件により得られる溶接金属の組成を、まず、マルテンサイト変態開始温度（以下、ＭS 点という）が550℃以下 360℃以上となる組成とする必要がある。ＭS 点が 600 ℃を超えると、マルテンサイト変態による膨張量が少なくなるとともに変態膨張の最大点が室温より高くなりすぎるため、変態後の冷却により再度熱収縮が生じ、これにより引張残留応力が発生するようになり、溶接継手の変形が大きくなる。またＭS 点が360℃未満では、冷却過程におけるマルテンサイト変態による膨張効果が十分でなく、熱収縮により引張残留応力が発生するようになり、溶接継手の変形が大きくなる。このようなことから、溶接金属の組成を、溶接金属のＭs 点が 373〜550 ℃となる組成に限定した。これにより溶接継手の変形が抑制され、耐溶接変形性が良好となる。
In order to obtain the weld metal of the present invention having such a state, first the martensite transformation start temperature (hereinafter referred to as M S) is used for the composition of the weld metal obtained not by the weld material but by the steel material, the weld material and the welding conditions. It is necessary to make the composition at a temperature of 550 ° C or lower and 360 ° C or higher. When M S point exceeds 600 ° C., since the maximum point of transformation expansion with expansion amount is reduced due to martensitic transformation is too higher than room temperature, cooled again cause thermal shrinkage by post transformation by a tensile residual stress which Will occur and the deformation of the welded joint will increase. In the M S point of less than 360 ° C., the expansion effect by the martensitic transformation in the cooling process is not sufficient, become residual tensile stress is generated by heat shrinkage, deformation of the welded joint is increased. For this reason, the composition of the weld metal was limited to a composition in which the Ms point of the weld metal was 373 to 550 ° C. Thereby, the deformation of the welded joint is suppressed, and the weld deformation resistance is improved.
溶接金属のＭS 点がこのような範囲になるには、溶接金属の組成を、Ｃ：0.20質量％以下、Cr：4.0 〜9.0 質量％、Ni： 0.3〜7.0 質量％を含有する鉄合金組成で、さらにSi：1.0 質量％以下、Mn：2.0 質量％以下を含み、あるいはさらにMo：2.0 質量％以下、Nb：1.0 質量％以下のうちの１種または２種を含み、残部Feおよび不可避的不純物からなる鉄合金組成とする。（以下、質量％は％と記す。）
Ｃは、マルテンサイトの硬さを増加し、溶接硬化性を増大し、低温割れを助長する元素であり、過度に含有すると膨張量の増大により溶接変形を引きおこしやすくなるため、できるだけ低減するのが望ましく、0.20％以下とする。なお溶接割れの観点から0.15％以下、好ましくは0.12％以下とするのが好ましい。
The M S point of the weld metal is in this range, the composition of the weld metal, C: 0.20 wt% or less, Cr: 4.0 to 9.0 mass%, Ni: 0.3-7.0 iron alloy composition containing by mass%, Furthermore, Si: 1.0% by mass or less, Mn: 2.0% by mass or less, or Mo: 2.0% by mass or less, Nb: 1.0% by mass or less, including one or two of the remaining Fe and unavoidable impurities The iron alloy composition is as follows. (Hereinafter, mass% is described as%.)
C is an element that increases the hardness of martensite, increases weld hardenability, and promotes low temperature cracking. If excessively contained, it tends to cause welding deformation due to an increase in expansion amount, so it is reduced as much as possible. Is desirable, and it is 0.20% or less. From the viewpoint of weld cracking, it is 0.15% or less, preferably 0.12% or less.
Crは、ＭS 点を低温とする元素であり、本発明の溶接継手における溶接金属としては重要な元素の一つであり、4.0％以上の含有を必要とする。Crの含有量が 9.0％を超えると、ＭS 点を 550℃以下とするには、溶接材料に高価なNiの多量添加および溶接材料の加工性を劣化させる元素の多量添加を必要とし、経済性、製造性の観点から問題がある。
Niは、オーステナイトを安定化する元素であり、ＭS 点を 550℃以下と低温とするために重要な元素である。このようなことから本発明では、Niを0.3 ％以上含有させる必要がある。一方、 7.0％を超える多量の含有は、溶接材料を高価なものとし経済的に不利となる。
Cr is an element that lowers the M S point at a low temperature, and is one of the important elements as a weld metal in the welded joint of the present invention, and needs to contain 4.0% or more. When the content of Cr exceeds 9.0%, the M S point to 550 ° C. or less, and requires a large amount addition of the element deteriorating workability multimeric added and welding materials of expensive Ni in the weld material, economic There is a problem from the viewpoint of productivity and manufacturability.
Ni is an element stabilizing austenite, is an important element for the M S point and 550 ° C. or less and a low temperature. Therefore, in the present invention, it is necessary to contain 0.3% or more of Ni. On the other hand, a large content exceeding 7.0% makes the welding material expensive and is economically disadvantageous.
さらにSiは、ＭS 点を低下させる作用を有し、ＭS 点低下のためには多く含有させるほうが好ましい。しかしSiは脱酸剤として溶接材料から主として供給され、溶接金属にSiを1.0 ％を超えて含有させると溶接材料の製造における加工性が低下する。このため、Siは1.0 ％以下に調整する。
Mnは、脱酸剤として溶接材料から供給されるが、2.0 ％を超えて含有させると、溶接材料の製造における加工性が低下する。このため、Mnは2.0 ％以下に調整する。
Further, Si has an action of lowering the M S point, and it is preferable to contain a large amount for decreasing the M S point. However, Si is mainly supplied from the welding material as a deoxidizer, and if Si is contained in the weld metal in an amount exceeding 1.0%, workability in the production of the welding material is deteriorated. For this reason, Si is adjusted to 1.0% or less.
Mn is supplied from the welding material as a deoxidizer, but if it is contained in an amount exceeding 2.0%, workability in the production of the welding material is lowered. Therefore, Mn is adjusted to 2.0% or less.
本発明では、さらにMo、Nbのうちの１種または２種を含有できる。Moは溶接金属の耐食性を向上させる目的として添加することができるが、2.0 ％を超えて含有させると、溶接材料の加工性が低下する。このため、Moは2.0 ％以下とするのが好ましい。一方、Nbは、ＭS 点を低下させる作用を有し、ＭS 点低下のためには多く含有させるほうが好ましい。しかし1.0 ％を超えて含有させると、溶接材料の製造における加工性が低下する。このため、Nbは1.0 ％以下に限定するのが好ましい。 In the present invention, one or two of Mo and Nb can be further contained. Mo can be added for the purpose of improving the corrosion resistance of the weld metal. However, if it exceeds 2.0%, the workability of the welding material is lowered. For this reason, Mo is preferably 2.0% or less. On the other hand, Nb has a function of lowering the M S point, and it is preferable to contain a large amount for reducing the M S point. However, if the content exceeds 1.0%, workability in the production of the welding material decreases. For this reason, Nb is preferably limited to 1.0% or less.
不純物元素であるＰ、Ｓは、鋼材の靭性等に悪影響を及ぼすため、それぞれ 0.020％以下、 0.010％以下とする。
上記した以外の元素については特に限定されないが、Ｖ，Cu，REM（すなわち希土類元素）をそれぞれ0.5 ％以下含有することは許容される。なお、上記した元素以外に鋼材、溶接材料に含有される元素が不可避的に含有されてもなんら問題はない。
Impurity elements P and S have an adverse effect on the toughness of steel materials, so they are 0.020% or less and 0.010% or less, respectively.
Elements other than those described above are not particularly limited, but it is allowed to contain 0.5% or less of V, Cu, and REM (that is, rare earth elements). In addition to the above-described elements, there is no problem even if elements contained in steel materials and welding materials are inevitably contained.
本発明では、溶接継手の変形を低減する観点から、溶接金属の化学組成が下記の (1)式を満足することが好ましい。
360≦719−795［Ｃ］−35.55［Si］−13.25［Mn］−23.7［Cr］
−26.5［Ni］−23.7［Mo］−11.85［Nb］≦550 ・・・ (1)
［Ｃ］：Ｃの含有量（質量％）
［Si］：Siの含有量（質量％）
［Mn］：Mnの含有量（質量％）
［Cr］：Crの含有量（質量％）
［Ni］：Niの含有量（質量％）
［Mo］：Moの含有量（質量％）
［Nb］：Nbの含有量（質量％）
本発明では、低合金鋼材を溶接に供し、溶接材料を用いて低合金鋼材同士を溶接し溶接継手とするが、上記した組成、特性の溶接金属が形成されるように低合金鋼材の組成に応じて溶接材料の組成、溶接入熱等の溶接条件を調整する。
In the present invention, from the viewpoint of reducing the deformation of the welded joint, it is preferable that the chemical composition of the weld metal satisfies the following formula (1).
360 ≦ 719-795 [C] −35.55 [Si] −13.25 [Mn] −23.7 [Cr]
−26.5 [Ni] −23.7 [Mo] −11.85 [Nb] ≦ 550 (1)
[C]: C content (% by mass)
[Si]: Si content (% by mass)
[Mn]: Mn content (% by mass)
[Cr]: Cr content (% by mass)
[Ni]: Ni content (% by mass)
[Mo]: Mo content (% by mass)
[Nb]: Nb content (% by mass)
In the present invention, the low alloy steel material is subjected to welding, and the low alloy steel materials are welded to each other using a welding material to form a weld joint. However, the composition of the low alloy steel material is such that a weld metal having the above-described composition and characteristics is formed. The welding conditions such as the composition of the welding material and welding heat input are adjusted accordingly.
本発明では、各層溶接で形成される溶接金属をそれぞれ上記した 550℃以下 373℃以上のＭS 点を有し、 (1)式を満足する組成の溶接金属になるように調整する。
これにより、溶接金属に生じる膨張、収縮が緩和され、溶接継手の変形が抑制されて耐溶接変形性が改善される。また本発明は、十字溶接継手を作製する場合も有効である。この場合も溶接金属が上記した本発明範囲の組成となるように、溶接材料、溶接条件を調整するのが好ましい。これにより溶接継手の変形が抑制される。
In the present invention, the weld metal formed by each layer welding is adjusted to have a MS point of 550 ° C. or lower and 373 ° C. or higher, respectively, and a composition satisfying the formula (1).
Thereby, the expansion | swelling and shrinkage | contraction which arise in a weld metal are relieve | moderated, the deformation | transformation of a welded joint is suppressed, and weld deformation resistance is improved. The present invention is also effective when producing a cross weld joint. Also in this case, it is preferable to adjust the welding material and welding conditions so that the weld metal has a composition within the range of the present invention described above. Thereby, deformation of the welded joint is suppressed.
また本発明は、隅肉溶接の他、突合せ溶接や円周溶接、補修溶接である肉盛り溶接等の場合にも適用できることは言うまでもない。 Needless to say, the present invention can be applied to fillet welding, fillet welding which is butt welding, circumferential welding, repair welding, and the like.
表１に示す化学組成の溶接材料を用いて鋼材（ＪＩＳ規格SM490 相当）を溶接して溶接継手を作製した。なお、表１にはJIS Z 3111に準拠して測定したデータを示す。溶接継手（図１）は600mm×600mm×9 mmの鋼材１に600 mm×140 mm×9 mmの鋼材２を隅肉溶接することにより作製した。
Steel materials (equivalent to JIS standard SM490) were welded using welding materials having chemical compositions shown in Table 1 to produce welded joints. Table 1 shows data measured according to JIS Z 3111. The welded joint (FIG. 1) was prepared by fillet welding a
溶接継手における溶接金属の化学組成とマルテンサイト変態開始温度（すなわちＭS 点）を表２に示す。なお表２には、ＭS 点の計算値と測定値を示す。
ＭS 点の計算値ＭSCは、下記の (2)式で算出した値である。
ＭSC＝719−795[Ｃ]−35.55[Si]−13.25[Mn]−23.7[Cr]−26.5[Ni]−23.7[Mo]
−11.85[Nb] ・・・ (2)
したがって (1)式は、下記の (3)式で表わされる。
Table 2 shows the chemical composition of the weld metal and the martensitic transformation start temperature (that is, the M S point) in the weld joint. Table 2 shows calculated values and measured values of the M S point.
Calculated M SC of M S point is a value calculated by the following equation (2).
M SC = 719-795 [C] −35.55 [Si] −13.25 [Mn] −23.7 [Cr] −26.5 [Ni] −23.7 [Mo]
−11.85 [Nb] (2)
Therefore, equation (1) is expressed by equation (3) below.
360≦ＭSC≦550 ・・・ (3)
またＭS 点の測定値は、直径３mm，長さ10mmの測定用試験片を採取し、変態点記録測定装置を用いて測定した値である。
360 ≦ M SC ≦ 550 (3)
The measured value of the M S point, collect a test piece for measuring a diameter of 3 mm, length 10 mm, is a value measured using a transformation point recording measuring device.
次いで、表３に記載した溶接条件（電流、電圧、溶接速度）で溶接継手を作製し、50℃以下に空冷した後、変形量を測定した。溶接継手の変形量を測定するにあたって、溶接継手を水平面上に載置し、鋼材２を垂直に保持した状態で、鋼材１の両端と水平面との距離ｄ1 ，ｄ2 を 0.1mm単位で測定した（図２）。こうして測定したｄ1 、ｄ2 値の平均値（＝（ｄ1 ＋ｄ2 値）／２）を、溶接継手の変形量として表３に示す。また表２に示したＭS 点の測定値も併せて示す。
Next, a welded joint was produced under the welding conditions (current, voltage, welding speed) described in Table 3, and after air cooling to 50 ° C. or less, the deformation was measured. When measuring the amount of deformation of the welded joint, place the welded joint on a horizontal plane and hold the
比較例では溶接継手の変形量が6.88〜9.02mmであったのに対して、発明例では変形量が5.62〜6.46mmであった。したがって発明例では溶接継手の変形量が減少することが確認できた。 In the comparative example, the deformation amount of the welded joint was 6.88 to 9.02 mm, whereas in the invention example, the deformation amount was 5.62 to 6.46 mm. Therefore, it was confirmed that the deformation amount of the welded joint was reduced in the inventive example.
１ 鋼材
２ 鋼材
３ 溶接金属
1
Claims (3)
The composition of the weld metal, the cooling process after welding cause martensitic transformation in and set that have a thermal expansion curve having the same amount of extension or contraction state and a martensitic transformation start time in the After cooling to room temperature formed The steel structure welded joint according to claim 1 or 2 , wherein:
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