US20070181223A1 - High-strength thick steel plate excellent in low temperature toughness at heat affected zone resulting from large heat input welding - Google Patents

High-strength thick steel plate excellent in low temperature toughness at heat affected zone resulting from large heat input welding Download PDF

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US20070181223A1
US20070181223A1 US10/594,660 US59466005A US2007181223A1 US 20070181223 A1 US20070181223 A1 US 20070181223A1 US 59466005 A US59466005 A US 59466005A US 2007181223 A1 US2007181223 A1 US 2007181223A1
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toughness
haz
tmcp
heat input
steel
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Minoru Ito
Akihiko Kojima
Masanori Minagawa
Yoichi Tanaka
Toshiei Hasegawa
Jun Otani
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Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium

Definitions

  • the present invention relates to a high strength thick steel plate excellent in low temperature toughness at heat affected zone (hereinafter referred to as an “HAZ”) used for ships, offshore structures, medium/high rise buildings, bridges, and so forth, more particularly relates to a steel plate having a thickness of 50 mm or more and a tensile strength of 490 to 570 MPa and having an excellent welded joint even in a case where welding with a welding heat input of 20 to 100 kJ/mm is conducted.
  • HZ high strength thick steel plate excellent in low temperature toughness at heat affected zone
  • Japanese Unexamined Patent Publication (Kokai) No. 55-026164 discloses an invention of securing fine Ti nitrides in the steel so as to reduce the austenite grain size in the HAZ and thereby improve the toughness.
  • Japanese Unexamined Patent Publication (Kokai) No. 03-264614 proposes an invention making use of complex precipitates of Ti nitrides and MnS as transformation nuclei of ferrite so as to improve the HAZ toughness.
  • Japanese Unexamined Patent Publication (Kokai) No. 04-143246 proposes an invention making use of complex precipitates of Ti nitrides and BN as precipitation nuclei of grain boundary ferrite so as to improve the HAZ toughness.
  • Ti nitrides end up becoming almost completely dissolved in the vicinity of the border with a welded metal in HAZ where the highest temperature reached exceeds 1400° C. (hereinafter also referred to as a “weld bond portion”). As a result, there is a problem that the effect of improvement of the toughness is lowered. For this reason, in steel utilizing the Ti nitrides as described above, it is difficult to meet the recent tough demands for the HAZ toughness or the required characteristics of the HAZ toughness in ultra-large heat input welding.
  • Steels containing Ti oxides as a method of improving the toughness in the vicinity of this weld bond portion are being used in various fields such as thick plates and steel shapes.
  • steel containing Ti oxides is very effective for improving toughness at the large heat input weld portion, and is promising in application to high tensile steels.
  • This principle is that the Ti nitrides, MnS, etc.
  • Ti oxides involve a problem that the number of particles dispersed into the steel cannot be increased that much. The reason is the coarsening or aggregation of the Ti oxides. It is believed that if the Ti oxides particles are increased, coarse Ti oxide particles of 5 ⁇ m or more, i.e., so-called inclusions, end up increasing. These inclusions of 5 ⁇ m or more size become initiation sites for fracture of a structure or cause a drop of the toughness and therefore are harmful. Therefore, this should be avoided. For this reason, in order to achieve a further improvement of the HAZ toughness, it was necessary to make use of oxides which are hard to coarsen and agglomerate and are more finely dispersed than Ti oxides.
  • Japanese Unexamined Patent Publication (Kokai) No. 06-293937 and Japanese Unexamined Patent Publication (Kokai) No. 10-183295 disclose inventions making use of Ti—Al complex oxides and Ti, Al, and Ca complex oxides produced by the addition of Al immediately after the addition of Ti or the complex addition of Al and Ca. By such inventions, it became possible to greatly improve HAZ toughness in the large heat input welding.
  • an object of the present invention is to provide a high-strength thick steel plate excellent in the low temperature toughness of the heat affected zone resulting from large heat input welding, which can realize excellent HAZ toughness even in a case of welding with a heat input of 20 to 100 kJ/mm for steel plate having a thickness of 50 to 80 mm, and a tensile strength of 490 to 570 MPa.
  • the inventors discovered that by defining the amount of addition of Ni and Ni/Mn ratio, the above problems could be advantageously solved. They engaged in extensive study and thereby completed the present invention for the first time.
  • the gist thereof is as follows:
  • a high-strength thick steel plate excellent in low temperature toughness at a heat affected zone resulting from large heat input welding characterized by containing, by wt %, 0.03-0.14% of C, 0.30% or less of Si, 0.8-2.0% of Mn, 0.02% or less of P, 0.005% or less of S, 0.001-0.040% of Al, 0.0010-0.0100% of N, 0.8-4.0% of Ni, 0.005-0.030% of Ti, and 0.003-0.040% of Nb, where Ni and Mn satisfy Equation [1], and a balance of iron and unavoidable impurities: Ni/Mn ⁇ 10 ⁇ Ceq ⁇ 3 (0.36 ⁇ Ceq ⁇ 0.42) [1]
  • a high-strength thick steel plate excellent in low temperature toughness at a heat affected zone resulting from large heat input welding as set forth in (1), characterized by further containing, by wt %, one or more of 0.0003-0.0050% of Ca, 0.0003-0.0050% of Mg, 0.001-0.030% of an REM and containing at least 100/mm 2 of grains of an oxide containing 0.0010-0.0050% of O and having an equivalent circle diameter of 0.005 to 0.5 ⁇ m.
  • a high-strength thick steel plate excellent in low temperature toughness at a heat affected zone resulting from large heat input welding as set forth in any one of (1) to (3), characterized by further containing, by wt %, one or more of 0.1-0.5% of Cr, 0.01-0.5% of Mo, 0.005-0.10% of V, and 0.1-1.0% of Cu.
  • FIG. 1 is a graph of a welding heat cycle corresponding to 45 kJ/mm.
  • FIG. 2 is a graph of the relationships among Ni/Mn, Ceq, and the simulated HAZ toughness.
  • FIG. 3 is a graph of an effect of improvement of the simulated HAZ toughness due to dispersion of fine oxides or B addition.
  • the inventors intensively studied the optimal chemical composition for improving the toughness of the base material itself for improvement of the HAZ toughness in the case where the Ceq was as high as 0.36 to 0.42, which becomes necessary for the high-strength thick steel plate. It has been conventionally known that Ni is an effective element improving the toughness of the matrix. However, it has not been known whether it is effective for improving the HAZ toughness in case of a high Ceq of 0.36 to 0.42. Therefore, the inventors first studied the influence of the amount of the Ni addition. For the study, they predetermined that an 0.003% or more of Nb addition is effective for securing the base material strength.
  • HAZ toughness For evaluation of the HAZ toughness, they employed the ductility/brittleness transition temperature in a Charpy impact test (vTrs) when imparting a heat cycle corresponding to electro-gas welding (heat input of 45 kJ/mm) shown in FIG. 1 .
  • vTrs Charpy impact test
  • FIG. 2 plots the synthetic HAZ toughness (vTrs) of the steel material used for the study classified for each Ceq with the Ni/Mn ratio plotted on the abscissa.
  • the inventors found that the HAZ toughness was improved by the addition of Ni in an amount of 0.8% or more satisfying equation [1].
  • the inventors further studied regarding the improvement of the HAZ toughness. They studied the following three methods as methods of improving the HAZ toughness. First is the method of suppressing the coarsening of the austenite grains at a high temperature, since in large heat input welding, the holding time at a high temperature becomes a long period. Therefore, the austenite grains coarsen, which lowers the HAZ toughness. Second is the method of suppressing the coarsening of the grain boundary ferrite, since the cooling time after the welding is long in large heat input welding, so the ferrite generated from the austenite grain boundaries coarsen. The coarse grain boundary ferrite becomes the cause of a drop in the HAZ toughness. Third is the method of refining the HAZ microstructure itself.
  • the inventors intensively studied a method of further improving the HAZ toughness by dispersing fine oxides in a process containing 0.03% of Nb and adding 0.8% or more of Ni in the case of a Ceq as high as 0.36 to 0.42.
  • the method of dispersing fine oxides they found the fact that, in such a process, by adjusting the amount of dissolved oxygen of the steel melt to 0.0010-0.0050% in the deoxidation process, then first deoxidizing the steel melt with Ti, and then deoxidizing the steel melt with Al, and further adding one or more of Ca, Mg, and REM, it is possible to disperse fine oxide particles having an equivalent circle diameter of 0.005 to 0.5 ⁇ m to 100/mm 2 or more.
  • the HAZ toughness could be further improved.
  • the result of comparison with the HAZ toughness obtained by only adding a proper amount of Ni is shown in FIG. 3 . Note that, the larger the amount of Ni, the finer the produced oxides, and the larger the number of particles. When the amount of Ni is 1.5% or more, it even becomes 1000/mm 2 or more. This is discovered this time. Further, for the amount of Si in the steel melt, the larger the amount of Si, the harder the oxide to form.
  • the amount of Si was preferably 0.30% or less and further preferably 0.20% or less.
  • the amount of dissolved oxygen before the Ti deoxidation exceeds 0.050% and the case where the sequence of the deoxidation elements is different, the oxide coarsens and the sufficient amount of fine oxide cannot be obtained. Therefore, almost no effect of suppression of coarsening of the austenite grains can be obtained.
  • the number of grains of the oxides having the equivalent circle diameter of 0.005 to 0.5 ⁇ m was obtained by preparing an extraction replica from the steel plate as the base material.
  • the inventors intensively studied the suppression of the coarsening of the grain boundary ferrite and the refining of the HAZ microstructure as above described second and third methods of improvement of the HAZ toughness.
  • the inventors clarified that the addition of B was effective particularly in the case where large heat input welding corresponding to 20 to 100 kJ/mm was conducted in a process where the Ceq was as high as 0.36 to 0.42 and Ni was added in an amount of 0.8% or more.
  • the reason for that, in terms of the suppression of the coarsening of the grain boundary ferrite, is the suppression of the production of grain boundary ferrite by a segregation of the solute B at the re-heated austenite grain boundaries.
  • the B nitrides precipitated at the austenite grain boundaries and in the inclusions in the austenite grains due to the addition of B, and a large number of fine ferrite grains of several micrometers using those as nuclei are present at the austenite grain boundaries and in the grains, whereby the HAZ structure is made finer.
  • the inventors compared the improvement of the HAZ toughness by the addition of B with the HAZ toughness obtained by only properly adding Ni. The results are shown in FIG. 3 . It is seen that the HAZ toughness is further improved by the addition of B. Further, FIG.
  • HAZ toughness in the case where the B is added in addition to the method of dispersing the above mentioned fine oxides.
  • the HAZ toughness is further improved by the dispersion of the fine oxides and the addition of B. It is considered that the improvement is due to the increase of the oxides acting as precipitation sites of the BN and thereby the greater refined HAZ microstructure due to the increase of the ferrite using the BN as the nuclei.
  • the inventors also studied the HAZ toughness when Cu, Cr, Mo, and V were added. As a result, they found that the HAZ toughness was not greatly lowered when they were added within ranges of 0.1-0.4%, 0.1-0.5%, 0.03-0.2%, and 0.005-0.050%.
  • the method of production of the steel plate according to the present invention is not particularly limited.
  • the steel plate may be produced by any known method. For example, a slab is formed from steel melt adjusted to the preferred composition described above by a continuous casting method, then is heated to 1000 to 1250° C., then is hot rolled.
  • C is an ingredient effective for improving the strength of the steel, so the lower limit is made 0.03%.
  • An excess addition produces large amounts of carbide and MA and remarkably lowers the HAZ toughness, therefore the upper limit was made 0.14%.
  • Si is an ingredient necessary for securing the strength of the base material and deoxidation, but in order to prevent the drop in the toughness due to the hardening of the HAZ, the upper limit was made 0.30%.
  • the upper limit of the content is made 0.20% or less in order to prevent the reduction of the oxygen concentration in the molten steel.
  • Mn is an ingredient effective for securing the strength and toughness of the base material and must be added in an amount of 0.8% or more, but the upper limit was made 2.0% within the range where the toughness, cracking property etc. of the welding zone were permissible. Further, concerning the upper limit of Mn, it is necessary to satisfy equation [1] indicating the relationship among the Ceq, Mn amount, and the Ni amount. This is based on the newly found fact by this study that the increase of Mn becomes the cause of production of a large amount of MA in the HAZ microstructure in the case where the Ceq is high and the effect of improvement of the HAZ toughness by Ni disappears. Ni/Mn ⁇ 10 ⁇ Ceq ⁇ 3 [1]
  • P is desirably as little as possible, but in order to reduce this industrially, enormous costs are entailed, so the range of content was made 0.02 or less.
  • Ni is an important element in the present invention and must be added in an amount of at least 0.8%. Further, concerning the lower limit of Ni, it is necessary to satisfy equation [1] showing the relationship of Ceq, the amount of Mn, and the amount of Ni. The upper limit was made 4.0% from the viewpoint of the production cost. Ni/Mn ⁇ 10 ⁇ Ceq ⁇ 3 [1]
  • Nb is an element effective for improving the strength of the base material by improving the quench bardenability, so is added in an amount of 0.003% or more.
  • the MA becomes easy to be produced in the HAZ regardless of the Ni/Mn ratio, while when it is added in an amount larger than 0.040%, a large amount of coarse MA having a long axis of 5 ⁇ m is produced in the HAZ and greatly reduces the HAZ toughness. Therefore, the upper limit of Nb is made 0.040%.
  • the amount of Nb is suppressed to 0.020% or less where almost no coarse MA having a long axis of 5 ⁇ m is produced in the case of the Ni/Mn ratio satisfying the above mentioned equation [1].
  • Al is an important deoxidation element, so the lower limit was made 0.001%. Further, when a large amount of Al is present, the surface quality of the slab is deteriorated, so the upper limit was made 0.040%.
  • Ti is added in an amount of 0.005% or more according to need in order to produce the Ti nitride and the Ti-containing oxide particles which become pinning sites necessary for suppressing the coarsening of the re-heated austenite grains.
  • its excess addition increases the amount of dissolved Ti and induces a drop in the HAZ toughness, therefore 0.030% was made the upper limit.
  • N is adjusted in the amount of addition, if necessary, in order to produce the Ti nitride and the B nitride particles at the austenite grain boundaries and in the grains during the cooling after the welding.
  • N In order to form the B nitride by binding with B, N must be added in an amount of 0.0010% or more, but its excess addition increases the amount of dissolved N and induces a drop in the HAZ toughness, so 0.0100% was made the upper limit.
  • Ca is added in an amount of 0.0003% or more, if necessary, in order to produce the Ca-based oxide particles acting as pinning grains necessary for suppressing the coarsening of the re-heated austenite grains.
  • excess addition produces coarse inclusions, so 0.0050% was made the upper limit.
  • Mg is added in an amount of 0.0003% or more, if necessary, in order to generate the Mg-based oxide particles acting as pinning grains necessary for suppressing the coarsening of the re-heated austenite grains.
  • excess addition produces coarse inclusions, so 0.0050% was made the upper limit.
  • a REM is added in the amount of 0.0001% or more, if necessary, in order to produce the REM-based oxide particles acting as pinning sites necessary for suppressing the coarsening of the re-heated austenite grains.
  • excess addition produces coarse inclusions, so 0.030% was made the upper limit.
  • the “REM” mentioned here represent Ce and La, and the amount of addition is the total amount of the two.
  • B is added in an amount of 0.0005% or more, if necessary, in order to cause the dissolved B to segregate at the austenite grain boundaries during the cooling after the welding and suppress the production of the grain boundary ferrite and further to produce BN at the austenite grain boundaries and in the grains.
  • its excess addition increases the amount of dissolved B, greatly raises the HAZ hardness, and induces a drop in the HAZ toughness, so 0.0050% was made the upper limit.
  • Cu is added in an amount of 0.1% or more, if necessary, in order to improve the strength and corrosion resistance of the steel.
  • the effect thereof is saturated at 1.0%, so the upper limit was made 1.0, but when it exceeds 0.4%, MA becomes easy to be generated and the HAZ toughness is lowered, therefore 0.4% or less is preferred.
  • Mo is an element effective for improving the strength and the corrosion resistance of the base material and is added in an amount of 0.01% or more, if necessary. The effect thereof is saturated at 0.5%, so the upper limit was made 1.0, but its excess addition induces a drop in the HAZ toughness due to the generation of MA, so 0.2% or less is preferred.
  • V is an element effective for improving the strength of the base material and is added in an amount of 0.005% or more, if necessary. The effect thereof is saturated at 0.5%, so the upper limit was made 0.10%, but its excess addition induces a drop in the HAZ toughness due to the generation of MA, so 0.050% or less is preferred.
  • Slabs were prepared by continuously casting the steel melt having the chemical compositions shown in Table 1.
  • the amounts of dissolved oxygen of the steel melt were adjusted to 0.0010%-0.0050% by Si before charging the Ti, then Ti was used for deoxidization, then Al was used for deoxidation, then any of Ca, Mg, or REM was added for deoxidation.
  • the slabs were re-heated at 1100 to 1250° C., then were hot rolled by the following two methods to produce steel plates having plate thicknesses of 50 to 80 mm.
  • One method was to roll the plate at a surface temperature within a range of 750-900° C., then cool it by water at a plate surface temperature within the temperature range of 200-400° C. after recalescence (described as TMCP in Table 2).
  • the other method of production is cooling with water down to room temperature after hot rolling, then tempering within a range of 500-600° C. (described as DQ-T in Table 2).
  • Table 2 shows the production conditions, plate thicknesses, and mechanical properties of the steel plates. Further, for D23-D31 and D46-D49, the numbers of fine oxide particles having equivalent circle diameters of 0.005 to 0.5 ⁇ m measured at any location of the steel plates were additionally described. The number of the oxide particles are found by preparing an extraction replica from any portion of the steel plate, observing this under an electron microscope with X10000 magnification in 100 fields or more (10000 ⁇ m 2 or more in observation area), and observing particles less than 0.1 ⁇ m by properly raising the magnification. Elemental analysis was conducted for each observed particle having a diameter of 0.005 to 0.5 ⁇ m and the oxide particles were counted.
  • All of the steel plates among D23-D31 and D46-D49 had fine oxide particles having equivalent circle diameters of 0.01 to 0.5 ⁇ m dispersed to 100/mm 2 within the range of the present invention. Note that it is seen from the comparison of D46 and D47 and D48 and D49 wherein elements other than Si are almost equal, that the smaller the amount of Si, i.e. 0.20% or less, the larger the amount of the oxides.
  • Each of these steel plates was made to abut against another steel plate and subjected to vertical one-pass butt welding in using electro-gas welding (EGW) or electro-slag welding (ESW) having welding heat inputs of 20 to 100 kJ/mm. Then, in the HAZ located at the center portion of the plate thickness (t/2), notches were formed at two locations, that is, the HAZ separated from the FL (Fusion Line) by 1 mm (HAZ 1 mm) and the FL.
  • a Charpy impact test was conducted at ⁇ 40° C. Table 2 shows the welding conditions and HAZ toughnesses. In the Charpy impact test here, use was made of JIS No. 4 2 mm V-notch full size test pieces.
  • Table 2 also describes the former austenite grain size in FL-HAZ 1 mm.
  • the “former austenite grain size in FL-HAZ 1 mm” described here is the average grain size obtained by measuring the grain size of the former austenite grains contained within a 2 mm range in the thickness direction centered by t/2 and the FL-HAZ 1 mm range by the cross-sectional method. Note that, the measurement was conducted by using particulate ferrite connected in a form of a net as the grain boundaries of the former austenite grains.
  • D1 to D49 are steels of the present invention.
  • the chemical compositions of the steels are properly controlled, therefore the large heat input HAZ toughness at ⁇ 40° C. is good while satisfying the predetermined base material performances.
  • the former austenite grain size in FL-HAZ 1 mm becomes finer than those of the others, i.e. 200 ⁇ m or less, and the large heat input HAZ toughness at ⁇ 40° C. becomes further higher.
  • D20 aiming at increasing the refined HAZ structure by adding B has a better HAZ toughness in comparison with D19 without addition of B and containing addition elements other than B in the equal amounts and exhibits a higher performance for also the large heat input HAZ toughness at ⁇ 40° C.
  • Comparative Steels C1 to C17 do not contain sufficient Ni for satisfying equation [1] or properly control the chemical compositions of the steels, so the large heat input HAZ toughness is insufficient. TABLE 1 Class Sym. C Si Mn P S Ni Nb Al Ti N Ca Mg Inv.
  • EGW 39 480 140 128 steel EGW 42 520 135 124 ESW 85 770 116 106 ESW 73 660 123 113 ESW 67 605 127 117 EGW 42 520 135 124 ESW 85 770 116 106 EGW 51 640 124 114 EGW 39 480 140 128 ESW 79 715 119 109 EGW 48 600 128 117 EGW 51 640 124 114 EGW 35 440 144 132 ESW 79 715 119 109 ESW 85 770 116 106 EGW 42 520 135 124 EGW 45 560 131 120 EGW 48 600 128 117 EGW 45 560 131 120 EGW 45 560 171 156 ESW 85 770 116 106 EGW 45 560 184 180 ESW 79 180 207 189 EGW 39 165 214 196 EGW 45 152 221 203 EGW 51 185 204 187 ESW 45 180 207 189 ESW 79 167 213 195 EGW 39
  • ESW 85 605 127 117 steel EGW 42 520 135 124 ESW 73 770 116 106 EGW 45 640 124 114 EGW 51 480 140 128 ESW 85 715 119 109 EGW 42 600 128 117 EGW 39 640 124 114 EGW 42 440 144 132 ESW 73 715 119 109 EGW 45 145 225 206 EGW 45 195 200 183 EGW 39 164 214 236 EGW 39 185 204 225 Comp.
  • Extraction replica was prepared from any portion of steel plate, and observed under electron microscope by ⁇ 10000 magnification in 100 fields or more (10000 ⁇ m 2 or more in observation area). However, particles of less than 0.1 ⁇ m were obtained at properly raising magnification. # Particles are counted including oxide by elemental analysis among particles of equivalent circle diameter of 0.005 to 0.5 ⁇ m and convert to number per 1 mm 2 .
  • EGW Electro-gas welding
  • ESW Electro-slag welding
  • Welding heat input is an average value in total length of welding
  • Common welding material is used in welding processes
  • Average grain size of former austenite grains contained within a 2 mm range in the thickness direction centered by t/2 and the FL-HAZ 1 mm range was measured by the cross-sectional method. Measurement was conducted by using particulate ferrite connected in a form of a net as the grain boundaries of the former austenite grains.
  • FL notches are layed down so as to equally divide WM and HAZ.
  • vE ⁇ 40- at each notch location is an average value of three test pieces.
  • the present invention provides thick steel plate satisfying the excellent toughness demands regarding destruction for ships, offshore structures, medium/high rise buildings, etc.

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US10/594,660 2004-04-07 2005-04-06 High-strength thick steel plate excellent in low temperature toughness at heat affected zone resulting from large heat input welding Abandoned US20070181223A1 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
JP2004-113278 2004-04-07
JP2004113278 2004-04-07
JP2005102041A JP4660250B2 (ja) 2004-04-07 2005-03-31 大入熱溶接による溶接熱影響部の低温靭性に優れた厚手高強度鋼板
JP2005-10241 2005-03-31
PCT/JP2005/007109 WO2005098068A1 (fr) 2004-04-07 2005-04-06 Plaque d'acier épaisse très résistante d’excellente résistance à basse température dans la zone affectée par la température de soudage du fait du soudage a haute température

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US20120027637A1 (en) * 2009-05-21 2012-02-02 Nippon Steel Corporation Steel for welded structure and producing method thereof
US8668784B2 (en) 2009-05-19 2014-03-11 Nippon Steel & Sumitomo Metal Corporation Steel for welded structure and producing method thereof
CN103938065A (zh) * 2014-04-22 2014-07-23 钢铁研究总院 一种大线能量焊接用钢中复合添加镁钛的方法
TWI468529B (zh) * 2009-04-27 2015-01-11 China Steel Corp High strength steels and compositions thereof for high welding heat welding

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JP4891836B2 (ja) * 2007-05-09 2012-03-07 株式会社神戸製鋼所 大入熱溶接における溶接熱影響部の靭性に優れた鋼板
JP5096088B2 (ja) * 2007-09-13 2012-12-12 株式会社神戸製鋼所 靭性および疲労亀裂発生抑制特性に優れた溶接継手
KR101018159B1 (ko) * 2008-05-15 2011-02-28 주식회사 포스코 저온인성이 우수한 고강도 강판 및 그 제조방법
KR100951296B1 (ko) * 2007-12-04 2010-04-02 주식회사 포스코 저온인성이 우수한 고강도 라인파이프용 강판 및 그제조방법
KR101142185B1 (ko) * 2007-12-07 2012-05-04 신닛뽄세이테쯔 카부시키카이샤 용접열 영향부의 ｃｔｏｄ 특성이 우수한 강 및 그 제조 방법
JP5273301B2 (ja) * 2010-11-22 2013-08-28 新日鐵住金株式会社 電子ビーム溶接継手及び電子ビーム溶接用鋼材
WO2012070360A1 (fr) * 2010-11-22 2012-05-31 新日本製鐵株式会社 Joint soudé par faisceau d'électrons, matériau d'acier pour soudage par faisceau d'électrons et leur procédé de fabrication
KR20120075274A (ko) * 2010-12-28 2012-07-06 주식회사 포스코 극저온 인성이 우수한 고강도 강판 및 그 제조방법
JP5612532B2 (ja) * 2011-04-26 2014-10-22 株式会社神戸製鋼所 低温靭性および溶接継手破壊靭性に優れた鋼板およびその製造方法
JP5811044B2 (ja) * 2012-06-13 2015-11-11 新日鐵住金株式会社 溶接性、溶接熱影響部靭性に優れた厚手高強度鋼板およびその製造方法
CN104364405B (zh) * 2013-06-13 2016-12-07 新日铁住金株式会社 焊接用超高张力钢板
JP5713135B1 (ja) 2013-11-19 2015-05-07 新日鐵住金株式会社 鋼板
CN103898418B (zh) * 2014-03-07 2016-05-04 舞阳钢铁有限责任公司 大厚度Ni系低温容器用钢板及其生产方法
CN105039865B (zh) * 2015-08-26 2017-07-14 江苏省沙钢钢铁研究院有限公司 一种高强度高韧性钢板及其制造方法
JP7260780B2 (ja) * 2019-06-17 2023-04-19 日本製鉄株式会社 大入熱溶接用高強度鋼板
JP7260779B2 (ja) * 2019-06-17 2023-04-19 日本製鉄株式会社 大入熱溶接用高強度鋼板
CN113186466B (zh) * 2021-04-27 2022-05-17 江苏省沙钢钢铁研究院有限公司 低温钢筋及其生产方法

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100258219A1 (en) * 2007-12-04 2010-10-14 Posco High-Strength Steel Sheet with Excellent Low Temperature Toughness and Manufacturing Method Thereof
US8647564B2 (en) 2007-12-04 2014-02-11 Posco High-strength steel sheet with excellent low temperature toughness and manufacturing thereof
TWI468529B (zh) * 2009-04-27 2015-01-11 China Steel Corp High strength steels and compositions thereof for high welding heat welding
US8668784B2 (en) 2009-05-19 2014-03-11 Nippon Steel & Sumitomo Metal Corporation Steel for welded structure and producing method thereof
US20120027637A1 (en) * 2009-05-21 2012-02-02 Nippon Steel Corporation Steel for welded structure and producing method thereof
US8920713B2 (en) * 2009-05-21 2014-12-30 Nippon Steel & Sumitomo Metal Corporation Steel for welded structure and producing method thereof
CN103938065A (zh) * 2014-04-22 2014-07-23 钢铁研究总院 一种大线能量焊接用钢中复合添加镁钛的方法

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SG151274A1 (en) 2009-04-30
KR100839262B1 (ko) 2008-06-17
EP1736562A1 (fr) 2006-12-27
JP4660250B2 (ja) 2011-03-30
JP2005320624A (ja) 2005-11-17
TW200538561A (en) 2005-12-01
WO2005098068A1 (fr) 2005-10-20
TWI295693B (en) 2008-04-11
KR20060130700A (ko) 2006-12-19
EP1736562A4 (fr) 2007-10-10
NO20065095L (no) 2007-01-03

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