KR100867139B1 - High Tensile Strength Steel Sheet Excellent in Toughness in Large Heat Input Heat-affected Zone - Google Patents

Abstract

The steel sheet of this invention is mass%, C: 0.02-0.05%, Si: 0.05-0.20%, Mn: 1.0-2.5%, P: 0.02% or less (not containing 0%), S: 0.005% or less (0% not included), Al: 0.01 to 0.05%, Ni: 0.2 to 2.0%, Cr: 0.5 to 2.0%, Ti: 0.005 to 0.025%, N: 0.004 to 0.010% Formulas (1) and (2) are satisfied.

    2.3% ≤ (Mn + 0.7 × Ni + Cr) ≤ 3.7% ‥‥ (1)

    (Cr / (Mn + 0.7 × Ni) ≥ 0.3 ‥‥ (2)

(In formula, Mn, Ni, Cr represent each element content (mass%).)

With such a configuration, excellent toughness can be ensured when welding is performed at high heat input.

Description

High Tensile Strength Steel Sheet Excellent in Toughness in Large Heat Input Heat-affected Zone}

1 is a graph showing the relationship between (Mn + 0.7 x Ni + Cr) and (GBF + FSP) amount or block size.

2 is a graph showing the relationship between (Mn + 0.7 × Ni + Cr) and HAZ toughness (vE0).

FIG. 3 is a graph showing the relationship between the area ratio of [Cr / (Mn + 0.7 × Ni)] and the needle-shaped MA (MA having an aspect ratio of 2.5 or more in diameter).

4 is a graph showing the relationship between [Cr / (Mn + 0.7 × Ni)] and HAZ toughness (vE0).

5 is a graph showing a range defined by the present invention in relation between the amount of Cr and (Mn + 0.7 × Ni).

(Technology)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high tensile steel sheet having excellent toughness of a high heat input welding heat affected zone, particularly in the case of a high heat input welding exceeding 500 kJ / cm. It relates to a high tensile strength steel sheet having a tensile strength of 590 MPa or more, which is excellent in toughness of the affected portion.

(Background)

For example, sub-marge arc welding and electro-slag welding, which are applied to box column assembly of building structures, may be subjected to high heat input welding in excess of 500 kJ / cm for more efficient construction. In general, however, it is known that when the heat input amount of weld increases, the structure of the weld heat affected zone (HAZ) becomes coarse and the toughness tends to be lowered. Various methods have been proposed.

In this manner, for example, the toughness of HAZ is suppressed by inhibiting coarsening of austenite grains by utilizing the pin stop effect of microdispersion of TiN and a composite compound (for example, Japanese Patent No. 3256118, a composite composed of Ti-containing oxide and MnS). A method of improving is proposed.

However, in the high heat input welding construction, when the heat affected zone near the weld metal is exposed to high temperature for a long time, TiN is mostly dissolved and the pin stop effect is not sufficiently exhibited. Moreover, since the latter complex oxide is difficult to uniformly finely disperse, there has been a lot of studies, but there is a problem that the effect is insufficient.

In addition, in order to improve HAZ toughness, a technique for miniaturizing metamorphic tissue in γ grains has been proposed, for example, a technique using TiN and BN (see Japanese Patent No. 1824290) as a ferrite metamorphic nucleus. However, even in this case, in the heat affected zone exposed to high temperature for a long time, most of the precipitates are dissolved and there is a problem that a sufficient effect cannot be obtained. In addition, a technique for promoting ferrite generation in a lip in which Ti oxide is dispersed has been developed (see, for example, Japanese Patent Application Laid-Open No. 05-017300). There is a problem that it is difficult.

칭성 향상원소인 Mn, Cr 등을 적극적으로 첨가함과 아울러, B를 첨가하므로써 베이나이트 블럭사이즈를 미세화시키는 기술(예컨대 일본특허 제 3602471호 공보)도 제안되어 있다. 그러나, 이 기술로 대입열 용접조건하에서 블럭사이즈(block size)의 미세화가 충분하다고는 말할 수 없다.In addition, C is made very low from the viewpoint of inhibition of MA (Martensite-Austenite constituent) generation, which is the starting point of destruction, and tissue micronization in γ grains,

In addition to aggressively adding Mn, Cr, and the like, which are the enhancement properties, a technique for miniaturizing the bainite block size by adding B (for example, Japanese Patent No. 3602471) has also been proposed. However, it cannot be said that this technique is sufficient for miniaturization of block size under high heat input welding conditions.

(Tasks to be solved by the invention)

The present invention has been made in view of the above circumstances, and the object thereof is excellent in the case of performing submagazine welding and electroslag welding with a high heat input exceeding 500 kJ / cm while high safety is required in parallel with the enlargement of the building structure. To provide a high strength steel sheet of 590MPa or more that can secure the HAZ toughness.

(Means to solve the task)

The steel sheet according to the present invention,

In mass% (same as below), C: 0.02 to 0.05%, Si: 0.05 to 0.20%, Mn: 1.0 to 2.5%, P: 0.02% or less (not including 0%), S: 0.005% or less (0 %), Al: 0.01% to 0.05%, Ni: 0.2% to 2.0%, Cr: 0.5% to 2.0%, Ti: 0.005% to 0.025%, and N: 0.004% to 0.010%, and include the following Formula (1) And (2).

    2.3% ≤ (Mn + 0.7 × Ni + Cr) ≤ 3.7% ‥‥ (1)

    (Cr / (Mn + 0.7 × Ni) ≥ 0.3 ‥‥ (2)

(In formula, Mn, Ni, Cr represent each element content (mass%).)

The steel sheet is also,

(a) Mo: 0.2% or less (not including 0%)

(b) at least one selected from the group consisting of V: 0.03% or less, Nb: 0.01% or less, and B: 0.0020% or less (provided that the following formula (3) is satisfied):

    (V + 2Nb + 10B) ≤ 0.03% ‥‥ (3)

(In formula, V, Nb, and B represent content (mass%) of each element.)

(c) Cu: 0.1-1.0%

(d) Ca: 0.0005 to 0.0030%

It may contain.

According to the present invention, excellent HAZ toughness can be secured even when sub-marge arc welding, electroslag welding, or the like with a large input heat of more than 500 kJ / cm is performed, so that a highly stable building structure can be manufactured in a shorter time. .

(The best form to carry out invention)

The present inventors continued their studies to obtain a high tensile strength steel sheet excellent in HAZ toughness (hereinafter referred to simply as "HAZ toughness") when high heat input welding exceeding 500 kJ / cm was performed. As a result,

(Ⅰ) To stably secure the high toughness of the heat affected zone,

Not only inhibiting MA by very low C (ultra low carbonization) but also controlling the shape of the MA (specifically, inhibiting the generation of needle-shaped MA),

Suppress coarse tissues grown at γ grain boundaries (grain boundary ferrite (GBF) + ferrite sideplates (FSP));

칭성 향상원소인 Mn, Ni 및 Cr을 적절히 함유시켜 이것을 실현시킬 수 있다는 것,It is necessary to miniaturize the block size of the metamorphic tissue in the? Grains.

That it can be realized by appropriately containing Mn, Ni and Cr, which is a

칭성 향상원소인 Nb, V 및 B로 이루어지는 군으로부터 선택되는 1종 이상을 첨가한 경우에는, 이들 원소의 함유량을 종합적으로 제한하고, MA 및 조대한 라스상 조직의 생성을 억제하면 HAZ 인성의 열화를 억제할 수 있다는 것을 알아내어, 본 발명에 이르렀다.(Ii) furthermore,

In the case where one or more selected from the group consisting of Nb, V, and B, which are enhancement properties, is added, the content of these elements is collectively limited, and the deterioration of HAZ toughness is suppressed when the formation of MA and coarse las-like structures is suppressed. It was found out that it can be suppressed, and the present invention was reached.

First, the above (i) will be described. The present inventors have described the amount (area%) and block size of (Mn + 0.7 × Ni + Cr) and the coarse structure (grain boundary ferrite (GBF) + ferrite side plate (FSP)) growing at γ grain boundaries in HAZ. We found that there is a correlation between and summarized these relationships. The results are shown in FIG.

From FIG. 1, in order to control the said (GBF + FSP) amount to 50 area% or less, it is necessary to make (Mn + 0.7xNi + Cr) 2.3% or more as shown by following formula (1). On the other hand, in order to reduce the block size to 40 μm or less, it can be seen that (Mn + 0.7 × Ni + Cr) needs to be 3.7% or less, as shown in the following formula (1). In order to further reduce the block size to 20 µm or less, (Mn + 0.7 × Ni + Cr) may be 3.3% or less.

   2.3% ≤ (Mn + 0.7 × Ni + Cr) ≤ 3.7% ‥‥ (1)

(In formula, Mn, Ni, Cr represents each element content (mass%).)

In addition, although FIG. 2 shows the relationship between (Mn + 0.7xNi + Cr) and HAZ toughness (vE0 measured by the method of the Example mentioned later), (Mn + 0.7xNi + Cr) is 2.3-3.7% of range. By controlling the amount of (GBF + FSP) inside and miniaturizing the block size, it was found that even in the case of high heat welding, excellent HAZ toughness can be secured at vE0: 100J or more.

The inventors also found that there is a relationship between [Cr / (Mn + 0.7 × Ni)] and the form of MA (specifically, the area ratio of needle-shaped MA having an aspect ratio (long diameter / short diameter) of 2.5 or more), These relationships are summarized. The results are shown in FIG. Here, the area ratio of needle-shaped MA means the ratio of needle-shaped MA with respect to the surface observed with the microscope.

3 shows that in order to control the area ratio of needle-shaped MA to 4% or less, it is necessary to make [Cr / (Mn + 0.7xNi)] 0.3 or more like following formula (2).

  [Cr / (Mn + 0.7 × Ni)] ≥ 0.3 ‥‥ (2)

(In formula, Mn, Ni, Cr represents each element content (mass%).)

1, 3, (GBF + FSP), the block size and the area ratio of the needle-shaped MA can be obtained as follows. That is, a tissue photograph was taken by microscopic observation, and the target tissue was selected from the photograph by the eye, and the ratio with respect to the observation surface under the microscope was measured by image analysis.

4 shows the relationship between [Cr / (Mn + 0.7 × Ni)] and HAZ toughness (vE0 measured by the method of Example described later), where [Cr / (Mn + 0.7 × Ni)] is 0.3 or more. By suppressing the formation of the needle-shaped MA, it was found that excellent HAZ toughness can be ensured at vE0: 100J or more even in the case of high heat input welding.

As described above, in order to optimize the balance of Mn, Ni, and Cr to reliably increase the HAZ toughness, and to secure the strength and toughness of the base material, the contents of Mn, Ni, and Cr need to be within the following ranges, respectively. have.

Mn  1.0 to 2.5%

칭성을 향상시켜 모재강도와 인성을 확보하는 데 유용한 원소이다. 또한, HAZ의 블럭사이즈의 미세화에도 유용한 원소이다. 이들 효과를 발휘시키기 위해서는 1.0% 이상 함유시킨다. 그러나 Mn이 과잉함유되면 MA가 증대하여 HAZ 인성이 열화한다. 따라서 Mn 량은 2.5% 이하로 제어한다.Mn is

It is an element that is useful for securing base material strength and toughness by improving the nickability. It is also an element useful for miniaturizing the block size of HAZ. In order to exhibit these effects, it contains 1.0% or more. However, excessive Mn increases MA and deteriorates HAZ toughness. Therefore, the amount of Mn is controlled to 2.5% or less.

Ni  0.2 to 2.0%

칭성을 향상시켜 모재의 강도와 인성을 확보함과 아울러, 열간 크랙의 방지에 효과적인 원소이다. 또한, HAZ의 블럭사이즈의 미세화에도 유용한 원소로서, 이들 효과를 발휘시키기 위해서는 0.2% 이상 함유시킨다. 한편, Ni가 과잉 함유되면 스케일 자국이 발생하기 쉬우므로, 2.0% 이하로 제어한다.Ni is

It is an element that is effective in preventing hot cracks while improving the toughness and securing the strength and toughness of the base metal. Moreover, it is an element useful also in refine | miniaturizing the block size of HAZ, In order to exhibit these effects, it contains 0.2% or more. On the other hand, if Ni is excessively contained, scale marks are likely to occur, so the amount is controlled to 2.0% or less.

Cr  0.5 to 2.0%

칭성을 향상시켜 모재강도와 인성을 확보하는 데 유용한 원소이다. 또한, HAZ의 블럭사이즈의 미세화에도 유용한 원소이다. 이들 효과를 발휘시키기 위해서는 0.5% 이상 함유시킨다. 그러나 Cr이 너무 많이 존재하면 MA가 증대하여 HAZ 인성이 열화한다. 따라서 Cr 량은 2.0% 이하로 제어한다.Cr is

It is an element that is useful for securing the base material strength and toughness by improving the toughness. It is also an element useful for miniaturizing the block size of HAZ. In order to exhibit these effects, it contains 0.5% or more. However, if too much Cr is present, the MA increases and the HAZ toughness deteriorates. Therefore, the amount of Cr is controlled to 2.0% or less.

Fig. 5 is a graph showing the relationship between the amount of Cr and (Mn + 0.7 × Ni), which is surrounded by the above formulas (1) and (2), the upper limit of the amount of Cr and the lower limit of (Mn + 0.7 × Ni). The range (the diagonal line) is shown. As shown in Fig. 5, when the relationship between Cr, Mn and Ni is within the range of the diagonal line, the HAZ toughness in the case of the high heat input welding can be reliably increased than in the prior art.

In order to reliably raise HAZ toughness as mentioned above and to provide other characteristics, such as the strength and toughness of a steel plate (base material), it is necessary to make component content of that excepting the above into the following range.

C: 0.02 ~ 0.05%

C is an element necessary to secure the base metal strength and the coarsening of the? Grains to secure the HAZ toughness. In order to exert such an effect, it is necessary to contain C at least 0.02%. However, when the amount of C is excessively contained, the MA is increased and the high temperature stability of TiN formed during casting is inferior, so that the HAZ toughness is deteriorated. It also causes deterioration due to low temperature crack generation. Therefore, the amount of C is controlled to 0.05% or less.

Si  0.05 to 0.20%

Si is an element necessary for deoxidation during steelmaking and is contained 0.05% or more. However, when the amount of Si is excessively contained, since MA increases and HAZ toughness deteriorates, it controls to 0.20% or less.

P: 0.02% or less (does not include 0%)

P is controlled to 0.02% or less because it causes deterioration of the base material toughness and destruction of the γ grain boundary due to segregation of P.

S: 0.005% or less (Does not include 0%)

Similarly to P, S also causes deterioration of the base material toughness and destruction of grain boundaries due to MnS segregation, and therefore S is controlled at 0.005% or less.

Al  : 0.01 ~ 0.05%

Al is an element necessary for deoxidation during steelmaking and is contained 0.01% or more. However, when Al contains excessively, coarse inclusions, such as alumina, increase and base metal toughness deteriorates. In addition, since MA increases and HAZ toughness also deteriorates, it is controlled to 0.05% or less.

Ti  : 0.005 ~ 0.025%

Ti is an element which bonds with N to form TiN, which in the steel of the present invention having low C is enhanced in high temperature stability and effectively contributes to the improvement of HAZ toughness by miniaturizing γ grains of HAZ. In order to exhibit such an effect, Ti is contained 0.005% or more (preferably 0.010% or more). On the other hand, when Ti is excessively contained, TiN coarsens and both the base metal toughness and the HAZ toughness deteriorate, thereby controlling it to 0.025% or less.

N: 0.004 ~ 0.010%

N is an element which combines with Ti to form TiN, and contributes to the improvement of toughness by miniaturizing γ grains of HAZ by TiN. In order to exhibit this effect, N amount is made into 0.004% or more. On the other hand, when N exists excessively, solid solution N will increase and both a base material toughness and a HAZ toughness will deteriorate. Therefore, N amount is controlled to 0.010% or less.

The content element defined in the present invention is as described above, the remainder is iron and unavoidable impurities, and as this unavoidable impurity, the incorporation of elements to be entered depending on the situation of raw materials, materials, manufacturing facilities and the like can be allowed. It is also possible to actively contain the following elements.

Mo  0.2% or less (Does not include 0%)

칭성ㆍ템퍼링 연화저항을 높이고, 모재의 강도ㆍ인성을 확보하는 데 유효한 원소로서, 이 효과를 발휘시키기 위해서는 Mo을 0.05% 이상 함유시키는 것이 바람직하다. 그러나, Mo이 과잉 함유되면 재결정 억제작용에 의해 압연후 γ립이 조대하게 되어, 변태조직의 블럭사이즈도 조대화한다. 따라서, 본 발명에서는 Mo 량을 0.2% 이하로 제어한다.Mo,

As an element effective in increasing the toughness and temper softening resistance and securing the strength and toughness of the base material, it is preferable to contain Mo 0.05% or more in order to exert this effect. However, when Mo is excessively contained, the? Grains after rolling are coarsened by the recrystallization inhibiting action, and the block size of the metamorphic structure is also coarsened. Therefore, in the present invention, the amount of Mo is controlled to 0.2% or less.

At least one selected from the group consisting of V: 0.03% or less, Nb: 0.01% or less, and B: 0.0020% or less (within the range of the following formula (3)):

     (V + 2Nb + 10B) ≤ 0.03% ‥‥ (3)

(In formula, V, Nb, and B represent each element content (mass%).)

칭성ㆍ템퍼링 연화저항을 향상시켜 모재의 강도ㆍ인성을 확보하는 데 유용한 원소이다. 그러나, V가 과잉 함유되면 HAZ 인성이 열화하므로, V 량은 0.03% 이하로 제어하는 것이 좋다.These V, Nb, and B are elements effective for securing the strength and toughness of the base material. V is

It is an element that is useful for securing strength and toughness of a base material by improving the softening and tempering softening resistance. However, when V contains excessively, HAZ toughness deteriorates, It is good to control V amount to 0.03% or less.

Nb is an element effective for miniaturizing the γ grain to secure the strength and toughness of the base material. However, since excessive Hb deteriorates HAZ toughness, it is preferable to control it to 0.01% or less.

칭성을 향상시켜 모재의 강도ㆍ인성을 확보하는 데 유용한 원소이다. 그러나, B이 과잉 함유되면, 철탄붕화물(鐵炭硼化物)이 석출되고 모재인성이 열화하므로, 0.0020% 이하로 제어하는 것이 바람직하다.B is

It is an element useful for improving the toughness and securing the strength and toughness of the base metal. However, when B contains excessively, iron carbide will precipitate and base metal toughness will deteriorate, It is preferable to control to 0.0020% or less.

In addition, when containing 1 or more types chosen from the group which consists of said V, Nb, and B, it is necessary to satisfy said Formula (3) also. By controlling (V + 2Nb + 10B) to 0.03% or less, generation of MA and coarse lath phase tissue can be suppressed as shown in (ii) above, and deterioration of HAZ toughness can be suppressed.

Cu  0.1 ~ 1.0%

칭성을 향상시키는 데 유효한 원소로서, 이 효과를 발휘시키기 위해서는 0.1% 이상 함유시키는 것이 바람직하다. 그러나, Cu가 과잉 함유되면 압연시에 열간크랙을 일으키기 쉬우므로 1.0% 이하로 제어하는 것이 바람직하다.Cu

As an element effective for improving the clarity, in order to exhibit this effect, it is preferable to contain 0.1% or more. However, if Cu is excessively contained, hot cracking is likely to occur at the time of rolling, so it is preferably controlled at 1.0% or less.

Ca  : 0.0005 to 0.0030%

Ca is an effective element for improving the HAZ toughness by controlling the shape of nonmetallic inclusions in the shape of a lip. In order to sufficiently exhibit such an effect, n is preferably contained by 0.0005% or more of Ca. However, when excessively contained, Ca inclusions coarsen and degrade the ductility of the base metal. Therefore, the amount of Ca is preferably made 0.0030% or less.

In order to make a steel plate with a tensile strength of 590 MPa or more, it is preferable to perform a heat treatment generally known. As an example, it is described in the following Example.

Hereinafter, an Example is given and this invention is demonstrated more concretely. The present invention is not limited by the following examples in the first place, and may be carried out with a suitable modification in a range suitable for the purpose of the preceding and later stages. These are all included in the technical scope of this invention.

[ Example ]

칭하고, 500℃로 템 퍼링하여 제조하였다. 또한, 열간압연후 곧바로

칭, 템퍼링을 행해도 좋다.The steel materials of the composition of Table 1 were melted and slab, heated to 1100 ° C., and hot rolled to a plate thickness of 50 mm. After that, reheat to 930 ℃

It was prepared by tempering to 500 ℃. In addition, immediately after hot rolling

You may perform ching and tempering.

And using the obtained steel plate, the base material strength was measured and HAZ toughness was evaluated as follows.

[Measurement of Base Material Strength]

From t / 4 (t is the plate thickness) of each steel sheet, a No. 4 test piece of JISZ 2201 was taken in a direction perpendicular to the rolling direction, and a tensile test was performed according to the method of JISZ 2241 to measure tensile strength (TS). And it was evaluated by the high tension thing that tensile strength is 590 Mpa or more.

[Evaluation of HAZ Toughness]

12.5mm thickness x 32mm width x 55mm length collected at t / 4 by simulating the thermal history of the heat affected zone near the bond when electroslag welding with welding input heat 800kJ / cm The test piece was heated at 1400 ° C. for 30 seconds, and was heat-treated in a high frequency induction heating apparatus at a cooling time (Tc) of 800 to 500 ° C .: 700 seconds (the test piece after the heat treatment was made of skin plate material (50 mm thickness) and Charpy impact). The test was carried out, the absorption energy (vE0) at the test temperature of 0 ° C was measured, and the absorption energy of 100 J or more was evaluated as being excellent in HAZ toughness.

These results are shown in Table 2.

Table 1

Table 2

From Table 1 and Table 2, it can consider as follows (However, the following No. shows the experiment No. of a table).

It satisfies the requirements specified in the present invention and is in the range of the diagonal line (range of the present invention) shown in FIG. It can be seen that the steel sheets 1 to 12 are high tensile steel sheets having good HAZ toughness.

On the other hand, No. which does not satisfy the provisions of the present invention. Each of 13-28 was in poor condition for the following reasons. That is, No. 13 deteriorated the HAZ toughness because the amount of C exceeded the upper limit.

Also no. 14 deteriorated HAZ toughness because Mn content and Ni content were insufficient.

No. 15 and No. Since 17 (Mn + 0.7 x Ni + Cr) exceeded the upper limit, No. Since 16 (Mn + 0.7xNi + Cr) was below the lower limit, all of HAZ toughness deteriorated.

No. 18, Cr amount is excessively contained, and also No. Since 19 contained excessive amount of Al, HAZ toughness deteriorated.

No. 20 had insufficient amount of N and deteriorated HAZ toughness.

Moreover, since No and 21 amounted Ti and N amount exceeded the upper limit, HAZ toughness deteriorated.

No. 22 had deteriorated HAZ toughness because [Cr / (Mn + 0.7 × Ni)] was below the lower limit.

No. 23 contained excessive Mo and deteriorated HAZ toughness.

No. In 24, each of V and B was in the prescribed range, but the HAZ toughness deteriorated because (V + 2Nb + 10B) exceeded 0.03%.

No. 25, Mn amount is excessively contained and No. 26, the amount of Ni contained in excess, No. 27, the amount of Ti contained excessively, and No. Since 28 contained N amount excessively, all HAZ toughness deteriorated.

As described above, the present invention can provide an excellent high tensile strength steel sheet having a toughness of 590 MPa or more even in the case of high heat input welding of more than 500 kJ / cm.

Claims (7)

As a steel plate, in mass% (hereinafter same), C: 0.02% to 0.05%, Si: 0.05% to 0.20%, Mn: 1.0-2.5%, P: 0.02% or less (does not include 0%), S: 0.005% or less (not including 0%), Al: 0.01% to 0.05%, Ni: 0.2-2.0%, Cr: 0.5-2.0%, Ti: 0.005-0.025%, and N: 0.004-0.010% containing, Also contains Mo: 0.05% to 0.2%, At least one component element selected from the group consisting of V: 0.03% or less, Nb: 0.01% or less, and B: 0.0020% or less, Cu: 0.1 ~ 1.0% Ca: contains 0.0005 to 0.0030%, A high tensile steel sheet composed of balance Fe and other impurities, wherein the components Satisfy the following formulas (1) and (2), 2.3% ≤ (Mn + 0.7 × Ni + Cr) ≤ 3.7% ‥‥ (1) (Cr / (Mn + 0.7 × Ni) ≥ 0.3 ‥‥ (2) (In formula, Mn, Ni, Cr represent each element content (mass%).) In the case of containing at least one component element selected from the group consisting of V: 0.03% or less, Nb: 0.01% or less, and B: 0.0020%, the following formula (3) is satisfied. High tensile steel sheet with excellent toughness of the weld heat affected zone. (V + 2Nb + 10B) ≤ 0.03% ‥‥ (3) (V, Nb, and B represent content (mass%) of each element) delete delete delete delete The high tensile strength steel sheet having excellent toughness of the heat input welding heat affected zone according to claim 1, wherein the steel sheet has a tensile strength of 590 MPa or more. The high tensile strength steel sheet having excellent toughness of the high heat input welding heat affected zone according to claim 1, wherein (Mn + 0.7 × Ni + Cr) is 3.3% or less.

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