KR20160078771A - High strength heat input flux cored arc welded metal joint having excellent impact toughness - Google Patents

Abstract

The present invention provides a high strength heat input flux cored arc welded metal joint having excellent impact toughness, comprising 0.03-0.1 wt% carbon (C); 0.1-0.5 wt% of silicon (Si); 0.8-2.0 wt% of manganese (Mn); 1.0-2.5 wt% of nickel (Ni); 0.01-0.2 wt% of molybdenum (Mo); 0.01-0.1 wt% of titanium (Ti); 0.0003-0.003 wt% of boron (B); 0.001-0.01 wt% of aluminum (Al); 0.003-0.008 wt% of nitrogen (N); 0.03 wt% or less of phosphorus (P); 0.03 wt% or less of sulfur (S); 0.03-0.07 wt% of oxygen (O); and the remaining consisting of iron (Fe) and inevitable impurities, wherein, the component contents of Mn, Ni, Mo, Ti, B, N, S and O satisfy formulas of 0.5<=Ti/O<=1.3, 6<=Ti/N<=15, 125<=Mn/S<=250, 6<=O/B<=40, 0.6<=(Ti+5B)/O<=1.4 and 10<=(5Ni+3Mn+2Mo)<=20.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a high strength, high heat flux cored arc weld metal part having excellent impact toughness,

The present invention relates to a high-strength welded metal part formed at the time of flux cored arc welding (FCAW) used for high-strength welded structures such as bridges, buildings, ships, offshore structures, steel pipes and line pipes, To a high-strength welded metal part formed during an adiabatic heat flux cored arc welding in order to improve welding productivity.

In recent years, construction of skyscrapers has been increasing due to rising land prices, and super-long bridges have been constructed in mountainous areas where islands and inland areas are connected or where winter temperatures are significantly lowered. The steel used has high strength and low temperature impact Humanity is required at the same time. In order to secure the stability of such a very large welded structure, the impact toughness characteristics of the welded portion are more important than anything else. Generally, in the case of heat flux cored arc welding for construction welding structures, the heat input range is about 15 ~ 45kJ / cm.

Generally, a weld metal joint formed during welding is formed by melting a welding material and diluting a part of the steel to form a molten pool, and coagulate to form a coarse columnar structure, and austenite grain boundaries Therefore, coarse grain boundary ferrite, Widmanstatten ferrite, martensite and M-Martensite Austenite constituent are formed, and the weld metal part is the area where impact toughness is most deteriorated in the high strength welded part.

Therefore, in order to secure the stability of the high-strength welded structure, it is necessary to control the microstructure of the welded metal portion to secure impact toughness of the welded metal portion. In order to solve this problem, Patent Document 1 controls the components of the welding material, but it has a problem that it is difficult to obtain sufficient weld metal toughness. In Patent Document 2, the composition of the alloy is controlled and ARM = 197-1457C-1140sol. Al + 11850N-316 (Pcm-C) satisfy the ARM: 40 ~ 80, but since there is no limitation of the oxygen content in the weld, the impact strength . In addition, in Patent Document 3, the slag forming agent is used in an amount of 0.5 to 3.0%, C: 0.04 to 0.2%, Si: 0.1%, Mn: 1.2 to 3.5%, Mg: 0.05 to 0.3% And the B content is 0.002-0.015%. However, since the oxygen and nitrogen content in the weld metal are not disclosed, it is difficult to secure the impact toughness of the weld metal portion have.

Japanese Laid-Open Patent Application No. 1999-170085 Japanese Patent Laid-Open No. 2005-171300 Japanese Patent Application Laid-Open No. 1998-180488

One aspect of the present invention is to provide a high strength substituted heat flux cored arc weld metal portion having a tensile strength of 500 MPa or more to ensure impact toughness.

An aspect of the present invention is a steel sheet comprising, by weight%, 0.03 to 0.1% of C, 0.1 to 0.5% of Si, 0.8 to 2.0% of Mn, 1.0 to 2.5% of Ni, 0.01 to 0.2% 0.003 to 0.003% of B, 0.001 to 0.01% of Al, 0.003 to 0.008% of N, 0.03% or less of P, 0.03 to less than or equal to 0.03% of S, 0.03 to 0.07% of O and the balance Fe and other impurities Ti / N? 15, 125? Mn / S? 250, and 6? O / B, wherein the content of Mn, Ni, Mo, Ti, B, N, S and O is 0.5? Ti / The present invention provides a high strength substituted heat flux cored arc weld metal part having excellent impact toughness satisfying the relational expression of (Ti + 5B) / O? 1.4 and 10? (5Ni + 3Mn + 2Mo)? 20.

According to the present invention, when performing the heat flux cored arc welding with a heat input of 15 to 45 kJ / cm 2 according to the present invention, the TiO-MnS-TiN composite oxide is dispersed to promote the acicular ferrite transformation, It is possible to provide a high strength substituted heat flux cored arc welded metal part having a high strength property having a tensile strength of 500 MPa or more and at the same time ensuring an excellent low temperature impact toughness by suppressing intergranular ferrite transformation in the weld metal part.

The present invention relates to a high-strength welded metal part for high-strength welded structure in which high-strength welded joint cored arc welding is carried out to improve welding productivity. The present invention relates to a method for finely dispersing fine TiO 2 and MnS, ) B is used to suppress intergranular ferrite to improve impact toughness characteristics.

Hereinafter, the high strength substituted heat flux cored arc weld metal part of the present invention will be described in detail.

In order to improve the impact toughness of a high strength superalloy heat weld metal of 500 MPa or more, the present inventor can not secure the impact toughness only by the conventional coarse grain boundary ferrite microstructure, thereby promoting the ferrite transformation in the weld metal, And the maximum amount of the needle-like ferrite is increased to obtain the high-strength and the high-strength heat-welded metal portion at the same time.

Based on such a study, the present invention provides a method for producing a TiO2-TiN-MnS composite oxide by uniformly distributing a composite oxide having a number of TiO-TiN-MnS composite oxide of 1.0 x 10 ⁷ / mm ³ and a size of 0.01 to 0.1 탆, The present invention has been made to provide a technique capable of suppressing intergranular ferrite transformation to 10% or less by forming 90% or more of acicular ferrite structure in the cored arc weld metal portion and securing [3] soluble B in the cored arc weld metal portion.

Hereinafter, [1], [2] and [3] will be described in more detail.

[1] TiO-MnS complex oxide management

The present inventors have found that when the ratio of Ti / O, Ti / N and Mn / S is adequately maintained in the weld metal, the number of Ti composite oxides is appropriately distributed to prevent coarsening of austenite grains during the solidification process of the weld metal, TiN and MnS precipitates are combined to form a TiO-TiN-MnS composite oxide. This TiO-TiN-MnS composite oxide promotes needle-shaped ferrite transformation favoring weld metal toughness. For this purpose, it is important to distribute the TiO-TiN-MnS composite oxide finely and uniformly. The inventors also investigated the size, quantity and distribution of the TiO-TiN-MnS composite oxide according to the ratio of Ti / O, Ti / N and Mn / S and found that the ratio of Ti / TiO-TiN-MnS composite oxide having a size of 0.01-0.1 μm was obtained at a density of 1.0 × 10 ⁷ / mm ³ or more when the Mn / S ratio was 125 to 250.

[2] microstructures, welded metal parts

It was found from the study of the present invention that the size, quantity and distribution of the TiO-TiN-MnS composite oxide according to the ratio of Ti / O, Ti / N and Mn / -TiN-MnS composite oxide is appropriately distributed in the austenite crystal grains, it is possible to preferentially form the acicular ferrite transformation as compared with the intergranular ferrite formed in the crystal grain boundaries as a role of the nonuniform nucleation site as the temperature decreases in the austenite I found out.

When TiO-TiN-MnS composite oxide is appropriately distributed in the weld metal, it promotes needle-shaped ferrite transformation in the crystal grain preferentially over the crystal grain boundary in the cooling process of the heat-welded metal portion to secure the composition ratio of the ferrite of the weld metal portion to 90% or more It is possible. This makes it possible to drastically improve the impact toughness characteristics of the weld metal portion of the heat input welded portion.

 

[3] The role of soluble boron in weld metal

The fact of the study of the present invention is that boron, which is dissolved separately from the composite oxide uniformly dispersed in the weld metal, diffuses into the grain boundaries to lower the grain boundary energy and suppress the intergranular ferrite transformation at grain boundaries Thereby promoting needle-bed ferrite transformation in crystal grains. In this way, the intergranular ferrite transformation is suppressed in the grain boundaries, and in the grain, the Ti composite oxide promotes the needle-shaped ferrite transformation and contributes to the improvement of the impact toughness of the substitution heat welded metal portion. The composition ratio of Ti / O, Ti / N, O / B, and (Ti + 5B) / O of the weld metal is important in order to exist as such a sphere B.

The high strength substituted high flux cored arc weld metal part having excellent impact toughness, which is one aspect of the present invention, comprises 0.03 to 0.1% of C, 0.1 to 0.5% of Si, 0.8 to 2.0% of Mn, 1.0 to 2.5 0.001 to 0.01% of Al, 0.003 to 0.008% of N, 0.03% or less of P, 0.03% or less of S, 0.03 to less than 0.03% of Mo, 0.01 to 0.2% of Mo, 0.01 to 0.1% of Ti, 0.0003 to 0.003% : 0.03 to 0.07%, the balance Fe and other impurities, and the content of Mn, Ni, Mo, Ti, B, N, S and O is 0.5? Ti / O? 1.3, 6? Ti / (Ti + 5B) / O? 1.4 and 10? (5Ni + 3Mn + 2Mo)? 20.

Hereinafter, the reasons for limiting the composition of the steel material will be described in detail. (All the composition of the following components means weight% unless otherwise specified.)

Carbon (C): 0.03 to 0.1%

Carbon (C) is an indispensable element in order to ensure the strength of the weld metal and ensure welding hardenability. Therefore, more than 0.03% of carbon is required. However, when the carbon content is more than 0.1%, the weldability is greatly reduced, and particularly, low-temperature cracking is likely to occur in the weld metal portion and the impact toughness is significantly lowered. Therefore, the content of carbon (C) is preferably 0.03 to 0.1%.

Silicon (Si): 0.1 to 0.5%

If the content of silicon is less than 0.1%, the effect of deoxidation in the weld metal is insufficient and the flowability of the weld metal is lowered. When the content of silicon exceeds 0.5%, transformation of the MA constituent in the weld metal is promoted, And adversely affects the susceptibility to welding at low temperature cracks. Therefore, the content of silicon (Si) is preferably limited to 0.1 to 0.5%.

Manganese (Mn): 0.8 to 2.0%

Mn is an essential element for improving deoxidation and strength in the weld metal part, and precipitates in the form of MnS around the Ti composite oxide, thereby promoting the formation of the needle-like ferrite favorable for improving the weld metal toughness. In addition, Mn forms a substitutional solid solution in the matrix to solidify the matrix to secure strength and toughness. For this purpose, Mn is preferably contained in an amount of 0.8% or more. However, when it exceeds 2.0%, it is not preferable because it forms a low-temperature transformed structure. Therefore, it is preferable to limit the content of manganese (Mn) to 0.8 to 2.0%.

Nickel (Ni): 1.0 to 2.5%

Ni is an essential element in the present invention because it enhances the strength and toughness of the matrix by solid solution strengthening. In order to obtain such an effect, it is preferable that the Ni content is 1.0% or more. If the Ni content exceeds 2.5%, it is undesirable because it affects the occurrence of high temperature cracks and increases the economic burden. But is preferably limited to 1.0 to 2.5%.

Molybdenum (Mo): 0.01 to 0.2%

Mo is an essential element in the present invention because it enhances the strength and toughness of the matrix by solid solution strengthening. In order to obtain such an effect, it is preferable that the Mo content is 0.01% or more. If the Mo content exceeds 0.2%, the hardenability is improved to affect the toughness of the weld metal for heat transfer, To 0.2%.

Titanium (Ti): 0.01 to 0.1%

Ti is an indispensable element in the present invention because it combines with O to form a fine Ti oxide. In order to obtain such a fine TiO 2 oxide dispersion effect, it is preferable to add 0.01% or more of Ti, but when it exceeds 0.1%, coarse TiO 2 oxides and coarse TiN precipitates are formed, To 0.1%.

Boron (B): 0.0003 to 0.003%

B is an element which improves the incombustibility and is required to be 0.0003% or more in order to be segregated in the grain boundary in the form of solubles to suppress intergranular ferrite transformation. However, if it exceeds 0.003%, the effect becomes saturated and welding hardenability is greatly increased, which is undesirable because the occurrence of low-temperature weld cracking and toughness are lowered. Therefore, the B content is limited to 0.0003 to 0.003%.

Aluminum (Al): 0.001 to 0.01%

Al is an element required for reducing the amount of oxygen in the weld metal as a deoxidizer, and the amount of Al is preferably 0.001% or more. However, if it exceeds 0.01%, coarse Al ₂ O ₃ oxides are formed, which hinders formation of TiO 2 complex oxide required for improving toughness, and therefore, it is preferably 0.01% or less.

Nitrogen (N): 0.003 to 0.008%

N is an indispensable element for forming TiN precipitates or the like in the Ti composite oxide, and its content is preferably set to 0.003% or more. However, if the nitrogen content exceeds 0.008%, the effect is saturated, and the increase in the amount of solid solution nitrogen present in the weld metal may lead to a decrease in toughness and strain aging. Therefore, the content of nitrogen (N) is limited to 0.003 to 0.008% .

Phosphorus (P): 0.030% or less

P is an impurity element promoting high-temperature cracking during welding, so it is desirable to control P as low as possible. In order to improve toughness and reduce cracks, it is recommended to keep it at 0.03% or less.

Sulfur (S): not more than 0.030%

S is an element necessary for MnS formation. It is preferable to set it to 0.03% or less for the precipitation of the complex precipitate of MnS. If there is more than that, it is not preferable since a low melting point compound such as FeS can be formed to cause high-temperature cracking.

Oxygen (O): 0.03 to 0.07% or less

O is an indispensable element that reacts with Ti to form a Ti composite oxide in a weld metal solidification, and the Ti oxide present in the mouth promotes the transformation of the needle-like ferrite in the weld metal. If the content of O is less than 0.03%, Ti oxide can not be formed properly in the weld metal part. If the content of O is more than 0.07%, an oxide which is not effective for the TiO2 and other FeO is generated, The content of oxygen (O) is preferably limited to 0.03 to 0.07% or less.

The weld metal part may contain 0.001 to 0.1% of Nb, 0.001 to 0.1% of V, 0.05 to 1.0% of Cr, 0.05 to 0.5% of W and 0.005 to 0.5% of Zr in order to further improve the mechanical properties One or more selected from the group consisting of the above-mentioned compounds may be further added.

Copper (Cu): 0.01 to 2.0%

Cu is an effective element for securing the strength and toughness due to the employment strengthening effect by being employed at the base. In order to achieve this, the Cu content should be 0.01% or more. If the Cu content exceeds 2.0%, the hardness of the weld metal increases to lower the toughness and promote the high temperature cracks in the weld metal. %. &Lt; / RTI &gt;

When Cu and Ni are mixedly added, the total amount thereof is preferably less than 3.5%. The reason for this is that when the content is less than 3.5%, the fillability is increased, and the toughness and weldability are adversely affected.

Niobium (Nb): 0.001 to 0.1%

Nb is an essential element for improving the incombustibility. In particular, it has an effect of widening the range of bainite formation even in a range where the Ar ₃ temperature is lowered and the cooling rate is low. However, when the content exceeds 0.1%, the weld metal portion promotes the formation of the martensite on the weld during welding, which adversely affects the toughness of the weld metal portion. Therefore, the content of Nb is preferably limited to 0.001 to 0.1%.

Vanadium (V): 0.001 to 0.1%

V is an element for accelerating ferrite transformation by forming VN precipitate. If it is more than 0.001%, if it exceeds 0.1%, a light image such as Carbide may be formed on the weld metal portion and may adversely affect the toughness of the weld metal portion. Is preferably limited to 0.001 to 0.1%.

Cr (Cr): 0.05 to 1.0%

If Cr content is less than 0.05%, strength can not be obtained. If the content is more than 1.0%, Cr may be deteriorated in weld metal toughness. Therefore, Cr is preferably set to 0.05 to 1.0% desirable.

Tungsten (W): 0.05 to 0.5%

W is an element which improves high-temperature strength and is effective for precipitation strengthening. However, when the content is less than 0.05%, the effect of increasing the strength is small, and it is not preferable. If the content is more than 0.5%, the weld metal toughness may be adversely affected. Therefore, the content of W is preferably limited to 0.05 to 0.5% or less.

Zirconium (Zr): 0.005-0.5%

Since Zr is effective for increasing the strength, it is preferable to add 0.005% or more. If it exceeds 0.5%, the toughness of the weld metal may be adversely affected. Therefore, the content of Zr is preferably limited to 0.005 to 0.5%.

In the present invention, at least one of Ca and REM may be further added to suppress the growth of crystal grains of old austenite.

Ca and REM are desirable elements because they stabilize the arc during welding and form oxides in the weld metal part. It also inhibits the growth of austenite grains during the cooling process and promotes the ferrite transformation in the ingot, thereby improving the toughness of the weld metal part. For this purpose, it is preferable to add 0.0005% or more of Ca and 0.005% or more of REM. If Ca is 0.05% and REM is more than 0.05%, a large oxide may be formed and the toughness may be adversely affected. As the REM, one or more of Ce, La, Y and Hf may be used, and any of the above effects can be obtained.

The remainder consists of Fe and unavoidable impurities.

Hereinafter, the component relation of the present invention will be described in detail

The ratio of Ti / O is preferably 0.5 to 1.3.

When the Ti / O ratio is less than 0.5, the number of Ti composite oxides required for the austenite grain growth inhibition and needle-like ferrite transformation in the weld metal is insufficient, and the Ti ratio contained in the Ti composite oxide becomes small, So that the percentage of the needle-shaped ferrite phases effective for improving the toughness of the weld heat affected zone is lowered. When the ratio of Ti / O exceeds 1.3, the austenite grain growth suppressing effect in the weld metal is saturated, and the ratio of the alloy component contained in the composite oxide becomes rather small, and the function as the nucleus generation site of the needle-shaped ferrite is lost.

The ratio of Ti / N is preferably set to 6 to 15.

In the present invention, when the Ti / N ratio is less than 6, the amount of TiN precipitates formed in the Ti composite oxide decreases, which is undesirable because it affects the needle-shaped ferrite transformation effective in improving toughness. The amount of nitrogen is increased and the impact toughness is lowered, which is not preferable.

The ratio of Mn / S is preferably 125 to 250.

In the present invention, when the Mn / S ratio is less than 125, the amount of MnS precipitates formed in the Ti composite oxide decreases, which is not desirable because it affects the ferrite transformation which is effective in improvement in toughness. When the ratio exceeds 250, And the impact toughness in the weld metal is lowered.

The ratio of O / B is preferably 6 to 40.

In the present invention, when the O / B ratio is less than 6, the amount of soluble boron diffusing to the austenite grain boundaries during the cooling process after welding is suppressed to suppress intergranular ferrite transformation. When the O / B ratio is more than 40, It is undesirable because the effect is saturated and affects toughness.

(Ti + 5B) / O is preferably 0.6 to 1.4.

In the present invention, when the ratio of (Ti + 5B) / O is less than 0.6, the number of Ti complex precipitates is insufficient, and when the ratio is more than 1.4, the amount of soluble B is decreased to suppress intergranular ferrite transformation, It is not desirable to improve the toughness of the negative.

(5Ni + 3Mn + 2Mo) is preferably 10 to 20.

In the present invention, when the ratio of (5Ni + 3Mn + 2Mo) is less than 10, it is not possible to secure a high strength welded metal portion of 500 MPa or more. If the ratio exceeds 20, the hardenability is increased to adversely affect the low temperature crack and toughness The upper bainite structure is formed, which is undesirable.

The microstructure of the weld metal portion of the present invention preferably includes an acicular ferrite of 90% or more and a grainboundary ferrite of 10% or less in an area fraction. It is important to maintain 90% or more of needle-shaped ferrite in order to secure the strength and toughness of the welded metal part. If it contains more than 10% of intergranular ferrite, it is not preferable for the weld metal toughness.

It is preferable that a TiO-MnS-TiN composite oxide having an average particle diameter of 0.01 to 0.1 탆 is distributed in the weld metal portion of 1.0 × 10 ⁷ / mm ³ or more. When the proper composition range of the present invention is maintained and the proper oxygen content in the weld metal portion is maintained, the TiO-MnS-TiN composite oxide having an average grain size of 0.01 to 0.1 탆 in the weld metal portion is distributed at 1.0 × 10 ⁷ / mm ³ or more .

The present invention can also be produced by welding methods other than high heat flux cored arc welding. At this time, if the cooling rate of the weld metal portion is high, it is preferable to use a small heat welding method in which the oxide is finely dispersed and the structure is fine, and therefore the cooling rate is high. For the same reason, steel cooling and Cu-backing methods are also advantageous to improve the cooling rate of welds. However, even when such known techniques are applied to the present invention, it is natural that they are interpreted as a simple change of the present invention within the scope of the technical idea of the present invention.

Hereinafter, the present invention will be described in detail with reference to examples. It should be noted, however, that the following examples are intended to illustrate the invention in more detail and not to limit the scope of the invention. The scope of the present invention is determined by the matters set forth in the claims and the matters reasonably inferred therefrom.

[ Example ]

A weld metal portion having the same composition as Table 1 was manufactured by FCAW applying a welding heat amount in the range of 35 to 45 kJ / cm. The composition ratio between the weld metal sub-alloy constituent elements to exhibit the effect of the present invention is shown in Table 2 .

Test specimens for the evaluation of the mechanical properties of the welded metal parts as described above were taken from the center of the welded metal part. The tensile test specimens were made with KS Specification No. 4 (KS B 0801) No. 4, 10 mm / min. Impact test specimens were prepared in accordance with KS (KS B 0809) No. 3 test specimens.

The size, number and spacing of the oxides, which have a significant impact on the impact toughness of the weld metal, were measured by point counting using an image analyzer and an electron microscope. At this time, the surface to be inspected was evaluated on the basis of 100 mm ² .

The impact toughness of the welded metal part of the FCAW heat transfer weld was evaluated by the Charpy impact test at -20 ° C after machining with an impact test piece after FCAW welding.

division Component composition (% by weight) C Si Mn P S Ni Mo Ti B
(ppm) N (ppm) Cu Al Cr Nb V Ca REM O
(ppm) Inventive Steel 1 0.04 0.35 0.94 0.008 0.005 2.1 0.01 0.03 24 45 - 0.001 - - - - - 480 Invention river 2 0.05 0.30 1.20 0.010 0.008 2.4 0.02 0.04 30 54 - 0.003 - - - - - 540 Invention steel 3 0.06 0.28 1.30 0.011 0.009 2.0 0.1 0.02 16 32 0.01 0.004 - - - - - 380 Inventive Steel 4 0.08 0.39 1.51 0.008 0.007 2.3 0.2 0.04 10 50 - 0.003 - - - - - 650 Invention steel 5 0.07 0.25 1.20 0.009 0.006 1.7 0.1 0.05 8 43 - 0.005 - - - - - 520 Invention steel 6 0.07 0.36 1.40 0.010 0.007 1.8 0.07 0.06 12 45 - 0.002 - 0.01 - - - 480 Invention steel 7 0.03 0.25 1.15 0.011 0.005 1.6 0.15 0.04 15 55 0.03 0.002 - - - - - 460 Inventive Steel 8 0.06 0.35 1.60 0.012 0.008 2.4 0.02 0.06 29 45 - 0.003 - - 0.01 - - 520 Invention river 9 0.04 0.28 1.83 0.010 0.008 2.3 0.03 0.07 15 52 - 0.003 0.02 - - 0.001 - 580 Invented Steel 10 0.05 0.30 1.20 0.009 0.006 2.4 0.03 0.08 6 60 - 0.003 - - - - 0.005 630 Comparative River 1 0.08 0.46 2.25 0.011 0.006 2.6 0.3 0.2 39 72 0.02 0.05 - - - - - 850 Comparative River 2 0.07 0.53 1.98 0.011 0.004 0.7 0.2 0.1 69 80 0.04 0.01 - - - - - 720 Comparative Steel 3 0.06 0.56 2.15 0.010 0.007 1.5 0.5 0.34 41 74 - 0.07 - - - - - 650 Comparative Steel 4 0.05 0.20 2.1 0.008 0.004 1.7 0.5 0.20 90 56 0.02 - - - - - - 770 Comparative Steel 5 0.01 0.68 1.16 0.013 0.008 2.6 1.1 0.58 58 71 0.012 - - - - - - 170 Comparative Steel 6 0.02 0.36 1.33 0.012 0.007 1.3 1.6 0.37 52 20 0.03 0.012 - - - - - 140 Comparative Steel 7 0.08 0.62 1.98 0.015 0.008 1.4 1.1 0.40 88 30 0.03 0.01 - - - - - 160 Comparative Steel 8 0.09 0.14 2.36 0.011 0.006 1.5 0.5 0.14 42 150 0.32 0.03 - - 0.03 - - 800 Comparative Steel 9 0.09 0.27 1.94 0.015 0.010 1.4 1.1 0.81 25 100 0.03 0.02 - - - - - 240 Comparative Steel 10 0.02 0.16 0.67 0.009 0.004 0.5 0.4 0.42 45 90 - 0.006 - - - - - 750

division Ti / O Ti / N Mn / S O / B (Ti + 5B) / O 5Ni + 3Mn + 2Mo Inventive Steel 1 0.6 6.7 188 20.0 0.9 13.3 Invention river 2 0.7 7.4 150 18.0 1.0 15.6 Invention steel 3 0.5 6.3 144 23.8 0.7 14.1 Inventive Steel 4 0.6 8.0 216 38.2 0.7 16.4 Invention steel 5 1.0 11.6 200 32.5 1.1 12.3 Invention steel 6 1.3 13.3 200 40.0 1.4 13.3 Invention steel 7 0.9 7.3 230 30.7 1.0 11.8 Inventive Steel 8 1.2 13.3 200 17.9 1.4 16.8 Invention river 9 1.2 13.5 229 38.7 1.3 17.1 Invented Steel 10 1.3 13.3 200 37.1 1.4 15.7 Comparative River 1 2.4 27.8 375 21.8 2.6 20.4 Comparative River 2 1.4 12.5 495 10.4 1.9 9.8 Comparative Steel 3 5.2 45.9 307 15.9 5.5 15.0 Comparative Steel 4 2.6 35.7 525 8.6 3.2 15.8 Comparative Steel 5 34.1 81.7 145 2.9 35.8 18.7 Comparative Steel 6 26.4 185.0 190 2.7 28.3 13.7 Comparative Steel 7 25.0 133.3 248 1.8 27.8 15.1 Comparative Steel 8 1.8 9.3 393 19.0 2.0 15.6 Comparative Steel 9 33.8 81.0 194 9.6 34.3 15.0 Comparative Steel 10 5.6 46.7 168 16.7 5.9 5.3

division Welding process and heat input TiO-MnS-TiN
Complex oxide Microstructure fraction of weld metal part (%) Welded metal part
Mechanical property Welding Process Welding heat input
(kJ / cm) Count
(Pieces / mm ³ ) Average size
(탆) Needle ferrite Intergranular ferrite The tensile strength
(MPa) vE _{-20 ° C}
(J) Inventive Steel 1 FCAW 40 2.3X10 ⁸ 0.011 91 9 5741 168 Invention river 2 FCAW 40 3.6X10 ⁸ 0.013 92 8 562 172 Invention steel 3 FCAW 35 2.7X10 ⁸ 0.014 91 9 568 157 Inventive Steel 4 FCAW 45 3.6X10 ⁸ 0.013 91 9 567 169 Invention steel 5 FCAW 40 4.4X10 ⁸ 0.014 93 7 573 156 Invention steel 6 FCAW 45 3.3X10 ⁸ 0.021 92 8 561 160 Invention steel 7 FCAW 40 2.6X10 ⁸ 0.014 92 8 573 149 Inventive Steel 8 FCAW 40 2.3X10 ⁸ 0.016 94 6 572 158 Invention river 9 FCAW 40 3.6X10 ⁸ 0.018 91 9 568 145 Invented Steel 10 FCAW 40 3.3X10 ⁸ 0.014 92 8 538 162 Comparative River 1 FCAW 39 1.0 × 10 ⁶ 0.045 46 54 557 42 Comparative River 2 FCAW 40 1.3 × 10 ⁶ 0.052 47 53 444 29 Comparative Steel 3 FCAW 38 1.2 × 10 ⁶ 0.053 44 56 451 46 Comparative Steel 4 FCAW 40 1.0 × 10 ⁶ 0.044 45 55 523 38 Comparative Steel 5 FCAW 45 1.3 x 10 ⁵ 0.039 37 63 556 54 Comparative Steel 6 FCAW 40 1.3 × 10 ⁶ 0.045 42 58 540 44 Comparative Steel 7 FCAW 35 1.0 × 10 ⁶ 0.046 44 56 541 42 Comparative Steel 8 FCAW 40 1.1 × 10 ⁵ 0.0439 42 58 539 57 Comparative Steel 9 FCAW 40 1.3 x 10 ⁵ 0.048 49 51 525 64 Comparative Steel 10 FCAW 40 1.2 × 10 ⁵ 0.043 42 58 523 52 Comparative Steel 11 FCAW 40 1.3 × 10 ⁶ 0.049 41 59 524 33

As shown in Table 3, Inventive steels 1 to 10, which are weld metal parts produced according to the present invention, have a number of TiO-MnS-TiN composite oxides in the range of ² × ^{10 8} / mm ³ or more, cases 1 X10 ⁶ gae / mm ³ compared to inventive steels of the comparative steel I shows the range of not more than are fairly uniform, yet while having a fine complex oxide water size can be seen well that the number thereof also increases significantly. On the other hand, in the case of the microstructure of the present invention, it is confirmed that the needle-like ferrite and the intergranular ferrite fraction have a fraction of 90% or more and 10% or less, respectively, so that the weldability can be greatly improved.

Claims (4)

The steel sheet according to any one of claims 1 to 3, wherein the steel sheet comprises, by weight, 0.03 to 0.1% of C, 0.1 to 0.5% of Si, 0.8 to 2.0% of Mn, 1.0 to 2.5% of Ni, 0.01 to 0.2% of Mo, 0.01 to 0.1% 0.003 to 0.003% of Al, 0.001 to 0.01% of Al, 0.003 to 0.008% of N, 0.03% or less of P, 0.03 to 0.03% of S and 0.03 to 0.07 of O, the balance Fe and other impurities, The content of Mo, Ti, B, N, S and O is 0.5? Ti / O? 1.3, 6? Ti / N? 15, 125? Mn / S? 250, 6? O / Ti + 5B) / O? 1.4 and 10? (5Ni + 3Mn + 2Mo)? 20, wherein the high impact strength heat flux cored arc weld metal part is excellent in impact toughness.
The weld metal according to claim 1, wherein the weld metal portion comprises 0.001 to 0.1% of Nb, 0.001 to 0.1% of V, 0.05 to 1.0% of Cr, 0.01 to 2.0% of Cu, 0.05 to 0.5% of W, 0.005 to 0.5% of Zr, %, And at least one selected from the group consisting of 0.0005 to 0.005% of Ca and 0.005 to 0.05% of REM, in addition to the high-strength substituted heat flux Cored arc weld metal part.
The high-strength substituted heat flux cored sheet according to claim 1, wherein the microstructure of the weld metal portion comprises an acicular ferrite having an area fraction of 90% or more and a grainboundary ferrite of 10% or less, Arc welded metal part.
The method of claim 1, wherein the weld metal portion has a TiO-MnS-TiN composite oxide having an average particle diameter of 0.01 to 0.1 占 퐉 of 1.0 x 10 ⁷ / mm ³ or more distributed therein. part.