KR20100050039A - High heat input arc weld metal joint having excellent low temperature impact toughness - Google Patents

High heat input arc weld metal joint having excellent low temperature impact toughness Download PDF

Info

Publication number
KR20100050039A
KR20100050039A KR1020080109126A KR20080109126A KR20100050039A KR 20100050039 A KR20100050039 A KR 20100050039A KR 1020080109126 A KR1020080109126 A KR 1020080109126A KR 20080109126 A KR20080109126 A KR 20080109126A KR 20100050039 A KR20100050039 A KR 20100050039A
Authority
KR
South Korea
Prior art keywords
metal part
weld metal
heat input
impact toughness
temperature impact
Prior art date
Application number
KR1020080109126A
Other languages
Korean (ko)
Inventor
정홍철
Original Assignee
주식회사 포스코
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 주식회사 포스코 filed Critical 주식회사 포스코
Priority to KR1020080109126A priority Critical patent/KR20100050039A/en
Publication of KR20100050039A publication Critical patent/KR20100050039A/en

Links

Classifications

    • 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
    • C22C38/02—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
    • C22C38/08—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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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

Abstract

PURPOSE: A high heat input arc welding metal part with excellent low-temperature impact toughness is provided to improve impact toughness of a welding metal part by adding boron. CONSTITUTION: A high heat input arc welding metal part with excellent low-temperature impact toughness is composed of C 03~0.2 weight%, Si 0.1~0.5 weight%, Mn 0.5~3.0 weight%, Mo 0.05~1.0 weight%, Ti 0.03~0.1 weight%, Mg 0.0005~0.005 weight%, B 0.0003~0.01 weight%, Al 0.005~0.05 weight%, N 0.004~0.005 weight%, P less than 0.03 weight%, S less than 0.03 weight%, O less than 0.03 weight %, Fe and inevitable impurities.

Description

High heat input arc welding metal part with excellent low temperature impact toughness {HIGH HEAT INPUT ARC WELD METAL JOINT HAVING EXCELLENT LOW TEMPERATURE IMPACT TOUGHNESS}

The present invention relates to a weld metal part when a high heat input SAW (Submerged Arc Welding) used in welding structures such as ships, construction, bridges, offshore structures, steel pipes, and line pipes, More specifically, a high heat input submerge having excellent low temperature impact toughness by promoting fine dispersion of fine (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates to promote acicula ferrite transformation. DE arc welding metal parts.

In recent years, with the trend of larger ships and higher building structures, structures have become larger in size, and steel materials used therein have been replaced by high strength and thick steel materials. In order to fabricate a structure in a given air by welding such high strength thick steel, high efficiency welding is inevitable, and the most widely used welding technique for welding thickened steel is submerged arc welding (SAW). Technology. In general, SAW is more advantageous in terms of productivity than general gas metal arc welding (GMAW) because the welding volume is large and the number of welding passes is reduced. Currently used SAW uses a large amount of heat input in the heat input range of about 30 ~ 300KJ / cm.

Generally, weld metal formed during high heat input welding coagulates, and a coarse columnar structure is formed, and coarse grain boundary ferrite and widmanstetten ferrite are formed along the austenite grain boundary in the coarse grain. This is formed and the low temperature impact toughness is bad.

Therefore, in order to secure the stability of the welded structure, it is necessary to control the microstructure of the welded metal part to secure impact toughness of the welded metal part. As a means to solve this problem, Japanese Patent Laid-Open Publication No. H11-170085 is a technique for defining the components of a welding material, but there is a problem that it is difficult to obtain sufficient toughness because it does not control the microstructure, particle size, etc. of the welding metal.

In Japanese Patent Laid-Open No. 2005-171300, C: 0.07% or less, Si: 0.3% or less, Mn: 1.0 to 2.0%, P: 0.02% or less, S: 0.1% or less, sol.Al: 0.04 to 0.4 ARM defined by ARM = 197-1457C-1140sol.Al + 11850N-316 (Pcm-C) in a composition consisting of%, N: 0.002 to 0.01%, Ti: 0.005 to 0.02%, B: 0.0005 to 0.005%: It is characterized by 40 to 80, but because there is no limitation in the oxygen content in the weld ARM, there is a problem that it is difficult to secure the impact toughness of the SAW high heat input weld metal.

In addition, Japanese Patent Laid-Open No. 10-180488 discloses slag generating material: 0.5 to 3.0%, C: 0.04 to 0.2%, Si: 0.1% or less, Mn: 1.2 to 3.5%, Mg: 0.05 to 0.3%, Ni: 0.5 It has good impact toughness, including ~ 4.0%, Mo: 0.05 ~ 1.0%, and B: 0.002 ~ 0.015%, but it does not control the oxygen and nitrogen content in the weld metal. There is a problem that is difficult to secure enough.

The present invention provides a high heat input submerged that can secure high strength and high toughness by promoting intramorbid needle ferrite transformation using (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composite precipitate. It is to provide an arc welding metal part.

In the present invention, by weight%, C: 0.03-0.2%, Si: 0.1-0.5%, Mn: 0.5-3.0%, Ni: 0.5-3.0%, Mo: 0.05-1.0%, Ti: 0.03-0.1%, Mg : 0.0005 ~ 0.005%, B: 0.0003 ~ 0.01%, Al: 0.005 ~ 0.05%, N: 0.004 ~ 0.008%, P: 0.03% or less, S: 0.03% or less, O: 0.03% or less, the rest is Fe and inevitable It is composed of impurities and satisfies 1.3≤Ti / O≤3.0, 8≤O / Mg≤20, 7≤Ti / N≤12, 0.8≤N / B≤1.5, 11≤ (Ti + 4B) / N≤16 It relates to a high heat input arc welding metal part excellent in low temperature impact toughness.

The present invention provides a welded metal part capable of securing high impact toughness and at the same time ensuring high impact toughness in a large heat input submerged arc welding with a welding heat input amount of 100 KJ / cm or more. In particular, (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates are finely dispersed in crystal grains to promote needle ferrite and polygonal ferrite transformation, thereby achieving high low temperature toughness. A high heat input submerged arc weld metal part is provided.

Hereinafter, the present invention will be described in detail.

The present inventors have studied the type and size of the needles ferrite and the oxides on the ferrites known to be effective in the toughness of the weld metal, and thus, (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composites. It was found that the amount of acicular ferrite in the weld metal part changes according to the size and number of precipitates, and thus the toughness of the high heat input submerged arc weld metal part changes.

Based on these studies, in the present invention

[1] The use of (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates in the submerged weld metal part together with Soluble B to promote needle ferrite transformation ,

[2] welding metals by controlling the number of (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates of 1.0 × 10 7 / ㎣ or more and controlling the size to 0.01 to 0.1 µm It can promote needle ferrite transformation in wealth.

These [1] and [2] are demonstrated concretely.

[1] Management of (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates and the role of soluble B in the weld metal part

If the ratio of Ti / O, O / Mg, Ti / N, and N / B in the weld metal is properly maintained, the number of (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates will be increased. Appropriate distribution has been shown to prevent coarsening of austenite grains in the solidification process of weld metal and to promote acicular ferrite and polygonal ferrite transformation. That is, if (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composite precipitate are properly distributed in the austenite grains, as the temperature decreases, the acicular ferrite becomes a function of heterogeneous nucleation sites. It is formed preferentially over the grain boundary ferrite formed at the grain boundaries. As a result, the weld metal part toughness can be significantly improved. For this purpose, it is important to distribute (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composite precipitate finely and uniformly.

In addition, boron, which is dissolved separately from the (Ti-Mg) O oxide and the (Ti-Mg) O- (Ti, B) N composite precipitate uniformly dispersed in the weld metal part, diffuses into the grain boundary to lower the energy of the grain boundary. It acts to suppress grain boundary ferrite transformation at grain boundaries, and diffuses into (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates to form B- around the oxides and composite precipitates. It forms a depleted zone to reduce hardenability and promotes acicular ferrite and polygonal ferrite transformation. The boron in the above-described solution contributes to improving the impact toughness of the weld metal part by suppressing grain boundary ferrite transformation at grain boundaries and promoting needle-like ferrite and polygonal ferrite transformation in grains.

[2] microstructures, weld metal

The facts of the present invention reveal that the (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composites in accordance with the ratio of Ti / O, O / Mg, Ti / N, N / B. The size, quantity, and distribution of the precipitates were as follows: 1.3≤Ti / O≤3.0, 8≤O / Mg≤20, 7≤Ti / N≤12, 0.8≤N / B≤1.5, 11≤ (Ti + 4B) / When N≤16, it was confirmed that (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates having a size of 0.01 to 0.1 µm were obtained at 1.0 × 10 7 / dl or more. When such (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composite precipitates are properly distributed in the weld metal, acicular ferrite and polygonal blades preferentially enter the grains rather than grain boundaries during cooling of the weld metal part. (Polygonal) By promoting ferrite transformation, the composition ratio of acicular ferrite and polygonal ferrite in the weld metal part can be secured more than 90%. For this reason, the low-temperature impact toughness of a weld metal part can be improved more.

Hereinafter, the composition of the weld metal part of the present invention will be described in detail (hereinafter by weight).

The content of carbon (C) is 0.03 to 0.2%. Carbon is preferably added in an amount of 0.03% or more as an essential element in order to secure the strength of the weld metal and to secure weld hardenability. However, when the carbon content exceeds 0.2%, weldability is greatly reduced, and low-temperature cracking is easily generated in the weld metal part, and the thermal shock toughness is greatly reduced.

The content of silicon (Si) is 0.1 to 0.5%. If the silicon content is less than 0.1%, the deoxidation effect in the weld metal is insufficient and the fluidity of the weld metal is insufficient. If the content of the silicon is more than 0.5%, the low temperature impact toughness is promoted by promoting the transformation of MA constituent in the weld metal. It is not preferable because it lowers the pressure and adversely affects the weld cracking sensitivity.

The content of manganese (Mn) is 0.5 to 3.0%. Manganese forms a solid solution in the matrix structure with an effective action of deoxidizing and improving strength in steel, thereby strengthening the matrix and solidifying the matrix to secure strength and toughness. However, if it exceeds 3.0%, it is not preferable because it generates low temperature metamorphic tissue.

The content of titanium (Ti) is 0.03 to 0.1%. Titanium is indispensable in the present invention because it combines with oxygen to form fine titanium oxide, as well as to form fine TiN precipitates. In order to obtain such a fine TiO oxide and TiN composite precipitate effect, it is preferable to add Ti or more to 0.03% or more.

The content of nickel (Ni) is 0.5 to 3.0%. Ni is an effective element which improves the strength and toughness of the matrix by solid solution strengthening. In order to obtain such an effect, it is preferable to contain Ni content of 0.5% or more, but when it exceeds 3.0%, it is not preferable because the hardenability is greatly increased and hot cracking may occur.

Molybdenum (Mo) is limited to 0.05 to 1.0%. Mo is an element that increases the hardenability and at the same time improves the strength, the content is 0.05% or more to secure the strength, but the upper limit is 1.0% to suppress the hardening of the weld metal portion and the occurrence of cold welding cracks.

The content of boron (B) is 0.0003 to 0.01%. B is an element that improves quenchability and segregates at grain boundaries and needs more than 0.0003% to suppress grain boundary ferrite transformation, but when it exceeds 0.01%, the effect is saturated and weld hardenability is greatly increased to promote martensite transformation. It is not preferable because it lowers the weld low temperature crack generation and toughness.

The content of magnesium (Mg) is 0.0005 to 0.005%. Mg is an essential element for forming an oxide, but more than 0.0005% is required, but if it exceeds 0.005%, the effect is saturated and the oxide is coarsened, which is not preferable because it adversely affects the toughness of the weld metal part.

The content of nitrogen (N) is 0.004 to 0.008%. N is an indispensable element for forming TiN precipitates, which increases the amount of fine TiN precipitates. In particular, the content is preferably 0.004% or more because it significantly affects TiN precipitate size, precipitate spacing, precipitate distribution, complex precipitation frequency with oxide, and high temperature stability of the precipitate itself. However, if the nitrogen content exceeds 0.008%, the effect is saturated and the toughness may be reduced due to the increase in the amount of solid solution nitrogen present in the weld metal.

The content of phosphorus (P) should be 0.030% or less. Since phosphorus is an impurity element that promotes high temperature cracking during welding, it is desirable to manage it as low as possible. In order to improve toughness and reduce cracking, it is desirable to control the amount to 0.03% or less.

The content of aluminum (Al) is 0.005 to 0.05%. Al is a necessary element because it reduces the amount of oxygen in the weld metal as a deoxidizer. In addition, in order to form fine AlN precipitates by combining with solid solution nitrogen, it is preferable to make Al content 0.005% or more. However, if it exceeds 0.05%, coarse Al 2 O 3 keys are formed, which hinders the formation of TiO oxide necessary for toughness improvement.

The content of sulfur (S) is preferably at most 0.030%. S is an element necessary for MnS formation. In order to precipitate the composite precipitate of MnS, it is preferable to make it 0.03% or less. If there is more than that, it is not preferable because a low melting point compound such as FeS can be formed to cause high temperature cracking.

The content of oxygen (O) is made 0.03% or less. O is an element that reacts with Ti and Mg to form (Ti-Mg) O oxide during the solidification of the weld metal, and this (Ti-Mg) O oxide promotes transformation of acicular ferrite in the weld metal. When the O content exceeds 0.03%, coarse Ti oxides and other oxides such as FeO are formed, which is not preferable because it affects the weld metal part.

The present invention satisfies 1.3 ≦ Ti / O ≦ 3.0. If the ratio of Ti / O is less than 1.3, the number of TiO oxides required for the inhibition of austenite grain growth and needle ferrite transformation in the weld metal is insufficient, and the Ti content in the TiO oxide is reduced so that it functions as a needle ferrite nucleation site. Therefore, the acicular ferrite phase fraction effective for improving the toughness of the weld heat affected zone is lowered. When the ratio of Ti / O exceeds 3.0, the austenite grain growth inhibitory effect in the weld metal is saturated, and the proportion of Mn and the like contained in the oxide is rather small, thus losing the function of the needle-like ferrite nucleation site.

The present invention satisfies 8 ≦ O / Mg ≦ 20. If the O / Mg ratio is less than 8, coarse (Ti-Mg) O oxides are formed in the weld metal, resulting in a small number of oxides, loss of function as acicular ferrite nucleation sites, and adversely affecting the impact toughness of the weld metal. It is not desirable because it is crazy. When the ratio of O / Mg exceeds 20, the number of MgO oxides is insufficient, and the number of (Ti-Mg) O oxides and (Ti-Mg) O- (Ti, B) N composite precipitates is significantly reduced, thus acicular ferrite and polygonal blades. It is not desirable because it does not contribute to ferrite transformation.

The present invention satisfies 7≤Ti / N≤12. If the ratio of Ti / N is less than 7, the amount of TiN oxides in which TiO oxides are formed decreases, which is undesirable because it adversely affects the needle ferrite transformation, which is effective for toughness improvement. It is not preferable because this increases and the impact toughness is lowered.

The present invention satisfies 0.8 ≦ N / B ≦ 1.5. If the ratio of N / B is less than 0.8, the amount of solid solution B, which diffuses into the austenite grain boundary during welding and suppresses grain boundary ferrite transformation, is insufficient.If the ratio of N / B exceeds 1.5, the effect is saturated. This is because the amount of solid solution nitrogen decreases the toughness of the weld heat affected zone.

The present invention satisfies 11 ≦ (Ti + 4B) / N ≦ 16. In the present invention, when the ratio of (Ti + 4B) / N is less than 11, the amount of solid solution nitrogen is not effective to improve the toughness of the weld metal part, and when it exceeds 16, it is not preferable because the number of TiN and BN precipitates is insufficient.

In the present invention, one or more selected from the group of Nb, V, Cu, Mo, Cr, W, and Zr is further added to the steel formed as described above.

The content of copper (Cu) is limited to 0.1 to 2.0%. Cu is an element that is effective to secure strength and toughness due to solid solution at the base. To this end, the Cu content should be contained at least 0.1%, but if it exceeds 2.0%, it is not preferable because it increases the hardenability in the weld metal part to lower toughness and promotes high temperature cracking in the weld metal.

In addition, in the case of complex addition of Cu and Ni, the sum thereof is preferably made 3.5% or less. The reason is that when it exceeds 3.5%, the hardenability increases, which adversely affects the toughness and weldability.

The content of niobium (Nb) is limited to 0.0001-0.1%. Nb is an essential element for improving the hardenability, and in particular, it is necessary to obtain bainite structure because it has an effect of lowering the Ar 3 temperature and widening the bainite formation range even in a low cooling rate range.

In order to expect the effect of improving strength, 0.0001% or more is required. However, if the content exceeds 0.1%, it is not preferable because it promotes the formation of phase martensite in the weld metal part during welding, which adversely affects the toughness of the weld metal part.

The content of vanadium (V) is limited to 0.005-0.1%. V is an element that promotes ferrite transformation by forming VN precipitates, but it requires 0.005% or more, but when it exceeds 0.1%, V forms a hardened phase such as carbide in the weld metal to adversely affect the toughness of the weld metal. Because it is not desirable.

Chromium (Cr) is limited to 0.05 to 1.0%. Cr increases the hardenability and also improves the strength. If the content is less than 0.05%, the strength cannot be obtained and if the content exceeds 1.0%, the toughness of the weld metal portion is degraded.

The content of tungsten (W) is limited to 0.05-0.5%. W is an effective element for improving high temperature strength and strengthening precipitation. However, less than 0.05% is not preferable because the strength increase effect is weak, and at 0.5% or more, it is not preferable because it adversely affects the weld metal part toughness.

The content of zirconium (Zr) is limited to 0.005-0.5%. Since Zr is effective in increasing the strength, it is preferable to add 0.005% or more, and when it exceeds 0.5%, it is not preferable because it adversely affects the toughness of the weld metal part.

In the present invention, one or two of Ca or REM may be further added to suppress grain growth of the old austenite.

Ca and REM are preferred elements because they stabilize the arc during welding and form oxides in the weld metal portion. In addition, it suppresses austenite grain growth during cooling and promotes ferrite transformation in the mouth, thereby improving the toughness of the weld metal part. To this end, it is preferable to add more than 0.0005% of calcium (Ca) and more than 0.005% of REM. However, when Ca is 0.05% and REM is more than 0.05%, a large oxide may be formed to adversely affect toughness. As REM, 1 type, or 2 or more types, such as Ce, La, Y, and Hf, may be used, and any of the above effects can be obtained.

Hereinafter, the microstructure of the weld metal part of the present invention will be described in detail.

In the present invention, the microstructure of the weld metal formed after the high heat input welding is preferably 90% or more of acicular ferrite and polygonal ferrite. This is because the needle-like ferrite structure can obtain high strength and high toughness at the same time, and polygonal ferrite is a microstructure that can obtain high toughness. In the case of mixed ferrite and bainite structure, the impact toughness is good, but the weld metal part has a low strength. In the case where the microstructure is the martesite and bainite mixed structure, the weld metal part has a high strength but the mechanical properties such as toughness of the weld metal part. This is undesirable because it is lowered and the low temperature crack susceptibility is increased.

In the present invention, the remaining tissues are composed of one or two or more of saltpeter ferrite, grain boundary ferrite, pearlite and bainite.

Hereinafter, an oxide and a composite precipitate present in the weld metal part of the present invention will be described in detail.

The oxide present in the weld metal part of the present invention has a great influence on the microstructure transformation of the weld metal part after welding. That is, the type, size, and number of oxides to be distributed are greatly affected. Particularly, in the case of high heat input welding metal parts, the cooling rate of the welding metal parts is slowed, so that the grains are coarsened. Lowers. In order to prevent this, it is important to uniformly disperse the (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composite precipitate in the weld metal at intervals of 0.5 μm or less.

In addition, the particle diameter of the (Ti-Mg) O oxide and the (Ti-Mg) O- (Ti, B) N composite precipitate is limited to 0.01 to 0.1 µm, and the critical number thereof is limited to 1.0 × 10 7 / cc or more. It is preferable. The reason is that when the particle size is less than 0.01 μm, it does not play a role of promoting the transformation of acicular ferrite in the high heat input welding metal part, and when the particle size is larger than 0.1 μm, there is little pinning effect on the austenite grain. This is because it behaves like a coarse non-metallic inclusion and adversely affects the mechanical properties of the high heat input welded metal part.

In this invention, it can manufacture also by other high heat input welding processes other than high heat input SAW. At this time, if the cooling rate of the high heat input metal part is high, the high heat input welding process having a high cooling rate is preferable because the oxide is finely dispersed and the structure is fine. For the same reason, steel cooling and Cu-baking methods are also advantageous in order to improve the cooling rate of the weld. However, even if the known techniques are applied to the present invention, it is natural that the present invention is merely a change of the present invention and is substantially within the scope of the technical idea of the present invention.

Hereinafter will be described in detail through an embodiment of the present invention.

(Example)

A weld metal part having a composition as shown in Table 1 was manufactured by SAW by applying a large input heat input heat input amount of 100 KJ / cm or more, and the composition ratio between the alloy elements of the weld metal part for showing the effect of the present invention is shown in Table 2.

The test pieces for evaluating the mechanical properties of the welded metal parts as described above were taken from the center part of the welded metal part, and the tensile test piece was used as the KS standard (KS B 0801) No. 4 test piece, and the tensile test was cross head speed. Test at 10 mm / min. Impact test pieces were prepared in accordance with KS standard (KS B 0809) No. 3 test piece.

The size, number and spacing of oxides and composite oxides, which have a significant effect on the toughness of the weld metal, were measured by the point counting method using an image analyzer and an electron microscope. At this time, the test piece was evaluated based on 100 mm 2.

The impact toughness of the high heat input weld metal was evaluated by the Charpy impact test at -20 ° C after machining into impact specimens.

division C Si Mn P S Ni Mo Ti B (ppm) Mg (ppm) N (ppm) Cu Al Cr Nb V Ca REM O (ppm) Inventive Steel 1 0.06 0.19 1.54 0.010 0.005 1.54 0.14 0.057 56 10 52 - 0.01 - - - - - 200 Inventive Steel 2 0.07 0.32 1.50 0.012 0.005 1.44 0.15 0.046 45 15 54 - 0.05 - - - - - 240 Invention Steel 3 0.08 0.25 1.48 0.011 0.004 1.65 0.15 0.063 52 17 53 0.5 0.04 - - - - - 280 Inventive Steel 4 0.08 0.22 1.48 0.008 0.005 1.54 0.12 0.040 50 25 50 - 0.03 - - - - - 280 Inventive Steel 5 0.07 0.16 1.60 0.011 0.004 1.50 0.10 0.045 45 30 50 - 0.01 - - - - - 250 Inventive Steel 6 0.07 0.14 1.50 0.009 0.005 1.65 0.12 0.050 42 20 54 - 0.02 - 0.1 - - - 280 Inventive Steel 7 0.10 0.25 1.48 0.011 0.005 1.45 0.15 0.048 45 14 55 0.4 0.02 - - - - - 260 Inventive Steel 8 0.11 0.35 1.52 0.012 0.006 1.55 0.18 0.060 46 22 65 - 0.01 - - 0.01 - - 240 Inventive Steel 9 0.09 0.28 1.50 0.010 0.005 1.48 0.20 0.044 40 30 52 - 0.01 0.1 - - 0.001 - 250 Inventive Steel 10 0.07 0.18 1.55 0.009 0.006 1.50 0.25 0.046 43 22 55 - 0.01 - - - - 0.005 260 Comparative Steel 1 0.03 0.06 1.25 0.011 0.006 2.60 0.19 0.01 29 3 92 0.2 0.05 - - - - - 350 Comparative Steel 2 0.05 0.13 1.93 0.011 0.004 1.71 0.20 0.025 69 5 110 0.4 0.01 - - - - - 320 Comparative Steel 3 0.06 0.06 1.25 0.010 0.007 1.61 0.010 0.014 21 7 74 - 0.07 - - - - - 350 Comparative Steel 4 0.04 0.19 2.0 0.008 0.004 1.75 0.15 0.02 105 60 56 0.2 - - - - - - 300 Comparative Steel 5 0.06 0.28 1.56 0.013 0.008 1.46 0.14 0.058 58 2 71 0.12 - - - - - - 170 Comparative Steel 6 0.06 0.26 1.53 0.012 0.007 1.50 0.16 0.057 52 3 140 0.3 0.12 - - - - - 240 Comparative Steel 7 0.05 0.22 1.58 0.015 0.008 1.51 0.12 0.04 41 One 270 0.3 0.1 - - - - - 260 Comparative Steel 8 0.07 0.14 1.56 0.011 0.006 1.52 0.11 0.024 42 One 180 0.32 0.3 - - 0.013 - - 200 Comparative Steel 9 0.06 0.37 1.74 0.015 0.010 1.44 0.17 0.081 11 One 100 0.3 0.2 - - - - - 140 Comparative Steel 10 0.05 0.26 1.66 0.009 0.004 0.05 0.15 0.042 45 4 130 - 0.06 - - - - - 250 Comparative Steel 11 0.06 0.23 1.72 0.008 0.004 1.30 0.14 0.03 52 3 230 0.5 0.1 - - - - - 290

division Ti / O O / Mg Ti / N N / B (Ti + 4B) / N Inventive Steel 1 2.9 20 11.0 0.9 15.3 Inventive Steel 2 1.9 16 8.5 1.2 11.9 Invention Steel 3 2.3 16.5 11.9 1.0 15.8 Inventive Steel 4 1.4 11.2 8.0 1.0 12.0 Inventive Steel 5 1.8 8.3 9.0 1.1 12.6 Inventive Steel 6 1.8 14 9.3 1.1 12.4 Inventive Steel 7 1.8 18.6 8.7 1.3 12.0 Inventive Steel 8 2.5 10.9 9.2 1.4 12.1 Inventive Steel 9 1.8 8.3 8.5 1.4 11.5 Inventive Steel 10 1.8 11.8 8.4 1.3 11.5 Comparative Steel 1 0.3 116.7 1.1 3.2 2.3 Comparative Steel 2 0.8 64 2.3 1.6 4.8 Comparative Steel 3 0.4 50 1.9 3.5 3.0 Comparative Steel 4 0.7 5 3.6 0.5 11.1 Comparative Steel 5 3.4 85 8.2 1.2 11.4 Comparative Steel 6 2.4 80 4.1 2.7 5.6 Comparative Steel 7 1.5 260 1.5 6.6 2.1 Comparative Steel 8 1.2 200 1.3 4.3 2.3 Comparative Steel 9 5.8 140 8.1 9.1 8.5 Comparative Steel 10 1.6 62.5 3.2 2.9 4.6 Comparative Steel 11 1.0 6.7 1.3 4.4 2.2

division Welding process and heat input (Ti-Mg) O and (Ti-B) N Needle Ferrite and Polygonal Ferrite Fraction Mechanical Properties of Welded Metal Parts Welding process Welding heat input (KJ / cm) Number of pieces Average size (㎛) Tensile Strength (MPa) Low Temperature Impact Toughness vE -20 ℃ (J) Inventive Steel 1 SAW 120 3.4 × 10 8 0.016 92 640 197 Inventive Steel 2 SAW 150 4.6 × 10 8 0.017 93 650 223 Invention Steel 3 SAW 120 3.7 × 10 8 0.012 95 680 210 Inventive Steel 4 SAW 100 4.6 × 10 8 0.016 94 660 235 Inventive Steel 5 SAW 180 6.4 × 10 8 0.018 93 650 220 Inventive Steel 6 SAW 190 5.2 × 10 8 0.025 92 630 220 Inventive Steel 7 SAW 220 3.6 × 10 8 0.013 94 640 198 Inventive Steel 8 SAW 130 4.3 × 10 8 0.026 93 660 188 Inventive Steel 9 SAW 130 5.6 × 10 8 0.024 95 665 241 Inventive Steel 10 SAW 110 5.3 × 10 8 0.014 96 620 209 Comparative Steel 1 SAW 120 3.0 × 10 6 0.045 56 650 44.7 Comparative Steel 2 SAW 120 4.3 × 10 6 0.051 55 640 64.4 Comparative Steel 3 SAW 120 2.5 × 10 6 0.054 64 650 58.8 Comparative Steel 4 SAW 120 3.0 × 10 6 0.064 55 660 46.2 Comparative Steel 5 SAW 120 2.5 × 10 5 0.037 47 650 57.04 Comparative Steel 6 SAW 130 2.5 × 10 6 0.056 52 680 47.0 Comparative Steel 7 SAW 130 3.0 × 10 6 0.043 49 665 56.4 Comparative Steel 8 SAW 230 4.1 × 10 5 0.046 53 610 46.9 Comparative Steel 9 SAW 130 2.8 × 10 5 0.041 69 610 58.2 Comparative Steel 10 SAW 230 3.4 × 10 5 0.046 55 620 56.7 Comparative Steel 11 SAW 130 2.6 × 10 5 0.043 61 625 57.6

As shown in Table 3, the number of (Ti-Mg) O and (Ti-Mg) O- (Ti, B) N composite precipitates prepared by the present invention was 3 × 10 8 / ㎣ or more. in contrast with the range, the comparative steels 4.3 × 10 6 pieces / in ㎣ showing a range equal to or less than comparison invention river over a fairly uniform, yet while gateu the fine complex precipitates size can be seen that the number thereof also increases significantly.

On the other hand, the microstructure of the steel of the present invention is composed of a high fraction of both the needle-like ferrite and polygonal ferrite fraction of more than 90% shows excellent toughness of the weld metal compared to the comparative steel.

Claims (9)

By weight%, C: 0.03-0.2%, Si: 0.1-0.5%, Mn: 0.5-3.0%, Ni: 0.5-3.0%, Mo: 0.05-1.0%, Ti: 0.03-0.1%, Mg: 0.0005- 0.005%, B: 0.0003 to 0.01%, Al: 0.005 to 0.05%, N: 0.004 to 0.008%, P: 0.03% or less, S: 0.03% or less, O: 0.03% or less, and the rest is composed of Fe and unavoidable impurities Low temperature shock to satisfy 1.3≤Ti / O≤3.0, 8≤O / Mg≤20, 7≤Ti / N≤12, 0.8≤N / B≤1.5, 11≤ (Ti + 4B) / N≤16 High heat input arc welding metal part with excellent toughness. The composition according to claim 1, wherein Nb: 0.0001 to 0.1%, V: 0.005 to 0.1%, Cu: 0.1 to 2.0%, Cr: 0.05 to 1.0%, W: 0.05 to 0.5% and Zr: 0.005 to 0.5% High-temperature heat arc welding metal parts excellent in low-temperature impact toughness, characterized in that the addition of one or two or more selected from the group consisting of. 3. The high heat input arc welding metal part having excellent low temperature impact toughness according to claim 1 or 2, wherein at least one of Ca: 0.0005 to 0.05% and REM: 0.005 to 0.05% is further added to the composition. . 3. The high heat input arc welding metal part having excellent low-temperature impact toughness according to claim 1 or 2, wherein the microstructure of the weld metal part is 90% or more of acicular ferrite and polygonal ferrite. [4] The high temperature thermal arc welding metal part having excellent low temperature impact toughness according to claim 3, wherein the microstructure of the weld metal part is 90% or more of acicular ferrite and polygonal ferrite. According to claim 1 or 2, wherein the weld metal portion (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composite precipitate having a particle diameter of 0.01 ~ 0.1㎛ 1.0 per 1㎣ A high heat input arc welding metal part having excellent low temperature impact toughness, characterized in that more than 7 × 10 pieces are distributed. 4. The weld metal part has 1.0 to 10 7 composite particles of (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composite precipitates having a particle diameter of 0.01 to 0.1 µm. The heat input arc welding metal part excellent in low-temperature impact toughness characterized by the above-mentioned distribution. The low temperature impact toughness according to claim 6, wherein the (Ti-Mg) O oxide and the (Ti-Mg) O- (Ti, B) N composite precipitate are uniformly distributed at intervals of 0.5 µm or less. Excellent heat input arc welding metal part. The low temperature impact toughness according to claim 7, wherein the (Ti-Mg) O oxide and (Ti-Mg) O- (Ti, B) N composite precipitate are uniformly distributed at intervals of 0.5 µm or less. Excellent heat input arc welding metal part.
KR1020080109126A 2008-11-04 2008-11-04 High heat input arc weld metal joint having excellent low temperature impact toughness KR20100050039A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1020080109126A KR20100050039A (en) 2008-11-04 2008-11-04 High heat input arc weld metal joint having excellent low temperature impact toughness

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020080109126A KR20100050039A (en) 2008-11-04 2008-11-04 High heat input arc weld metal joint having excellent low temperature impact toughness

Publications (1)

Publication Number Publication Date
KR20100050039A true KR20100050039A (en) 2010-05-13

Family

ID=42276248

Family Applications (1)

Application Number Title Priority Date Filing Date
KR1020080109126A KR20100050039A (en) 2008-11-04 2008-11-04 High heat input arc weld metal joint having excellent low temperature impact toughness

Country Status (1)

Country Link
KR (1) KR20100050039A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111850380A (en) * 2020-07-29 2020-10-30 南平市建阳区湛卢精密制造有限公司 Low-temperature carbon steel valve casting material and manufacturing process thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111850380A (en) * 2020-07-29 2020-10-30 南平市建阳区湛卢精密制造有限公司 Low-temperature carbon steel valve casting material and manufacturing process thereof
CN111850380B (en) * 2020-07-29 2021-08-10 南平市建阳区湛卢精密制造有限公司 Low-temperature carbon steel valve casting material and manufacturing process thereof

Similar Documents

Publication Publication Date Title
KR100910493B1 (en) Flux Cored Arc Weld Metal Joint Having Superior CTOD in Low Temperature
KR101271866B1 (en) High strength flux cored arc weld metal joint having excellent ultra-low temperature impact toughness
JP6576348B2 (en) Super high strength gas metal arc welded joint with excellent impact toughness
KR100833048B1 (en) Welding joint having excellent in toughness of high heat input welded zone
KR101143132B1 (en) Flux cored arc welded joint
KR20140084654A (en) Ultra high strength flux cored arc welded joint having excellent impact toughness
KR20130127189A (en) High strength and weather resistance flux cored arc weld metal joint having excellent ultra-low temperature impact toughness
KR100957940B1 (en) High strength Steel Plate for High Heat Input Welding having Welded Joint with Superior Impact Toughness in Weld Heat Affected Zone
KR20120074152A (en) Flux cored arc weld wire having excellent workability and low-temperature toughness in weld metal joint and weld metal joint using the same
KR101665696B1 (en) High strength flux cored arc weld metal joint having excellent impact toughness
KR100957982B1 (en) Steel for Welding Structure having Welded Joint with Superior CTOD Properties in Weld Heat Affected Zone
KR101180222B1 (en) High strength submerged arc welded metal having excellent low temperature toughness
KR100833047B1 (en) High strength welding joint having excellent in toughness of high heat input welded zone
KR101695982B1 (en) High strength submerged arc weld metal joint having excellent low-temperature impact toughness
KR101439698B1 (en) High strength gas metal arc weld metal joint having excellent ultra-low temperature impact toughness
KR20100050039A (en) High heat input arc weld metal joint having excellent low temperature impact toughness
KR101647148B1 (en) Flux cored arc weld wire for high tensile steel and weld metal joint using the same
KR101207722B1 (en) High strength steel plate for welding structure with superior haz toughness for high heat input welding and method for manufacturing the same
KR101568516B1 (en) Ultra-high strength gas-metal arc welded joint having excellent impact toughness
KR20120074705A (en) High strength steel plate for welding structure with superior haz toughness for high heat input welding and method for manufacturing the same
KR101568537B1 (en) Ultra-high strength submerged arc welded joint having excellent impact toughness
KR20160078771A (en) High strength heat input flux cored arc welded metal joint having excellent impact toughness
KR20120014413A (en) High strength steel plate for welding structure with superior haz toughness for high heat input welding and method for manufacturing the same
KR20140135141A (en) Ultra high strength flux cored arc welded joint having excellent impact toughness
KR20140084934A (en) Weld meterials and ultra high strehgth weld metal joint having excellent low temperature using the same

Legal Events

Date Code Title Description
A201 Request for examination
E902 Notification of reason for refusal
E601 Decision to refuse application