KR101853796B1 - Basic flux cored wire having good toughness at low temperature - Google Patents

Abstract

A base-based high-strength flux-filled wire is provided that exhibits excellent low temperature impact toughness and crack resistance.
The wire according to the present invention is a flux-filled wire filled with a flux in a shell metal, wherein 0.05 to 0.15% of C, 0.05 to 0.30% of Si, 0.5 to 3.0% of Mn, 0.5 to 3.0% of Mn, , Al: 1.5 to 4.0%, Ni: 2.0 to 4.0%, Cr: 0.05 to 0.3%, Mo: 0.1 to 0.4%, Zr: 0.01 to 0.2%, Nb: 0.01% 0.05 to 0.2% of at least one selected from the group consisting of Na, K, Li and Ca, 1.0 to 3.0% of F, 0.5 to 2% of CeO 2, Residual Fe and inevitable impurities, and the composition ratio of ((Mg + Al) / 2 + CeO) / 10 is 0.16 to 0.25.

Description

[0001] The present invention relates to a basic flux cored wire having good toughness at low temperature,

TECHNICAL FIELD The present invention relates to a base-based high-strength flux-filled wire, and more particularly, to a base-based flux-filled wire capable of welding at all positions and exhibiting low-temperature impact toughness and cracking performance.

The general tendency of steel structures in recent years is to increase the use of superfluous steel sheets due to superfine size and to reduce the thickness of steel sheets due to the use of high strength steels. For the first time, the strength of steel used for steel structure was about 200 mega pascals (Mpa). However, the highest grade of high strength products now has more than four times the strength of more than 800Mpa.

Welding is the most suitable method to produce such high-strength afterglow steels efficiently and efficiently. Flux cored arc welding technology is the most widely used welding technique for welding these steels. However, the most important required characteristics of the welded structure obtained by such welding is that it is required to minimize the heavy load of the structure and to be stable to withstand it, and it is important that the strength suitable for the steel and the impact toughness and cracking property of the welded joint are important .

In general, titania-based flux-charging wires are the most commonly used high-strength flux-filling wires, and the titania flux-charging wires are excellent in welding workability, but the amount of oxygen (O 2) ), It is very difficult to obtain excellent impact toughness at high strength.

In addition, the amount of diffusible hydrogen generated at low temperature cracks is 5 ~ 10ml / 100g, which is very vulnerable to low temperature cracking.

Accordingly, there is a demand for a welding material that satisfies the strength of the welded joint sufficiently and at the same time, excellent low temperature impact toughness and cracking property.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a basic-type flux-charging wire for gas-shielded arc welding which can secure high-temperature impact toughness and cracking resistance at high strength.

Further, the technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems which are not mentioned can be understood from the following description in order to clearly understand those skilled in the art to which the present invention belongs .

According to an aspect of the present invention,

A flux-charging wire filled with a flux in a shell metal,

0.05 to 0.15% of Si, 0.05 to 0.30% of Si, 0.5 to 3.0% of Mn, 1.5 to 4.0% of Mg + Al, 2.0 to 4.0% of Ni, And at least one selected from the group consisting of alkali metal Na, K, Li and Ca, 0.3 to 0.3% Mo, 0.1 to 0.4% Zr 0.01 to 0.2% Nb 0.01% (Mg + Al) / 2 + CeO (0), wherein the sum of the sum of Fe and Al in the total amount of the alkaline earth metal fluoride compounds is 1.0 to 3.0%, CaO is 0.5 to 2%, residual Fe and unavoidable impurities. ) / 10 is in the range of 0.16 to 0.25. The present invention relates to a basic-system flux-charging wire for gas-shielded arc welding.

According to the present invention having the above-described constitution, the kind of the fluorine compound (CaF2, MgF2, BaF2) and the amount of the fluorine compound (CaF2, MgF2, BaF2) can be controlled to ensure good slag peeling, bead securing and all-position welding. In addition, by controlling the amount and ratio of Mg + Al, oxygen reduction and impact toughness, which can adversely affect the welded joint, can be improved, and a basic flux-filling wire capable of securing a weak microcracking property at high strength by adding CeO 2 There is a useful effect in providing.

Hereinafter, the present invention will be described.

The basic flux-charging wire of the present invention preferably contains 0.05 to 0.15% of C, 0.05 to 0.30% of Si, 0.5 to 3.0% of Mn, 1.5 to 4.0% of Mg + , 2.0 to 4.0% of Cr, 0.05 to 0.3% of Cr, 0.1 to 0.4% of Mo, 0.01 to 0.2% of Zr, 0.01% or less of Nb and 0.03% or less of V, 0.05 to 0.2% of the total of one or more selected from the group of the arc stabilizer, 1.0 to 3.0% of F, and 0.5 to 2% of CeO 2, residual Fe and unavoidable impurities in the alkali and alkaline earth metal fluorine compounds. And the composition ratio of ((Mg + Al) / 2 + CeO) / 10 is 0.10 to 0.25.

Hereinafter, the compositional components of the flux-charging wire and the reason for limiting the content thereof will be described.

C: 0.05 to 0.15%

In the present invention, carbon is an austenite stabilizing element capable of securing the strength of the weld metal and ensuring cryogenic impact toughness of the weld metal. When the carbon content is low, all the austenite is not stabilized and therefore it is necessary to maintain a proper amount of carbon. And the lower limit was made 0.05% by weight.

On the other hand, when the carbon content exceeds 0.15% by weight, the weldability is significantly lowered and the carbon equivalent is increased, so that there is a problem that low-temperature cracks are likely to occur in the welded joint at the time of welding.

In view of this, in the present invention, it is preferable that the content of carbon (C) is limited to 0.05 to 0.15% by weight with respect to the wire (hereinafter, simply referred to as%).

Si: 0.05 to 0.3%

If the content of silicon is less than 0.05% in the present invention, the deoxidizing effect in the weld metal portion is insufficient and the flowability of the weld metal portion is deteriorated. When the content exceeds 0.3%, the transformation of the MA contituent in the weld metal is promoted The strength is increased sharply and it is undesirable because it affects the weld crack susceptibility.

Therefore, in the present invention, the content of silicon (Si) is preferably 0.05 to 0.3%.

Mn: 0.5 to 3.0%

In the present invention, Mn is an essential element which plays a role of improving the role and strength of a relatively weak deoxidizer. S reacts with S to form MnS first than FeS. Therefore, it is effective to prevent the formation of low melting point compound due to segregation of S and prevent cracking at high temperature.

In the present invention, it is preferable to limit Mn to 0.5 to 3.0%. If the content is less than 0.5%, it is difficult to secure the strength of the weld metal and the coarsening of the weld metal is accelerated due to insufficient penetration, . If it exceeds 3.0%, a low-temperature transformed structure is generated and the cracking property is lowered, which is not preferable.

Ni: 2.0 to 4.0%

In the present invention, Ni is an essential element for enhancing the strength and toughness of a matrix by solid solution strengthening. In order to obtain such an effect, it is preferable that the Ni content is 2.0% or more. If it exceeds 4.0%, the Ni content is greatly increased and the high temperature crack is likely to occur.

Therefore, in the present invention, the content of nickel (Ni) is preferably limited to 2.0 to 4.0%.

Mo: 0.3 to 1.0%

Mo is required to be added in an amount of 0.3% or more as an element for improving the strength of the base. However, when the content exceeds 1.0%, not only the strength improving effect is saturated but also welding hardenability is greatly increased. Therefore, martensitic transformation is promoted to cause generation of low-temperature weld cracking and toughness, which is undesirable.

In consideration of this, in the present invention, the content of molybdenum (Mo) is preferably 0.3 to 1.0%.

Cr: 0.05 to 0.3%

In the present invention, chromium (Cr) is an element effective for increasing the incombustibility and improving the strength. When the content is less than 0.05%, the above-mentioned effect can not be obtained. On the other hand, if the content exceeds 0.3%, there is a problem that the weld causes deterioration of the toughness of the welded part, which is not preferable.

In consideration of this, in the present invention, the content of chromium (Cr) is preferably limited to 0.05 to 0.3%.

A total of one or more selected from the group consisting of alkali metal Na, K, Li and Ca; 0.05 to 0.2%

Alkali metals Na, Li, K, and Ca classified as arc stabilizers are arc stabilized during welding, resulting in good workability. Therefore, in the present invention, it is preferable to limit the sum of one or more selected from the group of alkali stabilizers Na, Li, K and Ca to 0.05 to 0.2%. If the content is less than 0.05% , And when it is more than 0.2%, arc concentration increases with arc instability and fume generation is increased.

Mg + Al: 1.5 to 4.0%

In the present invention, Mg + Al reacts with oxygen in the molten metal as a strong deoxidizing agent to suppress the generation of nonmetallic inclusions, thereby improving the cleanliness of the weld metal. However, when the content is less than 1.5%, the effect due to the inclusion can not be expected. When the content is more than 4.0%, the amount of spatters generated increases and the slag foaming property deteriorates. Therefore, in the present invention, the content is preferably limited to 1.5 to 4.0% Do.

Alkaline and alkaline earth metal fluorine compounds F: 1.0 to 3.0%

The fluorine compound generates fluorine in the arc in a high-temperature arc and reacts with hydrogen during welding to cause a dehydrogenation reaction, thereby effectively reducing the diffusible hydrogen in the weld zone.

Further, in the present invention, it is preferable that the content of F in the fluorine compound is 1.0% or more for this effect by using the fluorine compound as the slag forming agent. However, if the content exceeds 3.0%, welding fumes may excessively occur due to high vapor pressure, and the slag viscosity may be excessively decreased to form unstable beads, which is not preferable.

In the present invention, it is preferable to use one or more of CaF2, BaF2, and MgF2 as the fluorine compound.

Zr: 0.01 to 0.2%

Zr is effective for increasing the strength and also serves as a deoxidizer, so that it is preferable to add Zr in an amount of 0.01% or more in the present invention. However, if it exceeds 0.2%, welding is undesirable because it tends to lower toughness and arcability of the welded part.

In view of this, it is preferable that the content of zirconium (Zr) is 0.01 to 0.2%.

Nb: not more than 0.01%, V: not more than 0.05%

Nb and V are added as impurities and precipitate at the grain boundaries to increase the strength of the welded portion by increasing the hardness of the weld as well as to increase the hardness and decrease the toughness of the weld metal. Is preferably 0.05% or less.

CeO 2: 0.5 to 2%

CeO 2 converts P and S to CeP or CeS 2 to remove impurities present in the grain boundaries in the weld joint to improve microcracking.

In the present invention, the content of CeO 2 is preferably 0.5 to 2%. If the content is less than 0.5%, it is difficult to improve the above-mentioned microcracking effect. If the content is more than 2%, the arc stability is lowered and the slag is excessively formed, This is because there is a possibility that

Composition ratio of ((Mg + Al) / 2 + CeO) / 10: 0.10 to 0.25

The flux-filled wire of the present invention satisfies all of the above-mentioned compositional compositions and has a composition ratio ratio defined by ((Mg + Al) / 2 + CeO) / 10 in order to satisfy excellent low temperature impact toughness and crack resistance. 0.25. ≪ / RTI > If the composition ratio is less than 0.10, deoxidation in the molten metal is insufficient and it is difficult to ensure stable low-temperature impact toughness. When the composition ratio exceeds 0.25, the amount of slag increases excessively, and deterioration of slagging property and hardening of weld joint There is a possibility that the low temperature impact toughness is lowered and cracks are generated.

The flux-filling wire of the present invention includes Fe and unavoidable impurities, wherein Fe includes Fe in the metal shell and Fe powder in the flux.

The basic flux-filled wire welding material proposed by the present invention is composed of a hoop, which is a mild steel material, as a shell, and a flux filled in the wire, and the weight ratio of the flux to the total weight of the flux-charged arc welding wire is 18 to 23%.

By satisfying the alloy composition described above, it is possible to solve the welding workability problem inherent in the basic-based welding material and to provide a welded joint capable of performing all-position welding and having excellent impact toughness and cracking properties.

The flux-filled wire of the present invention is preferably a basic flux-filled wire, and preferably has a basicity (B) value defined by the following relational expression 1 satisfying 0.5 to 4.5.

[Relation 1]

B = [(CaF 2 or BaF 2) + MgO + Na 2 O + 1/2 MnO] / [SiO 2 + 1/2 (Al 2 O 3 + ZrO 2)

The relational expression 1 is a formula of the basicity of the flux components, and it is preferable that the range of the relational expression satisfies 0.5 to 4.5. If the value of the basicity (B) defined by the relational expression 1 is less than 0.5, it may be titania-based flux, and crack resistance and low-temperature toughness, which are characteristics of the basic flux-cored wire, deteriorate. If the basicity value exceeds 4.5, the workability may be drastically lowered and the slag peeling property may deteriorate.

On the other hand, a welded joint obtained by welding using a high strength basic flux-filled wire satisfying the above alloy composition has a structure composed of 45% or more of acicular ferrite and 45 to 55% of low temperature phase (bainite and martensite) And exhibits excellent low temperature impact toughness with a tensile strength of 830 MPa or more and impact toughness at 40 DEG C of 80 J or more. In addition, the amount of diffusible hydrogen generated is 5 ml / 100 g or less, and thus, the amount of diffusible hydrogen generated is excellent.

Hereinafter, the present invention will be described in detail by way of examples.

(Example)

Each of the flux-filling welding wires having the composition shown in Table 1 was prepared. Then, flux welding was carried out using the welding wire under the conditions of a welding current of 40 to 260 A, a current of 25 to 26 V, a welding speed of 25 to 28 cm / min, and a welding heat input of 14 to 16 kJ / cm.

The composition of the welded joints after welding is shown in Table 2 below, and the results of evaluating the mechanical properties, cracking properties and slag solidification of the weld joints are shown in Table 3 below.

At this time, low carbon (C) tensile strength of 830 MPa or more was used as a base material for welding, and HSA 800 steel was used. Test specimens for evaluating the mechanical properties of the welded metal part as described above were taken from the central part of the welded metal part, and tensile test specimens were used for the KS standard (KS B 0801) No. 4 specimen. The tensile test was carried out at a cross head speed of 10 mm / min, and the impact test specimen was prepared in accordance with KS (KS B 0809) No. 3 test specimen.

Y-Groove specimens were prepared according to JIS Z3158, and the specimens were pre-heated (50 ℃), welding conditions (240A / 27V), welding speed (50cm / min) and heat input (7kJ / cm) The cracks (low-temperature cracks) appearing after 72 hours of welding using a welding machine were cut into five equal parts and visually measured.

On the other hand, due to the characteristics of the wire material for basic-type flux-filled arc welding, all position welding is inferior to the titania-based flux-charging wire, so the presence or absence of the welding workability of the electronic three- Vertical up welding was possible.

division
No.
Wire composition component (% by weight)

A * C Si Mn Mg + Al Ni Cr Mo Zr F Na CeO Comparative Example
1-1 0.08 0.10 1.1 2.0 3.2 0.19 0.18 0.08 2.1 0.12 0.20 0.12 2-1 0.07 0.11 1.3 2.1 3.3 0.21 0.19 0.08 2.2 0.10 0.40 0.15 foot
persons
Yes 3 0.10 0.12 1.2 2.2 3.3 0.20 0.19 0.07 2.1 0.11 0.50 0.16 4 0.08 0.09 1.2 2.5 3.4 0.22 0.20 0.09 1.9 0.10 0.55 0.18 5 0.07 0.10 1.3 3.0 3.2 0.18 0.18 0.09 2.0 0.11 0.50 0.20 6 0.06 0.11 1.0 3.3 3.1 0.21 0.17 0.07 2.0 0.11 0.60 0.23 7 0.08 0.13 1.4 3.8 3.4 0.20 0.21 0.10 2.1 0.12 0.60 0.25
ratio
School
Yes


One 0.06 0.10 1.2 0.8 3.2 0.21 0.17 0.06 2.0 0.10 - 0.04 2 0.07 0.11 1.3 1.4 3.1 0.20 0.18 0.07 2.1 0.11 - 0.07 3 0.07 0.12 1.4 1.0 3.3 0.22 0.19 0.08 2.0 0.11 0.50 0.10 4 0.09 0.11 1.2 1.5 3.2 0.19 0.20 0.08 2.0 0.12 0.60 0.14 5 0.08 0.13 1.3 4.2 3.2 0.18 0.21 0.06 2.0 0.11 1.00 0.31 6 0.06 0.12 1.2 4.4 3.3 0.21 0.22 0.09 2.1 0.12 0.80 0.30 7 0.05 0.11 1.1 4.6 3.5 0.21 0.18 0.07 2.1 0.11 1.20 0.33

In Table 1, A * denotes ((Mg + Al) / 2 + CeO) / 10

division No. Heat input
(kJ / cm) vE-40 ° C
(J) The tensile strength
(MPa) Elongation
(%) Cracking property Slag
Coagulability Overall assessment Comparative Example
1-1 14.2 78 830 17.8 △ ○ ○ 2-1 14.8 85 832 17.2 ○ ○ ○ foot
persons
Yes

3 14.6 96 855 18.0 ○ ○ ○ 4 15.2 85 842 18.6 ○ ○ ○ 5 15.4 92 852 15.8 ○ ○ ○ 6 15.4 88 860 16.2 ○ ○ ○ 7 15.2 75 885 18.2 ○ △ △ ratio
School
Yes
One 14.0 62 760 22.8 △ ○ X (tensile strength and impact toughness lower, cracking moderate) 2 14.4 69 800 20.8 △ ○ X (tensile strength and impact toughness lower, cracking moderate) 3 15.2 70 765 22.8 ○ ○ X (tensile strength and impact toughness are below) 4 14.8 72 810 20.6 ○ ○ X (tensile strength and impact toughness are below) 5 14.6 66 901 14.6 × △ × (under-cracking, slag-solidifying) 6 15.6 63 922 14.2 △ × X (Impact toughness is below, cracking is normal, slag is below coagulation) 7 15.2 58 940 13.8 × × X (Impact toughness is below, cracking is below, slag is below coagulation)

* In Table 3, " Good " indicates " Fair "

As shown in Tables 1 and 2, in the case of Inventive Example 3-7 (based on an amount of heat of 15 kJ / cm) in which flux-arc welding was carried out using the welding wire according to the present invention, the tensile strength was not less than 830 MPa In addition, it is possible to secure a low-temperature impact toughness at -40 ° C, and it is also stable in terms of cracking.

On the contrary, Comparative Examples 1-7 using the welding wire in which the composition and composition ratio were out of the range of the present invention all suffered from failure to satisfy the tensile strength required level (? 830 MPa) 69J) is difficult, and the solidification and cracking properties of the slag are not good.

Specifically, in the case of Comparative Example 3-4, although the cracking property was stable, the content of Mg + Al was small and the deoxidizing effect in the welding portion was insufficient, so that the tensile strength and impact toughness required in the present invention were not satisfied .

Further, in the case of Comparative Examples 1-2 and 5-7, the composition ratio of ((Mg + Al) / 2 + CeO) / 10) was outside the range of 0.10 to 0.25, and the tensile strength, The cracking property was not satisfied, and in the case of Comparative Example 6-7, the entire posture welding was also impossible.

In the case of Comparative Example 1-2 in which the composition ratio is less than 0.10, the tensile strength and the low-temperature impact toughness do not satisfy the requirements of the present invention, and the CeO 2 content required by the present invention is small, .

In the case of Comparative Example 5-7 in which the composition ratio ratio is more than 0.25, the content of Mg + Al and CeO 2 is larger than the range of the present invention, and the welded joint is hardened due to an excessive increase in tensile strength, And the cracking property was also deteriorated. In addition, the amount of spatter generated and the coagulation of slag decreased, so that it was impossible to weld all positions.

While the present invention has been particularly shown and described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of course, this is possible. Therefore, the scope of the present invention should not be limited to the above-described embodiments but should be defined by the following claims as well as equivalents thereof.

Claims (1)

A flux-charging wire filled with a flux in a shell metal,
0.05 to 0.15% of Si, 0.05 to 0.30% of Si, 0.5 to 3.0% of Mn, 1.5 to 4.0% of Mg + Al, 2.0 to 4.0% of Ni, And at least one selected from the group consisting of alkali metal Na, K, Li and Ca, 0.3 to 0.3% Mo, 0.1 to 0.4% Zr 0.01 to 0.2% Nb 0.01% (Mg + Al) / 2 + CeO (2) containing 0.05 to 0.2% of the total amount of the alkali metal and alkaline earth metal fluorine compounds, 1.0 to 3.0% of F, 0.5 to 2% of CeO 2, and residual Fe and unavoidable impurities. ) / 10 in the composition ratio of 0.16 to 0.25.