JP2000288781A - WIRE INCLUDING FLUX FOR Cu-Ni-Ti BASE HIGH ATMOSPHERIC CORROSION RESISTANT STEEL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire including flux for gas shield are welding which is suitable to the welding of Cu-Ni base seashore atmosphere corrosion resistant steel and can be applied to the whole posture welding and obtains good welding workability and gives, to the welded metal, the corrosion resistance to flying sea salt grain without damaging the corrosion resistance of a base material. SOLUTION: In the wire including the flux used in the case of executing the gas shield arc welding to the Cu-Ni-Ti base high atmosphere corrosion resistant steel material, the wire composition, to the total weight of the wire, is composed, of by wt.%, 3.5-8% TiO2, 0.03-0.15% C, 0.1-1% Si, 0.8-3% Mn, 1-5.5% Ni, 0.3-1% Cu and further, inevitably, <=0.03% P, <=0.01% S and <=0.05% Cr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used for steel structures such as bridges in an environment where salt damage is feared due to a high concentration of incoming sea salt particles, such as a beach area or an area where a snow melting agent is sprayed. Used for welding of Cu-Ni-Ti-based high weathering steel, which has good weldability, excellent weld metal performance, and excellent weather resistance against salt damage caused by flying sea salt particles at the weld joint. TECHNICAL FIELD The present invention relates to a flux cored wire for gas siled arc welding.

[0002]

2. Description of the Related Art Conventional weather-resistant steel has maintained corrosion resistance by forming a stable rust phase on the steel surface. However, when used in a beach area or an area where a snow melting agent is sprayed, a coating treatment or the like is required. It was necessary to perform a plating process.
The reason is that due to the atmosphere containing many incoming sea salt particles,
This was to prevent the salt attached to the surface of the steel material from inhibiting or destroying the formation of a stable rust layer exhibiting excellent corrosion resistance. However, in the case of the coating process, it is necessary to periodically change the paint, and there is a problem that the maintenance cost increases. In the case of plating, there is a problem such as peeling of plating.

[0003] From such a background, in an area where there are many incoming sea salt particles, there is no need for painting or plating.
A so-called naked steel material has been developed. The steel material contains Ni in an amount of 1.0 to 5.5% by weight based on the total weight of the steel material.
C, characterized in that the stable rust layer is prevented from being broken by flying sea salt particles containing Cu and Ti.
u-Ni-Ti steel.

On the other hand, TiO ₂ flux-cored wires are generally used because of their good welding work.
Further, as an example of a flux-cored wire for gas shielded arc welding to which Ni is added by several percent, see, for example,
No. 7695, JP-A-3-294093 and JP-A-5-5-2
No. 69592 discloses a flux-cored wire excellent in toughness.

[0005] However, when these flux-cored wires are used as they are in the Cu-Ni-Ti-based high weathering steel of the present invention, the chemical composition of the steel material and the chemical composition of the weld metal are not properly optimized. Therefore, the weather resistance of the welded joint portion against flying sea salt particles was not sufficient.

[0006]

The conventional flux-cored wire as described above is used as it is for the object of the present invention.
-When used for Ni-Ti high weathering steel, the chemical composition of the steel material and the chemical composition of the weld metal are insufficiently optimized,
The formation of a local battery electrochemically between the base metal and the weld metal easily deteriorates the weather resistance of the weld metal and the joint bond, and the weather resistance of the weld joint to flying sea salt particles is sufficient. Was not.

The present invention has been made to solve the above-mentioned problems, and is used for a steel structure such as a bridge in an environment where salt damage is feared due to a high concentration of incoming sea salt particles. When welding Cu-Ni-Ti high weathering steel, a gas shielded arc having excellent weldability, excellent weld metal performance, and excellent weatherability against salt damage caused by flying sea salt particles at a weld joint. An object of the present invention is to provide a flux cored wire for welding.

[0008]

Means for Solving the Problems The present inventors have proposed Cu-N
Intensive study of the component balance between i-Ti-based high weathering steel and the weld metal and the corrosion generation behavior caused by the contact potential caused by the balance has been carried out.
By optimizing the contents of u and Ti, a method has been found in which the components are balanced in the weld metal and the base metal components to improve the corrosion resistance against flying sea salt particles. Furthermore, the present inventors have proposed Cr which has been effective in improving the weather resistance of conventional weather-resistant steel.
However, it was found that under the environment of high concentration of sea salt particles, the weather resistance was significantly adversely affected, and it was found that it was necessary to regulate the amount of Cr in the wire.

[0009] The present invention is based on the above findings, and the gist thereof is as follows. Cu-Ni
A flux-cored wire used for gas-shielded arc welding of a Ti-based highly weather-resistant steel material, wherein the flux contains TiO ₂ : 3.5 by weight% based on the total weight of the wire.
-8%, C: 0.03-0.15%, Si: 0.1-1 in weight% in total in the shell and flux
%, Mn: 0.8 to 3%, P: 0.03% or less, Ni:
1 to 5.5%, Cu: 0.3 to 1%, S: 0.
A flux-cored wire for gas shielded arc welding, characterized in that the content is restricted to not more than 01% and Cr: not more than 0.05%.

[0010]

Embodiments of the present invention will be described below. First, the reasons for limiting the chemical composition of the flux-cored wire for gas shielded arc welding of the present invention and the operation thereof will be described.

TiO ₂ : 3.5-8.0% TiO ₂ is contained in the flux, is an arc stabilizer, and constitutes a main component of the slag forming agent. During welding, it encapsulates the weld metal and shields it from the atmosphere. In addition, it enables welding in all positions with appropriate viscosity. In addition, TiO ₂
Is partially reduced during the formation of the molten pool to produce Ti,
Further, nitrides and oxides are formed during the solidification process. These nitrides and oxides are finely and uniformly dispersed in the ferrite phase of the weld metal, thereby improving the weather resistance and also serving as a nucleus for forming intragranular ferrite, which has an effect of promoting the toughness of the weld metal. .

As described above, the amount of the slag forming agent containing TiO ₂ as a main component is 3.5% with respect to the total weight of the wire.
If it is less than 5, the bead cannot be formed by vertical welding, and the weather resistance of the welded joint portion is poor. On the other hand, if it exceeds 8%, Ti
The oxide becomes coarse inclusions, and the low-temperature toughness of the weld metal deteriorates. In addition, slag entrainment defects tend to occur during the solidification of the molten metal, which impairs the mechanical properties and weather resistance of the weld metal. Therefore was from 3.5 to 8% the amount of TiO ₂ as a percentage of the total wire weight.

The following components are amounts in total in the shell and flux. C: 0.03 to 0.15% C is added as an alloy component for ensuring the strength and toughness of the weld metal. If it is less than 0.03%, toughness is impaired due to insufficient strength of the weld metal and coarsening of the microstructure. On the other hand, when C is added in excess of 0.15%, the strength of the weld metal increases excessively, and the toughness deteriorates. For the above reasons, the addition amount of C is set to 0.03 to 0.15% in proportion to the total weight of the wire.

Si: 0.1-1% Si has the effect of reducing the amount of oxygen in the weld metal as a deoxidizing agent and improving the toughness, remains in the weld metal, and has the strength of the weld metal as an alloy component. And to ensure toughness. In addition, SiO generated by the deoxidation reaction
₂ is a slag for uniformly covering the whole bead.
However, if the addition amount is less than 0.1% based on the total weight of the wire, the strength of the weld metal is insufficient, and the encapsulation of the weld bead by the slag tends to be insufficient. 1% on the other hand
If added in excess of, the yield in the weld metal becomes excessive, deteriorating low-temperature toughness and causing uneven solidification of the molten slag. For the above reasons, the addition amount of Si is set to 0.1 to 1% based on the total weight of the wire.

Mn: 1-3% Mn also has the effect of reducing the amount of oxygen in the weld metal and improving toughness as a deoxidizing agent, and also remains in the weld metal and as an alloy component, the strength and toughness of the weld metal. Is added to ensure In addition, MnO generated by the deoxidation reaction
Is very effective for eliminating the solidification unevenness of the molten slag and for enclosing the slag thinly and uniformly on the bead surface. In addition, it also has a role as an arc stabilizer. If the addition amount is less than 1% based on the total weight of the wire, deoxidation becomes insufficient and toughness deteriorates. In addition, not only the yield is insufficient, but also sufficient weld metal strength cannot be obtained, but also adversely affects the slag encapsulation. On the other hand, if it exceeds 3%, the yield to the weld metal becomes excessive, the strength becomes excessive, and the toughness of the weld metal deteriorates. For the above reasons, the amount of Mn added is set to 1 to 3% based on the total weight of the wire.

P: not more than 0.03% P is always present as an impurity in the steel of the outer skin, but is an element effective for improving the weather resistance. However,
If the content exceeds 0.03%, hot cracking is likely to occur and the toughness of the weld metal is deteriorated. Therefore, it is necessary to limit the content to 0.03% or less.

Cu: 0.3 to 1% Cu elutes together with Fe in steel, suppresses crystallization and coarsening of rust particles during formation of the rust layer, and maintains high density of the rust layer, so that high concentration fly It is an indispensable element for improving the weather resistance under the environment of sea salt particles. In addition, Cu plating is applied to the surface of the wire for stabilizing the electrical conductivity and the feeding property of the wire, which also adds to the wire component. The effect is effectively exhibited by adding 0.3% or more, and the larger the amount added, the better. However, if it exceeds 1%, high temperature cracking is liable to occur and toughness is liable to deteriorate. To 0.3-1%.

Ni: 1 to 5.5% If Ni is contained in the weld metal surface rust layer in an amount of 0.5% or more, Ni in the weld metal is eluted together with Fe into the rust layer, and is substantially uniform in the rust layer. Will be included. Then, Cl derived from the flying sea salt particles attached to the rust layer surface
It suppresses the penetration of ions into the rust layer / base iron interface and suppresses the increase in Cl concentration inside the rust layer. This suppresses the crystallization and coarsening of the rust particles and brings about the effect of maintaining the denseness of the rust layer. Further, as the Ni content in the weld metal increases, the corrosion resistance of the weld metal is improved in a dry and wet repeated corrosive environment in an aqueous solution containing Cl ions. As described above, in order for Ni to be contained in the rust layer by 0.5% or more, the weld metal must contain Ni by 1% or more. The higher the Ni content, the better the weather resistance. However, if the Ni content exceeds 5.5%, there is a risk that hot cracking may occur during welding, and the cost increases. For the above reasons, the addition amount of Ni is set to 1 to 5.5% in proportion to the total weight of the wire. However, the yield of Ni contained in the flux-cored wire for gas shielded arc welding into the weld metal at the time of welding is almost 100%. Further, it is preferable that the amount of Ni added to the wire be equal to that of the steel material in accordance with the Ni content of the steel material serving as the base material.

S: 0.01% or less S is an inevitable impurity that deteriorates the weather resistance of the welded portion. If it exceeds 0.01%, the weather resistance deteriorates,
In order to deteriorate the toughness of the weld metal, it is necessary to limit it to 0.01% or less.

Cr: 0.05% or less Cr is an element that is sometimes used as an alloy component of weather-resistant steel. However, if contained in a weld metal, it impairs the weather resistance in an environment with many sea salt particles. It is preferable to reduce as much as possible. If the content is 0.05% or less, the inhibition on the weather resistance can be neglected, so the amount is limited to 0.05% or less. Note that the following includes 0%.

As the steel shell, a cold-rolled steel material and a hot-rolled steel material having good deep drawability from the viewpoint of flux filling and workability are used. The filling rate of the flux is not particularly limited, but is most preferably in the range of 10 to 30% with respect to the wire weight in consideration of drawability in production. There is no limitation on the cross-sectional shape of the wire, and a relatively simple cylindrical shape is preferable for a small diameter of 2 mm or less, and a hoop is used for a large diameter wire of about 2.4 to 3.2 mm. In general, those having a structure in which the inside is complicatedly folded are generally used. Further, in a so-called seamless wire having no break in the wire cross section, it is also effective to perform Cu plating treatment. In this case, the amount of Cu in the wire falls within the range of the present invention in terms of the weight of the entire wire including the plated portion. If the same effect is obtained.

[0022]

Next, the present invention will be described more specifically based on examples. Using a steel outer shell, the hollow portion of the outer shell was filled with flux, then drawn and finished to a diameter of 1.2 mm to prepare a flux-cored wire. Table 1 shows the component composition of the wire.

[0023]

[Table 1]

The above-mentioned wire was subjected to a welding workability test, a mechanical test (tensile test, impact test), and a corrosion resistance test. In the welding workability test, gas shielded arc welding was performed under the welding conditions shown in Table 2, and arc stability, spatter generation amount,
And the bead shape were evaluated, and their overall evaluation was performed.

[0025]

[Table 2]

Next, for a mechanical test, a weld metal test was performed under the welding conditions shown in Table 3 using the groove shown in FIG.
Test specimens were prepared. Table 4 shows the chemical components of the test plate. After welding, a tensile test specimen and a Charpy impact test specimen were sampled from the position shown in FIG. 1 and subjected to a room temperature tensile test and a Charpy impact test to evaluate mechanical properties (JIS Z3).
111). The test temperature of the tensile test was room temperature (2
0 ° C.), the test temperature of the Charpy impact test was −5 ° C., and −20 ° C.

[0027]

[Table 3]

[0028]

[Table 4]

Further, in order to evaluate the corrosion resistance of the weld metal in an environment with high concentration of sea salt particles, an exposure test was conducted for 7 years at a seaside area in Futtsu City, Chiba Prefecture. The point of exposure was 5 m away from the shore (average flying sea salt particle amount 1.3 mg / dm ² / d
ay). The weather resistance of the weld metal is two items of the evaluation of the appearance of the rust and the average thickness reduction obtained from the corrosion amount.
However, the average thickness reduction was performed only on one side. The condition of rust stabilization is evaluated by the rust layer's appearance score 1-4,
4 was the best case, indicating the formation of stable rust, and 1 was evaluated by an index indicating that a layered exfoliated rust was observed and stabilization of the rust and prevention of corrosion progress could not be expected.

The welding was performed using the chemical components Cu-Ni-
Using a Ti-based high weather resistance steel sheet, welding was performed on the X groove shown in FIG. Then, the excess metal was ground and the weld bead was set to 20T × 100W × 200L with the longitudinal direction.
(Mm) was used as a corrosion resistance exposure test piece.

[0031]

[Table 5]

Table 6 shows the results of the welding workability test, Table 7 shows the results of the deposited metal test, and Table 8 shows the results of the corrosion resistance evaluation by the exposure test.
Shown in

[0033]

[Table 6]

[0034]

[Table 7]

[0035]

[Table 8]

The comparative example No. 6 is Ti in the wire
Since O ₂ is less than 3.5%, the welding workability, particularly the encapsulation of slag, was poor, and the toughness was largely insufficient. Further, coupled with the fact that the amount of Cr exceeded 0.05%, stable rust was hardly formed and the amount of corrosion increased.

No. 7 shows that TiO ₂ in the wire is 8.0
%, The oxygen content of the weld metal increased, and S exceeded 0.01%, so that the toughness was greatly deteriorated. Further, since the TiO ₂ is over 8.0%, most non-metallic inclusions, corrosion resistance was not enough.

No. In No. 8, the weld bead shape was deteriorated because Mn in the wire was less than 1.0%. Also, M
n Increase in oxygen in the weld metal due to insufficient deoxidation and P
When it exceeds 03%, toughness is deteriorated. Also,
Since Cu is less than 0.3% and the Cr content exceeds 0.05%, the corrosion resistance is poor. In addition, although P exceeded 0.03%, the hot crack of the crater part in the fillet welding was also recognized, but the weld metal test and the exposure test were possible.

No. In No. 9, since the Si in the wire is less than 0.1%, the welding workability is remarkably deteriorated, the deoxidation is insufficient, the toughness of the weld metal is low, and the Cr content in the wire is also 0.05%. %, The corrosion resistance was poor.

No. 10: C in the wire is 0.03%
Therefore, the welding workability was deteriorated due to insufficient deoxidation, and the strength of the weld metal was also insufficient. No. 11
Since Ni in the wire exceeds 5.5%, hot cracking occurs in any of the welding workability, the weld metal test, and the joint welding with the X groove, and the mechanical test and exposure of the weld metal The test was omitted.

No. In No. 12, the amount of Mn in the wire was 3.0.
%, The strength was excessive and the toughness was deteriorated.
No. In No. 13, since the Cu content in the wire exceeded 1.0%, hot cracking occurred in the crater portion. Further, the toughness of the weld metal also deteriorated. Also, since Ni was less than 1.0%, the corrosion resistance was poor.

On the other hand, in the example of the present invention, no. It was confirmed that the wires of Nos. 1 to 5 can be welded in all positions, and the strength and the toughness are balanced while maintaining good welding workability. In addition, it was confirmed that it had excellent corrosion resistance to incoming sea salt particles.

[0043]

The flux-cored wire for gas shield arc welding according to the present invention is constituted as described above, and TiO _{2 which} provides good welding workability in all-position welding.
In the flux-cored wire, it is possible to impart excellent weld metal performance and excellent corrosion resistance to flying sea salt particles of the weld metal by using the optimal wire component for Cu-Ni-Ti high weathering steel. became.

[Brief description of the drawings]

FIG. 1 is a diagram showing a procedure for collecting a mechanical test piece.

FIG. 2 shows a groove shape when welding to collect a corrosion resistance test piece.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/58 C22C 38/58 (72) Inventor Atsutada Motoe 20-1 Shintomi, Futtsu-shi, Chiba New Japan (72) Inventor Kunio Koyama 20-1 Shintomi, Futtsu-shi, Chiba F-term (reference) Nippon Steel Corporation Technology Development Division 4E001 AA03 BB06 CA07 DB03 DC01 DC05 EA05 EA07 4E081 BA02 BB05 BB13 CA07 FA14 YB10 4E084 AA02 BA02 BA03 BA05 BA06 BA08 BA29 CA08 GA02 HA04

Claims (1)

[Claims] 1. A Cu-Ni-Ti-based high weathering steel to a flux-cored wire is use when gas shielded arc welding, in weight% in the flux for the total wire weight, _TiO 2: 3.5 to C: 0.03 to 0.15%, Si: 0.1 to 1%, Mn: 0.8 to 3%, P: 0. Gas shield characterized by containing 0.3% or less, Ni: 1 to 5.5%, and Cu: 0.3 to 1%, and S: 0.01% or less and Cr: 0.05% or less. Flux-cored wire for arc welding.