JP2003311471A - SOLID WIRE FOR GAS-SHIELDED ARC WELDING OF HIGH Ni BASED WEATHER RESISTANT STEEL - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire for gas-shielded arc welding which is suitable for the welding of high Ni based highly weather resistant steel, enables satisfactory welding operability, particularly satisfactory slag peeling properties and imparts corrosion resistance to sea salt to a weld metal without deteriorating the corrosion resistance of a base metal. <P>SOLUTION: The solid wire for gas-shielded arc welding of high Ni based weather resistant steel has a composition containing, by mass to the total mass of the wire, 0.03 to 0.15% C, 0.2 to 1.2% Si, 0.8 to 2.0% Mn, 1.0 to 5.5% Ni, 0.1 to 1.0% Cu, 0.01 to 0.1% Ti, 0.02 to 0.1% S, 0.0002 to 0.01% B, ≤0.025% P and ≤0.10% Cr, and preferably containing 0.01 to 0.3% Bi as well, and in which the content of S+Bi is 0.03 to 0.2%, and the balance Fe with inevitable impurities. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for steel structures such as bridges in environments where there is a danger of salt damage due to the presence of high concentrations of incoming sea salt particles, such as beach areas or areas where snow melting agents are sprayed. The present invention relates to a solid wire for gas shielded arc welding, which is used for welding of high Ni-based weather resistant steel, and has excellent weldability, excellent weld metal performance, and excellent weather resistance against salt damage in the welded joint.

[0002]

2. Description of the Related Art Conventional weathering steel maintains corrosion resistance by forming a stable rust phase on the steel surface. But,
When used in beach areas or areas where snow-melting agents are sprayed, it was necessary to apply coating or plating. The reason for this is that if there is a large amount of incoming sea salt, the rust layer, which was conventionally said to be a stable rust layer, cannot prevent the progress of rust. In recent years, in a rust layer containing Ni, dissociated sea salt-derived sodium ions (Na ⁺ ) and chloride ions (Cl ⁻ ) exist in the rust layer separated by the ion exchange function of the rust film itself. Na ⁺ is unevenly distributed near the ground iron to create a high PH and reducing environment, while Cl ⁻ is unevenly distributed near the surface of the rust layer and is effective for preventing the progress of rust such as a low PH environment. The mechanism has been shown, and so-called bare steel materials have been proposed that do not require painting or plating even in areas with a large amount of incoming sea salt (cited document; Material and environment vol.49, NO.1). , P30
-40 (2000)).

The steel material is characterized by containing Ni in an amount of 1.0% or more. When the initial rust occurs, Ni is taken into the rust layer, which is designed to prevent the subsequent rust development. . Ni is 1.0 even in weld metal
%, It is possible to form a stable rust layer even in an environment with a large amount of incoming sea salt by the same mechanism as steel, and to prevent further rust development. From such a viewpoint, for example, JP-A-3-47695, JP-A-3-29409, JP-A-5-269592 and the like disclose a high Ni-containing welding material as a welding material for high weather resistance steel. ing.

Further, the high Ni welding material is JIS Z32.
41 As represented by a covered arc welding rod for low temperature steel, it has been conventionally used as a welding material for tanks and the like used at low temperatures. Therefore, attach importance to toughness at low temperature,
For example, in JIS Z3241, P: 0.025% or less,
S: 0.020% or less Measures are taken such as defining inevitable components such as low values. Even if these high Ni welding materials are diverted, the high weather resistance of the weld metal can be realized as a welding material for high weather resistance steel, but this high Ni welding material tends to have poor slag peeling. Although the slag is thick as in submarine arc welding, and in the case of a large amount, the difference in thermal expansion between steel and slag is large, etc.
As with gas shield welding, the slag is thin, and when the amount is small, the slag sticks to the weld metal, and even if a chisel or the like is used, the slag is removed only at the portion hit by the chisel, and it takes time to remove the slag.

[0005]

As described above, the weld metal derived from the conventional high Ni-based welding wire is excellent in toughness at low temperature and can realize high weather resistance, but it can be used in a room temperature environment such as a bridge. In use, there is a problem of excessive quality, but when high productivity is required, there are problems such as poor slag peeling.
Then, this invention makes it a subject to secure good slag exfoliation property, and also makes it a subject to provide the solid wire for gas shielded arc welding of the high Ni type | mold weather resistant steel which improves the toughness fall by this.

[0006]

In view of the fact that the above high weathering steel is added with high Ni to maintain excellent corrosion resistance against flying sea salt, the inventors of the present invention also have high Ni in the welding material. The inventors have found a method of selecting a system, optimizing the contact potential balance with the steel to be welded, and achieving both good slag removability and good toughness by optimizing the welding wire components. Furthermore, Cr, which was effective for improving the weather resistance of conventional weather resistant steels, is
Rather, it has been found that it is necessary to control the amount of Cr in the wire because it has a markedly adverse effect on weather resistance. The present invention is based on the above findings,
The gist thereof is the following contents as described in the claims.

(1) A solid wire used for gas shielded arc welding of high Ni weathering steel, wherein the composition of the solid wire is C in mass% based on the total mass of the wire.
: 0.03 to 0.15%, Si: 0.2 to 1.2%,
Mn: 0.8-2.0%, Ni: 1.0-5.5%, C
u: 0.1 to 1.0%, Ti: 0.01 to 0.1%,
S: 0.02-0.1%, B: 0.0002-0.01
%, P: 0.025% or less, Cr: 0.10% or less, and the balance being Fe or unavoidable impurities, a solid wire for gas shielded arc welding of high Ni-based weathering steel. (2) Further, in mass%, Bi: 0.01 to 0.3% is contained, and the content of S + Bi is 0.03 to 0.2%.
The solid wire for gas shielded arc welding of high Ni-based weather resistant steel according to (1), characterized in that Here, the high Ni-based weather resistant steel refers to a steel material having excellent weather resistance by containing 1% or more of Ni, and JIS G 31
14 and weather resistant steel specified in JIS G 3125.

[0008]

Embodiments of the present invention will be described below. First, the reasons for limiting the chemical composition of the solid wire for gas shielded arc welding of the present invention and its action will be described. C is added as a component for ensuring the strength and toughness of the weld metal. If it is less than 0.03%, the toughness is impaired due to insufficient strength of the weld metal and coarsening of the microstructure. On the other hand, if added over 0.15%, the strength of the weld metal becomes excessive and the toughness deteriorates. For the above reason, C is 0.03 to the total mass of the wire.
It was set to 0.15%. All are shown in mass% below.

Si serves as a deoxidizing agent and has the effect of reducing the amount of oxygen in the weld metal and improving the toughness. Further, it remains in the weld metal and is added as an alloy component in order to secure the strength and toughness of the weld metal. SiO ₂ produced by the deoxidation reaction becomes slag together with the oxide of Mn described later,
It has the effect of adjusting the bead shape. If the amount added is less than 0.2% of the total weight of the wire, the strength of the weld metal will be insufficient, and the amount of slag will be small, so that the welding bead will not be sufficiently encapsulated. On the other hand, if added in excess of 1.2%, the yield in the weld metal becomes excessive, the low temperature toughness deteriorates, and uneven solidification occurs in the molten slag.
Further, the amount of Si needs to be controlled by the kind of shield gas, and 100% carbon dioxide gas shield makes Si higher,
In the Ar-carbon dioxide mixed gas shield, the higher the ratio of Ar, the lower the amount of Si is adjusted. For these reasons, S
i was 0.2 to 1.2%.

Mn acts as a deoxidizing agent to reduce the amount of oxygen in the weld metal and improve the toughness, and is added in order to migrate into the weld metal and secure the strength and toughness. The Mn oxide generated by the deoxidation reaction is the above-mentioned SiO.
_It forms a slag with ₂ , eliminates the uneven solidification of the slag, and the slag is very effective for encapsulating the bead surface. In addition, it also has a role as an arc stabilizer. If the amount added is less than 0.8%, deoxidation becomes insufficient and the toughness deteriorates. Also, sufficient strength of the weld metal cannot be obtained due to insufficient transfer into the weld metal. Also, the bead encapsulation of the slag is insufficient. On the other hand, if added over 2.0%,
The weld metal becomes excessively strong and deteriorates the toughness of the weld metal. For this reason, Mn is set to 0.8 to 2.0%.

Cu dissolves together with Fe in the steel during the formation of the surface rust layer, suppresses the crystallization and coarsening of the rust particles during the formation of the rust layer, and maintains the denseness of the rust layer. By adjusting the potential balance, improve the weather resistance under high-concentration sea salt environment. In addition, by applying Cu plating to the surface of the wire, the electrical conductivity and feedability of the wire are stabilized.
The effect is effectively exhibited by the addition of 0.1% or more, and the larger the addition amount, the better. However, if it exceeds 1.0%, high temperature cracking is likely to occur and the toughness is likely to deteriorate. It was set to 1 to 1.0%. Ti is an oxygen scavenger and forms an oxide, but also forms a nitride. The generated oxides and nitrides are finely and uniformly dispersed in the ferrite phase of the weld metal, and also serve as nuclei for the generation of intragranular ferrite, which has the effect of promoting the toughness of the weld metal. Also,
It also contributes to making the rust layer airtight. If it is less than 0.01%, the proper oxides and nitrides cannot be formed and the effect of improving the toughness is not obtained, and if it exceeds 0.1%, the Ti oxide becomes coarse inclusions and the weld metal Low temperature toughness deteriorates. In addition, a slag inclusion defect is likely to occur, which impairs the mechanical properties and weather resistance of the weld metal. Therefore, Ti is 0.0
It was set to 1 to 0.1%.

Ni is Fe when forming a rust layer on the surface of the weld metal.
At the same time, it is eluted into the rust layer and becomes almost uniformly contained in the layer. When Ni is contained in the rust layer in an amount of 0.5% or more,
It suppresses permeation of chloride ions (Cl ⁻ ) derived from flying sea salt adhering to the surface of the rust layer into the rust layer / base iron interface, and suppresses an increase in Cl ⁻ concentration in the inner layer of the rust layer. This suppresses crystallization and coarsening of the rust particles and brings about an effect of maintaining the denseness of the rust layer. To make Ni contained in the rust layer in an amount of 0.5% or more, Ni in the weld metal:
1.0% or more is required. The higher the content of Ni, the better the weather resistance of Ni. However, if it exceeds 5.5%, hot cracking in welding tends to occur and the cost also increases. For the above reasons, Ni is set to 1.0 to 5.5%.

However, Ni contained in the wire for gas shielded arc welding has a yield of about 100% in the weld metal when it is welded, and in order to reduce the potential difference with the steel material, Ni in the wire is preferable. It is better to add Ni in the same amount as steel. Further, preferably, in order to prevent hot cracking, C should be lowered as the amount of Ni is increased. Weld metal Ni: 3%, C: 0.9% or less, N:
It is advisable to set i: 5% and C: 0.7% or less as a guide. S
Is an element that deteriorates the toughness of the weld metal, and the lower the better for improving the toughness. On the other hand, for slag releasability,
The accumulation of S at the interface between the slag and the bead has a remarkable improving effect. From this point, the higher the S, the better. From the viewpoint of improving the toughness of the weld metal, the upper limit of its content is 0.1%, and from the viewpoint of improving the slag removability, the lower limit of its content is 0.02.
%, And the S content was 0.02 to 0.1%.

B has the effect of forming a nitride and enhancing the hardenability. B: If it is less than 0.0002%, most of it is consumed as a nitride, and the hardenability effect is not recognized. On the other hand, if it exceeds 0.01%, the hardenability becomes excessive, which causes a decrease in the toughness of the weld metal. Therefore, B: 0.0002 to 0.01%. Bi is
It is an element that has the same properties as S and deteriorates the toughness of the weld metal, and the lower the toughness, the better. On the other hand, the slag releasability is remarkably improved by the accumulation of Bi at the interface between the slag and the bead. From this point, the higher Bi is, the better. When S is sufficiently added, Bi may be small, the upper limit of its content is 0.3% from the viewpoint of improving the toughness of the weld metal, and the lower limit of its content is from the viewpoint of improving slag removability. Is 0.01%, and the Bi content is 0.01 to 0.
It was 3%.

As described above, S and Bi have the same property and can complement each other's deficiency. S + Bi
Is less than 0.03%, slag peeling is poor and 0.2%
If it exceeds 1.0, the toughness of the weld metal tends to be insufficient, and it is preferable to limit S + Bi to 0.03 to 0.2%. P is an element effective in improving weather resistance, but if it exceeds 0.025%, hot cracking is likely to occur or the toughness of the weld metal is deteriorated, so 0.025% or less. Limited to. Cr is an element that is baser than Fe and inhibits weather resistance in an environment with a lot of sea salt, so it is preferable to reduce it as much as possible. 0.10
If it is at most 0.1%, the inhibition of the weather resistance can be ignored, so the amount was made 0.10% or less. The following includes 0%.

[0016]

EXAMPLES Next, the present invention will be described more specifically based on examples. Table 1 shows a list of examples. A 1.2 mmφ solid wire having the components shown in Table 2 was prepared and tested. Welding tests were conducted under the conditions shown in Table 3 to evaluate the performance. In the test, welding workability such as bead shape and slag peeling property and toughness and strength of weld metal were tested. The toughness of JIS No. 4 test piece is 47 J at -20 ° C.
The above was considered good. The weather resistance is 4 x thickness 50 x 100 length so that the weld metal is located in the center from the welded joint.
Cut out a strip-shaped test piece of mm and apply it twice a day for 5 minutes /
After 6 months of accelerated exposure test with seawater, the degree of corrosion was investigated by comparison with the base metal. After 6 months, rust on the surface of the test piece was removed by pickling, and then abnormal corrosion holes were visually observed. Was recognized, and that the weld metal portion was recessed from the base metal by the roughness meter measurement was determined to be defective.

Example 1 is an example of the present invention, in which the composition of C was set low, the strength was adjusted, the content of Si was increased, the proportion of Mn was increased in proportion to Si, and the content of Ni was also increased. The welding method was carbon dioxide welding, and the bead shape was good in that the slag was uniformly covered and the slag peeling was good at S + Bi: 0.031%. In addition, the toughness of the weld metal is good, and the corrosion resistance test results are based on the base metal.
It was a good result because Ni was higher than (3Ni type). Example 2 is also an example of the present invention, in which the content of C is high, the strength is adjusted, and Si is low, and Mn is also low in proportion to Si. In addition, Ni and Cu were also designed to be low, and tested. The welding method was argon + carbon dioxide shield welding, the bead shape was good, and the slag peeling was good at S + Bi: 0.197%. The toughness of the weld metal was also good, and the corrosion resistance test results were also good.

Example 3 was also an example of the present invention, in which the composition was designed with B being high and Ti being low, and tested. The welding method is argon + carbon dioxide shield welding, the bead shape is good, and slag peeling is S
+ Bi: 0.292%, which was good. Further, the toughness of the weld metal was higher than that of the other because it was high in S + Bi, but it was a good value, and the corrosion resistance test result was also a good result comparable to the base metal. Examples 4 and 5 are also examples of the present invention.
The proper balance of Si and Mn was tested, and especially Example 5 was C.
Tested at a higher u. The welding method was carbon dioxide welding, and the bead shape and slag peeling were good. The toughness of the weld metal was also good, and the results of the corrosion resistance test were also comparable to those of the base metal.

Example 6 is also an example of the present invention, and a wire was designed and tested without Bi. The welding method was carbon dioxide welding, the bead shape was good, and the slag peeling was only S, but it was good. The results of the toughness and corrosion resistance test of the weld metal were also good. Example 7 is a comparative example, C is low, Si, M
The wire component was designed and tested with n being high for strength adjustment and low for Ni. The welding method was carbon dioxide welding, and the bead shape was poor due to excess slag. Slag did not have the effect of S, but it was almost good because Ni was low. Further, the toughness of the weld metal is N
There was no effect of i, Ti, and B, and although S was lower, it was unsatisfactory. Regarding the corrosion resistance, the effect of Ni was not exerted, and the amount of corrosion was large and it was poor.

Example 8 is also a comparative example, in which C is high and Si, M
n is low by adjusting the strength, and the wire component is designed with low Ni.
Tested with% argon + 20% carbon dioxide welding. The toughness of the weld metal was excessively low in C, the bead shape was poor due to insufficient slag, and the slag peeling was not effective due to S and was poor. Also,
The result of the corrosion resistance test was almost good due to the effect of Ni. Example 9 is also a comparative example, and although C, Si, and Mn are in the invention range,
P: 0.030% was used to design the wire composition, and carbon dioxide welding was tested. The toughness of the weld metal was low due to the effect of excess P, and the slag peeling was also poor with no effect of S and Bi. The results of the corrosion resistance test were almost good due to the effect of Ni.

Example 10 is also a comparative example, and although C, Si, and Mn are in the invention range, the wire component is designed with S: 0.12%,
Tested with carbon dioxide welding. The toughness of the weld metal was low due to the effect of excessive S, and the bead shape was also poor due to excessive slag flow, and slag separation was good due to the effect of S. Also, the corrosion resistance was good due to the effect of Ni. Example 11 is also a comparative example, and the effect of Ti was examined under the condition that P was not influenced by comparing P with 0.012%. The welding was carbon dioxide welding, and the toughness of the weld metal was P less than that in Example 9,
It improved, but it was not enough. S, B also removes slag
There was no effect of i and it was poor, and the corrosion resistance was almost good due to the effect of Ni. Example 12 is also a comparative example, and although C, Si, and Mn are within the invention range, the effects of Ti and Cu were examined with Ti: 0.12% and Cu: 0.08%. Welding is carbon dioxide welding,
The toughness of the weld metal was low due to the influence of excess Ti, and the bead shape was almost good, but the slag peeling was also poor because there was no effect of S and Bi. Further, the corrosion resistance was low in Cu, the difference in contact potential with the base material was large, and it was somewhat defective.

Example 13 is also a comparative example, and although C, Si, and Mn are within the scope of the invention, the effect of Bi: 0.4% Bi was examined. The welding was carbon dioxide welding, the toughness of the weld metal was low due to the effect of excess Bi, and the bead shape was also unevenly distributed due to uneven distribution of slag, but the slag peeling was good due to the effect of Bi.
Also, the corrosion resistance was good. Example 14 is also a comparative example,
C, Si and Mn are within the scope of the invention, but Ni: 6.3%, C
The effect of Ni and Cr was examined at r: 0.4%. The welding was carbon dioxide welding, and the toughness of the weld metal was good, but cracks were observed on the fracture surface of the Charpy test piece. The bead shape was a shape having a slightly large unevenness peculiar to high Ni, and the slag peeling was poor. The corrosion resistance was high Ni and the average weight loss was small, which was good, but pitting corrosion was observed in some places.

Example 15 is also a comparative example, and although C, Si, and Mn are within the scope of the invention, the effects of Cu and Cr were examined with Cu: 1.25% and Cr: 0.2%. Welding is carbon dioxide welding,
The toughness of the weld metal was almost good, but cracks were also observed on the fracture surface of the Charpy test piece. The bead shape was almost good, but the slag peeling was poor because of the effects of S and Bi. The corrosion resistance was high Ni and the average weight loss was small, which was good, but pitting corrosion was observed in some places.

[Table 1]

[Table 2]

[Table 3]

[0024]

INDUSTRIAL APPLICABILITY The gas shield arc welding wire of the present invention, when used for high Ni type high weather resistance steel, has high weather resistance equivalent to or higher than that of the base metal against sea salt corrosion. Slag releasability, which can be ensured and is a drawback of conventional high Ni steel welding, is improved, and good welding workability is obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeru Okita             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division

Claims (2)

[Claims] 1. A solid wire used for gas shielded arc welding of high Ni weathering steel, wherein the composition of the solid wire is% by mass relative to the total mass of the wire, C: 0.03 to 0.15%, Si: 0.2-1.2%, Mn: 0.8-2.0%, Ni: 1.0-5.5%, Cu: 0.1-1.0%, Ti; 0.01- 0.1%, S: 0.02-0.1%, B: 0.0002-0.01%, P: 0.025% or less, Cr: 0.10% or less, and the balance Fe or A solid wire for gas shielded arc welding of high Ni-based weather resistant steel, which is characterized by comprising unavoidable impurities. 2. Further, the content of Bi is 0.01 to 0.3% by mass, and the content of S + Bi is 0.03 to 0.2%. Solid wire for gas shielded arc welding of high Ni-based weather resistant steel as described in 1.