JP3265037B2 - Ni-Mo based TIG welding wire for cryogenic steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to 9% N used for LNG (liquefied natural gas), LEG (liquefied ethylene gas) and the like.
The present invention relates to a Ni-Mo based alloy TIG welding wire used for welding cryogenic steel such as i-steel, 5.5% Ni steel, and 3.5% Ni steel.

[0002]

2. Description of the Related Art TIG welding of cryogenic steel such as 9% Ni steel has advantages such as excellent hot cracking resistance and good mechanical properties of weld metal at cryogenic temperature.
-Mo-based TIG wire is used. Further, with the recent increase in the size of LNG tanks and the like, the thickness of extremely low-temperature steel such as 9% Ni steel has been increased, and the need for highly efficient automatic TIG welding is increasing.

However, when high efficiency, that is, high welding or high-speed welding is performed, a relatively large amount of slag is generated in a conventional Ni-Mo based wire, or the slag becomes pock-like, so that TIG welding is performed. There were problems such as the peculiar clean bead appearance being impaired, the arc state being deteriorated during formation, the bead shape being deteriorated, the penetration being unstable, and welding defects such as poor fusion and slag entrainment being liable to occur. In order to avoid these problems, it is necessary to grind the slag generation part with a grinder or to shape the defective bead shape, which leads to a decrease in the construction efficiency, and overall high efficiency Cannot be achieved, and there is a strong demand for a Ni-Mo based wire that enables high-efficiency TIG welding.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a bead-forming material having excellent weldability, that is, no slag is generated. Therefore, it is an object of the present invention to provide a Ni-Mo-based TIG welding wire that can easily perform high welding, high-speed high-efficiency TIG welding, and can obtain a healthy welding metal. .

[0005]

Means for Solving the Problems The present inventors have proposed Ar and A
In TIG welding using a Ni—Mo base wire using a mixed gas of r + He, Ar + H ₂ as a shielding gas,
For the purpose of ensuring excellent weldability and soundness under high-efficiency welding conditions, we conducted intensive studies on trace components and gas components of Ni-Mo based wires. As a result, in the Ni-Mo group if <br/> alloy containing trace amounts in the wire, or Ti which the wire surface to trace deposited, Ca, Mg, Al, an active element and O of Si, the gas components N In particular, we discovered the fact that, when performing high-efficiency welding, such as reacting during welding to make the arc unstable, forming slag on the bead surface, and deteriorating bead conformability, the weldability was greatly impaired. It has been newly found that by strictly controlling and managing the trace elements and gas components of the above, the weldability is remarkably improved, and highly efficient and sound TIG welding can be easily performed.

The present invention is based on the above findings, and the gist of the present invention is as follows: Ni: 68 to 82%, Mo: 17 to 23%, W: 2.0 to 4.5% by weight. %; Cu; 0.1 to 1.7%; Ti; 0.005 to 0.12%; Ca; less than 0.0025%; Mg; less than 0.0025%; Al; less than 0.050% , Si: less than 0.10%, O: less than 0.005%, N: less than 0.002%, and OX equivalent determined by the following equation (1): less than 0.220, remaining Is a Ni-Mo based TIG welding wire for cryogenic steel characterized by having a composition comprising Fe and unavoidable impurities.

OX equivalent = 50 {Ca (%) + Mg (%)} + Al (%) + 0.5Si (%) + 0.1Ti (%) + 10 {O (%) + N (%)} 1)

[0008]

The present inventors have found that in a Ni-Mo based alloy, T
Wires were prepared in which the elements of i, Ca, Mg, Al, Si and the gas components of O, N were variously changed, and 9% Ni shown in FIG.
Welding was performed under various conditions in a horizontal position where slag was most likely to occur in the steel groove and welding defects were also likely to occur, and the weldability and the soundness of the welded parts were investigated. FIG. 2 shows the effects of the welding speed and the OX equivalent on the slag generation rate on the weld bead surface (total bead surface slag length 表面 total bead length × 100). FIG. 3 shows the relationship between the number of defects per 1 m of welding length of the welded portion, the welding speed, and the OX equivalent. From FIG. 2, the slag generation rate increases as the value of the OX equivalent increases, but especially when the welding speed increases to 30 g / min or more, the slag generation rate increases sharply at the value of the OX equivalent of 0.220 or more. Became clear. Also, from FIG. 3, welding defects begin to occur when the value of OX equivalent is 0.220 or more, but particularly 20 cm / m
It became clear that the number of defects increased rapidly at welding speeds faster than in.

The present invention has been made based on the above experimental results, and the reasons for limiting various numerical values defined by the present invention will be described below. Ni is required to be 68% or more as a basic component for securing characteristics such as impact toughness and tensile strength at extremely low temperatures by making the weld metal an austenitic structure.
If it exceeds 82%, other basic components for securing properties such as tensile strength and hot crack resistance are insufficient, and properties for cryogenic steel cannot be obtained. Therefore, the amount of Ni is set to 68 to 82%.

Mo is required as a basic component for securing the tensile strength necessary for the weld metal for cryogenic steel and the resistance to high-temperature cracking during welding to 17% or more. Even if it exceeds 23%, the effect does not change. The workability of the wire is deteriorated. Therefore, M
The amount o is 17 to 23%. W is required to be 2.0% or more for cryogenic steel in order to improve the tensile strength of the weld metal, and if it exceeds 4.5%, the effect does not change and the workability of the wire is deteriorated. Therefore, the amount of W is set to 2.0 to 4.5%.

Cu is used in an amount of 0.1% in order to stabilize the austenitic structure of the weld metal, improve the impact toughness at extremely low temperatures, improve the hot workability of the wire, and secure productivity.
The above is necessary, and the effect does not change even if it exceeds 1.7%. Therefore, the amount of Cu is set to 0.1 to 1.7%.

Ti is required to be 0.005% or more in order to decrease the hydrogen embrittlement susceptibility of the weld metal, improve the ductility and toughness, improve the workability of the wire, and secure the productivity.
Even if it exceeds 0.12%, the effect does not change, and particularly in the case of high-efficiency welding, the weldability deteriorates, such as making the arc unstable during welding and promoting slag generation on the bead surface.
Therefore, the amount of Ti is limited to 0.005 to 0.12%.

When Ca becomes 0.0025% or more, particularly when performing high-efficiency welding, when Ca becomes 0.0025% or more, the melting of the wire becomes unstable and the arc at the time of welding also becomes unstable. Generate slag on the bead surface,
Furthermore, weldability deteriorates, such as deterioration of bead conformability. Therefore, the amount of Ca is restricted to less than 0.0025%.

When the content of Mg is 0.0025% or more, particularly when high-efficiency welding is performed, if the content becomes 0.0025% or more, the melting of the wire becomes unstable, and as a result, the arc at the time of welding becomes unstable. Generate slag on the bead surface,
Furthermore, weldability deteriorates, such as deterioration of bead conformability. Therefore, the Mg content is restricted to less than 0.0025%.

When the Al content is 0.050% or more, particularly when high-efficiency welding is performed, the Al content becomes 0.050% or more.
Making the melting of the wire unstable and consequently also the arc at the time of welding unstable, making the slag generation on the bead surface remarkable,
Further, the weldability is deteriorated, for example, by changing the viscosity of the molten metal to deteriorate the conformability of the bead. Therefore, the amount of Al is 0.0
Restrict to less than 50%.

If the Si content is 0.10% or more, particularly in the case of high-efficiency welding, if the content is 0.10% or more, slag generation on the bead surface is promoted and the weldability deteriorates. Therefore, the amount of Si is restricted to less than 0.10%.

When O becomes 0.005% or more, especially when performing high-efficiency welding, the above-mentioned Ti, Ca, Mg, Al,
In combination with the presence of Si, the melting of the wire becomes unstable, resulting in an unstable arc at the time of welding, the generation of slag on the bead surface, and the deterioration of the conformability of the bead. Therefore, the O content is restricted to less than 0.005%.

When N becomes 0.002% or more, especially when performing high-efficiency welding, the above-mentioned Ti, Ca, Mg, Al,
In combination with the presence of Si, the melting of the wire becomes unstable, resulting in an unstable arc at the time of welding, the generation of slag on the bead surface, and the deterioration of the conformability of the bead. In addition, blow holes are easily generated. Therefore, the N content is restricted to less than 0.002%.

It is a main component of the present invention to not only individually control and manage the active elements of Ti, Ca, Mg, Al and Si and the gas components of O and N, but also to limit the value of OX equivalent. When the OX equivalent is 0.220 or more, particularly when performing high-efficiency welding, the melting of the wire becomes unstable, resulting in an unstable arc at the time of welding, and slag is generated on the bead surface. The weldability is remarkably deteriorated, for example, the bead conformability is deteriorated, and further, welding defects such as poor fusion and slag entrainment occur frequently, thereby deteriorating the soundness of the welded portion. Therefore, the value of OX equivalent is 0.22
Limit to less than 0.

The wire of the present invention is made of a carefully selected raw material, melted and cast in a vacuum atmosphere, and the obtained ingot is formed into a coil by hot forging, which is used for resin coating, heat treatment, pickling, washing, etc. It can be manufactured by drawing to a predetermined wire diameter by cold working including the step of:

[0021]

EXAMPLES The effects of the present invention will be more specifically described below with reference to examples. Table 1 shows the chemical components of the wire. The wire diameter is 1.2 mm except for the wire symbol B14. The wire symbol B14 was finished to 1.6 mmφ because many breaks occurred at the stage of 1.55 mmφ in the wire drawing process. Table 2 shows the chemical components of the test steel sheet. Each of the steel plates has a thickness of 45 mm. Table 3 shows the welding conditions. Here, high welding (wire feed rate; 25-60 g / min) and high speed (welding speed; 25
５０50 cm / min) for high efficiency welding. FIG. 4 shows the procedure for laminating the weld metal, and the numerals indicate the number of layers.

Table 4 shows combinations of test wires and test steel sheets and performance test results. The test plate was a steel plate shown in Table 2 (plate thickness 4
5mm, width 200mm, length 750mm) and the front side is as shown in Table 3.
, And the back side was similarly welded under the conditions shown in Table 3. The slag generation rate was determined by measuring the length in the welding direction of slag generated on the surface of the final layer bead on the front side and the back side, and calculating the percentage of the total length of the slag to the bead length. Here, the reason for evaluating the final layer is that when slag occurs on the bead surface, slag also occurs on the bead surface of the next layer, and the slag generation rate increases due to the layering effect as the number of layers increases. is there. The integrity of the weld is determined by X-ray photography at the end of welding on the front side, and 25m deep from the front side after welding on the back side
The X-ray photograph was taken after the thickness of the weld was cut to a thickness of 60 mm and the width was 60 mm, and the total number of defects in each X-ray film was counted and evaluated.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

From the above results, the wire symbol A1 of the present invention
-A18 is excellent in weldability because slag hardly occurs on the surface of the weld bead even in high-efficiency welding, poor fusion,
It is clear that welding defects such as slag entrainment and blow holes are unlikely to occur and that sound welding can be easily performed.

On the other hand, the wire symbol B1 of the comparative example has a Mg content of 0.0025% or more, has a high slag generation rate, has poor weldability, and has many welding defects and lacks soundness. B2 has 0.0025% or more of Ca, has a high slag generation rate, is inferior in weldability, and has many welding defects and lacks soundness. B3 has a Ti content of more than 0.12%, has a high slag generation rate, is poor in weldability, and has many welding defects and lacks soundness. B4
Al has a content of Al of 0.05% or more, has a high slag generation rate, is inferior in weldability, and has many welding defects and lacks soundness. B5 is S
When i is 0.10% or more, the slag generation rate is high and the weldability is poor, and there are many welding defects and the soundness is poor.

B6 has an O content of 0.005% or more, has a high slag generation rate, is inferior in weldability, and has many welding defects and lacks soundness. B7 has an N content of 0.002% or more, has a high slag generation rate, is inferior in weldability, and has many welding defects and lacks soundness. B8, B9 and B10 have an OX equivalent value of 0.220.
As described above, the slag generation rate is high and the weldability is poor, and there are many welding defects and the soundness is poor. B11 has 0.0025 Ca
% And an OX equivalent value of 0.220 or more, the slag generation rate is high and the weldability is poor, and there are many welding defects and the soundness is poor. B12 has 0.0025% or more of Mg, 0.050% or more of Al and an OX equivalent value of 0.220 or more, has a high slag generation rate, has poor weldability, and has many welding defects and lacks soundness. B13 contains 0.10% or more of Si;
When O is 0.005% or more and the value of OX equivalent is 0.220 or more, the slag generation rate is high and the weldability is poor, and there are many welding defects and the soundness is poor. Since B14 has a Ti content of less than 0.005%, breakage occurs in the wire drawing process, and when the OX equivalent value is 0.220 or more, the slag generation rate is high and the weldability is poor, and there are many welding defects and soundness. Lack.

[0031]

As is clear from the above embodiments, the wire of the present invention has excellent weldability even in high-efficiency welding conditions in TIG welding of cryogenic steel, and easily obtains a sound weld. The industrial effect is remarkable, and the utility value is high.

[Brief description of the drawings]

FIG. 1 is a view showing the shape of a groove of 9% Ni steel for which weldability and soundness were investigated.

FIG. 2 is a diagram showing a relationship between a slag generation rate, a welding speed, and an OX equivalent.

FIG. 3 is a diagram showing the relationship between the number of welding defects, welding speed, and OX equivalent.

FIG. 4 is a view showing a procedure for laminating a weld metal performed under welding conditions (Table 3) of an example.

Continuation of the front page (72) Inventor Shohei Sato 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (56) References JP-A-6-63789 (JP, A) JP-A Sho 62-234690 (JP, A) JP-A-61-99598 (JP, A) JP-B-51-29104 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 35/30 C22C 19/03

Claims (1)

(57) [Claims] 1. Ni: 68 to 82%, Mo: 17 to 23%, W: 2.0 to 4.5%, Cu: 0.1 to 1.7%, Ti: 0.005% by weight. Less than 0.0025%, Mg; less than 0.0025%, Al: less than 0.050%, Si: less than 0.10%, O: less than 0.005%, N An OX equivalent controlled by less than 0.002% and determined by the following equation (1): 0.2
Ni-Mo for cryogenic steel, characterized by having a composition of less than 20 and the balance being Fe and inevitable impurities.
Base TIG welding wire. OX equivalent = 50 [Ca (%) + Mg (%)] + Al (%) + 0.5Si (%) + 0.1Ti (%) + 10 [O (%) + N (%)]… (1)