JPS6219959B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to automatic and semi-automatic welding wires, and more specifically, to excellent welding workability and thick plate tempering.
The present invention relates to a composite wire for carbon dioxide arc welding that can provide weld metal with excellent performance even after heat treatment that is compatible with Cr-Mo steel. Cr-Mo steel containers used in oil refining, chemical industry, high-temperature, high-pressure boilers, etc. are becoming larger, with higher temperatures and higher pressures being used for economic reasons, and the design strength is also increasing. Therefore, it is expected that the thickness of the container will become even thicker. In this way, as the container becomes thicker, the stress relief annealing time after welding becomes longer.
As the annealing time increases in this way, Cr-Mo
The tensile strength and impact value of weld metal tend to decrease gradually. The welding materials used therein are also required to have high performance. Conventionally, submerged arc welding and electroslag welding have been mainly used for these thick-walled containers, and carbon dioxide arc welding and shielded arc welding have also been used. However, when comparing submerged arc welding, electroslag welding, and carbon dioxide arc welding, submerged arc welding and electroslag welding have an extremely large amount of heat input, and as a result, the impact value of the weld metal tends to be low. This is due to large dendrite growth in the weld metal. Furthermore, between carbon dioxide arc welding and shielded arc welding, carbon dioxide arc welding is superior in terms of high welding efficiency and stable joint quality. In addition, compared to submerged arc welding, electroslag welding, and covered arc welding, carbon dioxide arc welding is a low-hydrogen welding method and can significantly ease the preheating conditions required to prevent cold cracking, and is suitable for welding thick-walled containers. The advantage of this method is that it is possible to significantly reduce welding costs by shortening welding time and saving welding materials by narrowing the groove. By the way, carbon dioxide arc welding can be roughly divided into two types depending on the wire used. One is by solid wire and the other is by composite wire. First, when solid wire is used, the melting speed of the wire is fast and high-efficiency welding with deep penetration is possible, but on the other hand, only a small amount of slag is scattered on the bead obtained by welding, and the bead appearance Because there is no slag to maintain the beautiful bead shape, the bead appearance is poor and the bead shape tends to be convex. In addition, when composite wire is used, the bead is uniformly covered with slag due to the slag forming agent, so the bead shape and appearance are very good, and the welding workability is also superior to solid wire. Due to the large amount of oxygen, the performance of the weld metal, especially the strength and impact value after stress relief annealing, was inferior to that of solid wire. Therefore, it is strongly desired to develop a composite wire for carbon dioxide arc welding that has good welding workability, suppresses the amount of oxygen in the weld metal, and provides a weld metal that has excellent crack resistance and mechanical properties even after stress relief annealing. was. In other words, the present invention reduces the total weight of the wire to
_TiO2 1.8~6.0%, C0.20% or less, Mn1.0~8.0%,
Cr1.0~4.0%, Mo0.5~1.5%, and Si0.3
% or even less than 0.015% in the flux, in the form of nitrides, and the remainder consists of ordinary slag forming agents including arc stabilizers. This is a Cr-Mo based composite wire for carbon dioxide arc welding, characterized by the fact that the outer sheath is filled. The reason why the composite wire for carbon dioxide arc welding according to the present invention has the above structure will be explained in detail below. First, regarding TiO ₂ , when TiO ₂ is added to the filling flux, it softens the arc and forms a highly viscous slag, so the droplets take on a fine and regular transition shape, as well as unnatural vertical or upward orientation. Even in this position, the molten metal becomes difficult to melt down. Furthermore, since slag smoothes the weld bead and improves the conformability of fillet beads, for example, it is highly effective in improving the fatigue strength of the weld. However, if the amount of TiO ₂ is less than 1.8%, welding workability is extremely poor and it is not practical. On the other hand, if it exceeds 6.0%, the viscosity of the slag becomes abnormally high, which deteriorates the bead encapsulation of the slag and deteriorates the bead shape. Therefore
TiO ₂ is limited to a range of 1.8% to 6.0% based on the total weight of the wire. Note that TiO ₂ in the wire of the present invention
Ingredients are TiO ₂ like natural rutile and artificial rutile.
Added by containing minerals. Further, it is desirable that the particle size range of TiO ₂ added to the wire of the present invention is a maximum particle size of 297 μm or less that does not interfere with flux filling. Next, C is added to give the weld metal tensile strength, but if it exceeds 0.20%, the impact value decreases.
Since it increases cracking sensitivity, it should be within the range of 0.20% or less. Mn is added to improve the tensile strength and toughness required for welded parts and to prevent pores generated during welding, but if it exceeds 8%, the quenching effect increases and weld cracking is likely to occur. If it is less than 1.0%, it will be difficult to obtain the required strength and toughness. Next, Cr and Mo are added to weld Cr-Mo steel to give strength to the welded part, but if the amount of Cr is less than 1.0% of the total weight of the wire, the required strength cannot be obtained. , and when it exceeds 4.0%, crack resistance deteriorates. Mo also increases impact toughness as well as strength, but if the amount is less than 0.5%, it is ineffective, and if it exceeds 1.5%, cracking resistance deteriorates. Si can be added mainly for the purpose of improving X-ray performance and workability, but if it exceeds 0.3% of the total weight of the wire, the impact value of the weld metal will decrease, so it is permissible up to 0.3% or less, but in practical use. From this point of view, the lower the Si content, the better the impact value. Note that C, Mn, Cr, Mo, and Si can be used alone or in the form of various alloys including iron alloys. Next, in the present invention, electrolytic metal manganese nitride, chromium nitride, aluminum nitride,
One or more of iron nitride and titanium nitride can be added such that N is 0.006 to 0.015% based on the total weight of the wire. In order to determine the appropriate amount of N to be added, the following experiment was conducted. Figure 1 shows the relationship between the impact value of the weld metal and the N content in the flux. In the test, the flux components were TiO ₂ 2.0%, C 0.12%, Mn 4.8%, Cr2. 0
%, Mo 0.82%, SiO ₂ 0.87%, Al ₂ O ₃ 1.50%, the amount added to the total weight of the wire was kept constant, and electrolytic metal manganese nitride was used as the N source, and the amount added was varied. A wire with a mild steel outer skin (1.6mm
φ) with a filling rate of 15% and a plate thickness of 25 mm.
Bevel angle of A387Gr22 (21/4Cr-1Mo steel) steel plate
45°, a V-shaped groove with a groove gap of 12.5 mm, and the current
350A, voltage 31V, speed 27cm/min, 100% CO ₂
Welding was carried out under the welding conditions of (flow rate 25/min), and after welding was completed, stress relief annealing was performed at a temperature of 650°C and a holding time of 12 hours, and JIS A-4 Sharpie impact pieces were collected from all welded metal parts. It is something.
As is clear from this figure, when the N content in the flux is 0.006% or more based on the total weight of the wire, the temperature is lower (600 to
690℃) The impact value after stress relief annealing is high. on the other hand
If it exceeds 0.015%, blowholes and pits will occur in the weld. Therefore, based on this knowledge, N is limited to a range of 0.006 to 0.15% based on the total weight of the wire. In addition to the above-mentioned components, the composite wire of the present invention can contain a slag forming agent including a conventional arc stabilizer as the remainder. The slag forming agents mentioned here include Al ₂ O ₃ , SiO ₂ , ZrO ₂ , FeO,
Refers to Na ₂ O and K ₂ O, and it is desirable that the sum of one or more types is 10% or less. As these additive raw materials, iron oxide, potassium feldspar, silica sand, zircon sand, alumina, etc. can be used as appropriate. Next, although alloy steel can also be used as the metal sheath material of the wire of the present invention, mild steel is usually used. Further, the cross-sectional shape of the wire is not particularly determined, and any wire may be used as long as it has excellent feedability and arc stability, similar to conventional flux-cored wires. That is, as shown in FIGS. 2 and 3, the cross section of the outer metal 1 may have a seam, or as shown in FIG. 4, it may be a so-called seamless wire without a seam. Note that in these figures, 2 is a filling flux. By the way, good results seem to be obtained if the flux filled into the wire is controlled within the range of 10 to 25% by weight of the wire. Also, the wire diameter is 2.0
Those less than mmφ are preferable for automatic and semi-automatic welding. Next, the effects of the present invention will be explained in more detail using Examples. Example Table 1 shows the filling flux composition of the prototype wire. Note that both of these wires have a mild steel outer shell.
It was finished to a diameter of 1.6 mm and had a simple butt cross-sectional shape as shown in Figure 2 with a filling rate of 15%. A387Gr22 (21/4Cr-1Mo steel) steel plate with a thickness of 25 mm is used as a V-shaped groove with a groove angle of 45 degrees and a groove gap of 12.5 mm. Current is 350 A, voltage is 31 V, speed is 27 cm/min, 100 mm.
Welded under the welding conditions of %CO ₂ (flow rate 25/min),
After welding, stress relief annealing was performed at a temperature of 690°C and a holding time of 16 hours, and JIS No. A-2 tensile test pieces and A-4 Sharpie impact pieces were collected from the center of the thickness of each weld metal plate. was used for testing. Table 2 shows the tensile strength and impact value of the obtained weld metal. As is clear from Table 2, Nos. 4 to 18 according to the present invention
This wire not only has good welding workability and bead appearance, but also has excellent X-ray performance, and a weld metal with excellent tensile strength and impact value was obtained. On the other hand, reference wire No. 1, in which TiO ₂ was less than the range specified by the present invention, had extremely poor welding workability and became impossible to weld. In addition, reference wire No. 20, in which TiO ₂ was added in an amount exceeding the range stipulated in the present invention, had an unreasonably high slag viscosity, resulting in deterioration of workability and frequent internal defects such as slag entrainment and poor fusion. The mechanical properties were also very poor. Reference wires Nos. 2 and 3 had Si added in an amount exceeding the range specified by the present invention, and although the welding workability, bead appearance, and X-ray performance were good, the impact value of the weld metal was very low. Reference wire No. 19 had N added beyond the range specified by the present invention, and although the welding workability and bead appearance were good, the X-ray performance showed that there were many internal defects such as blowholes and poor fusion. It became impossible to collect mechanical test pieces. Reference wire No. 21 had C added beyond the range specified by the present invention, and had good welding workability and bead appearance, but internal defects such as cracks and poor penetration occurred in X-ray performance. It became impossible to collect mechanical test pieces. Reference wire No. 22 had Mn added beyond the range stipulated in the present invention, and had good welding workability and bead appearance, but internal defects such as cracks and poor penetration occurred in X-ray performance. The impact toughness was also low.

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[Table] As detailed above, the present invention has particularly excellent welding workability and can provide weld metal with excellent performance even after heat treatment that is suitable for thick plate tempered Cr-Mo steel, so it can be used in various welding fields. The scope of application has been expanded, and its industrial value is extremely large.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the impact value of the weld metal and the N content in the flux with respect to the total weight of the wire.
FIG. 2, FIG. 3, and FIG. 4 are diagrams showing examples of wire cross-sectional shapes. 1: shell metal, 2: filling flux.

Claims (1)

[Claims] 1. TiO ₂ 1.8 to 6.0% based on the total weight of the wire,
C0.20% or less, Mn1.0~8.0%, Cr1.0~4.0%,
A Cr-Mo carbon dioxide gas arc welding composite wire characterized by having a metal sheath filled with a flux consisting of 0.5 to 1.5% Mo and the remainder being a normal slag forming agent including an arc stabilizer. 2 TiO ₂ 1.8-6.0% based on the total weight of the wire,
C0.20% or less, Mn1.0~8.0%, Cr1.0~4.0%,
Cr-Mo carbon dioxide gas arc welding characterized by the fact that the metal shell is filled with a flux consisting of 0.5 to 1.5% Mo, 0.3% or less Si, and the remainder is a normal slag forming agent including an arc stabilizer. composite wire. 3. The flux contains one or more types of metal powder in the form of nitride such that N0.006 to 0.015% based on the total weight of the wire, TiO ₂ 1.8 to 6.0%, C0.20
% or less, Mn1.0~8.0%, Cr1.0~4.0%, Mo0.5~
A Cr-Mo carbon dioxide gas arc welding composite wire characterized by having a metal sheath filled with a flux consisting of 1.5% and the remainder a normal slag forming agent including an arc stabilizer. 4. The flux contains one or more types of metal powder in the form of nitride such that N0.006 to 0.015% based on the total weight of the wire, TiO ₂ 1.8 to 6.0%, C0.20
% or less, Mn1.0~8.0%, Cr1.0~4.0%, Mo0.5~
1.5% Si, 0.3% or less Si, and the remainder is a slag forming agent containing an arc stabilizer.
Mo-based composite wire for carbon dioxide arc welding.