JPS58184097A - Gas shielded arc welding method of dead soft steel - Google Patents

Abstract

PURPOSE:To prevent the solidification cracking by welding thoroughly even if a steel material contg. a specific amt. of C is welded at a high speed in the stage of gas shielded arc welding of said material at the specific welding speed or above by contg. Ni in a filler for a compsoite wire at a specific weight ratio with the wire or above. CONSTITUTION:A stee material contg. 0.005-0.06% C is subjected to gas shielded welding at >=40cm/min welding speed. An Ni-contg. composite wire is used in this case and the content of Ni to be contained in the filler of said wire is specified so as to satisfy the equation in the ratio of Ni (w) based on the weight of the wire. In the equation, C(p); the content % of carbon in the steel material, C(t); the content % of carbon in the sheath of the wire, C(w); the content % of carbon in the filler based on the weight of the wire. At least the 1st layer is welded by using such wire.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for gas-shielded arc welding of ultra-low carbon steel using a composite wire.

In recent years, with advances in controlled rolling, there has been a trend towards lower carbon steel materials, including line pipe materials, in order to improve weldability or reduce costs.

Conventionally, the hot cracking susceptibility of the weld metal of these low carbon steel materials,
In particular, its weld solidification cracking susceptibility was generally thought to be low.

By the way, according to the studies of the present inventors, contrary to the conventional understanding, ultra-low carbon steel with a carbon content of 0.06 inches or less can be made by using existing composite wires with a carbon content of 40 (Ml/-).
It was found that when gas-shielded arc welding was performed at the above welding speed, weld solidification cracking was likely to occur despite the sufficiently low carbon content of the weld metal.

By the way, as a method to solve such weld solidification cracking of weld metal of ultra-low carbon steel, by using a composite wire with increased carbon content, C2, A gas-shielded arc welding method that controls the welding within an appropriate range was previously proposed (Japanese Patent Application No. 1982-1).
No. 40384).

On the other hand, the present inventors found that when ultra-low carbon steel materials with a carbon content of 0.06% or less were gas metal arc welded at a welding speed of 40 cwr/- or more, the As a result of extensive research into the various factors that affect weld solidification cracking, we discovered that nickel has a significant effect on low-order nickel.

In other words, by making the weld metal contain an appropriate amount of nickel that exceeds the required nickel-containing lid determined in accordance with the carbon content of the low-carbon weld metal, low-carbon welding can be achieved even when welding at a welding speed of 40 crR/- or more. We succeeded in completely preventing weld solidification cracking of weld metal.

The present invention was made based on the above findings, and
The gist of this is that carbon 0.005-0.06%
When gas-shielded arc welding steel containing Ni at a welding speed of 40 cm/#I or higher, the amount of nickel contained in the filler of the composite wire should be adjusted to the weight ratio of Ni to the wire.
(Steel carbon content) When the carbon content of the outer sheath material of the composite wire is expressed as C(1)chi, and the carbon content of the filler is expressed as C(W)aIb in terms of the overlapping ratio to the wire.

1\ 0.55 N i(w1≧2.0 (8,OC(p)+
Gas-shielded arc welding of ultra-low carbon steel, characterized in that at least the first layer is welded using a nickel-containing composite wire that satisfies the formula: 7.8 C(1) + 9.9 C(wl) Method and when nickel-containing steel materials containing 0.005 to 0.06% carbon are gas-shielded arc welded at a welding speed of 40 crn/- or more, the amount of nickel in the steel material ThN1 (p1%, contained in the filler of the composite wire) Ni (wl %)
, the carbon content of the steel material is C1p)', the carbon content of the outer skin material of the composite wire is Cft)%, and the carbon content of the filler is the weight ratio of the wire to C (when expressed as 0.45 N + (p) ) +0-55 N I(W+≧
2.0(8,OCfpi+7.8 C(t)+9.9
The present invention provides a gas-shielded arc welding method for ultra-low carbon steel, characterized in that at least the first layer is welded using a nickel-containing composite wire that satisfies the formula: cfW+).

The present invention will be explained in detail below.

In order to improve the cracking resistance and toughness of weld metal in high and low temperature ranges, it is believed that weld hot cracking in high temperature ranges will not occur if the carbon content of the weld metal is 0.
．． It was believed that this idea would hold true even if it was less than 1%.

However, according to the studies of the present inventors, the susceptibility to weld solidification cracking of low-carbon weld metal obtained by gas-shielded arc welding of ultra-low carbon steel using composite wire, which has been commonly used in the past, actually increases. Figure 1 was obtained.

That is, Figure 1 shows the relationship between carbon content (%) of weld metal and welding speed (c
Fig. 3 shows the relationship between weld solidification cracking (m/mM) and weld solidification cracking, using a steel plate with a carbon content of 0.01 to 0.16%, having the groove shape shown in Fig. 2, and having a copper backing C applied. A welded test specimen having the dimensions and shape shown in was prepared, and the outer skin material and the carbon lid having a carbon content of 0.02 to 0.08% were mixed at a weight ratio of 0.02 to the wire.
This was obtained by root welding using a composite wire containing a filler adjusted to ~0.10% under the welding conditions shown in Table 1, and the weld metal does not contain nickel.

In Table 1 and Figure 2, t: 2.5IIl, t2: 1.
511 Otori.

R,:22.5', R2:5', R,:2.7
It was set as 5R.

Also, in Fig. 3, W, :30011m, W2 and W, :100111, 11 :40011.
12:3011. t: 100 pieces.

As shown in Figure 1, the carbon content of the weld metal is 0.10
It was confirmed that weld solidification cracking occurs in region A where the welding speed is less than 51 and the welding speed is 40 cm/mM or more, but does not occur in region B. That is, the susceptibility to solidification cracking of the weld metal is different from conventional wisdom, and when the carbon content is below the limit carbon content (2), the susceptibility to solidification cracking of weld metal increases when the welding speed exceeds the limit.

The reason for this is thought to be that the δ phase solidification increases as the weld metal is reduced in carbon, and in order to reduce weld solidification cracking, it is necessary to suppress the δ phase as much as possible.
．． These are ultra-low carbon steels such as general structural steels and low-alloy steels for low temperature use, which contain 0.005% or more.

In order to investigate the effect of nickel, which is a γ phase-forming element, in order to suppress δ phase formation in low carbon weld metal, a composite wire containing nickel was fabricated, and further welding was performed using the same welding test method as shown in Figure 1. Fig. 4 was obtained by conducting a detailed investigation of weld solidification cracking in the root weld metal. By incorporating nickel into the composite wire, the upper limit of the carbon content in the weld solidification cracking region shifted to the lower carbon side.

:::□ In the figure, the Ni (%) of the composite wire is ■: 0%, ■20.8
%, ■: 1.7%, ■: 2.5%.

This revealed that nickel has an extremely significant effect on reducing the weld solidification cracking susceptibility of low carbon weld metals. In addition, when welding at a welding speed of less than 40 cm/llI#II, molten steel is continuously supplied to the final solidification part of the weld metal, so even if the weld metal is low carbon and does not contain nickel, welding No solidification cracking was observed.

In other words, the weld solidification crack of low carbon weld metal is 49 cm
This phenomenon occurred when gas-shielded arc welding was performed at a welding speed of /min or more. Due to metallurgical and mechanical conditions, weld solidification cracking is most likely to occur in the root weld metal, so as long as solidification cracking in the root weld metal can be prevented, there is no need to worry about solidification cracking in low carbon weld metal due to subsequent welding. . In order to prevent this welding solidification cracking of the root weld metal, it is necessary to
FIG. 4 suggests that it is sufficient to use a composite wire containing more than the amount of nickel such that (R)% is the upper limit for weld solidification cracking. Based on Figure 4,
The following equation could be obtained as a relation between c(R) in the welding solidification crack-free region and the amount of nickel Ni(b) in the composite wire.

0.55Ni (season≧2.2-2 IC(R)
(1) On the other hand, the present inventors
A large number of gas-shielded arc welding tests were carried out at the above welding speeds, and the carbon content of the steel material C(1) relative to the carbon content c(R) of the root weld metal and the carbon content of the outer skin material of the composite wire C(1)
) and the carbon content of the filler C(w), the following equation was obtained as a prediction equation for c(R).

C(R) = 0.38C(p)+0.37C(t
l+ O;47 C(w)+ 0.01 (2)(1
) and (2), weld solidification cracking of low carbon weld metal? In order to prevent this, it was found that the amount of nickel in the composite wire should satisfy the following formula.

0.55 N i fwl≧2.0 (8,0C(p)
+7.8C (t1+9.9C(w)) (3) Next,
Ultra-low carbon steel materials may contain nickel to ensure good weld toughness. When such nickel-containing ultra-low carbon steel is gas-shielded arc welded, nickel in the steel material naturally migrates to the weld metal, so the amount of nickel in the composite wire required to prevent welding solidification cracking and cracking is: The amount of nickel transferred from the steel material side (- can be reduced by the corresponding amount.

The contribution rate from the steel material side to the root weld metal formation during gas-shielded arc welding at a welding speed of 40 cIn/- or higher was 45%, and the contribution rate from the steel material side to the root weld metal formation during welding (because there is almost no oxidation loss of Ni-nickel in the steel material) Nickel” (9
1 corresponds to 20.45" (pi) of nickel in the composite wire.

Therefore, in order to completely prevent weld solidification cracking of the root weld metal when nickel-containing ultra-low carbon steel is gas-shielded arc welded, from the above reasons and equation (3), it is necessary to The amount of nickel in the equation should be determined to satisfy the following formula: 0.45 N
1lp) + 0.55 N i (b) ≧ 2.0 (8,
OC (p) + 7.8 C (0 + 9.90 (wl)
It should be noted that the composite wire used in the present invention may be any material as long as it satisfies the above-mentioned relationship, but it is preferable to add nickel to the filler in the form of metallic nickel and ferroalloy metal powder. From a practical standpoint, the amount added is usually 1.0 to 2.5% based on the weight of the wire.
is desirable.

As other filler components, the following can be used. In other words, in terms of wire weight ratio,
Manganese and silicon as deoxidizing agents and alloying agents are 0.5~
3. ．． 5%Mn5O11~1.5%SiO! ZrO2, Al2O3 and LteT+02.

One or more types of 5in2 can be added up to 20% in total,
In addition, various fluorides, arc stabilizers such as carbonate groups, and replenishers such as iron powder can be added.

Incidentally, as the outer skin material of the wire of the present invention, mild steel having excellent workability is used. Further, the cross-sectional shape of the composite wire does not need to be particularly determined, and it may be a folded wire or a seamless wire. Furthermore, the filler in the composite wire is preferably in the range of 10 to 30% by weight of the wire.

Next: The present invention will be further explained in detail with reference to Examples.

Example 1 A welding test specimen shown in FIG. 3 having the groove shape and shape shown in FIG. 2 was prepared using a thick plate having the chemical composition shown in Table 2. Using a composite wire of IIφ, the fourth
One-pass welding was performed under the welding conditions shown in the table, and solidification cracking of the weld metal was investigated.

The test results are shown in Table 5.

Items within the scope of the present invention (= indicates no weld solidification cracking in X-ray transmission test and weld bead cross-sectional inspection.

51 However, A = 2.0 (8,0C(p) + 7.80(1
) + 9.90 (W) ) B = 0.55 N i (
1) C" 0.45Ni (p) +0.55Ni (f10 mark indicates no cracks, Root welding was performed using the composite wire shown in Table 3 under the welding conditions shown in Table 7. The test results are shown in Table 8.

The products within the scope of the present invention showed no solidification cracking in X-ray transmission tests and weld bead cross-sectional inspections.

A = 2.0 (8,0C(p)+7.8C(11
+9.9C(wl)B = 0.55Ni(f) C= 0.45N 1(p) + 0.55N 1(f
10 mark indicates no crack, X mark indicates crack.

[Brief explanation of drawings]

Figure 1 is a chart showing the relationship between the solidification cracking area that occurs in all root welded steels, weld metal carbon content, and welding speed when ultra-low carbon steel is gas-shielded arc welded, and Figure 2 is a schematic diagram of the groove shape. Figure 3 is a schematic diagram showing the dimensions and shape of a welding test specimen, and Figure 4 is a diagram showing the effect of nickel on the susceptibility to solidification cracking that occurs in root weld metal during gas-shielded arc welding of ultra-low carbon steel. be. Figure 1 Welding metal return element i (X) Figure 2 Figure 3 Figure 1 Figure 4 0 0.05 0.10 0,15
0.20; Weld metal carbon content (%) Procedural amendment dated 57'124, 1980, Japan Patent Office Commissioner Shima 1) Indication of Haruki Tono 1 case Patent application No. 67101, 1981 Otemachi, Chiyoda-ku, Tokyo 2-6-3 Name (665) Nippon Steel Stock Food Coloring Representative Takeshi
1) Toyota 4th generation Osamu Address: 3-3-3-5, Nihonbashi, Chuo-ku, Tokyo Date of amendment order: Showa Year, month, day (shipment date) 6 Number of inventions to be increased by amendment

Claims (1)

[Claims] 1. Contains 0.005 to 0.061e of carbon! Steel; In,
When performing gas-shielded arc welding at a welding speed of 4 Q cm/1 Jul+ or more, the amount of nickel contained in the filler of the composite wire is N i twl in weight ratio to the wire,
The carbon content of the steel material is C(1)chi, the carbon content of the outer sheath material of the composite wire is 1 vil-C (t1%), and the carbon content of the filler is expressed as CHI in terms of weight ratio to the wire. 2
゜0 (8, OC(p)+ 7.80(t1+ 9.9
A gas-shielded arc welding method for ultra-low carbon steel, characterized in that at least the first layer is welded using a nickel-containing composite wire having a satisfactory metal formation of C(wl). 2. When performing gas-shielded arc welding of nickel-containing steel materials containing 0.005 to 0.06%'fr of carbon at a welding speed of 40α/mis or more, the amount of nickel in the steel material eN
I(pl%) - The amount of nickel contained in the filler of the composite wire is NI(w)% as a weight ratio to the wire, the amount of carbon in the steel is C(p)%, and the amount of carbon in the outer skin material of the composite wire is C(t). )
ts, when the amount of carbon in the filler is expressed as C1% by weight relative to the wire, 0.45N 1 (p) + 0.55N i (w) upper 2
゜0(8, OC(kawa+7.8 C(tl+9.9
A gas-shielded arc welding method for ultra-low carbon steel, characterized in that at least the first layer is welded using a nickel-containing composite wire that satisfies the formula: c(Wl).