JPS599273B2 - Electroslag welding wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides that when heat treatment is performed after welding,
The present invention relates to an electroslag welding wire for providing a deposited metal having a tensile strength of 1 or more and an excellent impact value.

Conventionally, in electroslag welding of extremely thick plates, heat treatment is performed after welding to refine the weld metal and its heat-affected zone in order to obtain a good impulse welding cost.

However, when welding high-strength base materials, good impact values are often not obtained even if heat treatment is performed after welding, and it is said to be less reliable. Furthermore, the key point of the currently used heat treatment method is rapid cooling after heating, and after raising the temperature to the austenitizing temperature, rapid cooling methods such as blast cooling, water spray cooling, oil cooling, etc. are adopted. Therefore, not only is large-scale equipment such as a cooling device and a transportation device required, but also deformation during rapid cooling cannot be avoided, and from this point of view it cannot be said to be a good method. For this reason, we considered trying to obtain a high-strength, high-impact weld metal using a slow cooling method, but we learned that good results could not be achieved using conventional electroslag welding wire. .

By the way, Table 1 shows the chemical composition and TlSO value (70C+14
Si + 8.8Mn + 3.5M0 + 1.8Cr: However, the element symbol indicates the weight% of each component), and the right column shows the thickness of the thick plate (SB49, plate thickness 50 mm) using these wires.
) when electroslag welded, 900'
It shows the tensile strength and impact value (0°C) when air-cooled after holding C/1 hour and then furnace cooling after holding 625°C/2 hours, but the relationship between tensile strength and impact value is qualitative. The relationship is almost inversely proportional, and there is no wire that satisfies both characteristics.

That is, as can be seen in Table 1, wires A, B, D, and E do not have sufficient tensile strength even though their impact values are relatively good, and wires C, F, G, and H do not have sufficient tensile strength. , I, although good tensile strength was obtained, the impact value was low and ultimately unsatisfactory.

The present invention has been made with attention to such circumstances, and uses a slow cooling method for heat treatment after welding, and
It is an object of the present invention to provide a wire for electroslag welding that provides a deposited metal that not only has a high tensile strength of g/Md or higher but also satisfies a good impact value.

After conducting various studies to achieve this purpose, we found that
It was discovered that the chemical components of the wire, particularly the contents of C, Mn, MO, and Si, play an important role, leading to the completion of the present invention.

That is, the wire of the present invention has C: 0.10%, Mn: 2.
00-3.00%, MO: 0.15-0.70%, Si
:0.10-0.40% is an essential component, the remainder contains unavoidable impurities and iron, and is 70C+14Si+8
．． A wire that can satisfy the condition 8Mn+3.5M0≧27 (however, the element symbol indicates the weight of each component),
Is it pulled by this wire? We were able to obtain a welded metal that satisfies both high performance and impact value.

Additionally, in the process of this research, in addition to the above essential components, B<0
．． 015%, Ti<0.10%, Al<0.25%, V
70C+14Si+8.8Mn+3.5M0
It has been found that the object of the present invention can be fully achieved with a wire that satisfies the following condition: +1.8Cr+5.3Ni+26.3V>27 (the element symbol indicates the weight of each component).

The structure and effects of the present invention will be explained below with a focus on each of the above-mentioned requirements. However, the following description and the description given as embodiments in the claims do not limit the present invention, and do not limit the present invention. However, it is within the technical scope of the present invention to carry out such modifications.

Generally made of high tensile strength steel with a weight of 50 kg/Md or more and a plate thickness of 10
For extremely thick plates exceeding 0 mm, the amount of carbon is increased in order to obtain strength at room temperature and strength at high temperatures.

However, in electroslag welding, a large heat input is used and the penetration rate of the base metal is high, so carbon in the base metal is inevitably diluted and transferred into the weld metal. However, it is well known that carbon mixed in the weld metal reduces the impact value, so it is considered desirable to keep the carbon content in the electroslag welding wire used here to a low level in advance. . Figure 1 is a graph showing the relationship between the carbon content in the wire and the impact value of the weld metal, where the base steel is SB49 and the other components in the wire are Mn:
0.90-1.40%, MO: 0.10-0.35%,
Si: 0.05-0.30%, remainder: unavoidable impurities and iron. The impact values plotted in the figure are the lowest values selected from numerous experimental results in consideration of safety. As is clear from Figure 1, the normally required impact value VEO〉2
, 1k9-m, the carbon content of the wire must be 0.
．． It was found that the content must be kept at 10% or less, and furthermore, in order to satisfy EO≧2.8k9-m, which is higher than the first class, the content must be kept at 0.07% or less. Next, Mn and M
However, both of these metals have the effect of increasing the strength of the weld metal and making the crystal grains finer. For example, M
If the n amount is less than 2.00%, sufficient strength cannot be obtained,
It was also found that if the MO content is less than 0.15%, the influence of dilution by the base material is large, and as a result, satisfactory strength cannot be obtained.

However, if Mn or MO is too large, the hardness will only increase, but there is a risk that the impact value will decrease.
% and 0.70% should be considered as upper limits. Although the effects of 11110Mn and MO are known to some extent, it has been found that these effects are particularly noticeable when heat treatment is performed after welding as described above.

Next is Si, which has a high deoxidizing effect, but if it is less than 0.10%, the deoxidizing effect is insufficient and pores may be generated in the weld metal, which is disadvantageous. On the other hand, the upper limit is not so important if we focus only on the deoxidizing effect, but when heat treatment such as normalizing or high-temperature annealing is performed, the effect of reducing the impact value due to Sl is significant, so the content exceeds 0.40%. I don't like that. As above, C. Mn. If the wire contains MO and Si within the specified range, the impact value can be significantly improved by heat treatment after welding. I learned that in order to achieve this goal (obtaining strength), I had to meet other requirements.

This requirement is, for example, as derived from Table 1, Tl
SO value (70C+14S1+8,8Mn+3.5M0+
1.8Cr: However, when the Cr content is zero, the final term is also zero). As a result of numerous experiments, we learned that in order to obtain a tensile strength of 50k9/MfL or higher, the TlSO value must be at least 27 or higher. As a result, we learned that the purpose of the present invention can be fully achieved as long as the wire satisfies each of the above conditions, but in the process of this research we also learned that other components may also play an important role. Ivy.

The components are B, Tl, Al, Cr, Ni,
B<0.015%, Ti<0.10%, Al 0.25
%, <0.05%, Cr<0.30%, Ni6.0%
More favorable results were obtained when one or more of the elements satisfying the following conditions were blended. Each of these metals is effective in improving strength, but B,
When used alone or in combination, Tl, Al, and the like not only prevent the coarsening of columnar crystals, but also have a remarkable effect of improving the impact value of the weld metal, similar to Nl. Of course, even if these elements are contained, the TlSO value must be 27 or more, but since B, Ti, and Al have little effect on the TlSO value, they can be almost ignored, and in the end, the TlSO value is as follows. It is given by a calculation formula. 70C+14Si+
8.8Mn+3.5M0+1.8Cr+5.3Ni+2
6.3VThe TlSO value is defined as mentioned above, but more specifically, it is desirable that the strength level of the weld metal is the same as or higher than the strength level of the base metal, and the TlSO value is
It is recommended that O+23 (minimum tensile strength value after complete annealing of pure iron) is greater than the minimum value of the base metal strength standard.

Next, S and N will be explained as elements that have a particularly large influence among unavoidable impurities.

A feature of electroslag welding is that even extremely thick plates are welded in one pass, and because the weld metal has little thermal history, it tends to form coarse columnar crystals.

Therefore, impurities with a low melting point tend to gather at grain boundaries, and S in particular causes cracking. Moreover, when using high carbon steel as a base material and applying the heat treatment as described above, the impact value reduction effect is particularly large.
In order to avoid these negative effects, the S content should be reduced to 0.03%.
It is recommended to keep it below. Next is N. As is well known in the art, N has a great effect of lowering the impact value. Figure 2 shows C: 0.04-0.1%,
Mn: 0.90-1.40%, MO: 0.10-0.3
5%, Si: 0.05 to 0.30% electroslag welding wire, welded the same base metal as in Figure 1, and heat treated under the same conditions. As in the case of FIG. 1, the lowest value is plotted. As is clear from Fig. 2, the impact value decreases as the N content increases, and VEO>2.11<
It can be seen that in order to provide 9-m, the content should be suppressed to 0.01% or less. Since the present invention is configured as described above, regardless of welding conditions, heat treatment temperature, slow cooling conditions, etc.
Consistently high tensile strength and impact values have been obtained, making it possible to further expand the scope of application of electroslag welding.

Next, embodiments of the present invention will be described.

Example 1 A base material (SB49N) with a plate thickness of 120 mm was electroslag welded under the following conditions, and then heat treated, and the results shown below were obtained.

Chemical composition of wire: C: 0.060%, Mn: 2.29%, MO: 0.55
%, Si: 0.28%, N: 0.004% TlSO=3
0.19 Chemical composition of base material: C: 0.25%, Mn: 0.82%, Si: 0.22%
Chemical composition of Fusitsukus: CaO: 19%, CaF2:1
0%, MgO: 4%, SlO2: 39%, MnO: 21
% Wire diameter: 3.2m7! Lφ Number of poles. Distance between two poles: 75mu Current/voltage: 500A, 45V Groove spacing: 35mm Heat treatment: 9000C/4 hours holding furnace cooling +6254C/8
Furnace cold joint strength after time holding Tensile strength: 51.5k9/M77l Impact value (VEO): 5.11kg-m Example 2 The following results were obtained using a base material (A5l6G7O) with a plate thickness of 111 mm.

Chemical composition of wire: C: 0.055%, Mn: 2.60%, MO: 0.44
%. Si: 0.38%, N: 0.005%T, SO-3
3.6 Chemical composition of base material: C: 0.24%, Mn: 1.13%, Si: 0.27%
Chemical composition of flux: Same as Example 1 Wire diameter: 3.
2mmφ Number of poles: 2 Distance between poles: 65m1L Current/voltage: 500A, 45 Groove spacing: 35mm Heat treatment: 90'C/Furnace cooling after 3 hours holding +625. C/6
Furnace cold joint strength after time holding. Tensile strength: 54.6 kg/Md Impact value (VEO): 4.8 kg-m Example 3 Using a base material (SB49N) with a plate thickness of 90 mm, the following results were obtained.

Chemical composition of wire: C: 0.04%, Mn: 2.12%, MO: 0.26%
, Si: 0.37%, Ni: 1.88% TlSO-36
．． 9 Chemical composition of base material: C: 0.25%, Mn: 0.92%, Si: 0.21%
Chemical composition of flux: Same as Example 1 Wire diameter: 3.
2mmφ Number of poles: 1 Current/voltage: 500A, 45V Groove spacing: 30mm Oscillation width: 50m71L Heat treatment: 9000C/2 hours followed by furnace cooling +620C/
Furnace-cooled joint strength after holding for 4 hours Tensile strength: 60.9k9/MIL Impact value (VEO): 6.1k9-m Example 4 Using a base material (SM5OA) with a plate thickness of 100 mm, the following results were obtained. .

Chemical composition of wire: C: 0.06%, Mn: 2.15%, MO: 0.50%
, Sl: 0.28%, Ti: 0.070%, B: 0.0
Chemical composition of 01% TlSO-28.1 base material: C: 0.15%, Mn: 1.35%, Si: 0.35%
Chemical composition of flux: Same as Example 1 Wire diameter: 3.
2mmφ Number of poles: 2 Distance between poles: 65mTfL Current/voltage: 450A, 50 Groove spacing: 35 Heat treatment: 91'C/Furnace cooling after 1 hour holding + 620℃/Furnace cold joint strength after 4 hour holding. Tensile strength: 52.

6k9/M7l Impact value: 7.7kg-m

[Brief explanation of the drawing]

Both FIGS. 1 and 2 are graphs showing the results of the present invention.

Claims (1)

[Claims] 1. A wire for electroslag welding of a welded joint of thick-walled steel plates that is heat treated after welding and then slowly cooled, the wire having C≦0.1.
0%, Mn: 2.00-3.00%, Mo: 0.15-
0.70% and Si: 0.10 to 0.40% as essential components, the remainder consists of inevitable impurities and iron, and 70C + 14Si + 8.8Mn + 3.5Mo≧2
50kg/mm^ after heat treatment, characterized by satisfying the following conditions: 7 (however, the element symbol indicates the weight% of each component)
An electroslag welding wire that provides deposited metal with a tensile strength of 2 or more. 2. The wire according to claim 1, wherein C≦0.07%. 3. The wire according to claim 1 or 2, in which S as an unavoidable impurity is suppressed to 0.03% or less. 4. The wire according to claim 1, 2 or 3, in which N as an unavoidable impurity is suppressed to 0.01% or less. 5 Electroslag welding wire for welded joints of thick steel plates that is heat treated after welding and then slowly cooled, C≦0.1
0%, Mn: 2.00-3.00%, Mo: 0.15-
Contains 0.70% and Si: 0.10 to 0.40% as essential components, and B≦0.015%, Ti≦0.10
%, Al≦0.25%, V≦0.05%, Cr≦0.3
0%, Ni≦6.0%, the remainder consists of unavoidable impurities and iron, and 70C+14Si+
8.8Mn+3.5Mo+1.8Cr+5.3Ni+2
It is characterized by satisfying the following condition: 6.3V≧27 (however, the element symbol indicates the weight percent of each component). Electroslag welding wire that provides weld metal with a tensile strength of 50 kg/mm^2 or more after heat treatment. 6 C≦0.
The wire according to claim 5, wherein the wire is 0.07%. 7. The wire according to claim 5 or 6, in which S as an unavoidable impurity is suppressed to 0.03% or less. 8. The wire according to claim 5, 6 or 7, in which N as an unavoidable impurity is suppressed to 0.01% or less.