JPS61119394A - Submerged arc welding material - Google Patents

Abstract

PURPOSE:To obtain a weld metal having both a high strength and a high toughness after an SR treatment by limiting a composition of a submerged arc welding wire for using a flux of a specified composition, and also managing the basicity to a limited weight ratio by an expression. CONSTITUTION:A composition of a wire used for a submerged arc welding for using a flux which contains 10-30% SiO2 and 5-20% CaF2 by a weight ratio, and also whose basicity is 1.5-4.0 contains 0.06-0.10% C, <=0.10% Si, 1.50-2.10% Mn, <=0.01% P, <=0.005% S, 2.60-3.00% Ni, 0.90-1.10% Cr, 0.40-0.60% Mo, and 0.07-0.10% Ti by a weight ratio, and consists of Fe and an impurity as the balance, and also the basicity derived from a formula I is set to 0.28-0.36wt%.

Description

[Detailed Description of the Invention] This invention aims to obtain a weld metal that requires both high strength and high toughness by submerged arc welding using a specific flux in welding thick high-strength pressure vessels, etc. Regarding welding wires that enable

<Prior art> Submerged arc welding is generally considered optimal for welding high-strength pressure vessels, etc. In this submerged arc welding, welding is often performed by selecting a welding wire (hereinafter simply referred to as wire) and flux with an appropriate chemical composition so that the chemical composition, mechanical properties, etc. of the weld metal are similar to those of the base metal. Are known.

The weld metal used in submerged arc welding for pressure vessels, etc. is required to have both high strength and high toughness in a well-balanced manner, but the weld metal is created by melting and solidifying the wire and base metal. In particular, it is extremely difficult to ensure high toughness, and for this reason, wires that have been added with metal elements that are effective in improving toughness, or fluxes whose properties have been improved to reduce the amount of chlorine in the weld metal are used. Various measures were taken, including the use of

In general, the target performance of weld metal in high-strength pressure vessels is normal temperature tensile strength (hereinafter referred to as TS) ≧75 mm f/-
Absorbed energy at -40°C (hereinafter referred to as VE-40) ≧ 3.5 Kgf-m is required as a '@ property, but if the above measures are adopted, specifically, 3.5 Ni-1,8Cr-0,50
For example, Ni
<2.5%, P>0.010% wire and an appropriate low-oxygen flux can be used in the welding state (for example, thin-walled pressure vessels are used as welded).
, it is possible to obtain a weld metal that meets the above target performance.

However, when welding thick, high-strength pressure vessels,
In order to remove the residual stress generated in the welding heat shadow field, heat treatment (hereinafter simply SR
However, this SR treatment reduces the strength and toughness of the weld metal. That is, in the case of a thick-walled pressure vessel, it is extremely difficult, in fact, almost impossible, to obtain a weld metal that satisfies the above-mentioned target performance after the SR treatment.

Therefore, in the production of thick-walled pressure vessels involving SR treatment, it has been desired to develop a technique for obtaining a weld metal that satisfies the above target performance.

<Object of the invention> The present invention aims to provide a welding wire that can be used in submerged arc welding with a specified flux to obtain a weld metal that satisfies the target performance even after SR treatment. be.

<Structure of the Invention> The present inventors have conducted intensive experimental research with the intention of developing a welding wire that achieves the above object in submerged arc welding of thick-walled pressure vessels. As a result, it was found that under the conditions of using a specific flux containing CaF2, an increase in the Ni content in the wire increases the strength and improves the toughness, and that tempering embrittlement is suppressed by reducing the P content of the wire. It is possible to improve the toughness after the SR treatment and to suppress the increase in cracking susceptibility caused by the increase in 84 minutes.
u + Cr) / 20 + Mo / 15 + V / 10 + 5 B (less than W)) It has been found that the balance between strength and toughness can be optimized by the value of K.

That is, the present invention provides C0,06~Q, lQw or less, S
i0. ] Ow or less, Mn 1.50 to 2.10
w or less, P0.010w or less, s0. oo5w or less, Ni2.60 to 3,00w or less, Cr 0.9
0~1.10w or less, Mo 0.40~0.60w
Hereinafter, Ti 0.07 to 0. tow or less, the remainder substantially consisting of Fe and incorrigible impurities, and PCM is 0.28 to 0. :36 W or less.

Next, the reasons for limiting the components of the wire and flux in the present invention will be explained. All component percentages below refer to w or less.

■ It is an element necessary to ensure wire 04 strength. If it is less than 0.06%, the strength of the weld metal cannot be ensured sufficiently, and if it is 0.10%, it is impossible to prevent low temperature cracking and high fan cracking after welding. When this becomes sufficient, a large decrease in toughness occurs, which is undesirable.

Si: Added as a deoxidizing agent, but in terms of toughness, a small amount is allowed up to <0°10% to prevent island martensite formation, but if it exceeds 0.10%, toughness decreases. In addition, there is a risk of embrittlement during use.

Mn: A minimum content of 1.50% is required to ensure strength and deoxidize, but if it exceeds 2.10%, there is a risk of decreased toughness, occurrence of embrittlement during use, and occurrence of cold cracking in welded parts.

p: The less the better for toughness and weld hot cracking susceptibility <0
．． Although it is permissible up to 0.010%, if it exceeds 0.010%, it becomes difficult to ensure toughness and reduce susceptibility to welding hot cracking.

S: Like P, the less the better, and if it exceeds 0.005%, it becomes difficult to ensure toughness and reduce susceptibility to welding hot cracking.

Ni: An element that is extremely effective in ensuring both strength and toughness, and if it is less than 2.60%, the effect is insufficient;
If it exceeds 00%, there is a risk of welding hot cracking.

Cr1 is a necessary element to ensure strength, 0.90%
If it is less than 1.1%, sufficient strength cannot be obtained, and if it exceeds 1.10%, there is a risk of welding cold cracking and embrittlement during use.

It is an element necessary to ensure MO2 strength, and if it is less than 0.40%, sufficient strength cannot be obtained, and if it exceeds 0.60%, there is a risk of welding cold cracking occurring.

Ti° is an element necessary to ensure both strength and @ properties.
If it is less than 0.07%, sufficient strength and toughness cannot be obtained, and if it exceeds 0.10%, there is a risk of welding cold cracking occurring.

PCM: If it is less than 0.28%, well-balanced strength and toughness cannot be ensured, and if it exceeds 0.36%, it becomes difficult to ensure toughness.

■Flux SiO□: If it is less than 10%, the appearance of the weld bead will deteriorate and workability will deteriorate. Moreover, if it exceeds 30%, Si in the weld metal increases and toughness decreases, which is not preferable.

CaF: An effective component for reducing oxygen in weld metal, but if it is less than 5%, its effect is insufficient, and if it exceeds 20%, too much harmful fluorine gas is generated, deteriorating the working environment. This is not desirable in terms of health and safety.

Basicity: If it is less than 1.5, the oxygen content of the weld metal and the prevention of blowholes will be insufficient89, and if it exceeds 4.0, the viscosity of 7 lux will increase and welding defects such as slag inclusion will occur frequently.

<Effect of the invention> The present invention will be described in detail with reference to Examples.

Table 1 Chemical composition of steel plates for grooves (w or less) Steel plates (1) with chemical compositions shown in Table 1 in the order of 100 plate thicknesses are fitted with grooves (21 (a) =26 decoy, b=
10yyx, (=l 3■), using a wire with a diameter of 4mmφ with the chemical composition shown in Table 2 and a flux with the chemical composition shown in Table 3, and various welding conditions according to the welding conditions shown in Table 4. Submerged arc welding was performed to obtain various weld metals as examples of the present invention and comparative examples. The chemical composition of the obtained weld metal is shown in Table 5. For these weld metals, welding 11 and USR9&H1 (600°C x 12h furnace cooling) TS and VE-40 are based on J ISK (e)1
The results are shown in Table 5.

Table 3 Chemical composition of flux (w or less) Table 4
Welding conditions Comparative examples (1) to (1) using wires whose chemical compositions are outside the scope of the present invention in Table 5
Regarding 131, despite using Fl flux, all except f2+ +51 +91 are VE after SR processing.
-40, TS either;

TS'';? 751'ff/-).
21+51 +91 is TS and VE-4 after SR treatment
0 satisfies the target performance, but (2) is high C,
Samples (5) and (9) were found to be unsuitable due to their high Mn content, which caused weld metal cold cracking, and sample (9), which caused weld metal hot cracking due to their high Ni content. Comparative examples (141 + 151) used a wire with a chemical composition within the range of the present invention, but (141 used a flux with a low basicity, so the toughness was insufficient, and +151 used a flux with a high basicity of 7 lac). This is an example in which poor fusion occurred.

In contrast to these comparative examples, all of the invention examples (Di) to (D6) have a TS of 75 KIf/- or more after the SR treatment.

VE-4Q showed good results of 6.5 and 9 f-m or more.

The relationship between the TS and PCM of the weld metal shown in Table 5 is shown in the graph in Figure 2 for VE-40 and PCM in the l container.
The relationship with CM is shown in the graph in Figure 3, and VE- after SR processing is
The relationship between 40 and PCM is shown in the graph in Figure 4.
The relationship between the PCM of the weld metal and the PCM of the wire is shown in the graph of FIG.

In FIGS. 2 to 5, O indicates an example of the present invention as welded, O indicates an example of the present invention, ○ indicates an example of the present invention after SR treatment, and ゛) indicates an example of the present invention after SR treatment.

That is, the TS after SR processing is 751'lf/- or more.

In order to make VE-40 more than 3.5Kff-m, PC
It is necessary to set M in the range of 0.26 to 0.32%, and in order to obtain this PCM value of the weld metal, the PcMt-
It is necessary to set it to 0.28-0.36%. That is understood.

In addition, all of the comparative examples above the 3.5 Kff-m line in FIG. 4 have welding defects or insufficient TS.

As explained above, the welding wire of the present invention can be used after SR treatment to obtain a weld metal that has both high strength and high toughness required for a high-strength pressure vessel. It is extremely practical as a manufacturing month for meat pressure containers.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the groove shape of a steel plate, Figure 2 is a graph showing the relationship between TS and PCM of weld metal, and Figure 3 is a graph showing the relationship between VE-4Q and PCM of as-welded weld metal. Figure 4 is a graph showing the relationship between VE- of weld metal after SR treatment.
FIG. 5 is a graph showing the relationship between 4Q and PCM, and FIG. 5 is a graph showing the relationship between PCM of weld metal and PC, M of wire. l: steel plate, 2: groove

Claims (1)

[Claims] (1) SiO_210~30wt%, CaF_25~2
A wire used for submerged arc welding using a flux containing 0 wt% and having a basicity of 1.5 to 4.0 below, comprising 0.06 to 0.10 wt% of C, Si0
．． 10 wt% or less, Mn 1.50 to 2.10 wt%, P
0.010wt% or less, S0.005wt% or less, Ni
2.60~3.00wt%, Cr0.90~1.10w
t%, Mo0.40~0.60wt%, Ti0.07~
Contains 0.10wt%, the remainder consists of Fe and unavoidable impurities, and the following PCM is 0.28 to 0.36w
A submerged arc welding material characterized by being in the range of t%. Basicity=CaO+MgO/SiO_2 PCM=C+Si/30+(Mn+Cu+Cr)/20
+Mo/15+V/10+5B (wt%)