JPS6240996A - Submerged arc welding wire for low-temperature steel - Google Patents

Abstract

PURPOSE:To form a weld metal having excellent low-temp. toughness in submerged arc welding by incorporating Si and Al as an essential component into a wire compsn., limiting the contents of P, S, O and N, adequately adding Mn, Ni, Cu and Mo thereto and specifying the carbon equiv. thereof. CONSTITUTION:The submerged arc welding wire for low-temp. steels is composed by incorporating, by weight %, <=0.07% C, <=0.2% Si and 0.002-0.50% Al as the essential component therein. Further, P is limited to <=0.20%, S to <=0.020%, N to <=0.0050% and O to <=0.0150%. In addition, the compsn. contains >=1 kinds among 0.5-3.0% Mn, 0.5-12% Ni, 0.02-3.0% Cu and 0.1-2% Mo and the balance Fe and inevitable impurities in which CE is limited to 0.2-1.0. The CE refers to the carbon equiv. of IIW and is determined by the formula. An adequate ratio each of Ti and B are further incorporated therein if necessary. The excellent low-temp. toughness is provided to the weld metal by the fused wire having such compsn.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a submerged arc wire for low-temperature steel, and more specifically to obtaining a weld metal having excellent low-temperature toughness in submerged arc welding of low-temperature steel. This relates to a submerged arc wire that can be used.

(Prior Art) In recent years, construction of important structures such as oil drilling auxiliary equipment has been actively carried out in the development of undersea energy. The size of structures is increasing year by year, and the number of structures used in cold regions is increasing. Against this background, high efficiency and excellent fL
There is a demand for the development of 7R quality welding technology. Covered arc welding is mainly used for welding various structural steels. Gas shield welding and submerged arc welding are applied. Among these methods, the submerged arc welding method is particularly capable of increasing the welding current and is easy to apply to the multiple separation welding method, so it is used in many fields as an extremely highly efficient method.

By the way, as a typical method for improving the low-temperature toughness of weld metal, there is a method described in Journal of the Welding Society Vol.
n.

A widely used method is to add Ti-B to give the weld metal a uniform and fine ashcular ferrite (hereinafter referred to as AF) structure. Furthermore, in the recent energy situation (2), many fabricators require good toughness to be obtained even in double-sided single-layer and double-sided multilayer welding with -40υ or less and high heat input welding (45 KJ/cIn) or higher. Become a friend.

(Problems to be solved by the invention) In the case of the above-mentioned high heat input welding, the toughness is increased in the part that is reheated in the primary A bath.According to the study by the present inventors, The main cause of the decrease in toughness in the reheating zone is high carbon martensite (hereinafter referred to as M
＊I think this is largely due to the generation of Shirasuri.

Therefore, zero in the weld metal which promotes the formation of martensite.
It is believed that lowering the amount of 0 is effective. fact,
It has been found that by using a latent arc wire with low O3l, the oit'e in the weld metal can be lowered and the toughness of the reheated zone can be improved. However, the sum as welded (
Since the toughness of AW and I-Rufu actually decreases, there is still room for further improvement regarding this point.

In view of the above-mentioned circumstances, it is an object of the present invention to provide a latent arc wire joint that can provide excellent low-temperature toughness in both the AW section and the reheat section during latent arc welding of low-temperature steel.

(Means for Solving the Problems) The present inventors aimed to develop a submerged arc wire for low-temperature steel welding that can obtain a weld metal with good chemical composition and low-temperature toughness throughout the welded joint. After various observations of these weld metals, it was found that the cause of the decrease in toughness was C.
By lowering the
The amount of 0 increases, making it impossible for TI-B to work effectively, resulting in pro-eutectoid ferrite (hereinafter referred to as PF).
It was found that this is because the precipitation of L7i increases and the precipitation of AP becomes difficult. Therefore, in order for Ti-B to work effectively, 00 in the weld metal must be kept low. As a result of examining methods for this purpose, it was found that adding a deoxidizing agent to these wires was effective, and after examining various effects of deoxidizing agents, it was found that kl was the most suitable. It is thought that not only the deoxidizing power is suitable, but also the toughness is further improved because the At and TI oxides assist in the generation of AF.

The present invention has been made based on such knowledge, and the gist thereof is that the essential components are 0:0.07 or less, 81:0.2 or less, and A1:0.002-0.50% by weight. Toshi, P:
0.020 or less% 8: 0.020% or less, ”: 0.
0050, bottom.

0: limited to 0.0150X or less, and Mn: 0
．． 5 to 3.0, Ni: 0.5 to 1 296'
, Ou: 0.0 2-3.0 KMo: Q,
Contains one or more of the following, or further contains T.
L: 0.05 to 05%, B: 0.005 to 0.1, the remainder is Fe and inevitable impurities, and CE is 0.2 to 1.0. A low-temperature steel pool arc wire is characterized by:

However, CE is the carbon equivalent of IIW and CE=C+ 1
76Mn+ 1/15 (Cu+Nl) + 115
(Or+Mo+V) (However, calculation is performed based on weight.

) It is.

The present invention will be explained in detail below.

(for production) First, the basic components of the wire of the present invention will be described.

First of all, the lower C and n is better, but at least 0.07
The precipitation of M- in the weld metal is sufficiently suppressed if the
I can't do it.

Next, Si acts as a deoxidizing agent and lowers O and improves toughness, but if too much Si deteriorates toughness, it must be kept below 02.

MafCAt has a stronger deoxidizing power than Ti, Mn, Si, and B, and has a weaker deoxidizing power than EMr Mg r Oa.

For this reason, Al is not completely oxidized in the arc like [M etc.], but the curved part moves to the molten pool and then oxidizes, so the zero concentration in the weld metal can be kept low, and the TI in the molten pool can be kept low. It can prevent overoxidation of B and oxidation of B, and the effect of Ti-H can be further improved. The oxidized Aff deteriorated the toughness and became worn.
Considering that i remains in the weld metal excessively and increases the amount of O, the appropriate range is 0.002 to 050.

On the other hand, P segregates at grain boundaries, weakens the binding force between grains and deteriorates toughness, so it must be limited to as low as possible, but if it is less than 0020, it will not be harmful.

Next, since S also deteriorates toughness like P, it is necessary to limit it to 0.020 or less.

Also, N is particularly harmful to toughness and is at least 0.0050%
The following restrictions must be met.

Furthermore, 0 forms ij:Ti oxide in the weld metal and AP
However, since the molten pool is sufficiently supplied by the molten slag, there is no need to add O to the wire, and if there is a large amount of O in the wire, the added components will cause arcing. It is necessary to limit the hardenability of the weld metal to at least 0.0150X or less. One of l-Mn, Ni, and Oul Mo to properly hold and generate a uniform fine nanostructure to improve low-temperature toughness.
More than seeds must be added.

First, Mn is necessary for deoxidizing and providing appropriate hardenability of the weld metal, promoting AP precipitation, and improving the toughness of the weld metal, and its appropriate range is 0.5 to 3. It is OX. 0.5%
If the amount is less than 3,09, the formation of AP will not be sufficient.If the amount is more than 3,09, upper bainite (hereinafter referred to as UB) will be formed and the toughness will deteriorate.

Next, Nl is a necessary component to impart appropriate hardenability to the weld metal, strengthen the ferrite base, increase the plastic deformability of the weld metal, and improve toughness, and its appropriate range is 0.
．． 5 to 12. If the amount is less than 0.05, the effect will be small, and if it is added in excess of 12, there will be a greater risk of high temperature side n in the weld metal.

In addition, Ou is a component suitable for maintaining double-hardenability and increasing toughness without promoting the formation of M umbrellas, and its appropriate range is 10.
．． 02-3.0X. Addition of less than 0.02 will have little effect, and addition of more than 3.0 will increase the risk of high temperature side n in the weld metal.

Furthermore, Mo is an effective component for maintaining the hardenability of bath-welded metal especially in high heat input welding, and its appropriate range is 01 to 0.
It's on the 20th. If it is less than 0.1, the effect is not sufficient; 2. If added in excess of ON, UB will be generated and the toughness will deteriorate.

Furthermore, if the hardenability of the weld metal is insufficient, PP will precipitate, and if it is too hard, UB will precipitate and the toughness will deteriorate. Hardenability is determined by CE, which is the carbon equivalent of IIW, and OF must be in the range of 0.2 to 1.0.

That is, when %OR is less than 0.2, the hardenability of the weld metal is insufficient and PF is generated, and when %OR exceeds 1.0, UB is generated and the toughness is deteriorated.

However, CE is the carbon equivalent of ITW, 0K=0+1/6Mn+1/15 (Cu+Nl)+
175 (Or+Mo+V) (However, the calculation is performed in weight%.) The most effective effect can be obtained by combining the 7 lux of the present invention wire 1JTi-B type, that is, the flux containing Ti oxide and B oxide. However, if it is to be combined with a flux that does not contain Ti oxide or B oxide, it is better to add one or both of Ti and H to the wire.

That is, in the Ti1i arc or molten pool, a part of it dissolves into the matrix due to the redox reaction, and the rest becomes an oxide, but this oxide becomes the nucleus for AF generation and increases the toughness, so it is added at least 0.05%. There is a need. However, if too much 7rT+ is dissolved in the matrix, the toughness will deteriorate, so the amount of T1 added must be less than 0.05%.

′! ! However, B also exists in the weld metal in the form of oxidation-reduction reactions in the arc and molten pool. Since it makes N harmless and improves toughness (add more than 1,005%), it should be noted that N is dissolved in the matrix and ffB also segregates at grain boundaries, suppressing the formation of PF and improving toughness. If the improvement becomes excessive,
Since it promotes the production of Me, the appropriate range must be less than 0.1.

Wire with the above component composition and flux containing Ti oxide and B oxide (does not necessarily need to be included in plantings where Ti or B is added to the wire)
By using together the following in O:007, 81:
01-03 X% Ae: 0 (102-0, 05 X,
P: 0.020X or less, S: 0.020% or less, N:
0.005X step down, 0:0.012~0045, month Mn: 0.5~2.5 K, Ni: 0.2~
6.5K, Ou: 0.02-1.2X, Mo:
Contains one or more of 0.03 to 0.7 N, and has a
It is now possible to obtain a weld metal with a component composition in which E is 02 to 06, and both the AW part and the reheated part of the weld metal exhibit excellent low-temperature toughness even in an impact test at -60°C.However, (lElj is determined using the ITW carbon equivalent formula, which is the same as the above formula.

Note that this wire can be manufactured by melting raw metal, casting, forging, rolling, drawing and plating to about 1.0 to 7.0 m-ψ.

Next, the effects of the present invention will be described in more detail with reference to Examples.

(Example) Table 1 shows the chemical components of the wires of the present invention and comparative examples.

Note that the wires other than W2 contain more than a trace amount of O because ordinary wires are plated with copper to improve rust prevention and conductivity. No copper plating was experimentally applied to W2. -! In addition, the wire diameter is 4.8 m'c.

Flux is NB-55E for single layer welding on both sides, NB-5
5L was used for double-sided multiple welding. These fluxes are commercially available Ti-B bond fluxes,
Further, Fl is a flux that does not contain Ti or B.

Table 2 shows the component composition of these 7 lacs.

Table 2 The test steel plates are shown in Table 3.

Both Pi and P2 are controlled rolled steel, and Pl is 50kg steel.
p2 is 60 kg steel.

Table 4 shows welding conditions.

Figure 1 shows the sampling locations of the test pieces. In the figure (j)
(b) shows the procedure for collecting test pieces from double-sided multilayer welds, 1 is an impact test piece of the AW part, 2 is an impact test piece of the reheated part, 3 is an impact test piece of the reheated part. A sample for chemical analysis is shown.

Table 5 shows the test results.

The products using the wire according to the present invention show good values for n, whereas the products using the WRI wire have a high value of 0 (At is not added, so the reheating section Since Me is generated in the weld metal, and the impact value of the part including the reheated part is WB2 wire, since At is not added, the oil in the weld metal increases, PP precipitates, and the toughness of the AW part decreases. The value has deteriorated.

#-tOB is too high when using WB2 wire
B is generated, and the toughness is deteriorated in both the AW part and the reheated part.

Furthermore, in the case of a large wire using WB2 wire, the AN was too high and the toughness of both the AW part and the reheated part deteriorated.

(Effects of the Invention) As is clear from the above examples, the present invention makes it possible to provide a welding wire that can impart extremely good f'Lk low-temperature toughness to welded metal, and the industrial effects are extremely significant. It is.

[Brief explanation of drawings]

FIG. 1(a) is a diagram illustrating the procedure for collecting test specimens from a double-sided single-layer welded portion (b) and a double-sided multilayer welded portion. 1... AW section impact test piece sampling position% 2... Reheating section test piece sampling position 3... Sample sampling position for chemical analysis. Agent: Patent attorney Masaaki Akizawa, Mitsugai (2 people)

Claims (2)

[Claims] (1) Essential components are C: 0.75 or less, Si: 0.2% or less, Al: 0.002 to 0.50% by weight, P: 0
．． 020% or less, S: 0.020% or less, N: 0.00
50% or less, O: limited to 0.0150% or less, and Mn: 0.5 to 3.0%, Ni: 0.5 to 12%,
Cu: 0.02-3.0%, Mo: 1 of 0.1-2%
1. A latent arc wire for low-temperature steel, characterized in that the balance is Fe and unavoidable impurities, and has a CE of 0.2 to 1.0. However, CE is the carbon equivalent of IIW, and CE=C+1/6Mn+1/15(Cu+Ni)+1/
5 (Cr+Mo+V) (However, calculation is performed in weight%.) (2) Essential components are 0:0.07% or less, Si: 0.2% or less, Al: 0.002 to 0.50% in weight%, P
: 0.020% or less, S: 0.020% or less, N: 0.
0.0050% or less, O: limited to 0.0150% or less, and Mn: 0.5-3.0%, Ni: 0.5-12%C
Contains one or more of u: 0.02 to 3.0%, Mo: 0.1 to 2%, and Ti: 0.05 to 0.5%, B:
Contains one or more of 0.005 to 0.1%, with the remainder being F.
e and unavoidable impurities, and CE is 0.2 to 1
．． A submerged arc wire for low-temperature steel, characterized in that the temperature is 0. However, CE is the carbon equivalent of IIW, and CE=C+1/6Mn+1/15(Cu+Ni)+1/
5 (Cr+Mo+V) (However, calculation is performed in weight%.)