JPS61232089A - Submerged arc welding method of cr-mo steel - Google Patents

Abstract

PURPOSE:To obtain a weld metal which has high strength and high toughness and decreases the embrittlement by tempering by combining a low-Si wire consisting of specific chemical components and a calcined flux contg. a large amt. of metallic carbonate and executing submerged arc welding of a Cr-Mo steel. CONSTITUTION:The wire is composed of 0.04-0.16wt% C, <=0.10% Si, 0.4-1.1% Mn, 2.0-3.8% Cr, 0.9-1.6% Mo and the balance Fe and inevitable impurities. The calcined flux is composed of 3.5-12% metallic carbonate in terms of CO2, 10-25% SiO2, 1.50-3.00 basicity determined by the formula, 0.05-0.50% C, 0.010-0.050 ratio of the content of C with respect to the content of the metallic carbonate in terms of CO2 and <=2.5% in total of >=1 kinds among 0.5-5.0% >=1 kinds of Ca and Mg, <=2.0% Si, <=2.0% Mn, <=1.0% Al, <=1.0% Ti. The submerged arc welding is made possible with the low diffusible hydrogen content and difficulty in the generation of a low-temp. crack by the above-mentioned combination of the wire and flux.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a submerged arc welding method for Cr-Mo steel, particularly 2-) Cr-I Mo steel (A387, Gr
22 steel) and 3Cr-IMo steel (A387.Gr21
When manufacturing welded structures of Cr-Mo steel such as steel, we ensure high strength and toughness while improving cracking resistance, which is a problem in welding work, and reduce the degree of tempering embrittlement during use. Cr-M yields small weld metal.

This invention relates to a method for submerged arc welding of steel.

(Prior Art) 2-) Cr-M such as Cr-I Mo steel and 3Cr-IMo steel.

Steel has traditionally been widely used in various medium- and high-temperature pressure vessels for the petrochemical industry and the atomic crab industry, but as these welded structures have recently become larger and the conditions of use have become more severe, Accordingly, from the viewpoint of safety, the performance level required of welded parts, especially weld metal, is becoming extremely high in order to prevent brittle fracture.

The weld metal of Cr--Mo steel as described above, when as welded, is extremely hardened because it contains a large amount of Cr+Mo, which has high hardenability, and exhibits extremely low toughness.

For this reason, post-weld heat treatment (hereinafter referred to as SR treatment) is performed after welding in the manufacturing stage of a structure to remove stress during welding and to improve softening and toughness.

However, when the structure becomes larger and extra-thick materials are used, the number of welded joints increases, or there are restrictions on the hardness of welded parts, the SR treatment time becomes longer.
Tempering parameters T P (TP
=TX (20+logt)XIO-3, T; heating temperature (°K), t; holding time (hr)) increases,
A phenomenon occurs in which toughness also decreases as strength decreases,
It becomes difficult to ensure high toughness of the weld metal before the structure is used.

Furthermore, what is important about the performance required of Cr-Mo steel weld metals is that these structures are used in the temperature range where temper embrittlement occurs (375° to 575°C). In order to prevent brittle fracture after long-term use or during use, it is necessary to reduce the degree of tempering embrittlement during use as much as possible. In particular, 2-4-Cr-I
Mo steel and 3Cr-IM.

In the case of steel weld metals, the degree of temper embrittlement is greater than that of other Cr-Mo steel weld metals, and therefore regulations regarding temper embrittlement during use have become considerably stricter.

Note that when examining the degree of temper embrittlement during use, accelerated embrittlement treatment (hereinafter referred to as SC treatment) is usually employed. Various studies have been conducted to improve the performance of these weld metals, and in order to increase the toughness after SR treatment and reduce the degree of temper embrittlement caused by SC treatment,
In addition to reducing the amount of oxygen and impurity elements such as P and Sb+Sn+As in the weld metal, recent research has revealed the effect of reducing the amount of Si as much as possible.

There have been various proposals for the development of welding materials and welding methods for obtaining weld metals with such compositional designs, such as ``Submerged arc welding method for high-temperature chromium-molybdenum steel'' published in Japanese Patent Application Laid-Open No. 57-85693. In particular, S
By welding a wire with a low i content (0.10% or less) in combination with a specific highly basic flux, the weld metal has a Si content of 0.10% or less, a P content of 0.012% or less, and an oxygen content of 0.10% or less. It is proposed to improve the low-temperature toughness and temper embrittlement resistance of weld metal by reducing the amount to 0.040% or less.

On the other hand, in addition to the above-mentioned demands for the performance of weld metals, there are also strong demands from the viewpoint of welding work to lower the preheating temperature and to omit the dehydrogenation intermediate annealing treatment for the purpose of reducing manufacturing costs. This includes 2-4-Cr-I Mo steel and 3C
Welding metal of Cr-Mo steel such as r-IMo steel is difficult to weld due to its hardenability! Because it has extremely high strength, it is prone to cold cracking, so in order to prevent cold cracking, a high preheating temperature is required, and an intermediate annealing treatment for dehydrogenation is required in the manufacturing process. Depends on being there.

In this case, rather than using a highly basic molten flux that contains a large amount of hydrogen during melt production and has a large adverse effect due to moisture absorption during use, various metal carbonates such as CaCO3゜Mg CO can be used as a composition. The use of highly basic sintered fluxes that can contain CO
The gas is extremely advantageous because it can lower the water vapor partial pressure in the arc atmosphere and significantly reduce the amount of diffusible hydrogen in the weld metal.

However, when a large amount of metal carbonate is included to prevent cold cracking, pock marks, which are surface defects on the bead that affect welding workability, occur frequently, and the composition is based on highly basic components. However, the amount of oxygen in the weld metal increases significantly, resulting in a decrease in toughness. This means that the C0. This is because the gas acts as an oxidizing gas at high temperatures, and in order to prevent the adverse effects of the oxidizing properties of the 002 gas, various types of deoxidizing agents are added to the calcined flux containing this type of metal carbonate. It is necessary to add a deoxidizing element.

In conventional sintered fluxes, Si has been mainly added (and Mn+AltTi, etc.).

However, the sintered flux containing a large amount of metal carbonate was used, especially for the purpose of lowering the St of weld metal, in the above-mentioned Japanese Patent Laid-Open No. 57
As a problem when welding is performed in combination with a wire with a low Si content as disclosed in Japanese Patent No. 85693,
In order to suppress the occurrence of pock marks and the increase in the amount of oxygen in the weld metal, it is necessary to add a large amount of deoxidizing elements such as Si or Mn + AIT Ti. Although it is effective in preventing oxygen and reducing the amount of oxygen in the weld metal, it also increases the yield in the weld metal.

2 +cr -IMOf! Cr-M such as 4 and 3Cr-IMo steel.

In steel weld metal, Si or Mn+A+T
An increase in the amount of t beyond an appropriate amount reduces the toughness of the SR treatment and increases the degree of temper embrittlement caused by the SC treatment. In addition, when welding is performed using a fired type 7-six containing a large amount of metal carbonate in combination with a low-Si wire, the amount of C in the weld metal increases due to the oxidizing property of COt gas, which is similar to that of a highly basic molten type flux. There was a problem that the toughness was lower than that when used, and the toughness after SR tended to decrease due to insufficient hardenability, and the high-temperature strength tended to decrease.

(Problems to be Solved by the Invention) The present invention provides 2-) metal carbonates that are advantageous in preventing cold cracking when producing welded structures of Cr-Mo steel such as Cr-I Mo steel and 3Cr-IMo steel. Even if a sintered flux containing a large amount of The purpose is to provide a submerged arc welding method.

(Means for solving the problems) The gist of the present invention is (1) C0.04 to 0.16% by weight.
%, Si 0.10% or less, Mn 0.4-1.1%, C
The wire contains 2.0 to 3.8% of r, 0.9 to 1.6% of Mo, and the remainder is Fe and unavoidable impurities, metal carbonate of 3.5 to 12% in terms of CO2 amount, and SiO2.
10 to 25%, and has a basicity B represented by the following formula (1) of 1.50 to 3.00, and further has a basicity of 00.
05-0.50% and metallic carbon 0.010=0.050
, a total of 0.5 of one or two of Ca or Mg
~5.0%, S52.0% or less, Mn2.
Firing mold 7 containing one or more of the following: 0% or less, AJl, 0% or less, Ti 1.0% or less, in total 2.5% or less
C characterized by combining latches and welding
r-Mo steel submerged arc welding method, and (2
) In weight%, C0.04-0.16%, Si0.10%
Below, Mn 0.4-1.1%, Cr 2.0-3.8
%, Mo 0.9-1.6%, and V 0.0
1~0.10 jg, Nb0.01~0.06%, Bo
, 001 to 0.015%, the remainder being Fe and unavoidable impurities, metal carbonate in an amount of 3.5 to 12% in terms of C02, and SiO210.
~25%, and the basicity B expressed by the following formula (11) is 1.50 to 3.00, and further co, os
~0.50%, and contains a total of 0.5 to 5.0% of one or two types of ratio of C amount to CO□ amount conversion value of metal carbonate, and Si2.0% or less, Mr+2. 0% or less,
All, 0% or less, Ti 1.0% or less, or 2
Cr-Mo characterized in that welding is performed by combining a sintered flux containing 2.5% or less of Cr-Mo in total.
In the method of submerged arc welding of steel.

The present inventors prototyped wires with various component systems and fluxes with various compositions, and conducted detailed studies on combinations of these wires and flan/x. As a result, 2+
Cr-1Mo steel and 3Cr-IM.

In order to improve the toughness of weld metal of Cr-No steel such as steel after SR treatment and to reduce the degree of temper embrittlement during use due to SC treatment, it is necessary to lower oxygen (0,035% or less) and lower St ( Q, 10% or less) is essential, and first of all, it is necessary to reduce the amount of Si in the wire as much as possible.

Furthermore, when welding is performed using such a low St wire (Si 0.10% or less) in combination with a sintered flux containing a large amount of metal carbonate to prevent cold cracking, a problem arises. In order to suppress the occurrence of pockmarks and increase in oxygen content, Ca or Mg (
It is necessary to suppress the amount of Si+Mnt, Al, and Ti, which can cause slag seizure and deteriorate the performance of the weld metal if they are added at the same time and remain in the weld metal in excess of an appropriate amount.

Furthermore, it has been found that adding V, Nb and B in a limited range to the wire is effective in increasing high temperature strength and further increasing toughness, and the above Cr-M.

The above-mentioned problems have been solved by developing a method for welding steel.

(effect) Hereinafter, the present invention will be explained in detail along with its operation.

The present invention is realized by using a wire having the specified chemical composition in combination with a sintered flux having a specified composition. First, the reason for limiting the range of the chemical composition of the wire will be described.

C must be in the range 0.04-0.16%.

If it is less than 0.04%, strength will be insufficient, hardenability will decrease, and high toughness after SR treatment will not be obtained. On the other hand, 0.16
%, high temperature cracking is likely to occur.

Si is added to the weld metal in order to ensure high toughness after SR treatment and to reduce the degree of temper embrittlement during use. It is preferable to reduce the content to 10% or less, and therefore the chemical components of the wire need to be as low as possible, and are limited to 0.10% or less.

Mn must be between 0.4 and 1.1%. 0.4%
If it is less than this, the weld metal will lack strength, the oxygen content will increase, and the toughness after SR treatment will decrease. However, when the amount exceeds 1.1%, the degree of temper embrittlement due to SC treatment increases and hot cracking becomes more likely to occur, as in the case where St increases.

The present invention mainly focuses on 2+Cr-i MO steel and 3Cr-
I.M.

Since the target is steel, it is necessary to contain Cr and Mo, which correspond to the base metal, in the weld metal in order to ensure oxidation resistance and creep resistance. Cr of wire is 2.6
% or less than 0.9%, the effect of improving the strength of the weld metal becomes weak. However, Cr is more than 3.8% and Mo is 1%.
．． If it exceeds 6%, hardenability increases, causing weld cracking and S
The toughness decreases after the R treatment and the degree of temper embrittlement due to the SC treatment increases.

Cr St+ Mnt Cr+ in the above limited range
When attempting to obtain a weld metal with higher strength or toughness than the resulting weld metal by using a wire containing Mo, it is effective to include V, Nb or B in the weld metal. It is. In this case, adding V, Nb or B to the flux requires consideration of fluctuations in the yield of these elements due to welding conditions, etc. 5 On the other hand, adding V, Nb or B to the flux requires consideration of variations in the yield of these elements due to welding conditions, etc. 5 On the other hand, adding V, Nb or B as a component of the wire This makes it possible to stably add a predetermined amount to

■ and Nb are elements that increase the high-temperature strength without significantly reducing the toughness of the weld metal when added in appropriate amounts.
Nb can be contained in a range of 70.01 to 0.010% and Nb 0.01 to 0.06%. However, ■ is (1, 10
If the Nb content exceeds 0.06%, the high-temperature strength increases, but the toughness after SR treatment decreases significantly.

By containing B in the range of 0001 to 0.015%, the toughness after SR treatment can be further improved. If B is less than 0.001%, the effect is small;
If it exceeds 15%, hot cracking tends to occur.

In addition to the limited chemical components mentioned above, unavoidable impurities such as P and S that are inevitably contained during wire melting and manufacturing are elements that promote tempering embrittlement, and should be kept as low as possible (P
≦0.015%, S60.010%). Similarly, regarding Al and nitrogen mixed during wire melting manufacturing, Al should be 10.05% or less and nitrogen should be 0.0%.
If it is less than 15%, it is acceptable, and the wire surface has good rust prevention and electrical conductivity.
Plating also does not impair the effects of the present invention.

Next, the reasons for limiting the components of the sintered flux used in combination with the wire having the chemical components defined above will be described.

In order to reduce the amount of diffusible hydrogen in the weld metal and prevent the occurrence of cold cracking, CaCO3+ MgC0, +BaC
Metal carbonates such as O3 are converted to CO2 amount (CO.

The content must be 3.5% or more (same as the amount of gas generated). In this case, the amount of diffusible hydrogen determined by WES1003 (gas chromadrographic method) is that even after being left in a flux atmosphere for about 4 hours, the weld metal 100
．． It shows a value of 4 to 5 cc or less per g, and the preheating temperature is 20
The temperature can be lowered to about 50°C below 0°C, and it is also possible to omit the dehydrogenation intermediate annealing treatment after welding.

However, the content of metal carbonates is 12% in terms of CO2 amount.
If it exceeds the amount, the amount of CO2 gas generated will be excessive, and in narrow gap welding of extremely thick materials, arc instability, slag blow-up,
Welding workability becomes poor due to poor bead shape and slag entrainment.

When SiO2 is contained in a large amount exceeding 25%, the amount of Si in the weld metal increases due to the reduction reaction between slag and metal in the molten pool, which increases the degree of embrittlement especially after SC treatment. . Furthermore, as a result of lowering the basicity of 72x, the amount of oxygen in the weld metal increases, making it impossible to obtain high toughness even after SR treatment.

Furthermore, if 5in2 is less than 10%, the slag will lack viscosity, and if it exceeds 25%, the slag viscosity will become too large, resulting in poor welding workability such as poor bead shape and poor slag removability.

Basicity B expressed by the following formula (1) is 1.50 to 3.00%
Must. If the basicity B is less than 1.50, the oxygen content level of the weld metal becomes high, and high toughness after SR treatment cannot be obtained. However, when the basicity B exceeds 3.00, welding workability becomes poor, such as arc instability, poor bead shape (convex bead), and occurrence of slag entrainment.

In Equation (1), CaO and MgO are calculated based on the converted oxide amount of CaCO5 and MgCO3 contained as metal carbonates (CaCO5% x 0.56, MgC
05X0.48), and for SiO2, the amount includes the amount of SiO2 in water glass (silicate) when added for granulation of flux.

C is required to be in the range of 0.05% or more and 0.50% or less, and the amount of C is commensurate with the content of the specific acid salt relative to the CO2 equivalent value of the metal carbonate content. It suppresses the increase in the amount of oxygen in the weld metal and also suppresses the occurrence of pock marks. Furthermore, limiting the amount of C added by the amount of CO2 gas generated effectively supplies C into the weld metal, improves hardenability, and prevents a decrease in toughness and strength after SR treatment.

o, oio ungrooved, the effect of C addition is not clear,
The amount of oxygen in the weld metal increases, and the amount of C is also lower than when a highly basic molten flux is used, leading to insufficient hardenability and a decrease in toughness and strength after SR treatment. However, if the addition of C exceeds 0.050,
The increase in the amount of C in the weld metal increases, making hot cracking more likely to occur. In addition, the form of C added is Fe in addition to C powder.
- It may be C1 or carbide contained in metal powder such as Mn, and is not particularly limited.

The total of one or two types of Ca or Mg is %0.5~
Must be added within a range of 5.0%. Ca and Mg do not cause slag burning on the bead surface, unlike when a large amount of deoxidizing elements such as S 11 Mn + All + Ts are added, and they remain in the weld metal and improve the performance of the weld metal. without any negative impact,
Suppresses the increase in the amount of oxygen in weld metal and the occurrence of pock marks. However, when the amount of Ca or Mg added is less than 0.5% in total of one or both of Ca or Mg, it is effective in reducing the amount of oxygen in the weld metal and preventing the occurrence of pock marks. do not. On the other hand, Ca or Mg
If the total of one or two of these exceeds 5.0%, welding operations will be defective (arc instability, bead waveform disturbance, meandering bead, slag entrainment).

Furthermore, the above C and Ca or Mg (or Ca +
The combined addition of Mg (both Mg and Mg) makes it possible to reduce the oxygen content of the weld metal to the same or the same amount as when using a highly basic molten flux, even when using a fired flux containing a large amount of metal carbonate. This makes it possible to easily reduce it to the following. This remarkable effect of reducing the amount of oxygen in the weld metal due to the simultaneous addition of Cr/Ca or Mg is due to the excessive oxidation of the droplet surface during the transition stage from the wire tip to the droplet falling into the molten pool in the arc atmosphere. This is thought to be due to the synergistic effect of preventing the deoxidation of the molten pool and promoting sufficient deoxidation reaction at the deoxidation reaction stage of the molten pool.

In other words, when using a firing type 7-six containing a large amount of metal carbonate, the droplets melted and detached from the wire tip are
Due to the oxidizing nature of CO□ gas generated by the decomposition reaction of metal carbonates during transfer in the arc atmosphere, the surface of the droplet is excessively oxidized, resulting in a significant enrichment of oxygen in the molten metal, resulting in welding. The amount of oxygen in the metal increases significantly.

On the other hand, C in the flux falls into the molten metal and performs a deoxidation reaction in the molten pool, and the CO gas generated at this time lowers the oxygen partial pressure in the arc atmosphere.
Suppresses oxidation of the droplet surface.

On the other hand, since Ca and Mg also have a low boiling point and a high vapor pressure at their melting point, they lower the oxygen partial pressure in the arc atmosphere and, like C, work to suppress oxidation of the droplet surface. In addition, in the deoxidation reaction stage of the molten pool, C can carry out a sufficient deoxidation reaction in the high temperature range during the process of solidification of the molten metal, and at the same time Ca +
In the case of a fired flux in which Mg is also granulated, the portion contained within each particle falls into the molten pool and performs a deoxidizing reaction.

Furthermore, Ca and Mg are elements that have an extremely high affinity for oxygen, and can contribute to the deoxidation reaction in the molten pool even in the low temperature range just before the molten metal solidifies. Furthermore, the generation of CO gas due to the reaction of C in the molten metal and the reaction (including vaporization) of Ca and Mg result in intense boiling and agitation of the molten pool. It promotes the deoxidation reaction of Si + Mn + A7 + Ti etc. when added in small amounts as well as the levitation of various oxides and CO gas produced.
Enables significant oxygen reduction in weld metal.

Si2.0% or less, Mn2.0% or less, AA'1.0%
Hereinafter, one type of Ti of 1.0% or less, or a total of 2.5% or less of two or more types, can be added in the form of metal powder or alloy powder. These elements reduce the amount of oxygen in the weld metal and suppress the occurrence of pock marks, but if they are added in large amounts exceeding the above limited range, Si + M in the weld metal
The amount of n+ AA+ Ti increases, and the toughness decreases after the SR treatment and the degree of temper embrittlement due to the SC treatment increases.

In addition to the above-mentioned limited components, Zr is effective in reducing the amount of oxygen in the weld metal when added in an amount of 1.0% or less.
If it exceeds %, roughness becomes noticeable on the bead surface and slag burning occurs. In addition, B can be added as long as it is a small amount of 0.08% or less in terms of B2O3i,
In that case, it is effective in improving the toughness after SR treatment.

(Example) Example 1 2- of the chemical components shown in Table 1 and the plate thickness t = 80 mm.
) Cr-I Mo steel (Bl) and 3Cr-IMo steel (B2) in the shape shown in FIG.
50 mm.

R1 = 6111111 R1α = 4° U-groove groove, and wires with chemical components shown in Table 2 (W1 to W20 each 4.
0iiφ) and the sintered flux (
As shown in FIG. 1 (bl), a narrow gap multi-layer welding test of one layer and one bus welding was conducted using the combinations of F1 to F24).

Welding conditions are 500-550 Amp-26-28 Vo
A! -30~35c1n/1nin (AC power supply)
, preheating temperature 50-75℃, interpass temperature 150-250℃
It is. Note that post-heat treatment for the purpose of dehydrogenation after welding was omitted.

First, arc stability, bead shape, appearance, and welding workability such as the presence or absence of slag entrainment and cracking were investigated by observation during welding and by an X-ray transmission test conducted 96 hours or more after the completion of welding.

Next, for the weld metal that has been subjected to SR treatment at 690°C for 15 hours (furnace cooling), a notch B is made in the center of the weld metal, centering on the position of t2 = 20 mm in the plate thickness direction, as shown in Fig. 1 (C). JISJ No. 2 m's V notch Charpy impact test piece A and 6mmφ high temperature tensile test piece C1 with the same tensile test piece, analysis sample from the same position, SR
After the treatment, the weld metals were further subjected to the SC treatment of the thermal cycle shown in FIG. 2, and impact test pieces were taken in the same manner as after the SR treatment described above and each was subjected to the test. These results are shown in Table 4 (welding workability, mechanical performance of weld metal) and Table 5.
Shown in the table (chemical composition of weld metal).

Tests/161-10 and A30-36 are examples of the present invention, and both have good welding workability, high strength and toughness after SR treatment, and high performance welding with a small degree of temper embrittlement due to SC treatment. metal is obtained. On the other hand,
, %11-29 and %37-43 are comparative examples.

/1611 is because the wire (W12) contains too much 81, and /1612 is because the wire (W13) contains a large amount of Ti.
The amount of i increased, and especially the toughness after SCM processing significantly decreased. In No. 413, the wire (W14) had too little C+MnJi, so pock marks were observed, and as the strength decreased, the amount of oxygen in the weld metal increased, and the toughness after the SR treatment decreased.

In A14, hot cracking occurred because the amount of C in the wire (W15) was too large. A15 is wire (W16) Si, M
Because the amount of n was too large, the amount of SfrMn in the weld metal increased and the toughness after SC treatment decreased. In A16, low temperature cracking occurred because the content of metal carbonate in the flux (Fll) was too low. Since A17 contained too much metal carbonate of 7 lux (F12), the arc became unstable and the welding workability was extremely poor, such as slag blow-up, poor bead shape, and slag entrainment.

/VL18 has a large amount of SiO2 in the flux (F13) and has too low basicity, so the amount of oxygen in the weld metal increases,
The toughness after SR treatment was significantly reduced. In rot No. 19, the amount of SiO2 in the flux (F14) was large, and the amount of Si in the weld metal increased, resulting in a large decrease in toughness after SC. In addition, A
618 and A19 had poor slag removability because the flux contained too much SiO2f.

/1620 had too high a basicity of 7 lux (Pls), resulting in poor bead shape and slag entrainment. /1621 has too much Fe-8i added (Si amount) in the flux (F16), which causes slag seizure and increases the amount of Si in the weld metal, resulting in low toughness both after SR treatment and SC treatment. Ta. A22 is flux (Fz7
) Pockmarks occurred frequently because the amount of deoxidizing agent added was too small relative to the metal carbonate content.

In /1623, since the amount of C added to the flux (F'18) was too small, the amount of C in the weld metal decreased and the amount of oxygen increased, resulting in a decrease in strength and toughness after SR treatment. A
In No. 24, hot cracking occurred because the amount of C added to the flux (F19) was too large. A25 is flux (F20)
Slag seizure occurred because the amount of Ti added was too large, and the total amount of Si and Ti added was too large, and the amount of Ti in the weld metal increased, resulting in a significant decrease in toughness after SC treatment. .

In A26, the amount of Mg added to the flux (F21) was too large, resulting in poor bead shape and slag entrainment. A27 is because the amount of Mn added to flux (F22) is too large, and /1628 is the AI of flux (F23)!
Since the amount added was too large, the amount of Mn or Al in the weld metal increased, and the toughness after SR treatment decreased. Wash 2
9, slag burning occurred because the total amount of SirMn, Al, and Ti added to the flux (F24) was too large.
Furthermore, the toughness after the SR treatment and the SC treatment decreased.

A37 has too much V in the wire (Wl7), so
38 has too much Nb in the wire (Wl8), so /
In 1639, since the amount of V and Nb in the wire (Wl 9 ) was too large, the toughness after the SR treatment and the SC treatment decreased, respectively. In the case of Ma40, cracks occurred because the amount of B in the wire (W2-0) was too large. A41 is flux (
Fl3) has a large amount of SiO□ and has too low basicity, resulting in poor slag removability, and an increased amount of oxygen in the weld metal, resulting in a significant decrease in toughness after SR treatment.O scrap 42 is flux (Fl6) Because the amount of St added was too large, slag seizure occurred, and the amount of St in the weld metal increased, resulting in low toughness both after the SR treatment and the SC treatment. A43 is flux (F24) S i + Mn r
Because the total amount of Alr Ti added was too large, slag seizure occurred and the toughness after the SR treatment and the SC treatment decreased.

Example 2 Sintered flux (Fl.

F7. F9. The film was re-dried at 350°C for 1 hr, and immediately after that and in the atmosphere (temperature 24-25°C).
, humidity 64-68%) for 4 hr, WES100
3 (gas chromatography method), the amount of diffusible hydrogen in the weld metal was measured. Table 6 shows the results.

Test/161-3 is metal carbonate in CO2 equivalent value, 3
．． Flux containing 5% or more (Fl, F7. F9
), the amount of diffusible hydrogen was 100% in the deposited metal even after being left in the atmosphere for 4 hours. On the other hand, /i64 had a low metal carbonate content in the flux (Fil) and showed a significantly higher value than when the above flux was used. In addition, in the remarks column of Table 6, the presence or absence of low-temperature cracking in the narrow gap multi-layer welding test conducted in Example 1 is also written.

Table 1 Chemical composition of steel sheet (weight%) Note 1) Formula (1): Basicity B Note 2) Type of deoxidizer: Fe-8i (40%Si
0.3% C).

Si powder, Fe-Mn (75%Mn5%C), Fe-
Al (51A11), Al powder, Fe-Ti (70 Ti
).

Ti powder, C powder, Ca-8i (60%Ca 40%S
i).

Ca Mg' (80% Ca 20% Mg) + Mg powder.

Note 3) Remainder: 20. Na20. L1□03 and unavoidable impurities 1 He... He 1
Flux symbol * mark: Applicable flux No mark: Comparative flux Note 2) The amount of diffusible hydrogen is the average value of each three pieces. 3) Judgment O mark: Pass, × mark: Reject (effect of the invention) The present invention is Cr-Mo Steel, especially 2-) Cr I M
When manufacturing various welded structures such as O steel and 3Cr IMo steel by submerged arc welding, the amount of diffusible hydrogen in the weld metal is low and the low-temperature cracking strength is low. To occur (<
It is possible to lower the preheating temperature and omit the dehydrogenation intermediate annealing treatment, and it also ensures high strength and toughness with good welding workability, and the degree of tempering embrittlement during use is small. This is a submerged arc welding method for CrMo steel that makes it possible to obtain weld metal, and has extremely high industrial effects.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the sampling position of the impact test piece and the tensile test piece and the notch position of the impact test piece in Example 1 (al is the groove shape, (b) is the layered method, (C) is the sampling position of the impact test piece and the tensile test piece, Figure 2 is a schematic diagram of the thermal cycle of accelerated embrittlement treatment. Calligraphy (spontaneous) May 10, 1985

Claims (1)

[Claims] 1. In weight%, C0.04-0.16%, Si0.10
% or less, Mn0.4-1.1%, Cr2.0-3.8%
, Mo0.9 to 1.6%, the balance being Fe and unavoidable impurities, a metal carbonate of 3.5 to 12% in terms of CO_2 amount, SiO_210 to 25%, and the following: Basicity B expressed by the formula is 1.50 to 3
．． 00, and furthermore, C is 0.05 to 0.50%, and the ratio of C amount to the CO_2 amount conversion value of metal carbonate content (C%/CO_2%) is 0.010 to 0.050 Ca.
Or a total of 0.5 to 5.0% of one or two types of Mg
and containing 2.0% or less of Si, 2.0% or less of Mn,
Al 1.0% or less, Ti 1.0% or less, or 2
Cr-Mo characterized in that welding is performed by combining a sintered flux containing 2.5% or less of Cr-Mo in total.
Submerged arc welding method for steel. Basicity B=(CaO%+MgO%+CaF_2%)/(
SiO_2% + 0.5Al_2O_3%) (weight%) 2. In weight%, C0.04-0.16%, Si0.10
% or less, Mn0.4-1.1%, Cr2.0-3.8%
, contains Mo0.9 to 1.6%, and further contains V0.01 to
0.10%, Nb0.01-0.06%, B0.001
~0.015%, and the remainder is Fe.
and unavoidable impurities, and metal carbonate.
3.5-12% in O_2 amount conversion value, SiO_210-2
5%, and the basicity B expressed by the following formula is 1.
50 to 3.00, and further C0.05 to 0.50
% and the ratio of C amount to CO_2 amount conversion value of metal carbonate (C%/CO_2%) is 0.010 to 0.050, C
Total of one or two of a or Mg 0.5 to 5.0
%, and one or two of Si 2.0% or less, Mn 2.0% or less, Al 1.0% or less, Ti 1.0% or less
Cr-Mo, characterized in that welding is performed in combination with sintered flux containing 2.5% or less of Cr-Mo in total.
Submerged arc welding method for steel. Basicity B=(CaO%+MgO%+CaF_2%)/(
SiO_2% + 0.5Al_2O_3%) (weight%)