JPS63220993A - Submerged arc welding method for 9cr-1mo steel - Google Patents

Abstract

PURPOSE:To improve the cracking resistance of weld metal and the bead quality by combining a wire containing specific weight % Mn, Cr, Si, etc., with welding flux containing prescribed % CaF2, Al, SiO2, etc., to perform the welding. CONSTITUTION:The component composition of the wire is made to, by weight ratio, 0.01-0.15% C, 0.4-2.5% Mn, 8.0-11.0% Cr, 0.5-1.2% Mo, 0.05-1.3% Ni, 0.03-0.30% V, 0.02-0.12% Nb, 0.005-1.5% Al, 0.004-0.100% N, <=0.05% Si and <=0.01% O. The component composition of the flux is made to 25-70% CaF2, 8-30% CaO or MgO, 2-35% Al2O3 or ZrO2, 0.5-7% Al and <=5% SiO2 which are combined with the wire to perform the welding. Since the intercrystalline cracking is prevented, the cracking resistance of a welded zone and the bead quality are improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an improvement in a submerged arc welding method used for welding 9Cr-1Mo steel used in boilers, etc. of thermal power generation and nuclear power generation. This invention relates to a sapmano 7-ri welding method that produces a weld metal with excellent crack resistance, toughness, hot strength properties, and bead shape by combining the component wires, 7-hupkus.

(Conventional technology) In recent years, with the increase in the size of thermal power plants, POI2-
It has come to be used under pressure.

Conventionally, in the submerged arc welding method for 9Cr-Mo steel, alloy welding materials have been selected depending on the steel type from the viewpoints of high temperature strength, oxidation resistance, and toughness; for example, 9Cr-I
A combination of Mo, 9Cr-IMoNb-V or 9Cr-2MoNl+-V steel wire and molten or sinter-formed 7 lux is used.

For example, in Japanese Patent Application Laid-open No. 59-82189, a specific amount of C.
,Si,Mn,C",Mo,Ni
, BtO*, etc., for submerged arc welding, and JP-A-59-274113 discloses specific amounts of C1Si, Mn, Cr, Mo, and Ni.

Wires containing Nb, V and Sin, Ca F 2, Ca
b.

JP-A-60-2'31591 discloses a flux for submerged arc welding consisting of AI, 0, , M, O, etc., and a wire containing specific amounts of C, Mo1N1Ni, REM, CaCOs, CaF 2.CaO, MgO
Submerged 7- consisting of -5iO□, A 1.0, etc.
A submerged arc welding method is shown in 1111, which is performed in combination with an upx for welding. Also, JP-A-01
-1497 publication Niha specific i'ri, REM.

A submerged arc welding method is disclosed in which the amount of 0SN1Si%Mn in the weld metal is specified using a welding material containing C, Cr, Mo, and Nb.

However, although the above welding materials and welding methods have been variously studied from the viewpoint of basic properties such as high temperature strength, oxidation resistance, and toughness, or from the viewpoint of sub-crackability, grain This method has not been sufficiently studied from the viewpoint of preventing minute cracks occurring in the field, and is not satisfactory. A weld metal with a single martensitic structure is produced, but in this case S added as a deoxidizer to the wire or flux
i, or Si reduced from the slag agent SiO2 tends to concentrate and form a low melting point eutectic with sMo and Ni, and oxygen in the weld metal precipitates as oxides such as Mob, NiO, or 5iOz. However, this often causes cracks, and to prevent such cracks, Si
The amount of harmful components such as n and Si added to the wire or 7 lux is limited as much as possible. Further, the 0 that forms the above-mentioned oxides is also harmful, and reducing these is extremely important to prevent cracking, but from this point of view, none of the conventional welding materials are satisfactory.

(Problems to be Solved by the Invention) The present invention completely prevents welding cracks that occur at the grain boundaries of martensite + 7-carrite mixed structure or martensite single structure weld metal using 9Cr-1Mo steel wire. The object of the present invention is to provide a submerged arc welding method for 9Cr-1Mo steel that can obtain excellent high-temperature strength and toughness.

(Means for solving the problems) The gist of the present invention is that C: 0.01-0.15
wt%, Mn: 0.4-2.5 wt%, Cr: 8.0
-11.0wt%, Mo: 0.5-1.2wt%, N
+: 0.05 to 1.3 wt%, V: 0.03 to 0.
30wt%, Nb:0.02-0.12wt%, A
I: 0.005-1.5wt%, N: 0.004-0
．． 100wt%, Ca Si: 0.051% or less, O: O, O1wk% or less
F2: 25-70 wt%, CaO% MgO or 2 a: 8-30 wt%, AlzOs, ZrO2
Seed or 2Jffl: 2-35wt%, AI: 0.5
A submerged arc welding method for 9Cr-1Mo steel characterized by containing ~7 wt% and SiO□: limited to 5 wt% or less in combination with welding 7 fixes that do not substantially contain Si. be.

(Action) C, Mn%Cr, Mo%Ni, V, Nb and (/N is 9
It is an essential component in order to have the basic properties of high temperature strength and toughness as a wire for Cr-IMOlQ, and it also contains Si,
Al and O are extremely important requirements for preventing intergranular cracking, which is the objective of the present invention.

First, the components added to the wire will be sequentially explained below.

C: O, old to 0.15 wt% C is necessary from the viewpoint of maintaining strength, but the upper limit was set to 0.15 wt% from the viewpoint of cracking resistance. That is, in the weld metal of SCrlMo steel, C has high hardenability and hardens the welded part, causing cold cracking. Therefore, in order to completely perform welding, preheating to a considerably high temperature is required, which seriously reduces welding efficiency. If the C amount is less than 0.01wt%, it will be difficult to ensure strength, so the lower limit is set to 0.0.
It was set to 1 wt%.

Mn: 0.4-2.5wt% Mn is an essential component not only for deoxidizing but also for maintaining strength. If it is less than 0.4 wt%, no deoxidizing effect can be expected, so the lower limit was set at 0.4 wt%. Also, the upper limit is 2.5wt%
The reason for this is that if it exceeds this, the toughness will decrease.

Cr:8. Q~11. Owt% Cr is a basic component of 9Cr 1Mow4 and is an element that imparts oxidation resistance, but in addition, in the present invention, M23CI,
Since it precipitates finely as a groove forming element of M a C and further improves the wet strength properties, the lower limit is set at 8.0 t%, which is the precipitation limit of M23Cs, and if it exceeds 11%, a ferrite phase is formed in the weld metal. The upper limit is 1 because the toughness and strength decrease.
It was set at 1%.

MO: 0.5 to 1.2 wt% Mo is an element that significantly increases high-temperature strength through solid solution strengthening, but if it is less than 0.5 wt%, no effect can be expected, so the lower limit was set to 0.5 wt%. If it exceeds 1.2 wt%, a coarse ferrite phase will occur and the toughness will deteriorate, so the upper limit was set at 1.2 wt%.

Ni: 0.05 to 1.3 wt% Ni is an element effective in reducing embrittlement during use, and +l'l
It is an essential element for welding materials that are used at high temperatures and pressures for long periods of time. If the content is less than 0.05 wt%, the effect cannot be obtained, and if it exceeds 1.3 wt%, the high temperature strength and crackability deteriorate, so the upper limit was set at 1.3 wt%.

V: 0.03-0.30wt% ■ is an element that significantly increases high-temperature strength, and V + C3
In addition to precipitating as M23C, some of M and C also enter
It is effective in suppressing the coarsening of crystal grains, but if it is less than 0.03 wt%, this effect cannot be obtained, and if it exceeds 0.30 wt%, the strength will decrease, so the upper limit should be set at 0.30 wt%.
%.

Nb: 0.02-0.12wt% Nb increases high-temperature strength through the precipitation of NbC, and the subsequent fine precipitates, M x j C! , M a C, etc., so it is effective in improving creep rupture strength at high temperatures for long periods of time.

However, if it is less than 0.02wt%, it has no effect, and if it is less than 0.02wt%, it has no effect.
If it exceeds 12 wt%, the precipitates will coagulate and become coarser, reducing the strength, so the lower limit is 0.02 wt% and the upper limit is 0.1.
It was set to 2wt%.

A1:Q, 005-1.5wt% A1 is an element that exhibits an excellent deoxidizing effect, significantly reduces oxygen in the weld metal, and is extremely effective in preventing intergranular cracking. If it is less than 0.005 wt%, the effect cannot be obtained, and 1
．． If it exceeds 5wt%, the hot forgeability will deteriorate and the wire's! i1! Therefore, the A1 content in the wire must be 0.005 to 0.15 wt%.

Si: o, 05 wt% or less In order to reduce the Si in the weld metal to 0.70 wt% or less, it is essential to reduce the Si content in the wire to 0.051% or less. Ill, Si in the weld metal is 7
It also migrates from Si and 5iOz in the lattice.

In the present invention, as described later, Si is contained in the 72x.
is not added to a large extent, and S i O2 is limited to 5 wt% or less throughout the 7 lux. This Si
Due to O2, Si in the weld metal can be up to about 0.65 wt%, and 60 to 90% of the Si in the wire is transferred to the molten metal. Therefore, it is necessary to limit the Si content in the wire to 0,051% or less.

0:0. When the O content in the old at% or less wire exceeds 0.01 wt%, not only does the toughness decrease, but also intergranular cracking occurs.

The above are the wire components and contents particularly defined in the present invention, but in addition to these, P, S, etc. are included in amounts as unavoidable impurities.

As mentioned above, the wire in the present invention is made of 9Cr1Mo
In series steel wire, excessive amount of A1 is added to increase Si and O.
By limiting the content of , cracks occurring at the grain boundaries of the weld metal are prevented.

By the way, the 7 lux used in the present invention is used in combination with the above-mentioned wire to ensure prevention of grain cracking and to obtain excellent mechanical properties and bead shape. CaO and/or MFIOlAlzOi
It is necessary to specify the content of and/or Z r O2,5iO-1A1.

The reason for adding each component will be explained in detail below.

CaF2: 25-70wt% CaF2 increases the basicity of slag and significantly reduces the amount of oxygen in the weld metal, and is used to produce a low-oxygen weld metal as in the present invention and prevent grain ¥1' cracking. It is essential as a 7 lux component. Furthermore, CaF2 is 7
It has been found that the melting point of the lux can be lowered and a good bead shape can be obtained. If the amount of CaFz added to the entire 7 lux is less than 25 wt%, the effect will not be obtained (or 70 wt%).
If it exceeds %, the fluidity becomes excessive, the bead toe becomes unstable, and the bead appearance deteriorates.

CaO and/or M110: 8-30wt%Ca
Both O and MgO are strong basic components and are effective in reducing the amount of oxygen in the weld metal.
CaO and MgO are highly refractory components, and the melting characteristics of blanks containing a large amount of CaF2, which has a low melting point, are 111! It is effective for adjusting the bead shape.

Such an effect cannot be obtained when CaO and/or MgO is less than 8 wt%, and when it exceeds 30 wt%, the melting point of 7 lux is exceeded, making melting difficult and causing defects such as undercuts.

A I 20 s and/or Z ro a: 2-35
wt%Δ1,0. and Z'02 also have a high melting point and are effective in adjusting the fluidity of molten slag and shaping the joint shape.Such effects of Altos and ZrO2 are important when used in multilayer welding. However, if the basic component of 7lux is only CaF't-CaO-MgO, the bead ridges will not be smooth and will be uneven.
The addition of LO and/or ZrO* improves the compatibility between beads, and defects such as slug-in and undercut are not generated.
If O2 is less than 2wt%, such an effect cannot be obtained, and 3
When it exceeds 5 to t%, slag is likely to be caught in the weld metal, and undercuts are likely to occur.

SiO2:5 wt%t% SiO2 is an effective component for adjusting the viscosity of slag and improving the bead appearance, while 5iOz is reduced in the arc atmosphere and removes Si and oxygen from the weld metal. increase, causing grain ￥iL cracks. Therefore, considering the transfer of Si from the wire, it is necessary to limit Si to 5 wt % or less with respect to the entire 7 lacs in the blanks of the present invention. In the firing type 7-fux, water solution is used as a fixing agent during granulation, and a large amount of 5iO
Contains z, and in normal 7 lux, 3~
4wt% of SiO2 is mixed in, and 1wt% is added to the normal 7 lac as an unavoidable impurity in the powder raw material.
It contains a certain amount of S i O2. Therefore, in the 7FAX of the present invention, S r Oz is not used to a large extent as a powder raw material.

Sl: The present invention focuses on S in the weld metal from the viewpoint of preventing grain cracking;
The deoxidizing agent function is mostly achieved by 81, and Si is not used as a deoxidizing agent as much as possible.

Al: 0.5-7.0wt% As mentioned above, A1 is an essential component from the viewpoint of preventing intergranular cracking, and by adding it from the wire as well as from the 7x, the A1 content in the weld metal can be stabilized. become In addition, adding Al from 7 lux is important for preventing gas defects such as blowholes and pockmarks, and this effect is difficult to obtain by adding Al from wire alone. The amount added can be selected depending on the A1 content of the wire to be combined, but 0.5
~7wt% is good, and if it is less than 0.5wt%, gas defects are likely to occur in the weld metal, and if it exceeds 7wt%, the slag removability will deteriorate and lead defects will also be impaired, so the limit should be set. 0.5@t%, with an upper limit of 7wt%.

The essential components of the blanks in the present invention have been described above, but the raw materials for adding these components can be added in the form of single substances, compounds, ores, or molten blanks containing the above components. That is, as the raw material used, C
aF=: Fluorite, molten form 7 lux, etc., Cab: Lime carbonate, molten form 7? Tsuku 6 grade, MgO: Magnesia clinker
, spinel, fused blanks, etc., Al2O3: alumina, spinel, fused blanks, etc., Al = total fiAl
, Fe-A1, etc.

The effects of the welding method of the present invention will be explained below using examples.

(Example) First, steel having the composition shown in Table fjS1 was produced in a vacuum melting furnace and then forged, rolled and wire-drawn to produce a wire of 4.0 m-φ. Among the wires shown in Table 1, W1~
W8 is a wire used in the present invention, and W9 to W15 are wires used in comparative examples.

Next, Submano 7-iron welding I flux having the composition shown in Table 2 was prepared. In this case, the raw materials used were an ore powder composite and alumina cement, which are commonly used as molten 7 lux raw materials. All 7 lacs were granulated using water glass as a sticking agent and heated at 500℃XII+r.
This is a 7-lac firing mold that was fired under the following conditions. In addition, the second
Of the 7 hooks in the table, F1 to F5 are the 7 hooks used in the method of the present invention.
? Tux and F6 to Fil were used in comparative examples.

Using the above-mentioned wire and 7 wires, 20 types of submerged arc welding were carried out according to the steel plates shown in Table 3, the welding conditions shown in Table 4, and the JIA procedure shown in FIG. 1. There are two types of welding lengths.

Table 5 shows the combinations of 7 faxes and wires in the welding carried out and the results of the accuracy test of the welded part.

To determine the accuracy of the weld, first observe the appearance of the weld, and then
After heat treatment at ℃X21+r, X-ray transmission test (JI
S Z 3104) was used to investigate the presence or absence of cracks. A high temperature tensile test piece (JIS Z
05 (i7, diameter: 6--φ) and impact test piece (JIS
Z 2202 No. 4) was sampled and each test was conducted. The high temperature tensile test was carried out at 500°C, and the impact test was carried out at 0°C.

The accuracy results for the above welded parts are shown in Table 5 (1 m on the right).

Inventive Examples No. 001 to No. 7 had excellent welds, but as shown in Table 5 for the individual reasons for No. 8 to No. 20, C and Cr in the wire were ,M
o%Ni, V, Nb, Al, N, Si content inappropriate;
Furthermore, CaFt in the flux, Cao + M go
.

S + Oi A I z Ox + Z r Oz $
3 Yo (/ Improper addition of H, S to 7 feet)
The addition of i caused problems such as poor bead shape, cracking, and deterioration of mechanical properties.

(Effects of the Invention) As described above, the present invention does not cause cracks in submerged welding of 9Cr-1Mo steel, and it is possible to obtain a welded part with excellent mechanical properties such as high temperature strength and impact value. This is a welding method that satisfies the bead shape and X#a performance. SC used in various power generation boilers, pressure vessels, etc.
When submerged arc welding rlMo steel, the reliability of the welded joint can be significantly improved by the present invention.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the groove shape and +rt layer procedure used in Examples.

Claims (1)

[Claims] (1) C: 0.01 to 0.15 wt%, Mn: 0.4 to 2.5 wt%, Cr: 8.0 to 11.0 wt%, Mo: 0.5 to 1.2 wt%, Ni: 0 .05-1.3wt%, V: 0.03-0.30wt%, Nb: 0.02-0.12wt%, Al: 0.005-1.5wt%, N: 0.004-0.100wt % and limited to Si: 0.051% or less, O: 0.01wt% or less, CaF_2: 25-70wt%, one or both of CaO and MgO: 8-30wt%, Al_2O_3 , one or two types of ZrO_2: 2 to 3
5 wt%, Al: 0.5 to 7 wt%, and SiO_2: limited to 5 wt% or less, which is carried out in combination with a welding flux that does not substantially contain Si. Arc welding method.