JPH0479752B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to welding high-strength Cr-Mo steel, more specifically, welding high-strength 2.25-3% Cr-1% Mo steel containing one or both of Hb and V. In welding,
The present invention relates to a submerged arc welding method capable of obtaining a weld metal with excellent toughness and creep properties. (Prior Art) 2.25-3% Cr-1% Mo steel has been widely applied to equipment used at high temperatures such as boilers and chemical reaction vessels as a material with excellent high-temperature properties. In this field, there are generally many thick plate structures, and submerged arc welding, which can obtain a large amount of welding, is often used for welding. On the other hand, in recent years, it has been expected that the thermal efficiency of these facilities and structures will be further improved by improving the performance of materials from the viewpoint of energy and resource conservation.
High strength 2.25~3%Cr-1%Mo containing V etc.
Steel has been developed and is about to be put into practical use. In response to this, there is a desire for higher strength welding materials, but currently welding materials with mechanical performance (toughness, creep properties, etc.) commensurate with the increased strength of steel plates have not yet been obtained. do not have. In other words, steel plates can be processed and heat treated relatively freely during manufacturing, so their structure is uniform.
Materials with good performance can be easily obtained by controlling performance through heat treatment, whereas weld metal has a non-uniform cast structure and there are restrictions on heat treatment after welding, so it is difficult to simply weld. If the metal only contains Nb, V, etc., the strength will certainly increase, but the toughness will deteriorate proportionally. Furthermore, when trying to ensure toughness, there were problems such as not being able to obtain the necessary strength characteristics. (Problems to be Solved by the Invention) The present invention has been developed in view of these circumstances, and is a high-strength 2.25 to 3% Cr-1% Mo steel containing one or both of Nb and V. The object of the present invention is to provide a method for obtaining a weld metal with excellent toughness and creep properties in submerged arc welding. (Means for solving the problem) In order to achieve the above object, the present inventors
So-called 2.25~ containing one or two types of and V
We have conducted extensive research in order to find a method to obtain a weld metal with good toughness and creep properties in submerged arc welding of 3% Cr-1% Mo steel. As a result, solid wire and sintered flux are used, but in doing so, the chemical composition of the solid wire and the chemical composition and basicity of the sintered flux are regulated, and their chemical composition is adjusted with particular consideration to component yield. We discovered that it is possible by regulating it. That is, the submerged arc welding method for high-strength Cr-Mo steel according to the present invention uses Cr: 2.00 to 3.25%.
Contains Mo: 0.90 to 1.10%, and 1 of Nb and V
High strength 2.25~3%Cr-1% containing species or two
When submerged arc welding Mo steel using a solid wire and sintered flux, the solid wire contains C: 0.06-0.13% and Mn: 0.20-0.20%.
1.20%, Cr: 2.00~3.50% and Mo: 0.90~1.20%
Contains as an essential component, and Si≦0.30%, Ni≦
0.20%, O≦0.015%, and the sintered flux contains _SiO2 : 7 to 20% and MgO
Contains as essential components one or two of CaF2 and _CaF2 : 35 to 65%, and metal carbonate (in terms of _CO2 ): 1 to 5%, and has a basicity B of 2.5 as shown by the following formula (1). ~4.0
and B=[(%CaF ₂ )+(%CaO)+(%MgO)+(
%BaO) + (%SrO) + (%Na ₂ O) + (%K ₂ O) + (%Li ₂ O) + 0.5 × {(%Mn
O) + (%FeO)}] ÷ [(%SiO ₂ ) + 0.5 × {(%Al ₂ O ₃ ) + (%TiO ₂ ) + (%ZrO ₂
)}]...(1) At least one of the solid wire and the sintered flux contains one or two of Al and Ti and Nb.
and V in a manner that satisfies the following formulas (2) to (4). [Al] _A + [Ti] _A = {[Al] _W ×W _Al + [Al
] _F ×F _Al } + {[Ti] _W ×W _Ti + [Ti] _F ×F _Ti }=0.01~0
.06%……(2) [Nb] _A = [Nb] _W ×W _Nb + [Nb] _F ×F _N
b = 0.005 to 0.035%……(3) [V] _A = [V] _W ×W _V + [V] _F ×F _V
=0.10~0.50%...(4) However, [x] _A : Weight % of x component in weld metal [x] _W : Weight % of x component in wire [x] _F : Weight % of x component in flux Weight % W _X : Yield coefficient of x component from wire _F
is 2.2 to 3.5. Pc=6×[Cr] _A +6×[Mo] _A +13×[Nb
] _A +24[V] _A /100×[C]……(5) However, [Cr] _A = [Cr] _W ×W _Cr [Mo] _A = [Mo] _W ×W _Mp [C] _A = [ C] _W × W _C Furthermore, the present invention further provides Co in at least one of the solid wire and the sintered flux according to the following formula (6).
It is characterized by containing satisfactorily the following. [Co] _A = [Co] _W ×W _Cp + [Co] _F ×F _Cp = 0
.02-0.06%...(6) The present invention will be explained in more detail below. As mentioned above, the object of the present invention is to
High strength 2.25~3%Cr-1% containing species or two
This method is applied to welding Mo steel to obtain a weld metal with good toughness and creep properties, and in particular, the above formulas (2) to (6) describe each component necessary to achieve this. The amount ([x] _A ) is supplied from solid wire and/or sintered flux, and the yield rate of these into weld metal is determined based on the following equation (A). _[ x] _A = [x] _W ×W _X + [x] _{F × F} W _X : Yield coefficient of the x component from the wire F _X : Yield coefficient of the x component from the flux Note that the yield coefficients W _X and _F It cannot be determined uniformly because it is affected by the flux composition (e.g. type and compounding ratio of slab forming agent, arc stabilizer, gas generating agent, etc.), welding conditions, etc., but in practical terms it is shown in Table 1. That's right.

[Table] Also, among the necessary components, C, Si, Mn,
Regarding Ni, Cr, and Mo, it is better to add them exclusively to the solid wire mainly from a cost perspective, but as for Al, Ti, Nb, and V, their effect is less if the content in the weld metal is the same. are the same,
Either solid wire or sintered flux may be added. (Function) Next, the function of each component in the present invention will be described. First, the reason for limiting the chemical components in the solid wire will be explained. C: 0.06 to 0.13% C is an element necessary to improve the hardenability of weld metal and ensure room temperature strength, high temperature strength, and toughness, and for this purpose, 0.06% or more is required. However, if it exceeds 0.13%, the room temperature strength becomes too high, the toughness decreases, and the cracking resistance deteriorates. Therefore, the amount of C in the wire is
The range shall be 0.06-0.13%. Si≦0.30% Si has a deoxidizing effect and is an element that improves the conformability of weld metal, but if it exceeds 0.30%, the toughness of weld metal deteriorates, so the amount of Si in the wire should be 0.30% or less. . Mn: 0.20-1.20% Mn has a deoxidizing effect and also has the effect of improving the toughness of weld metal, and for this purpose, 0.20% or more is required. However, if it exceeds 1.20%, the creep strength will decrease. Therefore, the amount of Mn in the wire should be in the range of 0.20 to 1.20%. Cr: 2.00~3.50%, Mo: 0.90~1.30% Since Cr and Mo are the basic constituent elements of 2.25~3%Cr-1%Mo steel, the present invention also requires a certain amount of Cr and Mo in the wire. and the respective amounts are Cr: 2.00~3.50% and Mo: 0.90~1.20%
The range of In addition, Cr is less than 2.00%, Mo is
The effect of the present invention is similarly recognized even when the Cr content is less than 0.90%, but since these steel types are not normally used at high temperatures, and steels with a Cr content of more than 3.50% are not applicable due to cost considerations, the present invention does not apply them. We have decided to exclude this range. Ni≦0.20% Ni has the effect of improving toughness, but if it exceeds 0.20%, the room temperature strength becomes too high and the weld metal and crack resistance deteriorate. Also, it has little effect on increasing creep strength. Therefore, the amount of Ni in the wire should be 0.20% or less. O≦0.015% O greatly affects the toughness of weld metal,
The amount of O in the weld metal depends on the type of wire and flux combination used. In the present invention, by setting the O content in the wire to 0.015% or less and using such a solid wire and a sintered flux having a specific composition, it is possible to achieve O≦0.030% in the weld metal, resulting in good toughness. It is possible to obtain a weld metal having the following properties. Pc (in weld metal): 2.2 to 3.5 Furthermore, in the present invention, the ratio of carbide-forming elements to carbon (parameter:
We have discovered that by controlling Pc) to a specific value, it is possible to suppress the unnecessarily increased room-temperature strength of the weld metal, secure toughness, and improve creep strength. That is, for that purpose, it is necessary to control Pc within the range of 2.2 to 3.5. If Pc is less than 2.2, the creep strength will be too low, and if it exceeds 3.5, the room temperature strength will be too high and the toughness will deteriorate. Note that Pc is a ratio defined as in the following equation. Pc=6×[Cr] _A +6×[Mo] _A +13×[Nb
] _A +24[V] _A /100×[C] However, [Cr] _A = [Cr] _W ×W _Cr [Mo] _A = [Mo] W _× W _Mp [C] _A = [C] _W ×W _C Therefore, in the present invention, if necessary,
It is preferable to regulate the content of C, Cr, and Mo in the wire within the range of the amounts of C, Cr, and Mo in the wire and in consideration of the component yield coefficient so that Pc is in the range of 2.2 to 3.5. Next, the reason for limiting specific components in the wire and/or flux will be explained. Nb (in weld metal): 0.005-0.035% Adding a small amount of Nb has the effect of increasing the strength of weld metal (room temperature strength, high temperature strength, creep strength).
0.005% or more is required. However, if it exceeds 0.035%, the room temperature strength becomes too high and the toughness deteriorates significantly. Therefore, Nb should be added so that the amount of Nb in the weld metal is in the range of 0.005 to 0.35%.
The component is included in at least one of the wire and flux in consideration of the component yield coefficient from the wire and flux. V (in weld metal): 0.10 to 0.50% Like Nb, V also has the effect of increasing the strength of weld metal (room temperature strength, high temperature strength, creep strength), and for this purpose, it is necessary to contain 0.10% or more in weld metal. is necessary. However, if it exceeds 0.50%, the room temperature strength becomes too high and the toughness deteriorates significantly. Therefore, V is the amount of V in the weld metal.
The flux is contained in at least one of the wire and the flux in consideration of the component yield coefficient from the wire and the flux so as to be in the range of 0.10 to 0.50%. Al and/or Ti (in weld metal): 0.01 to 0.06% Both Al and Ti have a deoxidizing effect and also have the effect of refining grains and improving toughness. Al, Ti 1
0.01% or more of one or two species is required. but,
If it exceeds 0.06%, the room temperature strength will become too high and the toughness will deteriorate. Therefore, Al
and Ti are one or two types of Al and Ti in the weld metal.
The amount of seeds is in the range of 0.10 to 0.06%, taking into consideration the component yield coefficient from the wire and flux, and is included in at least one of the wire and flux. Co (in weld metal): 0.02 to 0.06% When Co is added, the room temperature strength of weld metal increases.
It has the effect of increasing creep strength without significantly affecting high temperature strength. However, Co in the weld metal
If the amount exceeds 0.60%, toughness will deteriorate.
Therefore, in the present invention, if necessary, at least one of the wire and the flux is added so that the amount of Co in the weld metal is in the range of 0.02 to 0.60%.
Co can be contained. Next, the reasons for limiting the slag forming agent etc. of the sintered flux will be explained. SiO ₂ : 7-20% SiO ₂ has the effect of increasing the fluidity of slag and improving the weld bead shape, and for that purpose 7%
The above is necessary. However, if it exceeds 20%, the basicity of the slag decreases, and the toughness and cracking resistance of the weld metal deteriorate. Therefore, in the flux
The amount of _SiO2 is in the range of 7 to 20%. MgO and/or _CaF2 : 35-65% Both MgO and _CaF2 have the effect of increasing the fluidity of the slag, improving the bead shape, increasing the basicity of the slag, and improving the toughness of the weld metal. For this purpose, 35% or more of one or both of MgO and CaF ₂ is required, but if it exceeds 65%, arc stability deteriorates and slag removability deteriorates significantly. Therefore, the amount of one or both of MgO and _CaF2 in the flux is
It should be in the range of 35-65%. Note that MgO includes the MgO equivalent value generated by decomposition of MgCO ₃ . Also,
Other metal fluorides ( _{BaF2 ,}
It has been confirmed that other materials (such as Na ₃ AlF ₆ , MgF ₂ , NaF, etc.) have similar effects. Metal carbonate (CO ₂ equivalent): 1 to 5% CO ₂ from metal carbonate has _the effect of reducing the amount of hydrogen in the weld metal and improving cracking resistance. 1% or more is required. However, if it exceeds 5%, the amount of oxygen in the weld metal increases, the toughness deteriorates, and pockmarks are likely to occur on the bead surface. Therefore, the amount of metal carbonate should be in the range of 1 to 5% in terms of _CO2 . In addition, as a supply source of CO ₂ , CaCO ₃ ,
Examples include metal carbonates such as BaCO ₃ and MgCO ₃ , but they all have similar effects as long as they have the same CO ₂ equivalent value. Basicity B: 2.5 to 4.0 In the present invention, in addition to limiting the numerical values of the above-mentioned components in the sintered flux used, the basicity B shown by the following formula (1) is set to 2.5.
~4.0 is required. B = [(%CaF ₂ ) + (%CaO) + (%MgO) + (
%BaO) + (%SrO) + (%Na ₂ O) + (%K ₂ O) + (%Li ₂ O) + 0.5 × {(%Mn
O) + (%FeO)}] ÷ [(%SiO ₂ ) + 0.5× {(%Al ₂ O ₃ ) + (
%TiO ₂ ) + (%ZrO ₂ )}]...(1) However, if B is less than 2.5, the amount of oxygen in the weld metal will increase, and the toughness and hot cracking resistance will deteriorate. Moreover, if it exceeds 4.0, the arc becomes unstable and the bead shape deteriorates, which is not preferable. In addition, in calculating formula (1),
It also includes equivalent values for oxides such as CaO, MgO, and BaO produced by the decomposition of metal carbonates such as CaCO _{3 ,} MgCO ₃ , and BaCO 3 . Note that the Nb and V-containing high-strength Cr-Mo steel targeted in the method of the present invention contains Cr: 2.00 to 3.25% and
This steel contains Mo: 0.90 to 1.10%, and further contains one or both of Nb and V in appropriate amounts. Of course,
Submerged arc welding conditions are not particularly limited. (Example) Next, an example of the present invention will be shown. Example 1 Multilayer welding (laminated method: 2 passes/1 layer)
I went there. The groove shape is as shown in Figure 1.
In addition, the welding conditions are: Leading electrode: 550A (AC power supply) - 31V
-60cm/min, trailing pole: 550A (AC power supply) -33V-
60cm/min, temperature between preheating passes: 200~250℃. Table 6 shows the results of an investigation into welding workability, cracking resistance of the weld metal, and mechanical performance when wires and fluxes were welded in combination as shown in Table 5. The chemical composition of the weld metal at that time is also listed in Table 5. Note that tests for evaluating mechanical performance were conducted in accordance with the procedures shown in Table 7. In Table 6, Tests No. 1 to No. 5 are examples of the present invention, and show good results in all of welding workability, cracking resistance of weld metal, and mechanical performance. On the other hand, Tests No. 6 to No. 12 are comparative examples that do not satisfy at least one of the constituent requirements of the present invention, and are considered as follows. In No. 6, the wire and weld metal compositions deviate from the requirements of the present invention (C is too low and Si, Pc are too high), so the toughness of the weld metal deteriorates. In No. 7, the wire and weld metal compositions deviate from the requirements of the present invention (Nb and V are too low, and Mn is too high), so the creep rupture strength of the weld metal is low. In No. 8, the wire and weld metal composition deviates from the requirements of the present invention (C, Ni, Al + Ti are too high, Pc is too low), so the room temperature strength of the weld metal increases, and cracking resistance and toughness deteriorate. At the same time, creep rupture strength is low. In No. 9, the wire and weld metal composition deviates from the requirements of the present invention (Mn, Al + Ti are too low, Nb, V,
(Co and Pc are too high), the room temperature strength of the weld metal becomes too high and the toughness deteriorates. In No. 10, the flux composition deviates from the requirements of the present invention (SiO ₂ is too low, MgO+CaF ₂ , and basicity B is too high), resulting in poor welding workability. In No. 11, the flux composition deviates from the requirements of the present invention (CO ₂ is too high, MgO + CaF ₂ , Pc is too low), so welding workability and cracking resistance of the weld metal deteriorate, and the oxygen content of the weld metal deteriorates. The amount increases and the toughness deteriorates. No. 12 has a flux composition that deviates from the requirements of the present invention (SiO ₂ is too high and CO ₂ is too low).
The cracking resistance of the weld metal deteriorates, as well as its toughness.

【table】

【table】

【table】

【table】

[Table]
(Note 1) 6×(%Cr)＋6×(%Mo)＋13×(%Nb)＋
24×(%V)
Pc=

Claims (1)

[Claims] 1% by weight (the same applies hereinafter), Cr: 2.00 to 3.25%
and Mo: 0.90 to 1.10%, and high strength 2.25 to 3% Cr-1 containing one or both of Nb and V.
When submerged arc welding %Mo steel using a solid wire and sintered flux, the solid wire contains C: 0.06-0.13%, Mn: 0.20-0.
1.20%, Cr: 2.00~3.50% and Mo: 0.90~1.20%
Contains as an essential component, and Si≦0.30%, Ni≦
0.20%, O≦0.015%, and the sintered flux contains SiO ₂ :7 to 20% and MgO
Contains as essential components one or two of CaF2 and _CaF2 : 35 to 65%, and metal carbonate (in terms of _CO2 ): 1 to 5%, and has a basicity B of 2.5 as shown by the following formula (1). ~4.0
and B=[(%CaF ₂ )+(%CaO)+(%MgO)+(
%BaO) + (%SrO) + (%Na ₂ O) + (%K ₂ O) + (%Li ₂ O) + 0.5 × {(%Mn
O) + (%FeO)}] ÷ [(%SiO ₂ ) + 0.5 × {(%Al ₂ O ₃ ) + (%TiO ₂ ) + (%ZrO ₂
)}]...(1) At least one of the solid wire and the sintered flux contains one or two of Al and Ti.
A submerged arc welding method for high-strength Cr-Mo steel, characterized by containing Nb and V so as to satisfy the following formulas (2) to (4). Note [Al] _A + [Ti] _A = {[Al] _W ×W _Al + [Al
] _F ×F _Al } + {[Ti] _W ×W _Ti + [Ti] _F ×F _Ti }=0.01~0
.06%……(2) [Nb] _A = [Nb] _W ×W _Nb + [Nb] _F ×F _Nb = 0
.005~0.035%...(3) [V] _A = [V] _W ×W _V + [V] _F ×F _V =0.10~0.50%...(4) However, [x] _A : In the weld metal Weight % of x component in wire [x] _W : Weight % of x component in wire [x] _F : Weight % of x component in flux _{W X :} Yield coefficient of x component from wire F Yield coefficient of x component: 2. The submerged arc welding method according to claim 1, wherein Pc expressed by the following formula (5) is 2.2 to 3.5. Pc=6×[Cr] _A +6×[Mo] _A +13×
[Nb] _A +24[V] _A /100×[C]……(5) However, [Cr] _A = [Cr] _W ×W _Cr [Mo] _A = [Mo] _W ×W _Mp [C] _A = [C] _W × W _C 3 The submerged arc welding method according to claim 1 or 2, characterized in that at least one of the solid wire and the sintered flux contains Co so as to satisfy the following formula (6). How to do it. [Co] _A = [Co] _W ×W _Cp + [Co] _F
×F _Cp = 0.02~0.06%……(6)