JPH0811312B2 - Cr-Mo series low alloy heat resistant steel welding steel wire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a welding steel wire for gas shielded arc welding of a Cr—Mo based low alloy heat resistant steel.

(Prior art) In recent years, Cr-Mo low alloy heat-resistant steel containers used in nuclear power plants, thermal power plants, and chemical plants such as oil refining have become extremely thick due to the increase in equipment size and reaction process. Also, the usage conditions tend to be severer. That is, it has been demanded that these steel materials and welded parts be extremely thickened, have high strength and high toughness, and sufficiently withstand long-term use under various harsh environments. Of course, as with the above, it is necessary to secure strength and toughness for a high-strength design in order to reduce the plate thickness as much as possible, and to reduce the plate thickness as much as possible.

Therefore, as the conventional steel wire for Cr-Mo-based low alloy heat resistant steel gas shielded arc welding, those described in JP-A-57-85692 and JP-A-59-193789 have been proposed.

It is effective to add a small amount of V, Nb, etc. to improve the strength, but if a large amount is added, high strength can be obtained, but toughness decreases and temper embrittlement increases.

On the other hand, to secure toughness, impurity elements such as P, Sb, Sn, and As that affect temper embrittlement and Si or Mn that promotes grain boundary segregation of these elements should be kept low, and a small amount of V Even if efforts are made to add B and B, there is a limit in securing toughness by increasing strength.

In addition, strength / toughness and temper parameters (= [heat treatment temperature after welding] (° K) + {20 + log [heat treatment time] (h
r)} 10 ^-3 , hereafter referred to as TP),
It can be easily obtained by lowering TP, but lower toughness. On the other hand, with high toughness, the strength decreases although it can be obtained by increasing TP.

As described above, the development of a welding material that can obtain high strength at high TP to enable high-temperature and high-pressure operation by increasing the efficiency of the pressure vessel and at the same time ensure high toughness is extremely difficult with conventional techniques, and many The reality is that there are problems.

(Problems to be Solved by the Invention) The present invention is a steel wire for gas shielded arc welding, which eliminates the above-mentioned drawbacks of the conventional products, and at the same time obtains high strength and high toughness even at high TP, and provides a good quality weld. The purpose is to provide an excellent wire that can be obtained.

(Means for Solving Problems) The gist of the present invention is a welding steel wire using an Ar—CO ₂ mixed gas or an Ar—O ₂ mixed gas as a shield gas, wherein C 0.04% or more by weight% is 0.10 or more. % Or less, Si 0.25% or more
0.60% or less, Mn 0.65% or more 1.20% or less, Cr 2.20% or more
Less than 2.70%, Mo 0.90% or more 1.20% or less, V 0.10% or more
0.75% or less, N 0.0150% or less, and Nb 0.0
Contains 2% or more and 0.10% or less and / or B 0.006% or less,
A steel wire for Cr-Mo-based low alloy heat resistant steel welding, characterized in that it contains Cu 0.40% or less as necessary and the balance is iron and inevitable impurities.

That is, the wire of the present invention is appropriately selected and limited in its composition, and particularly contains V 0.10% or more and 0.75% or less, N 0.0150% or less, and Nb 0.02% or more and 0.10% or less and / or
B 0.006% or less is contained, and if necessary, Cu content is 0.40% or less, which makes it possible to obtain high strength at high TP, which was difficult to obtain with conventional wires, and at the same time, to secure high toughness. To demonstrate.

(Function) The reasons for limiting each constituent component of the wire of the present invention will be described in detail below.

C is a component effective for improving the strength of weld metal, but 0.10
If it exceeds%, minute blowholes are generated. While 0.04
If it is less than%, the strength equivalent to steel cannot be secured.

Si and Mn are essential components as a deoxidizer, strength,
It is also an effective component for adjusting toughness. However, if the contents of Si and Mn exceed 0.60% and 1.20%, respectively, the strength is excessively increased and the toughness is lowered. In addition, tempering and embrittlement also increase. On the other hand, in order to obtain a sufficient deoxidizing effect, it is necessary to contain Si in an amount of 0.25% or more and Mn in an amount of 0.65% or more.

Cr is an essential element for oxidation resistance, hydrogen resistance, and stabilization of the high-temperature strength of the weld metal. Considering workability and weldability, Cr was set to 2.20% or more and less than 2.70% according to the target purpose.

Mo is an element that is essential for ensuring the high-temperature strength of weld metal and preventing temper embrittlement. If it exceeds 1.20%, temper embrittlement is promoted. On the other hand, if it is less than 0.90%, no sufficient effect can be obtained.

V has the effect of refining the crystal grain size of the weld metal and is an effective component for measuring the strength increase.
If it exceeds%, the strength becomes excessive and the toughness deteriorates. On the other hand, if it is less than 0.10%, a sufficient effect cannot be obtained.

N, like C, is an effective component for improving the strength of the weld metal, but if it exceeds 0.0150%, blowholes and pits occur, so it was determined to be 0.0150% or less.

By containing Nb and / or B as a selective component in the wire of the present invention, high strength can be obtained even at high TP and high toughness can be secured. Nb makes the grain size of the weld metal finer, improves toughness, reduces temper embrittlement, is also used as a deoxidizer, and is an effective component for increasing strength. However, Nb is 0.10
If it exceeds%, the strength becomes excessive and the toughness deteriorates. On the other hand, if it is less than 0.02%, a sufficient effect cannot be obtained.

Further, since B is a strong deoxidized carbide forming component, addition of this to the wire makes the crystal fine, improves toughness, and reduces temper embrittlement. However, if it exceeds 0.006%, hot cracking tends to occur in the weld metal, so the content was made 0.006% or less.

When V is not present, even if only Nb is added, the weld metal hardens excessively and the toughness deteriorates, and B also results in lowering the crack resistance of the weld metal. , Nb and / or B is effective in that high TP and high strength and high toughness can be stably obtained at the same time.

Although the above is the basic component of the wire of the present invention, the wire of the present invention can further contain Cu in the following range.

Cu is generally applied by plating on the wire surface for the purpose of improving rust resistance, corrosion resistance and wire feedability.
%, The cause of hot cracking and deterioration of toughness, so 0.
It was set to 40% or less. Also, for reactor vessels, there is a case where Cu plating is not applied in consideration of the effect on irradiation embrittlement.

As a result of welding using the wire having the components as described above, it was found that the weld metal performance sufficiently satisfied the predetermined characteristics.

The effects of the present invention will be more specifically described below with reference to examples.

(Example) Table 1 shows the steel wire used for the experiment. Wire symbol 1
4 to 4 are wires of the present invention, and wire symbols 5 to 13 are wires for comparison, which are outside the scope of the present invention. Board thickness 20 mm 2.
After processing the 1 / 4Cr-1Mo steel sheet into the groove shape shown in FIG. 1, multilayer welding was performed using the wires shown in Table 1 under the welding conditions shown in Table 2. 690 ℃ × 12hr for test material after welding
After welding, heat treatment (hereinafter referred to as SR) was performed, and as shown in Fig. 2, tensile test pieces (normal temperature tensile JISZ3111A-1, high temperature tensile JISG056710mmφ) and abrasive test pieces (JISZ31124).
Was collected and subjected to a mechanical test. Further, the above impact test pieces were subjected to embrittlement heat treatment under the conditions shown in FIG.
Called)) was conducted. Table 3 shows these test results and welding workability results.

As is clear from Tables 1 and 3, the wires of wire symbols 1 to 4 according to the present invention not only have good X-ray transmission test results and welding workability evaluation results, but also have desired strength, toughness, and burntness. Excellent performance is also obtained for the embrittlement index, which indicates the return embrittlement property.

On the other hand, when the comparative examples are individually explained, the wire of the symbol 5 has C and V of 0.13% and 0.85% which exceed the component requirement range of the present invention in order to obtain high strength. However, the toughness and brittleness index were low, and minute blowholes were generated in the weld metal. Symbol 6
The wire is Nb alone added, the amount of which is 0.013%, which is less than the component requirement range of the present invention, and Mn is 1.25%, which exceeds the component requirement range of the present invention.
Although the results of the line penetration test and the welding workability evaluation are good, the strength is low and the target value cannot be satisfied. However, the toughness and brittleness index are good. The wire of symbol 7 has V of 0.022%, which is less than the component requirement range of the present invention, and B of 0.0073%, which exceeds the component requirement range of the present invention. However, the effect of composite addition is not obtained, and the strength is low, The X-ray transmission test failed. The wire of the symbol 8 is the one in which only V is added alone, and the amount thereof is 0.041% within the component requirement range of the present invention, but the strength is low like the wire of the symbol 6, and the target value cannot be satisfied. The wire of symbol 9 is a composite additive wire of V, Nb, and B, but the content of Nb is 0.124, which exceeds the component requirement range of the present invention.
%, The strength is too high, and the toughness and brittleness index are poor. Also, in terms of welding workability, slag peeling was slightly poor. The wires 10 and 11 are made of Si in 10 for the purpose of improving toughness and temper embrittlement characteristics.
, 11, Mn is 0 below the component requirement range of the present invention.
Although it was 20% and 0.52%, blowholes were generated in the weld metal due to insufficient deoxidation, and impact test pieces could not be collected. The wire of symbol 12 is Nb, B for the purpose of improving strength.
And N were 0.0172%, which exceeds the component requirement range of the present invention, but high strength was obtained, but blow holes were generated in the weld metal to such an extent that impact test pieces could not be collected. The wire of symbol 13 is a wire containing V and Nb.
Is 0.019%, which is less than the component requirement range of the present invention, and C
Although it was a low value of 0.03%, the X-ray transmission test result and the welding workability evaluation test were good, and the toughness and brittleness index were excellent, but the target strength could not be satisfied.

From the above results, in addition to containing V and N, Nb
It can be seen that even if B and / or B are added, the excellent effect cannot be exhibited unless the added amount is appropriate.

(Example 2) A 2/1 / 4-1Mo steel plate having a plate thickness of 50 mm was processed into a narrow groove as shown in Fig. 3, and inner wire symbols 2 and 5 of the wire shown in Table 1 were used.
1 pass under the welding conditions shown in Table 4 using 3 wires of 13 and 13.
/ 1 layer welding was performed. After welding, SR was applied at 690 ° C. for 24 hours, and JIS Z3111A-2 No. 4 tensile test piece a and JIS Z3112 No. 4 test piece b for normal temperature tension were sampled from the position shown in FIG. 4 and tested. The results are shown in Table 5.

In this way, even when welding is performed by the narrow groove welding method, the wire belonging to the scope of the present invention (wire symbol 2) can provide excellent weld metal performance, and the arc is stable in the groove and spattering is possible. There is little occurrence of slag, and welding workability with good slag peeling is shown. On the other hand, the wires (wire symbols 5 and 13) outside the scope of the present invention have problems in X-ray characteristics and performance.

(Effects of the Invention) As described above, the steel wire of the present invention not only has good welding workability, but also obtains a weld metal having high strength and high toughness at the same time even at high TP. It can contribute to the expansion of its application range in the field of use of steel.

[Brief description of drawings]

1 and 3 are explanatory views showing the groove shape used in the examples, FIG. 2 is an explanatory view showing the embrittlement heat treatment conditions used in the examples, and FIG. 4 is a tensile test used in the examples. It is a figure which shows the sampling position of a piece and an impact test piece. a: Tensile test piece, b: Impact test piece.

Claims (2)

[Claims] 1. A steel wire for welding which uses an Ar—CO ₂ mixed gas or an Ar—O ₂ mixed gas as a shielding gas, and in% by weight, C 0.04% or more and 0.10% or less, Si 0.25% or more and 0.60% or less. , Mn 0.65% to 1.20%, Cr 2.20% to 2.70%, Mo 0.90% to 1.20%, V 0.10% to 0.75%, N 0.0150% or less, and Nb 0.02% to 0.10% and / Or B
A steel wire for heat-resisting Cr-Mo low alloy heat-resistant welding, characterized by containing 0.006% or less and the balance being iron and inevitable impurities. 2. A steel wire for welding, which uses an Ar-CO ₂ mixed gas or an Ar-O ₂ mixed gas as a shielding gas, and in% by weight, C 0.04% or more and 0.10% or less, Si 0.25% or more and 0.60% or less. , Mn 0.65% to 0.20%, Cr 2.20% to 2.70%, Mo 0.90% to 1.20%, V 0.10% to 0.75%, N 0.0150% or less, and Nb 0.02% to 0.10% and / Or B
A steel wire for Cr-Mo-based low alloy heat resistant steel welding, containing 0.006% or less and Cu 0.40% or less, and the balance being iron and inevitable impurities.