JPS6310096A - Tig welding wire for cr-mo steel - Google Patents

Abstract

PURPOSE:To improve the strength, notch toughness, etc., of a weld metal by incorporating C, Si, Cr, etc., as essential components into the titled wire at specific weight %, controlling Ni, N, etc., to prescribed % or below and consisting the balance of iron and impurities. CONSTITUTION:The component compsn. of the TIG welding wire is composed, by weight %, of 0.03-0.15% C, 0.40-0.80% Si, 0.60-1.30% Mn, 1.00-1.50% Cr, and 0.45-0.60% Mo as the essential components, is incorporated therein with <=0.30% Ni, <=0.012% N, and <=0.010% O, and is composed of the balance Fe and inevitable impurities. The C in such compsn. components assures the strength of the weld metal, the Si improves the notch toughness, and the Cr, Mo and Mn assure the high-temp. strength. The Ni and N respectively improve the toughness and strength. A slight amt. of the O prevents the generation of defects. All of the strength, notch toughness and tempering embrittlement characteristic of the weld metal are, therefore, improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to the use of Cr-Mo%4, for example ICr-17M
o S14 or 1”/4 Cr-'12Mo steel T
This relates to welding wire used for IG welding.

(Prior art) In recent years, Cr-Mo pressure vessels used in nuclear equipment, thermal power plants, and chemical plants such as oil refining have become increasingly large due to the increase in size of equipment and progress in reaction processes.
There is a trend towards extremely thick walls and harsher usage conditions. While there are demands for improvements in high-temperature strength, high-temperature creep properties, etc. of materials used in such pressure vessels, there have been no very strict requirements regarding notch toughness at low temperatures of materials for the steel grades targeted by the present invention. There wasn't.

However, due to the situation described above, securing toughness has become increasingly difficult in recent years. Therefore, efforts have been made in the past to suppress impurity elements such as P, Sb, Sn, and As, which affect embrittlement due to annealing, and Si and Mn, which promote grain boundary segregation of these elements, to a low level.

In addition, TIG welding is more effective than normal MAG welding because it
SI and M in the wire are high due to the high yield of weld metal such as n.
Progress has been made to improve toughness, which has the advantage that even if n, etc. are kept to a low value, no reduction in strength or welding defects due to insufficient deoxidation will occur.

As a wire for TIG welding, JP-A-58-97493
The one described in the publication relates to a TIG wire made of 80 kg f/m" high tensile strength steel that was invented for offshore structures, penstocks, etc., and contains a large amount of TIG wire to ensure strength. Therefore, in order to ensure toughness, it is essential to reduce Si in wire components.

The one described in Japanese Patent Publication No. 61-11157 is 90r-
This relates to a wire for welding 2Mo steel, and it is extremely difficult to apply this wire to other steel materials. This is because if the contents of Cr and Mo, which are the basic components, are not adjusted to match the target steel material, Cr will have excess or deficiency in oxidation resistance, corrosion resistance, and high-temperature slope, and 1Mo will have excess or deficiency in high-temperature strength. occurs.

In addition, this wire has a low 81 and low Mn to ensure toughness.

The one described in JP-A-57-159293 has rcdpsI in the wire, high Mn and Mo, and Nl as other elements.
It is intended to improve toughness and welding workability by containing one or more of Cr, TI or 281 or more, and further containing a large amount of oxygen.

Furthermore, the method described in JP-A-58-100994 discloses that 1 to I V4Cr-'72 Mo steel is Ar-02
Or, it relates to a wire that is welded using an Ar-CO2 mixed gas as a shielding gas, and the wire component range is set so that excellent strength and toughness can be obtained only when this mixed gas is used. However, if shielding gas is used,
If Ar is used alone, it will affect welding workability, especially arc droplet migration and slag flaking9, and the yield of each component element in the weld metal will change slightly, making it difficult to obtain the required strength and toughness. There is a possibility that it will not be possible.

(Problems to be Solved by the Invention) The present invention has been made as a result of considering the above-mentioned circumstances and conducting intensive research.
It is an object of the present invention to provide a TIG welding wire for Cr-Mo steel that suppresses the temper embrittlement and provides good low-temperature toughness during welding.

(Means for Solving the Problems) The gist of the present invention is that C: 0.03 to 0.15 excellent in terms of weight;
SI: 0.40-0.80%, Mn: Q, 60
-1.30mm, Cr: 1.00-1.50%, Mo
: Contains 0.45~0.60% as an essential component, N
i: 0.30% or less, N: 0.012% or less, O: 0.
010% or less, with the remainder consisting of iron and inevitable impurities.

The present invention can exhibit excellent effects by specifying the chemical composition of the wire as described above.

The reason for configuring the components of the wire of the present invention in this way, and the functions and effects thereof will be described below.

(Function) C is an extremely important element that increases the strength of the weld metal, but if it exceeds 0.15%, the cracking susceptibility of the weld metal increases, so the maximum content was set at 0.15%. On the other hand, 0.03
If it is less than 0.0%, the required nationality cannot be secured.
0.3% or more is necessary.

St is a deoxidizing element for weld metal, and traditionally it was desirable to keep it at an extremely low value from the perspective of preventing burnout and embrittlement, but it is important to ensure toughness and prevent weld defects such as blow holes due to insufficient deoxidation However, if added in excess, the strength of the weld metal becomes excessive and the notch toughness decreases, so the upper limit was set at 0.80%.

Like St, Mn is an element that deoxidizes the weld metal and increases the strength of the weld metal, but when it exceeds 1.30%, the quenching effect increases, increasing the f'L sensitivity of the weld metal and deteriorating the toughness. Therefore, Mn is maximum 1.30 in wire.
%. On the other hand, if it is less than 0.60%, the required strength cannot be ensured, so 0.60% or more is necessary.

Cr and Mo Fi, the steel types to which the wire of the present invention can be used are I Cr-'72 Mo y14 and I V4 as mentioned above.
Cr -'9 Mo jl (etc. (r - Mo 11), so Cr and Mo ensure the welding material of the cometal thread, and make the high temperature strength and oxidation resistance of the weld metal decoy equal to that of the base material. Cr: 1.00 to 1.50% to obtain the weld metal composition between base metals, etc.
, Mo: 0.45-0.60 was determined.

Nl is an effective element for improving the toughness of weld metal, but 0.3
When it exceeds 0%, the quenching effect increases, the toughness decreases, and the amount of embrittlement shift before and after the embrittlement-promoting heat treatment increases.

N is an element that increases the strength of weld metal, and its effective amount is different from C, but as the N content increases, there is a tendency for toughness to decrease and welding workability also deteriorates, so 0.
It has been decided that the number will be 012 or below.

A small amount of 0 has the effect of increasing the toughness of the weld metal, but 0.0
If it exceeds 10%, it will have an adverse effect on toughness and welding workability, and welding defects such as minute blowholes and bits will occur in the weld metal, so it was determined to be 0.010 or less.

The above are the basic components of the wire of the present invention, but in the wire of the present invention, other restrictions may be placed on KAt and Cu as necessary.

At has a function as a deoxidizing component and is not particularly added to the wire itself, but a sufficient amount is acceptable for wire manufacturing.

Further, although Cu is a precipitation hardening element, it is not particularly added to the wire itself, but an amount sufficient to plate the surface of the wire with copper for rust prevention is acceptable.

The wire of the present invention can be manufactured by rolling and drawing a steel ingot in the same way as ordinary wire, and applying copper plating if necessary.

The reason why the wire constructed according to the above explanation is applied to TIG welding is to obtain a weld metal with good low-temperature toughness and less embrittlement caused by burning, which cannot be obtained with conventional wires and welding methods, as well as to achieve excellent welding of this wire. This is to achieve good workability, particularly good molten M transferability and slag removal.

(Example) A steel plate with the chemical composition shown in Table 1 has a plate thickness R=
A test plate with a groove of 25mm, θ = 45°, and D = 12mm was made, and TIG welding was performed under the welding conditions shown in Table 2 using a wire with a diameter of 1.2smφ and the composition shown in Table 3. did.

After welding is completed, post-weld heat treatment is performed at 680°C for 1 hr.
A JIS-A No. I round bar tensile test piece and a JIS-4 Charpy impact test piece were taken from a position centered at the center of the groove of the test material, 12.5 m below the plate thickness surface of the weld metal, and the tensile test and impact test specimens were taken. The test was conducted. Further, the Charpy impact test piece after the post-weld heat treatment was subjected to embrittlement promoting heat treatment under the conditions shown in FIG. 2, and an impact test was conducted. The results of these tests are shown in Table 4.

No. 1 Thorn Chemical composition of steel plate (H) Table 4 Mechanical test results notes Water 1 Average value of 3 Charpy impact test pieces * 3 Arc stability, spatter generation 2 Judgment for workability * 4 Individual absorbed energy values Large variation (range FM5.1-16
．． 9) Book 5 Welding Defects Described as a reference value In Table 4, the wire symbol A for the present invention wire KMt
The -E wire not only has good welding workability, but also has excellent weld metal performance in strength, notch toughness, and embrittlement properties.

On the other hand, to explain the comparative examples individually, the wire symbol F is a wire symbol F, which was conventionally considered as a measure to improve notch toughness and embrittlement due to burning.
Although the O content was 0.0112%, which exceeds the range of the present invention, the strength was slightly lower, but the average absorbed energy value was good, but the individual variations were large, and the workability was also slightly poor. there were. Wire symbol G is 81. for the purpose of improving strength and toughness. Mn, Ni and N exceed the range of the present invention by 0.85% and 1°40%.

The wires containing 0.34% and 0.0151% had the highest strength among the wires examined this time, but their toughness and embrittlement properties were poor, and their workability was also poor. there were. The wire symbol H is St for the purpose of improving toughness.
However, no improvement in soft toughness was observed and the hardening and embrittlement properties were poor.

The wire symbol work contains 0.16% of 1cc which exceeds the range of the present invention for the purpose of improving strength, but although strength is obtained, the toughness is low, and 0 also exceeds the range of the present invention. The workability was also somewhat poor because it contained 'l. Wire symbol J is wire symbol F.I) SI
It contains 0.34% of KN, which is slightly more than that of KN, and contains 0.0176% of KN, which exceeds the range of the present invention, for the purpose of further improving the strength, but the toughness and embrittlement properties are poor, and the welding workability is also poor. Met. The wire symbol contains Mn of 0.49% less than the range of the present invention for the purpose of improving toughness, and 0 contains 0.0224% of Mn that exceeds the range of the present invention, but this seems to be due to insufficient deoxidation. Welding defects occur,
In addition, welding workability was also poor.

(Effects of the Invention) As described above, the wire of the present invention can obtain the throughput, excellent notch toughness, and embrittlement properties shown in the examples, as well as ensure strength. Workability can be obtained.

[Brief explanation of drawings]

Figure 1 shows the groove shape of the test plate used in the example, Figure 2 shows the embrittlement promoting heat treatment conditions used in the example, and Figure 3 explains the amount of embrittlement shift. It is a diagram. 1 recognition 2 burnt 1 Koji Niibu “7.6 balls”

Claims (1)

[Claims] In weight%, C: 0.03 to 0.15%, Si: 0.40 to 0.80%, Mn: 0.60 to 1.30%, Cr: 1.00 to 1 .50%, Mo: 0.45-0.60% as essential components, Ni: 0.30% or less, N: 0.012% or less, O: 0.010% or less, and the balance is iron and unavoidable components. A TIG welding wire for Cr-Mo steel characterized by comprising impurities.