JPS60231591A - Wire for submerged arc welding of cr-mo group low alloy steel - Google Patents

Abstract

PURPOSE:To obtain a titled wire that can obtain a weld metal excellent in oxidationproofness, tenacity and strength by containing Cr, Mo as basic components and specifying compositions made of C, Si, Mn, O, rare earth elements, N, Ni and the rest Fe and Al. CONSTITUTION:The wire contains 0.5-10.5wt% Cr, 0.3-2.5% Mo and satisfies following conditions for inevitable impurities: <=0.19% C, <=0.6% Si, <=1.6% Mn, <=0.01% O. Further, it contains essentially 0.01-1.0% reare earth elements, 0.010-0.040% N, 0.1-1.2% Ni, and when necessary, contains one kind or more 0.01-0.20% Ti, 0.001-0.025% B, 0.01-0.30% V, 0.01-0.10% Nb and the balance Al with other inevitable impurities of <=0.10% Fe. By this composition, a wire for submerged arc welding of Cr-Mo group low alloy steel that forms a excellent weld metal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applicability] The present invention relates to a wire for submerged arc welding of Cr-Mo based low alloy steel, and more specifically to a wire for welding Cr-Mo based low alloy steel. The present invention relates to a wire for submerged arc welding that can yield a weld metal with excellent toughness, toughness, and strength.

The wire for submerged arc welding of the present invention can be used in various chemical industry plants such as petrochemicals, high temperature and high pressure boilers, etc.
When welding construction using Cr-Mo based low alloy steel such as Cr-Mo steel or 9Cr-IMoNb-V steel,
Alternatively, it is used as a welding material during repair welding.

[Prior art] CR-M□ type low alloy steel as mentioned above has excellent high temperature oxidation resistance and high temperature strength properties, and is widely used for various chemical industrial plants and high temperature and high pressure boilers. There is. However, the environment in which these materials are used has recently become increasingly severe, and welding materials have come to be required to have even higher performance than ever before.

Furthermore, there is a strong demand for the development of welding materials that exhibit excellent low-temperature toughness values so that they can withstand use in low-temperature environments.

[Problem that the invention seeks to solve]

Although the high-temperature oxidation resistance of conventionally used Cr-Mo welding materials for low-alloy steel has been achieved by adjusting the Cr content, its low-temperature toughness has been poor, and recent attention has been focused on it. It is no longer possible to satisfy the current demand for ``balance of high strength and high toughness''.

The present inventors paid attention to such circumstances and developed Cr-M.

An object of the present invention is to provide a wire for submerged arc welding that provides a weld metal that is particularly high in strength and exhibits excellent toughness even at low temperatures without impairing the features of welding wires conventionally known for welding low-alloy steels. Various studies were conducted as follows.

[Technical means to solve problems]

The wire for submerged arc welding for Cr-Mo-based low alloy steel according to the present invention has Cr as a basic component: 0.5 to 10.596 (same as 2 or less by weight) M○2 0.3 to 2.5 %f and unavoidable impurities C-, S 1%
Regarding MnsO, satisfy the following conditions: C: 0.19% or less Si: 0.6% or less Mn: 1.6% or less 0: 0.0196 or less, and rare earth elements: 0.01 to 1.0% N : 0.010-0.040% Ni: 0.1-12%, or in addition to these, Ti: 0.01-0.20% B: 0.001-0.02Elf V: It contains one or more elements selected from the group consisting of 0.01 to O, aO96, and the remainder consists of Fe, 0.10% or less of A1, and other inevitable impurities.

[Effect]

The reasons for determining the types and content ranges of the constituent quarters are as follows.

Cr: 0.5-10.5% Mo: 0.8-2.5% The welding wire of the present invention is as described above.

The base material to be welded is low-alloy steel, more specifically 0.5Cr-0.5Mo steel, (1-1.25)C
r −1M o fjI4.2.25 Cr −I M
o steel, 8 Cr-IM.

Steel, 5Cr-0,5Mo Steel, 9Cr-IMo
Examples include steel, 9Cr-IMo-Nb-V steel, 9Cr 2Mo steel, and the like. Cr and MO in these steel materials are essential components to ensure the required performance as a co-metallic welding material and to make the high-temperature strength and high-temperature oxidation resistance of the weld metal equivalent to that of the base metal. The content of both is determined by the high temperature strength of the base material and the high temperature acid resistance lI/carp 1r shot 1 piece - 1 piece) i
Yu! Each was determined as described above so as to obtain the desired results.

C: 0.19% or less Si: 0.6% or less Mn: 1.6% or less 0: 0.01% or less All of these elements are said to be inevitably mixed into steel as unavoidable impurities. Although it has one aspect, it is also an optimal element that exhibits the following functions on the other side.
It exerts a certain effect depending on its presence in small amounts. However, if there is too much, the following problems will appear. That is, C is an extremely important element as a strengthening element for weld metal, and although it exhibits its effect even in a very small amount, it is preferable to leave it in an amount of about 0.04% or more. However, if it is too large, the weld metal becomes susceptible to cracking, so it must be kept at 0.19% or less. Like C, Si also acts as a strengthening element for the weld metal and is also an important component as a deoxidizing agent.
l (preferably 0.02% or more) will effectively exhibit its effect, but if it is too large, the weld metal will become more susceptible to temper embrittlement and cracking, so it must be kept at 0.6% or less. . Mn contributes to improving the toughness of the weld metal and also acts effectively as a reinforcing element, and these effects are exhibited in small amounts (preferably 0.2% or more). However, in the case of cr-Mo based low alloy steel, too much Mn increases the susceptibility of the weld metal to temper embrittlement, so the upper limit was set at 1.6%. Further, a very small amount of 0 has the effect of increasing the notch toughness of the weld metal, but if it exceeds 0.01Ly), there is a tendency to actually inhibit the notch toughness.

Rare earth elements: 0.01 to 1.096 Rare earth elements, represented by Ces Las y, Sm, etc., have a remarkable effect of reducing the oxygen content in the weld metal and increasing the notch toughness. It is an extremely important additive element for improving hardenability, and must be contained in an amount of 0.0196 or more in order to effectively exhibit its effect. However, the above-mentioned effects reach a saturation state at around 1.096, and if more than 1.0% is added, it creates intermetallic compounds with various coexisting elements and remains in the weld metal, reducing the cleanliness of the weld metal. It is necessary to keep it below.

A more preferable content of rare earth elements is 0.1 to 0.5%.

N: 0.010-0.040% N forms fine nitrides with rare earth elements and Cr, and N
It is an essential component that has the effect of refining the crystal grains by solid solution in the matrix, thereby improving the notch toughness and temper embrittlement susceptibility of the weld metal. % or more. However, if it is too large, welding defects are likely to occur and welding workability is also reduced, so it should be kept at 0.040% or less.

Ni: 0.1 to 1.2% This is an important component for increasing the toughness of weld metal, and the content of 0.1% to 1.2% is important for increasing the toughness of weld metal.
It must be contained at least 1%. However, if it is too large, the high-temperature creep properties of the weld metal will deteriorate, so it must be kept below 1296. Especially (11,25)Cr
In O,5Mo series and 2.25Cr-, the amount of Nl is preferably suppressed to 0.3% or less in consideration of tempering brittleness.

Al: 0.10% or less Al is unavoidably mixed in as a deoxidizing component added at the steel manufacturing stage, but if it is too large, it will have an adverse effect on the creep resistance of the weld metal. Moreover, in the coexistence with rare earth elements, the toughness of the weld metal is significantly reduced, and the effect of adding rare earth elements is diminished. Therefore, in order to avoid such problems, the Al content should be 0.10% or less, more preferably 0.0%.
It should be kept below 5%.

Ti: 0.01 to 0.2096 B: 0.001 to 0025% v: o, oi to o, ao% Nb: 0.01 to 0.10% All of these elements increase the high temperature strength of the weld metal. The effect is not exhibited effectively below the respective lower limit values. Among these, B increases the hardenability of the weld metal in addition to the above-mentioned effects, and is significantly exhibited in coexistence with truncated metal. However, if T I %■ and Nb exceed the upper limits, the toughness of the weld metal will sharply decrease, and if B exceeds the upper limit, the high temperature creep characteristics of the weld metal, especially the creep ductility, will deteriorate, making it impossible to put it into practical use. .

The welding wire of the present invention contains the above elements, with the remainder consisting of iron and other unavoidable impurities. These unavoidable impurities include P, 5n Since it segregates in the field and causes tempering embrittlement, both should be suppressed to 0.01% or less.

In addition, as long as the above requirements are met, it has excellent notch toughness and high temperature strength regardless of whether the flux used in combination is a molten type or a sintered type, and regardless of the welding conditions or post-weld heat treatment conditions. A Cr-MO based weld metal can be obtained.

〔Example〕

Cr-M submerged arc welding wires having the chemical composition shown in Table 1 were prepared, and each wire was combined with the sintered flux or molten flux shown in Table 2 as shown in Table 3, and AS
TM standard A387, Gr.

11, same Gr, 22, same Gr, 21 name, and 9Cr
IMo-Nb-V steel as well as 9Cr-2M.

Submerged arc welding experiments were conducted using steel as the base material to investigate welding workability.

In addition, each of the obtained weld metals was subjected to stress relief annealing (SR) using the heat pattern shown in Fig. 1, and a part of the weld metal was subjected to annealing and embrittlement heat treatment (SC) using the Hild pattern shown in Fig. 2.
was added, and mechanical strength tests (room temperature tensile test and impact test) were conducted on each test piece.

The results are summarized in Table 3. However, as the test pieces for the mechanical strength test, a tensile test piece was cut out from section A in FIG. 3, and a 2 mm V notch Charpy impact test piece was cut out from section B.

From Tables 1 to 3, the following considerations can be made.

Wire Nos. (W-1,) to (W-14) are examples that satisfy all the specified requirements of the present invention, and the obtained weld metal has no toughness and strength after SR or (SR+SC). also shows high values.

On the other hand, wires NO. (W-15) to (W-27) are comparative examples that lack any of the requirements stipulated in the present invention.
There are problems with toughness or strength as described below.

W-15: This is an example of a 1.25Cr-0,5Mo wire, but since it does not contain rare earth elements, the toughness improvement effect is not sufficient.

W-16: This is an example of a 2.25Cr-1Mo wire, and although it contains an appropriate amount of N, it does not contain any rare earth elements, and has too much Alfi+, resulting in poor welding workability.

W-17, 18: This is an example of a 2.25Cr-1Mo wire. W-17 contains an appropriate amount of rare earth elements, but the amount of N is insufficient. It is not possible to sufficiently increase the g?resistance.In addition, since W-18 has too much N, blowholes occur in the weld metal.

This is an example of W 19 : 2”/, i Cr I Mo-based wire, and the contents of rare earth elements and N are appropriate, but the toughness value is low due to too much Al.

W-20: This is an example of 8Cr-1Mo based wire, and the toughness value is low due to insufficient amount of rare earth elements.

W-21: Same < 3 This is an example of a Cr-I Mo wire, and the amounts of rare earth elements and N are appropriate, but the deoxidizing effect of rare earth elements cannot be fully utilized because the amount of 0 is too large. . Therefore, although the strength can be compensated to some extent by the addition of V, the toughness value is low.

W-22: 9Cr-1MO-Nl) - This is an example of V-based wire, but since rare earth elements are not added and Ni4 and Vi are outside the specified range, the strength is higher than necessary and the toughness is poor. is insufficient.

W-23: This is an example of a 9Cr-2Mo wire. Although the amount of rare earth elements is within the appropriate range, the amount of N is outside the specified range, so the toughness is low even though it contains an appropriate amount of Ni.

W-24 to 26: Examples of adding Ti, V, or Nb. Although the amounts of rare earth elements and N are appropriate, the strength of the weld metal becomes higher than necessary because of too much Ti, SV, or Nb. The toughness is low.

W-27: 550° because Bfi exceeds the specified range
The creep rupture elongation after CX1000 hours is very low at 5%.

This is an example of W 28:2”/4Cr 1Mo wire,
Because there was too much C, one of the main components, cracks occurred in the bead after welding. This cracking was also visually observed on the bead surface. Also, the strength is higher than necessary.

W-29: Similarly, this is an example of a 2φ1/Cr-I M □ wire, but because of too much Sl, the toughness after SR as well as after SR+SC is particularly poor.

W-80: This is an example of a 2 1/4 Cr-1Mo wire with an unnecessarily large amount of Mn. The toughness after SR is good, but it deteriorates markedly after SR + SC, making it unsuitable for practical use. I don't get it.

〔Effect of the invention〕

The present invention is constructed as described above, but the key point is that appropriate amounts of rare earth elements, N, and Ni are actively contained in the Cr-MO type low alloy steel wire, and especially zero
By limiting the amount of It has now become possible to provide a submerged arc welding wire for cr-M□-based low alloy steel that can be obtained.

[Brief explanation of drawings]

Figure 1.2 is a diagram showing the heat pattern of stress relief annealing (SR) and tempering embrittlement heat treatment (SC) of the weld metal adopted in the examples, and Figure 3 is the collection of specimens for mechanical testing of the weld metal. It is an explanatory view showing a position. Applicant Kobe Steel, Ltd. Figure 1 690'CX8 Hr

Claims (1)

[Claims] The ill contains Cr: 0.5 to 10.5% (weight i%: the same applies hereinafter) as a basic component, and MCI: 0.3 to 2.5%, as well as unavoidable impurities such as C - and S. 1%
Regarding Mn, 0, the conditions of C: 0.19% or less, Si: 0.6% or more, Mn: 1.6% or less, 0: 0.01% or less, and rare earth elements: 001 to 1. ．． 096 N: 0.010 to 0.04096 Ni: Essentially contains 0.1 to 1.2%, the balance is Fe, and Al of 0.1096 or less
and other unavoidable impurities (2)
Contains Cr: 0.5-10.5% (vff1%: the same hereinafter) as a basic component, Mo: 0.8-2.5%, and C, Si, Mn5, which are unavoidable impurities.
Regarding O, C: 0.19% or less, Si: 0.6% or less, Mn: 1.6% or less, o: o, ot% or less, and rare earth elements: 0.01-10% N: Essentially contains 0.010-0040% Ni: 0.1-1.2%, and Ti: 0.01-0.20% B: 0.001-0.0254 V: 0.01-0. 8096 Nl): 0.01 to 0.10% Submerged arc welding of cr-Mo based low alloy steel characterized by containing one or more elements selected from the group consisting of: and consisting of avoidable impurities. Wire for.