JP4513466B2 - Welded joints and welding materials - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is used for containers, reaction tubes, parts, etc. exposed to high-temperature atmospheres in heat exchange type hydrocarbon reformers and waste heat recovery equipment in petroleum refining, and has weldability and metal dusting resistance. The present invention relates to a weld joint made of a base metal and a weld metal that are high Cr-high Ni-Fe alloys having excellent properties, and a welding material used for producing the weld joint.

  In reformers for petroleum refining and the like, ammonia production apparatuses using petroleum and the like, hydrogen production apparatuses, and the like, heat exchange for waste heat recovery is frequently used in order to increase energy efficiency. On the other hand, demand for clean energy such as hydrogen gas and methanol gas is expected to increase significantly in the future, and reformers that are indispensable for their production are required to be large, highly efficient and suitable for mass production. .

Usually, a metal material such as a reaction tube of the above apparatus is exposed to a reaction gas containing H ₂ , CO, CO ₂ , H ₂ O, and a hydrocarbon (such as methane) at a temperature of about 1000 ° C. or higher. . In this temperature range, the surface of the metal material is selectively oxidized with elements such as Cr and Si, which have a higher tendency to oxidize than Fe and Ni, and forms a dense oxide film. Thereby, corrosion of a metal material is suppressed.

  However, in order to effectively use the heat of high-temperature gas, heat exchange in the temperature range of 400 to 700 ° C, which is lower than before, is important. In this temperature range, high Cr used for reaction tubes, heat exchangers, etc. -Corrosion associated with the carburization phenomenon of high Ni-Fe alloy metal materials becomes a problem. That is, in a portion having a relatively low temperature such as a heat exchanger, the formation of an oxide film having a corrosion-inhibiting effect is delayed, so C atoms are adsorbed on the surface of the metal material from the gas and carburization occurs in the metal material.

  When a carburized layer containing carbides such as Cr and Fe is formed in the metal material, the portion expands and fine cracks are likely to occur. Furthermore, when the carbide formation in the metal material is saturated, so-called metal dusting occurs in which the metal powder generated by the decomposition of the carbide from the surface of the metal material is peeled off and corrosion consumption proceeds. The peeled metal powder promotes carbon deposition on the surface of the metal material. If the clogging in the pipe expands due to such wear, carbon deposition, or the like, there is a possibility of causing a failure of the apparatus. Therefore, sufficient consideration must be given to the selection of the material as the apparatus member.

  Patent Document 1 discloses a metal material that secures metal dusting resistance by including Cu in a high Cr-high Ni-Fe alloy with an increased amount of Al. Patent Document 2 discloses a high Cr-high Ni-Fe alloy welded joint with improved carburization resistance as described above.

JP 2003-73763 A JP 2002-235136 A

  The metal material disclosed in Patent Literature 1 has a viewpoint of suppressing weldability, particularly cracking that occurs in a weld heat affected zone (hereinafter referred to as “HAZ”), which is a problem when welding a high Ni-based alloy with an Al content. There are no considerations. For this reason, it cannot be said that it has sufficient weldability when considering the use to a structure accompanied by welding construction.

  The welded joint disclosed in Patent Document 2 is intended to prevent caulking, which is a problem in an apparatus for producing petroleum products by thermal decomposition such as an ethylene plant, and causes a problem in a more severe environment. The metal dusting resistance and weldability cannot be satisfied at the same time.

  The present invention has been made in order to solve the above-described problems, and the object thereof is excellent in an environment where metal dusting is likely to occur, such as a heat exchange type hydrocarbon reforming apparatus and a waste heat recovery apparatus. It is to provide a welded joint and a welding material having corrosion resistance and excellent in high temperature strength and weldability.

  In addition, “under the environment of a heat exchange type hydrocarbon reformer, a waste heat recovery unit, etc.” specifically means that hydrocarbon and carbon monoxide alone or in total, 1 vol% or more, hydrocarbon, carbon monoxide And an atmosphere containing hydrogen alone or a total of 25 vol% or more and 1000 ° C. or less.

  The present inventors have studied a welded joint that has excellent weldability while ensuring metal dusting resistance.

The base metal and the weld metal forming the welded joint exhibit a large ductility decrease in the range of the liquidus temperature (T _L ) and the solidus temperature (T _S ). In addition, there is a temperature region in which the ductility decreases again as the temperature becomes lower (less than T _S ). The former temperature region is called a solidification brittleness temperature range (BTR), and the latter temperature region is called a ductility-dip temperature range (DTR). Cracks in the HAZ of welded joints include the following: (a) When subjected to a welding heat cycle, the base metal grain boundary heated to a high temperature close to the boundary with the weld metal melts, and the strain added by welding causes BTR. There are “liquefaction cracks” that occur when exceeding, and (b) “ductility-reducing cracks” that occur when strain exceeding DTR is applied when subjected to a welding heat cycle.

In order to suppress this ductile drop cracking, it is effective to increase the lowest ductility value in _DTR (minimum ductility value, hereinafter referred to as ε _DTR ). For that purpose, P, S, Al, Ti, etc. It is necessary to reduce the content of elements that easily cause grain boundary embrittlement.

However, in order to ensure metal dusting resistance, it is necessary to contain Cu in addition to high concentration of Al. Al is not only the grain boundary embrittlement induced to form a gamma ^'phase as a solid solution in grains (Ni ₃ (Al, intermetallic compound Ti)), increasing the intragranular strength, Cu also in grains To form a fine intermetallic compound and increase the intragranular strength.

  Therefore, metal materials with metal dusting resistance have extremely high intragranular strength compared to conventional high Cr-high Ni-Fe alloys, which may cause many ductile drop cracks in HAZ in welded joints. is there.

Therefore, the present inventors have focused on Mo in order to strengthen the grain boundary and maintain the intra-granular / grain boundary strength balance and raise ε _DTR to prevent ductile drop cracking.

That is, Mo is a carbide forming element, and has an action of suppressing the growth of the carburized layer and improving the resistance to metal dusting. Furthermore, Mo is generally used as an element that increases the strength by solid solution in the grains, but when the content thereof is 15% by mass or less, the grain boundary strengthening action is more prominent. Therefore, not only elements that promote grain boundary embrittlement such as P and S, but also HAZ that is promoted by intragranular strengthening by adding Al and Cu, which are essential for ensuring metal dusting resistance. ductility dip cracking, to strengthen grain boundaries by containing proper amounts of Mo as an essential element, it can be prevented by increasing the epsilon _DTR by balancing the intragranular / grain boundary strength.

  In addition, when a large amount of B, which is a grain boundary strengthening element, is included, it promotes melting of the grain boundary to induce liquefaction cracking, and at the time of solidification of the weld metal, the liquid phase is significantly concentrated to lower the melting point of the liquid phase and solidify cracking. Significantly increases sensitivity. For this reason, when it contains B, it is necessary to provide restrictions on the content.

Furthermore, Si, an element that improves carburization resistance, promotes melting of grain boundaries and induces liquefaction cracking when it is contained in a large amount. This significantly increases the susceptibility to solidification cracking. For this reason, even when Si is contained, it is necessary to provide a restriction on the content thereof.
As described above, high Cr- containing, in mass%, Cr: 15-35%, Ni: 40-78%, Al: more than 2% and less than 4.5%, Mo: 3.5-15%, Cu: 0.53-5.5% Based on high Ni-Fe alloy, Al, Si and Cu for ensuring metal dusting resistance, Mo (and B) for strengthening grain boundaries, and P and S for promoting grain boundary embrittlement If the components are adjusted so that the following formula (1) or (2) is satisfied, welding that ensures metal dusting resistance and at the same time undergoes a welding heat cycle will not cause ductile degradation cracks in HAZ. A joint can be obtained.

When not containing B
24P + 1.28Mo + 0.9Si-32S-0.12Cu-0.05Al ≥ 4.23 (1)
When containing B
24P + 1.28Mo + 0.9Si + 20B-32S-0.12Cu-0.05Al ≥ 4.23 (2)
However, the element symbol in the formula (1) or (2) means the content (% by mass) of the element.

  The gist of the present invention is a welded joint shown in any one of the following (A) to (G) and a welding material shown in any of the following (H) to (N).

(A) Both the base metal and the weld metal are in mass%, C: 0.01 to 0.45%, Si: 0.01 to 2%, Mn: 0.1 to 2% , P: 0.03% or less, S: 0.01% or less, Cr: 15 to 35%, Ni: 40 to 78%, Al: more than 2% and less than 4.5%, Mo: 3.5 to 15%, N: 0.001 to 0.2% and Cu: 0.53 to 5.5% , and the following (1 ) Welded joint with excellent metal dusting resistance, characterized by satisfying the formula, and the balance being Fe and impurities.

24P + 1.28Mo + 0.9Si-32S-0.12Cu-0.05Al ≥ 4.23 (1)
However, the element symbol in the formula (1) means the content (% by mass) of the element.

(B) at the weld joint according to the above (A), are both base metal and weld metal, instead of a part of Fe, by mass%, T i: 0.01~1.4%, Ta: 0.05~5%, V: 0.01 to 1%, Zr: 0.01 to 1.4%, Nb: 0.01 to 1.4%, and Hf: One to one selected from 0.01 to 1% Welded joints.

  (C) In the welded joint according to the above (A) or (B), the base material and the weld metal both include REM: 0.005 to 0.3% in mass% instead of part of Fe. Welded joints with excellent metal dusting resistance.

(D) Both the base metal and the weld metal are in mass%, C: 0.01 to 0.45%, Si: 0.01 to 2%, Mn: 0.1 to 2% , P: 0.03% or less, S: 0.01% or less, Cr: 15 to 35%, Ni: 40 to 78%, Al: more than 2% and less than 4.5%, Mo: 3.5 to 15%, N: 0.001 to 0.2% and Cu: 0.53 to 5.5% , B: Metal dusting resistance including at least one selected from 0.0005 to 0.03%, Ca: 0.0005 to 0.02% and Mg: 0.0005 to 0.02%, and satisfying the following formula (2) Excellent weld joint.

24P + 1.28Mo + 0.9Si + 20B-32S-0.12Cu-0.05Al ≥ 4.23 (2)
However, the element symbol in the formula (2) means the content (% by mass) of the element. When B is not contained, 0 is substituted for “B” in the equation (2).

(E) In the welded joint described in the above (D), both the base metal and weld metal, instead of a part of Fe, by mass%, T i: 0.01~1.4%, Ta: 0.05~5%, V: 0.01 to 1%, Zr: 0.01 to 1.4%, Nb: 0.01 to 1.4%, and Hf: One to one selected from 0.01 to 1% Welded joints.

  (F) In the welded joint according to (D) or (E) above, the base material and the weld metal both include REM: 0.005 to 0.3% in mass% instead of part of Fe. Welded joints with excellent metal dusting resistance.

  (G) characterized in that it is used in an atmosphere containing hydrocarbon and carbon monoxide alone or in total of 1 vol% or more, hydrocarbon, carbon monoxide and hydrogen alone or in total of 25 vol% or more and 1000 ° C. or less. The weld joint excellent in metal dusting resistance according to any one of (A) to (F) above.

(H) in mass%, C: 0.01~0.45%, Si : 0.01~2%, Mn: 0.1~2%, P: 0.03% or less, S: 0.01% or less, Cr: 15~35%, Ni: 40 -78%, Al: more than 2% and less than 4.5%, Mo: 3.5-15%, N: 0.001-0.2% and Cu: 0.53-5.5% , satisfying the following formula (1), the balance being A welding material used for producing the welded joint according to the above (A), which comprises Fe and impurities, by the TIG welding method.

24P + 1.28Mo + 0.9Si-32S-0.12Cu-0.05Al ≥ 4.23 (1)
However, the element symbol in the formula (1) means the content (% by mass) of the element.

(I) In the welding material described in (H) above, instead of a part of Fe, in mass% , T i: 0.01 to 1.4%, Ta: 0.05 to 5%, V: 0.01 to 1%, Zr The weld joint according to (B) above is manufactured by the TIG welding method, including at least one selected from: 0.01 to 1.4%, Nb: 0.01 to 1.4% and Hf: 0.01 to 1% Welding material used to do.

  (J) In the welding material described in (H) or (I) above, the REM: 0.005 to 0.3% in mass% instead of part of Fe is included in (C) above A welding material used for producing such a welded joint by the TIG welding method.

(K) By mass%, C: 0.01 to 0.45%, Si: 0.01 to 2%, Mn: 0.1 to 2% , P: 0.03% or less, S: 0.01% or less, Cr: 15 to 35%, Ni: 40 -78%, Al: more than 2% and less than 4.5%, Mo: 3.5-15%, N: 0.001-0.2% and Cu: 0.53-5.5% , B: 0.0005-0.03%, Ca: 0.0005 A welded joint according to (D) above characterized by containing at least one selected from -0.02% and Mg: 0.0005-0.02% and satisfying the following formula (2) by TIG welding Welding material used to make.

24P + 1.28Mo + 0.9Si + 20B-32S-0.12Cu-0.05Al ≥ 4.23 (2)
However, the element symbol in the formula (2) means the content (% by mass) of the element. When B is not contained, 0 is substituted for “B” in the equation (2).

(L) in the weld material described in the above (K), instead of a part of Fe, by mass%, T i: 0.01~1.4%, Ta: 0.05~5%, V: 0.01~1%, Zr : A welded joint according to (E) above, characterized by containing one or more selected from 0.01 to 1.4%, Nb: 0.01 to 1.4% and Hf: 0.01 to 1% by TIG welding Welding material used to do.

  (M) In the welding material described in the above (K) or (L), in the above (F), which includes REM: 0.005 to 0.3% by mass% instead of part of Fe A welding material used for producing such a welded joint by the TIG welding method.

  (N) Welding a member to be used in an atmosphere containing hydrocarbon and carbon monoxide alone or in total of 1 vol% or more, hydrocarbon, carbon monoxide and hydrogen alone or in total of 25 vol% or more and 1000 ° C. or less The welding material having excellent metal dusting resistance according to any one of (H) to (M) above, which is a material.

  Since the welded joint according to the present invention is excellent in metal dusting resistance and weldability, it can be used for heating furnace tubes, pipes or heat exchanger tubes in petroleum refining, and the welding workability and durability of the apparatus. And safety can be greatly improved. In addition, the welding material according to the present invention is optimal for producing the above-described welded joint by the TIG welding method.

  In the present invention, the reason for limiting the chemical composition of the base metal of the welded joint and the weld metal is as follows. In the following description, “%” display of the content of each element means “mass%”.

C: 0.01 to 0.45%
C is an element having an effect of increasing the strength of the base metal and the weld metal of the welded joint, but if the content is less than 0.01%, the high temperature strength is insufficient. On the other hand, if the content exceeds 0.45%, the toughness of the welded joint decreases. Therefore, the content of C is set to 0.01 to 0.45%. The content of C is preferably 0.2 to 0.4%, and most preferably 0.25 to 0.4%.

Si: 0.01-2%
Si is an element having a deoxidizing action when a metal material is melted. Si also forms a Si oxide film under the Cr oxide film on the surface of the welded joint to suppress the intrusion of C into the welded joint, and increases the activity of C in the welded joint, thereby reducing the metal resistance. It is an element that also has the effect of greatly improving sting properties. For this reason, Si is contained 0.01% or more. However, when the content exceeds 2%, the hot workability and weldability of the base material are deteriorated. Therefore, the Si content is set to 0.01 to 2%. The lower limit of the Si content is preferably 0.05%, more preferably 0.06%. Further, the upper limit of the Si content is desirably 1%, and more desirably 0.5%.

Mn: 0.01~2%
Mn is an element that has an effect of suppressing brittleness during hot working of a base material due to S contained as an impurity and is effective for deoxidation during melting. In order to acquire these effects, it is necessary to contain Mn 0.01% or more. However, if the Mn content exceeds 2%, the activity of C in the welded joint made of the base metal and the weld metal is lowered, and the formation of oxide films of Cr and Al on the welded joint surface is hindered. As a result, since the penetration of C from the atmosphere is promoted, metal dusting is likely to occur. Therefore, the Mn content is set to 0.01 to 2%. The Mn content is preferably 0.05 to 1.0%, and most preferably 0.1 to 0.8%.

P: 0.03% or less P is an impurity element mixed in from raw materials when melting metal materials, causing a decrease in corrosion resistance, degrading hot workability and weldability, and therefore reducing as much as possible. It is desirable to do. Therefore, the content of P is set to 0.03% or less. The P content is preferably 0.02% or less, and most preferably 0.01% or less.

S: 0.01% or less S is also an impurity element mixed from raw materials when melting a metal material, causing a decrease in corrosion resistance, degrading hot workability and weldability, and reducing as much as possible. It is desirable. Therefore, the S content is set to 0.01% or less. The S content is preferably 0.007% or less, and more preferably 0.002% or less.

Cr: 15-35%
Cr has the effect of delaying the growth of the carburized layer by combining with C that has penetrated into the welded joint in a high-temperature use environment, thereby ensuring good metal dusting resistance. This effect is exhibited when the content is 15% or more. However, if its content exceeds 35%, the toughness is lowered and hot workability is deteriorated, which makes it difficult to manufacture the base material. Therefore, the Cr content is 15 to 35%. The Cr content is preferably 18 to 33%, more preferably 25.2 to 33%.

Ni: 40-78%
Ni is an element that maintains the high-temperature strength and the structural stability and has the effect of enhancing the corrosion resistance by coexisting with Cr. Ni also has the effect of suppressing the occurrence of metal dusting. These effects are exhibited when the Ni content is 40% or more, but even if it exceeds 78%, the effects are saturated. Therefore, the Ni content is 40 to 78%. The Ni content is preferably 48 to 78%, more preferably 50 to 78%. Most preferred is 56-78%.

Al: more than 2% and less than 4.5%
Al is an element having a deoxidizing action when a metal material is melted. Al forms an Al oxide film on the lower layer of the Cr oxide film on the surface of the welded joint or on the outermost surface of the welded joint, suppresses the intrusion of C into the metal material and increases the activity of C in the metal material, It also has the effect of significantly improving metal dusting resistance. Furthermore, Al also has the effect of increasing high-temperature strength by the precipitation of intermetallic compounds such as Ni ₃ Al. In order to obtain these effects, the Al content must be more than 2%. However, when the content is 4.5% or more, the hot workability and weldability of the base material are remarkably deteriorated. Therefore, the Al content is more than 2% and less than 4.5%. The Al content is preferably less than 4%, and more preferably less than 3.7%. The lower limit of the Al content is preferably 2.6%.

Mo: 3.5-15%
Mo is a carbide-forming element and is an element that suppresses the growth of the carburized layer and enhances the metal dusting resistance and strengthens the grain boundary. In order to obtain these effects, it is necessary to contain 3.5% or more of Mo. However, if the Mo content exceeds 15%, an intermetallic compound is precipitated in the grains, and the intragranular strength is remarkably increased, and hot workability, manufacturability, and weldability are reduced. Therefore, the Mo content is set to 3.5 to 15%. The preferable content is 4 to 12%, and more preferably 5 to 10%.

N: 0.001 to 0.2%
N is an element having an action of increasing the activity of C in the base material and improving the resistance to metal dusting. This effect is insufficient when its content is less than 0.001%. However, if the N content exceeds 0.2%, a large amount of Cr or Al nitride is formed, and hot workability and weldability are significantly reduced. Therefore, the N content is set to 0.001 to 0.2%.

Cu: 0.015 ~5.5%
Cu is an element that increases the activity of C in the welded joint, suppresses the growth of the carburized layer, and improves the metal dusting resistance. This effect is exhibited by containing 0.015% or more of Cu. However, when Cu is contained exceeding 5.5%, the toughness of the base metal and the weld metal is lowered, and the hot workability is remarkably lowered. It also significantly increases weld solidification cracking susceptibility. Accordingly, the content of Cu is set to 0.015 to 5.5 percent. The Cu content is preferably 0.02 to 4.8%, and more preferably 0.05 to 4.2%.

  In addition, since the Al content exceeds 2% in the welded joint of the present invention, sufficient metal dusting resistance can be obtained even if the Cu content is reduced. Therefore, the Cu content is most preferably 2% or less from the viewpoint of weld solidification cracking sensitivity.

The base material and the weld metal constituting the welded joint of the present invention may have the chemical composition described above, with the balance being Fe and impurities. Further, from the viewpoint of further enhancing the metal dusting resistance, instead of a part of Fe, T i: 0.01~1.4%, Ta: 0.05~5%, V: 0.01~1%, Zr: 0.01~1.4% Nb: 0.01 to 1.4% and Hf: 0.01 to 1% may be included (in the examples, these elements are referred to as “first group elements”). .

Ti, Ta, V, Zr, both Nb and Hf are carbide forming elements has an effect of improving the metal dusting resistance by suppressing the growth of the carburized layer. The These effects become remarkable, their respective T a is less than 0.05%, Ti, V, Zr, Nb and Hf are not less than 0.01%. However, when there is too much content of these elements, it will have a bad influence on hot workability, manufacturability, toughness, and weldability.

Therefore, the content of the case of incorporating one or more selected from these elements, T i is from 0.01 to 1.4%, Ta is 0.05 to 5% V is 0.01 to 1% Zr is 0.01 to 1.4%, Nb is 0.01 to 1.4%, and Hf is 0.01 to 1%. The content of these elements, their respective T i is 0.01 to 0.8%, Ta 0.5 to 5% 0.01 to 0.8% Both Zr and Nb are, to a from 0.01 to 0.6% Both V and Hf are is desirable, further desirable are their respective T i is 0.01 to 0.4%, Ta is 1 to 3%, Zr and Nb are both 0.02 to 0.8%, V is 0.01 to 0.3%, Hf is 0.02 to 0.6% It is.

  From the viewpoint of improving corrosion resistance, the base metal and weld metal of the welded joint of the present invention may contain REM: 0.005 to 0.3% in place of part of Fe. REM is a general term for a total of 17 elements of Sc and Y and lanthanoid elements.

  REM has the effect of increasing the uniformity of the oxide film containing Cr and Al formed on the surface of the welded joint in the usage environment, improving the adhesion, and improving the corrosion resistance. This effect becomes remarkable when the content is 0.005% or more. However, if its content exceeds 0.3%, a coarse oxide is formed, leading to a reduction in toughness and hot workability, and an increase in surface flaws. Therefore, the content when REM is added is 0.005 to 0.3%. The REM content is preferably 0.005 to 0.1%, more preferably 0.005 to 0.07%.

  From the viewpoint of improving hot workability and grain boundary strength, the base metal and weld metal of the welded joint of the present invention are replaced with a part of Fe, B: 0.0005 to 0.03%, Ca: 0.0005 to 0.02%, and Mg: One or more selected from 0.0005 to 0.02% may be included (in the examples, these elements are referred to as “second group elements”).

  These elements are all elements that have an effect of increasing hot workability and grain boundary strength. These effects become remarkable when the content is 0.0005% or more. However, if the B content exceeds 0.03%, the melting of the grain boundary is promoted to induce liquefaction cracking, and when the weld metal solidifies, the liquid phase is remarkably concentrated and the melting point is lowered to lower the melting point. Increase significantly. As a result, the welded joint made of the base material and the weld metal becomes brittle and causes a decrease in hot workability and weldability. If the Ca or Mg content exceeds 0.02%, it is present in the alloy in a solid solution state, and conversely, hot workability and weldability are reduced.

  Therefore, the content in the case of containing one or more selected from these elements is 0.0005 to 0.03% for B and 0.0005 to 0.02% for Ca and Mg, respectively. Any element is desirably 0.0005 to 0.015%, and more desirably 0.0005 to 0.012%.

  In the welded joint of the present invention, Al and Cu for ensuring metal dusting resistance, Mo and B for strengthening grain boundaries, and P and S for promoting grain boundary embrittlement are expressed by the following formula (1) or (2): It is necessary to adjust the components so as to satisfy the equation. When the following expression (1) or (2) is satisfied, a welded joint that does not cause ductile deterioration cracking in HAZ when subjected to a welding heat cycle can be obtained while ensuring metal dusting resistance.

When not containing B:
24P + 1.28Mo + 0.9Si-32S-0.12Cu-0.05Al ≥ 4.23 (1)
When containing B:
24P + 1.28Mo + 0.9Si + 20B-32S-0.12Cu-0.05Al ≥ 4.23 (2)
However, the element symbol in the formula (1) or (2) means the content (% by mass) of the element.

  The welded joint according to the present invention is particularly an atmosphere containing hydrocarbon and carbon monoxide alone or in total of 1 vol% or more, hydrocarbon, carbon monoxide and hydrogen alone or in total of 25 vol% or more and 1000 ° C. or less. Excellent metal dusting resistance below. For this reason, if this welded joint is applied to a member such as a reaction tube or peripheral equipment in an oil refining heat exchange type hydrocarbon reformer or waste heat recovery unit, the welding workability, durability and safety of the device are improved. It can be greatly improved.

  In the above, the component which comprises a base material and a weld metal was demonstrated. Both the base metal and the weld metal have chemical compositions within the same content range for each component, but this does not mean that the base metal and the weld metal must have exactly the same chemical composition. That is, each component of the base material and the weld metal should be within the above-mentioned content range. For example, the base metal C may be 0.10% and the weld metal C may be 0.15%.

  The welded joint of the present invention can be produced by various welding methods such as TIG welding and MIG welding. In addition, after the welding, the surface may be subjected to a surface processing treatment such as pickling, shot blasting, and grinder polishing. What is necessary is just to select the welding material of the composition from which the composition of the said weld metal is obtained according to the welding method and welding conditions to employ | adopt. In addition, when TIG welding is employed, it is desirable to use one shown in any of (H) to (N) described above.

  Metal materials having chemical compositions shown in Table 1 were melted in a high-frequency heating vacuum furnace. After forging each metal material ingot by the usual method, it was subjected to solution heat treatment at 1200 ° C, and 60 ° V groove processing of 1.5mm butt portion was performed. Thickness 12mm, width 50mm, length 150 A test piece for a confined weld crack test of mm and a metal dusting resistance evaluation test piece having a thickness of 4 mm, a width of 10 mm and a length of 20 mm were prepared.

Using the obtained restraint weld crack test specimen, restraint welding was performed around the periphery, and using a welding material (welding wire) with an outer diameter of 1.2 mm prepared in advance from each base material, welding current 150 A, welding voltage Multi-layer prime welding was performed by TIG welding under conditions of 15 V and a welding speed of 10 cm / min to obtain a welded joint. Here, the chemical composition of the weld metal is the same as that of the base metal because dilution hardly occurs in the case of TIG welding. Six sections of this welded joint were extracted and examined with an optical microscope with an enlarged field of view of 200 times to investigate the presence of HAZ cracks.
Next, using a test piece for evaluating metal dusting resistance of each metal material, the volume ratio was 1000% at 630 ° C. in an atmosphere of 26% H ₂ -60% CO-11.5% CO ₂ -2.5% H ₂ O. After a test for holding for a time, the surface deposits on the test piece were removed, and after ultrasonic cleaning, the presence or absence of pits was examined with an optical microscope. The results are also shown in Table 1. Metal dusting resistance is targeted to prevent pits by 200 hours.

  Furthermore, a tensile test was performed at 800 ° C. on a welded joint of each metal material using a round bar test piece having a diameter of 6 mm in parallel with the welded portion at the center. Tensile strength (TS [MPa]) was measured and high temperature strength was evaluated. The results are also shown in Table 1.

  “X” in “Weldability” in “Evaluation” in Table 1 means that HAZ cracks were observed even at one location for the six observation cross sections, and “○” indicates that HAZ cracks were completely observed. It means what did not exist. In addition, “x” in “Metal dusting resistance” indicates that pits occurred in less than 200 hours, “△” indicates that pits occurred in 200 hours or more and less than 500 hours, and “○” indicates 500 hours or more. A pit occurred in less than 1000 hours, and “◎” means a pit did not occur in 1000 hours.

As shown in Table 1, in Nos. 1 to 3 where the Al content and / or the Cu content deviate from the range defined in the present invention, the high temperature strength was sufficiently secured, and HAZ cracks did not occur. The metal dusting resistance could not be secured. When the content of S, P or Mo is outside the range defined by the present invention No. 4 to 7 (No. 5 and 7 further Cu is outside the range defined by the present invention) , metal dusting resistance Although the strength at high temperature was good, HAZ cracking occurred and weldability was deteriorated. In No. 8, where the Mo content is outside the range defined in the present invention, HAZ cracking occurred and weldability was deteriorated. This is a result of excessive Mo content, significant grain boundary strengthening, and relative grain boundary embrittlement.

In contrast, in No.9~ 15,17~21,23~ 32 satisfies all of the conditions specified in the present invention, weldability was of course also excellent metal dusting resistance and high temperature strength.

Since the welded joint according to the present invention is excellent in metal dusting resistance and weldability, it can be used for heating furnace tubes, pipes or heat exchanger tubes in petroleum refining, and the welding workability and durability of the apparatus. And safety can be greatly improved. In addition, the welding material according to the present invention is optimal for producing the above-described welded joint by the TIG welding method.

Claims (14)

Both the base metal and the weld metal are in mass%, C: 0.01 to 0.45%, Si: 0.01 to 2%, Mn: 0.1 to 2% , P: 0.03% or less, S: 0.01% or less, Cr: 15 to 35 %, Ni: 40 to 78%, Al: more than 2% and less than 4.5%, Mo: 3.5 to 15%, N: 0.001 to 0.2% and Cu: 0.53 to 5.5% , and the following formula (1) Satisfactory weld joint with excellent metal dusting resistance, characterized in that the balance consists of Fe and impurities.
24P + 1.28Mo + 0.9Si-32S-0.12Cu-0.05Al ≥ 4.23 (1)
However, the element symbol in the formula (1) means the content (% by mass) of the element. In the welded joint of claim 1, both the base metal and weld metal, instead of a part of Fe, by mass%, T i: 0.01~1.4%, Ta: 0.05~5%, V: 0.01~1 %, Zr: 0.01 to 1.4%, Nb: 0.01 to 1.4%, and Hf: 0.01 to 1%, and a welded joint having excellent metal dusting resistance.   3. The metal dusting resistance according to claim 1, wherein the base metal and the weld metal both contain REM: 0.005 to 0.3% in mass% instead of part of Fe. Excellent welded joint. Both the base metal and the weld metal are in mass%, C: 0.01 to 0.45%, Si: 0.01 to 2%, Mn: 0.1 to 2% , P: 0.03% or less, S: 0.01% or less, Cr: 15 to 35 %, Ni: 40 to 78%, Al: more than 2% and less than 4.5%, Mo: 3.5 to 15%, N: 0.001 to 0.2% and Cu: 0.53 to 5.5% , and B: 0.0005 to 0.03 %, Ca: 0.0005 to 0.02% and Mg: 0.0005 to 0.02% selected from the group consisting of one or more and satisfying the following formula (2), welding excellent in metal dusting resistance Fittings.
24P + 1.28Mo + 0.9Si + 20B-32S-0.12Cu-0.05Al ≥ 4.23 (2)
However, the element symbol in the formula (2) means the content (% by mass) of the element. When B is not contained, 0 is substituted for “B” in the equation (2). In the welded joint of claim 4, both the base metal and weld metal, instead of a part of Fe, by mass%, T i: 0.01~1.4%, Ta: 0.05~5%, V: 0.01~1 %, Zr: 0.01 to 1.4%, Nb: 0.01 to 1.4%, and Hf: 0.01 to 1%, and a welded joint having excellent metal dusting resistance.   6. The welded joint according to claim 4 or 5, wherein both the base metal and the weld metal include REM: 0.005 to 0.3% in mass% instead of part of Fe. Excellent welded joint.   It is used in an atmosphere containing hydrocarbon and carbon monoxide alone or in total of 1 vol% or more, hydrocarbon, carbon monoxide and hydrogen alone or in total of 25 vol% or more and 1000 ° C or less. A welded joint excellent in metal dusting resistance according to any one of 1 to 6. By mass%, C: 0.01~0.45%, Si : 0.01~2%, Mn: 0.1~2%, P: 0.03% or less, S: 0.01% or less, Cr: 15~35%, Ni: 40~78% Al: more than 2% and less than 4.5%, Mo: 3.5 to 15%, N: 0.001 to 0.2% and Cu: 0.53 to 5.5% and satisfy the following formula (1), the balance being Fe and impurities A welding material used for producing the welded joint according to claim 1 by TIG welding.
24P + 1.28Mo + 0.9Si-32S-0.12Cu-0.05Al ≥ 4.23 (1)
However, the element symbol in the formula (1) means the content (% by mass) of the element. In the welding material according to claim 8, instead of a part of Fe, by mass%, T i: 0.01~1.4%, Ta: 0.05~5%, V: 0.01~1%, Zr: 0.01~1.4% A welding material used for producing a welded joint according to claim 2 by TIG welding, comprising at least one selected from Nb: 0.01 to 1.4% and Hf: 0.01 to 1%.   The welding material according to claim 8 or 9, wherein the welded joint according to claim 3 includes REM: 0.005 to 0.3% in mass% instead of a part of Fe, and manufactured by a TIG welding method. Welding material used to do. In mass%, C: 0.01 to 0.45%, Si: 0.01 to 2%, Mn: 0.1 to 2% , P: 0.03% or less, S: 0.01% or less, Cr: 15 to 35%, Ni: 40 to 78% Al: more than 2% and less than 4.5%, Mo: 3.5-15%, N: 0.001-0.2% and Cu: 0.53-5.5% , B: 0.0005-0.03%, Ca: 0.0005-0.02% And Mg: containing at least one selected from 0.0005 to 0.02%, and satisfying the following formula (2): used for producing a welded joint according to claim 4 by a TIG welding method Welding material.
24P + 1.28Mo + 0.9Si + 20B-32S-0.12Cu-0.05Al ≥ 4.23 (2)
However, the element symbol in the formula (2) means the content (% by mass) of the element. When B is not contained, 0 is substituted for “B” in the equation (2). In the welding material according to claim 11, instead of a part of Fe, by mass%, T i: 0.01~1.4%, Ta: 0.05~5%, V: 0.01~1%, Zr: 0.01~1.4% Nb: 0.01-1.4% and Hf: 0.01-1% It contains 1 or more types selected from 0.01%, The welding material used in order to produce the welded joint which concerns on the TIG welding method characterized by the above-mentioned.   The welding material according to claim 11 or 12, wherein the welded joint according to claim 6 includes REM: 0.005 to 0.3% in mass% instead of a part of Fe, and manufactured by a TIG welding method. Welding material used to do.   It is a material that welds members used in an atmosphere containing hydrocarbon and carbon monoxide alone or in total of 1 vol% or more and hydrocarbon, carbon monoxide and hydrogen alone or in total of 25 vol% and below 1000 ° C. The welding material excellent in metal dusting resistance according to any one of claims 8 to 13.