KR101210113B1 - Carburization-resistant metal material - Google Patents

Abstract

The present invention provides a metal material excellent in workability and metal dusting resistance suitable as a material for decomposition furnaces or reforming furnaces in petroleum refining, petrochemical plants, etc., heating furnaces, heat exchangers and the like.
In mass%, C: 0.08 to 0.4%, Si: 0.6 to 2.0%, Mn: 0.05 to 2.5%, P: 0.04% or less, S: 0.015% or less, Cr: 18 to 30%, Ni: 20% or more 30 Less than%, Cu: 0.5 to 10.0%, Al: 0.01 to 1%, Ti: 0.01 to 1%, N: 0.15% or less, O (oxygen): 0.02% or less, and the balance consists of Fe and impurities And a carburized metal material characterized by satisfying the following formula (1). Moreover, you may contain 1 type, or 2 or more types of Co, Mo, W, B, V, Zr, Nb, Hf, Mg, Ca, Y, La, Ce, and Nd.
C? 0.062 x Si + 0.033 x Cu-0.004 x Cr + 0.043. (One)
Here, the element symbol in (1) formula shows content in the mass% of the element.

Description

CARBURIZATION-RESISTANT METAL MATERIAL}

The present invention is a metal material which is high in high temperature strength and excellent in corrosion resistance, and particularly used in a carburizing gas atmosphere containing a hydrocarbon gas, a CO gas, or the like, in particular, by a decomposition furnace or reforming in a petroleum refining or petrochemical plant, etc. The present invention relates to a metal material that is excellent in weldability and metal dusting resistance suitable as a material for a furnace or a heat exchanger.

Clean energy fuels such as hydrogen, methanol, gas to liquids (GTL) and dimethyl ether (DME) are expected to see significant increases in the future. Therefore, a reforming apparatus for producing such a synthesis gas is required to be enlarged, and further, a device having higher thermal efficiency and suitable for mass production is required. Moreover, in the conventional reforming apparatus in petroleum refining, petrochemical plant, etc., or the ammonia manufacturing apparatus which uses petroleum etc. as a raw material, a hydrogen manufacturing apparatus, etc., in order to further improve energy efficiency, the heat exchange for heat recovery is used abundantly. have.

In order to effectively utilize the heat of such a hot gas, heat exchange in the temperature range of 400-800 degreeC lower than what was conventionally used has become important, and it is used in a reaction tube, a heat exchanger, etc. in this temperature range. Corrosion due to carburization of high Cr-high Ni-Fe alloy-based metal materials is a problem.

Usually, a synthetic gas, i.e., H _2, CO, CO _2, gas containing hydrocarbons, such as H ₂ O, and methane is more temperature naejineun before and after the metallic materials and 1000 ℃, such as the reaction tube to be produced in the reactor such as described above I'm in contact. In this temperature range, on the surface of the metal material, elements such as Cr and Si, which have a greater tendency to oxidize than Fe and Ni, are selectively oxidized, and a dense coating such as Cr oxide and Si oxide is formed, whereby corrosion is suppressed. By the way, in a relatively low temperature part, such as a heat exchange part, since the diffusion of an element from the inside of a metal material to the surface becomes inadequate, formation of the oxide film which has a corrosion inhibitory effect is late, In addition, a composition containing such hydrocarbons Since gas of carbide changes into carburizing property, C invades from metal material surface and carburizing occurs.

In an ethylene cracking furnace tube or the like, when carburization proceeds and a carburized layer made of carbides such as Cr and Fe is formed, the volume of the portion expands. As a result, fine cracks tend to occur, and in the worst case, the pipe in use is broken. In addition, when the metal surface is exposed, carbon precipitation (caking) using a metal as a catalyst occurs on the surface, accompanied by a decrease in the channel flow path area and a decrease in heat transfer characteristics.

Also in the furnace tube of the catalytic cracking furnace which raises the octane number of naphtha obtained from the distillation of crude oil, the carburizing property which consists of hydrocarbon and hydrogen becomes difficult, carburizing and metal dusting generate | occur | produce.

On the other hand, in an environment where gas carburizing property in a reforming tube, heat exchanger or the like is more difficult, carbides are supersaturated, and graphite is precipitated directly thereafter, so that the base metal is peeled off and the base metal is thinned, that is, metal Corrosion consumption called dusting progresses. In addition, the peeled metal powder becomes a catalyst and generates caulking.

If such cracks, abrasions, or blockages in the tube are enlarged, a device failure or the like may occur, and as a result, there may be an operation interruption, and sufficient consideration is required for selecting a material as the device member.

In order to prevent corrosion by such carburizing and metal dusting, various measures have been examined conventionally.

For example, Patent Document 1 discloses Cr in an amount of 11 to 60% (mass%, or less) regarding metal dust resistance in an atmosphere gas of 400 to 700 ° C containing H ₂ , CO, CO ₂ , H ₂ O. The Fe-based alloy or Ni-based alloy containing) is proposed. Specifically, Fe-based alloys containing 24% or more of Cr and 35% or more of Ni, Ni-based alloys containing 20% or more of Cr, and 60% or more of Ni, and alloy materials in which Nb is further added to these alloys. It is shown that the invention is excellent. However, only by increasing the Cr or Ni content of the Fe-based alloy or the Ni-based alloy, a sufficient carburizing inhibitory effect is not obtained, and a metal material having further metal dust resistance is required.

In addition, the method disclosed in Patent Document 2 relates to the Group VIII, Group IB, Group IV and Group V of the Periodic Table of the Element for Corrosion by Metal Dusting of High-Temperature Alloys Containing Iron, Nickel and Chromium. It is intended to protect the alloy surface by attaching at least one of the metals and mixtures thereof to the surface by usual physical or chemical means, annealing in an inert atmosphere, and forming a thin layer having a thickness of 0.01 to 10 µm. In this case, Sn, Pb, Bi, etc. are said to be especially effective. However, even if this method is effective initially, there exists a possibility that a thin layer may peel by use over a long term, and an effect may become ineffective.

Patent document 3 describes the metal dusting resistance of a metal material in an atmosphere gas of 400 to 700 ° C. containing H ₂ , CO, CO ₂ , H ₂ O, and the interaction with C from the viewpoint of the solute element in iron. In addition to increasing the protection of the oxide film, the addition of elements that make stable carbides among metal materials such as Ti, Nb, V, and Mo, or the interaction coefficients of Si, Al, Ni, Cu, Co, etc. It is disclosed that an alloying element in which Ω represents a positive value is effective for suppressing metal dusting. However, raising Si, Al, etc. may lead to a decrease in hot workability and weldability, and there is room for improvement in consideration of manufacturing stability and plant construction surface.

Next, in order to block the contact of the carburizing gas to the metal surface, a method of pre-oxidizing the metal material or a method of performing the surface treatment is disclosed.

For example, Patent Document 4 and Patent Document 5 disclose a method of preliminary oxidation of low Si 25Cr-20Ni (HK40) heat resistant steel or low Si 25Cr-35Ni heat resistant steel under conditions of 100 hours or more at a temperature near 1000 ° C. Patent Document 6 discloses a method of performing preliminary oxidation in an atmosphere of an austenitic heat resistant steel containing 20 to 35% Cr. In addition, Patent Document 7 proposes a method of heating a high Ni-Cr alloy in vacuum and producing a scale coating to improve carburizing resistance.

In Patent Document 8, the content of Si, Cr, and Ni satisfies Si <(Cr + 0.15Ni-18) / 10, thereby forming a Cr-based oxide film having high adhesion even in an environment subjected to a heating and cooling cycle, thereby resulting in high temperature. Austenitic alloys having excellent carburizing resistance have been proposed even in an environment exposed to corrosive gas under the following conditions. Patent Document 9 contains Cu and rare earth elements (groups Y and Ln) to form a uniform oxide film having a high Cr concentration in the coating film, and exhibits excellent austerity resistance of scale even in an environment subjected to a heating and cooling cycle. Knight-based stainless steel is proposed. In addition, Patent Document 10 proposes a method of improving carburizing resistance by forming a concentrated layer of Si or Cr by surface treatment. However, these conventional techniques require special heat treatment and surface treatment, and are inferior in economy. In addition, since the restoration (scale regeneration) of the scale after a preliminary oxidation scale or a surface treatment layer peels is not considered, after a damage occurs, the effect after that cannot be expected.

Patent Document 11 proposes a stainless steel pipe having a Cr content of 20 to 55% having a Cr content of 10% or more and having a Cr deficiency layer having a lower concentration than that of the base material Cr formed on the surface of the steel pipe. However, the improvement of the weldability which becomes a problem in Cu containing steel is not examined.

In addition, a method of adding H ₂ S to the atmosphere gas has also been considered. However, since H ₂ S may significantly lower the activity of the catalyst used for reforming, its application is limited.

In Patent Document 12 and Patent Document 13, it is proposed to suppress gas dissociable adsorption (gas / metal surface reaction) by containing an appropriate amount of one or two or more of P, S, Sb, and Bi. Since these elements segregate on the metal surface, carburizing and metal dusting corrosion can be largely suppressed without adding excessively. However, since these elements segregate not only on the metal surface but also on the grain boundaries of the metal grains, problems remain in hot workability and weldability.

By adding Cu, it is also proposed to improve corrosion resistance and gap corrosion resistance. Patent Document 14 discloses that by containing Cu, the corrosion resistance is increased while S and O are extremely reduced to improve the hot workability improvement effect by B. Patent Document 15 describes "-Cr + 3.6Ni + 4.7Mo + 11.5Cu". GI appearing as The value (General Corrosion Index) is set to 60 to 90, and the CI value (Crevice Corrosion Index) to be expressed as "Cr + 0.4Ni + 2.7Mo + Cu + 18.7N" is 35 to By setting it as 50, it is described to improve the outstanding corrosion resistance and gap corrosion resistance in a sulfuric acid and sulfate environment. In patent document 16, while improving Cu content, hot workability is improved by adding B exceeding 0.0015% and suppressing oxygen content low. All of these limit the upper limit of the C content low in order to avoid deterioration of the corrosion resistance. Therefore, solid solution strengthening of C cannot be expected and sufficient high temperature strength cannot be obtained. Therefore, it is inappropriate as a metal material used for high temperature.

(Patent Document 1) Japanese Patent Application Laid-Open No. 9-78204 (Patent Document 2) Japanese Patent Application Laid-Open No. 11-172473 (Patent Document 3) Japanese Unexamined Patent Publication No. 2003-73763 (Patent Document 4) Japanese Patent Application Laid-open No. 53-66832 (Patent Document 5) Japanese Patent Application Laid-open No. 53-66835 (Patent Document 6) Japanese Patent Application Laid-Open No. 57-43989 (Patent Document 7) Japanese Patent Application Laid-Open No. 11-29776 Patent Document 8: Japanese Unexamined Patent Publication No. 2002-256398 (Patent Document 9) Japanese Patent Application Laid-Open No. 2006-291290 (Patent Document 10) Japanese Unexamined Patent Publication No. 2000-509105 Patent Document 11: Japanese Unexamined Patent Publication No. 2005-48284 Patent Document 12 Japanese Unexamined Patent Publication No. 2007-186727 (Patent Document 13) Japanese Unexamined Patent Publication No. 2007-186728 (Patent Document 14) Japanese Patent Application Laid-open No. Hei 1-21038 (Patent Document 15) Japanese Patent Application Laid-Open No. 2-170946 (Patent Document 16) Japanese Patent Application Laid-Open No. 4-346638

As described above, various techniques for improving metal dusting resistance, carburizing resistance, and coking resistance of metal materials have been proposed in the related art, but all require special heat treatment and surface treatment, which requires cost and effort. . In addition, since there is no repair (scale regeneration) function of the scale after the preliminary oxidation scale or the surface treatment layer is peeled off, subsequent damage to the metal cannot be suppressed. Moreover, the weldability of a metal material also has a problem.

Further, as an improvement in the metal material itself, as described above, but also a method of adding a H ₂ S during a tube of the reforming device or apparatus for manufacturing the atmospheric gas of the synthesis gas to suppress metal dusting, H ₂ S is a hydrocarbon Since there is a possibility that the activity of the catalyst used for reforming may be remarkably reduced, the metal dust suppression technique by adjusting the components of the atmosphere gas is only limitedly applied.

This invention is made | formed in view of the said phenomenon, The objective is to suppress the surface reaction of a carburizing gas and a metal in a decomposition furnace tube for ethylene plants, a heating furnace tube for a contact reforming furnace, and a reforming furnace tube of synthesis gas. By providing a metal material which has metal dusting resistance, carburizing resistance, and caking resistance, and further improved weldability.

MEANS TO SOLVE THE PROBLEM As a result of analyzing the phenomenon which C invades in a metal in the molecular state, it turned out that it progresses in the small process which consists of following (a)-(c).

(a) Gas molecules made of C compounds such as hydrocarbons and CO come closer to the metal surface.

(b) Gas molecules which have become close are dissociated and adsorbed onto the metal surface.

(c) The dissociated atom C invades and diffuses in a metal.

And as a result of examining various methods of suppressing the above phenomenon, the following methods (d) and (e) were found to be effective.

(d) Actively forming an oxidative scale on the metal surface during use of the metal material, thereby preventing contact between the gas molecules made of the C compound and the metal.

(e) On the metal surface, the dissociative adsorption of the gas molecule which consists of C compounds is suppressed.

And as a result of examination of the oxidation scale which has the blocking effect of (d), it became clear that the oxidation scale which consists of Cr and Si acts effectively. In particular, in a carburizing gas environment such as an ethylene plant cracking furnace tube, a catalytic furnace furnace tube or a synthesis gas reformer tube, the oxygen partial pressure in the gas is low. It was found that it is possible to form an oxidation scale mainly composed of and to form an oxidation scale mainly composed of Si on the metal side.

On the other hand, as a result of further studies from the viewpoint of dissociative adsorption of (e), when a proper amount of precious metal elements such as Cu, Ag, and Pt, and elements of Groups VA and VIA of the periodic table are added, a gas molecule composed of a C compound It has been found to exert an effect of suppressing dissociative adsorption of. In particular, in addition to being inexpensive among the noble metal elements, Cu is also low in solvent or solidification problems when contained in Fe-Ni-Cr-based metal materials. Therefore, it is preferable to use Cu.

And according to these methods (d) and (e), although each can effectively suppress C invading in a metal in the said small process (a)-(c), these methods (d) and (e) By simultaneously applying), it was found that a significant improvement in metal dusting resistance, carburizing resistance and caulking resistance can be expressed.

However, when an element such as Si or Cu is added, the corrosion resistance can be improved, but weldability is deteriorated. In particular, cracks due to grain boundary melting in a region affected by the heat cycle of rapid heat and quench by welding, that is, a weld heat affected zone (hereinafter referred to as "HAZ") are likely to occur. This means that the grain boundary becomes low when Si, Cu, etc. segregate in the base material grain boundary, but at this time, when a welding heat cycle is applied and heated directly below the melting point, the grain boundary melts and is torn and cracked due to thermal stress during welding. This occurs. This is a HAZ crack. Therefore, when used as a weld structure, it is necessary to suppress this kind of welding crack.

Therefore, the present inventors examined various methods that can suppress HAZ cracking during welding even when a considerable amount of Si and Cu are added to improve the corrosion resistance. As a result, it came to the knowledge that HAZ cracking can be suppressed by the method of following (f) and (g).

By increasing the content of (f) C, Cr-based carbides are precipitated at the base material grain boundary, thereby raising the melting point of the grain boundary.

(g) By depositing Cr carbide having a high melting point, suppressing grain coarsening of the HAZ portion when a welding heat cycle is applied, thereby increasing the grain boundary surface area, thereby reducing the segregation of Si, Cu and the like at the grain boundaries.

Based on this finding, in the metal material containing 18-30% or 22-30% of Cr, the content of C, Si, and Cu was changed in various ways, and when HAZ cracking sensitivity was examined, Si, Cu, and It became clear that the minimum of C content which can prevent HAZ cracking changes with content of Cr. Specifically, the higher the content of Si and Cu causing the lower melting point of the grain boundary, the higher the allowable lower limit of the C content, and the higher the content of Cr constituting the carbides that increase the melting point of the grain boundary, the lower the allowable lower limit of the C content I could see it going down.

And from the systematic test result which changed each component in various ways, the relationship formula of C content which can prevent HAZ crack and each content of Si, Cu, and Cr was experimentally estimated. As a result, by satisfying the following formula (1), knowledge was obtained that excellent HAZ cracking resistance could be obtained together with excellent metal dusting resistance.

C? 0.062 x Si + 0.033 x Cu-0.004 x Cr + 0.043. (One)

Here, the element symbol in (1) formula shows content in the mass% of the element.

This invention is completed based on such knowledge, and the summary is as showing to following (1)-(3). Hereinafter, this invention is called invention (1)-this invention (3), respectively. Collectively, it may be called the present invention.

(1) In mass%, C: 0.08 to 0.4%, Si: 0.6 to 2.0%, Mn: 0.05 to 2.5%, P: 0.04% or less, S: 0.015% or less, Cr: 22 to 30%, Ni: 20 % Or more and less than 30%, Cu: 0.5 to 10.0%, Al: 0.01 to 1%, Ti: 0.01 to 1%, N: 0.15% or less, O (oxygen): 0.02% or less, the balance being Fe and impurities A carburizing resistant metal material, comprising the following formula and satisfying the following formula (1).

C? 0.062 x Si + 0.033 x Cu-0.004 x Cr + 0.043. (1) Here, the element symbol in (1) formula shows content in the mass% of the element.

(2) In mass%, C: 0.08 to 0.4%, Si: 0.6 to 2.0%, Mn: 0.05 to 2.5%, P: 0.04% or less, S: 0.015% or less, Cr: 18 to 30%, Ni: 20 % Or more and less than 30%, Cu: 0.5 to 10.0%, Al: 0.01 to 1%, Ti: 0.01 to 1%, N: 0.15% or less, O (oxygen): 0.02% or less, the balance being Fe and impurities A carburizing resistant metal material, comprising the following formula and satisfying the following formula (1).

C? 0.062 x Si + 0.033 x Cu-0.004 x Cr + 0.043. (One)

Here, the element symbol in (1) formula shows content in the mass% of the element.

(3) The carburized metal material according to the above (1) or (2), further comprising at least one component selected from at least one of the first to fifth groups shown below. .

First group: In mass%, Co: 10% or less,

2nd group: in mass%, Mo: 2.5% or less and W: 5% or less,

Third group: in mass%, B: 0.1% or less, V: 0.5% or less, Zr: 0.1% or less, Nb: 2% or less and Hf: 0.5% or less,

Fourth group: in mass%, Mg: 0.1% or less and Ca: 0.1% or less,

Fifth group: in mass%, Y: 0.15% or less, La: 0.15% or less, Ce: 0.15% or less and Nd: 0.15% or less.

The metal material of this invention has the effect of suppressing the surface reaction of a carburizing gas and a metal, and is excellent in metal dusting resistance, carburizing resistance, and coking resistance. Moreover, since weldability is improved, it can be used for welding structural members, such as a decomposition furnace, a reforming furnace, a heating furnace, and a heat exchanger in a petroleum refining or a petrochemical plant, and can improve the durability and operation efficiency of an apparatus drastically. Can be.

Particularly, since it is suitable as a reaction tube used in heat exchange in a lower temperature range (400 to 800 ° C.) than a conventional target, or as a metal material used in a heat exchanger, metal dusting which is a problem in this temperature range is effectively prevented. It becomes possible to suppress it.

In the present invention, the reason for limiting the composition range of the metal material is as follows. In addition, in the following description, "%" display of content of each element means the "mass%."

C: 0.08-0.4%

C is one of the important elements in the present invention. In addition to increasing the strength at a high temperature, carbides are formed by bonding with Cr or the like to achieve an effect of improving weldability. In particular, in the metal material of this invention which raises content of Si and Cu, the effect is remarkable. In order to fully exhibit this effect, 0.08% of content is required. However, when 0.4% is exceeded, since the toughness of an alloy will become extremely bad, an upper limit shall be 0.4%. Preferably, it is more than 0.1% and 0.35% or less, and a more preferable range is more than 0.15% and 0.25% or less.

Si: 0.6∼2.0%

Si is one of the important elements in this invention. Because of a strong affinity with oxygen, forming a Si-based oxide scale in the lower layer of Cr ₂ O ₃ scale layer such as the protective oxide, and blocks the carburizing gas. This effect is exhibited by containing 0.6% or more. However, when it exceeds 2.0%, weldability will fall remarkably, and an upper limit shall be 2.0%. A preferable range is 0.7 to 2.0%, and a more preferable range is 0.8 to 1.5%.

Mn: 0.05 to 2.5%

Mn not only has a deoxidation ability but also improves workability and weldability, so that Mn is added at 0.05% or more. In addition, since Mn is an austenite generating element, it is also possible to replace a part of Ni with Mn. However, excessive addition inhibits the carburizing gas barrier performance of the protective oxide scale layer, so the upper limit of the Mn content is 2.5%. Preferable range is 0.1 to 2.0%. More preferable range is 0.7 to 1.6%.

P: 0.04% or less

Since P reduces hot workability and weldability, the upper limit of P is made 0.04%. Especially when there is much content of Si and Cu, the effect becomes important. The upper limit with preferable P is 0.03%, and a more preferable upper limit is 0.025%. However, since it has a function of suppressing the dissociative adsorption reaction on the metal surface of the carburized gas, P may be contained when the weldability can be reduced.

S: 0.015% or less

Since S deteriorates hot workability and weldability like P, the upper limit of S is made 0.015%. Especially when there is much content of Si and Cu, the effect becomes important. The upper limit with preferable P of S is 0.01%, and a preferable upper limit is 0.003%. However, like P, since it has a function of suppressing the dissociative adsorption reaction on the metal surface of the carburizing gas, S may be contained when the weldability can be reduced.

Cr: 18-30% or 22-30%

Cr stably forms oxidation scales such as Cr ₂ O ₃ and blocks carburizing gases, thereby providing sufficient carburizing resistance, metal dusting resistance, and coking resistance even in a severe carburizing gas environment. do. In addition, weldability is improved by bonding with C and forming carbide. Especially when there is much content of Si and Cu, the effect becomes important. In order to fully exhibit this effect, 18% or more of content is required. However, excessive addition deteriorates tissue stability with workability, so the upper limit is made 30%. The minimum with preferable Cr content is 19%, More preferably, it is 22%, More preferably, it is 23%. Moreover, the upper limit with preferable Cr content is 28%, More preferably, it is 27%.

Ni: 20% or more and less than 30%

Ni is an element necessary for obtaining a stable austenite structure in accordance with Cr content, and a content of 20% or more is required. Moreover, when C immerses in a metal material, it has a function which reduces the immersion rate. In addition, there is a function to secure the high temperature strength of the metal structure. However, in addition to the high cost and manufacturing difficulties, the excessively necessary content may promote coking and metal dusting, especially in a gaseous environment containing hydrocarbons, and therefore the upper limit of the Ni content is limited to less than 30%. A preferable range is 22.5%-less than 30%, and a more preferable range is more than 25% and 29.5% or less.

Cu: 0.5-10.0%

Cu is one of the important elements in the present invention. Cu suppresses the surface reaction of a carburizing gas and a metal, and greatly improves metal dust resistance. Moreover, since it is an austenite generating element, it is also possible to substitute a part of Ni with Cu. In order to exhibit the improvement effect of metal dust resistance, it is necessary to contain 0.5% or more. However, when it contains exceeding 10.0%, weldability will fall, Therefore, an upper limit of content is made into 10.0%. Preferable content is 1.0 to 6.0%. More preferable content is 2.1 to 4.0%.

Al: 0.01% to 1%

Al is an effective element for improving the high temperature strength. Moreover, since it has high affinity with oxygen, it also has an effect as a deoxidizer, becomes a part of the constituent element of an oxidizing scale, and improves the gas barrier property. Especially in this environment with strong carburizing property, the effect can be expected. In order to exhibit this effect, it is effective to contain 0.01% or more. On the other hand, when it exceeds 1%, weldability will be inhibited. Therefore, content of Al is made into 0.01 to 1%. The preferred range is 0.12 to 0.8%. More preferable range is 0.2 to 0.6%.

Ti: 0.01% to 1%

Ti is an element effective for improving the high temperature strength. Moreover, since it has affinity with oxygen, it becomes a part of the constituent elements of the oxidizing scale, and improves the gas barrier property. Especially in this environment with strong carburizing property, the effect can be expected. Therefore, it contains actively. In order to exhibit this effect, it is effective to make it contain 0.01% or more. However, when it contains excessively, since workability and weldability will fall, 1% is made into an upper limit. The preferred range is 0.12 to 0.8%. More preferable range is 0.2 to 0.6%.

N: 0.15% or less

N does not need to be contained. When it contains, it has the effect | action which raises the high temperature strength of a metal material. However, when the content exceeds 0.15%, workability is inhibited. Therefore, content of N makes 0.15% an upper limit. The upper limit is preferably 0.05%. Moreover, in order to acquire the effect of raising the high temperature strength of a metal material, it is preferable to contain 0.0005% or more, More preferably, it contains 0.001% or more.

O (oxygen): 0.02% or less

O (oxygen) is an impurity element mixed in from a raw material or the like when the metal material is solvented. When the content of O (oxygen) exceeds 0.02%, a large amount of oxide-based inclusions are present in the metal material, and workability is lowered, causing damage to the surface of the metal material. Therefore, the upper limit of O (oxygen) is made into 0.02%.

Next, in addition to the method of this invention (1) or this invention (2), this invention (3) regarding the metal material which improves strength, ductility, and toughness is demonstrated.

The present invention (3) further contains at least one component selected from the graphs of at least one of the first to fifth groups shown below in the metal material defined in the present invention (1) or (2). It is made into a carburized metal material, characterized in that.

First group: In mass%, Co: 10% or less,

2nd group: in mass%, Mo: 2.5% or less and W: 5% or less,

Third group: in mass%, B: 0.1% or less, V: 0.5% or less, Zr: 0.1% or less, Nb: 2% or less and Hf: 0.5% or less,

Fourth group: in mass%, Mg: 0.1% or less and Ca: 0.1% or less,

Fifth group: in mass%, Y: 0.15% or less, La: 0.15% or less, Ce: 0.15% or less and Nd: 0.15% or less.

Hereinafter, these arbitrary additional elements are demonstrated in order.

1st group (in mass%, Co: 10% or less)

Since Co has an effect of making the austenite phase stable, a part of the Ni component can be substituted, and therefore, Co may be contained as necessary. However, if the content exceeds 10%, the hot workability is lowered. Therefore, the content is made 10% or less when Co is contained. From a viewpoint of hot workability, a preferable range is 0.01 to 5%, and a more preferable range is 0.01 to 3%.

2nd group (in mass%, Mo: 2.5% or less, W: 5% or less)

Since both Mo and W are solid solution strengthening elements, you may contain either or both as needed. However, when it contains Mo, when the content exceeds 2.5%, the workability is reduced and structure stability is inhibited. When Mo is included, the content is made 2.5% or less. Mo content becomes like this. Preferably it is 0.01 to 2.3%. Moreover, when it contains W, when the content exceeds 5%, since workability is reduced and structure stability is inhibited, when it contains W, the content shall be 5% or less. W content becomes like this. Preferably it is 0.01 to 2.3%.

Third group (in mass%, B: 0.1% or less, V: 0.5% or less, Zr: 0.1% or less, Nb: 2% or less, Hf: 0.5% or less)

Since B, V, Zr, Nb, and Hf are all effective elements for improving high temperature strength characteristics, one or two or more of these may be contained as necessary. However, when it contains B, since the weldability will fall when the content exceeds 0.1%, when it contains B, the content shall be 0.1% or less. B content becomes like this. Preferably it is 0.001 to 0.05%. In the case where V is contained, the weldability is lowered when the content exceeds 0.5%. Therefore, when V is contained, the content is made 0.5% or less. V content becomes like this. Preferably it is 0.001 to 0.1%. In the case of containing Zr, the weldability is lowered when the content exceeds 0.1%. Therefore, the content is made 0.1% or less when Zr is included. Zr content becomes like this. Preferably it is 0.001 to 0.05%. In the case where Nb is included, the weldability is lowered when the content exceeds 2%. Therefore, when Nb is included, the content is made 2% or less. Nb content becomes like this. Preferably it is 0.001 to 0.1%. In addition, in the case where Hf is contained, the weldability is lowered when the content exceeds 0.5%. Therefore, when Hf is contained, the content is made 0.5% or less. Hf content becomes like this. Preferably it is 0.001 to 0.1%.

Fourth group (in mass%, Mg: 0.1% or less, Ca: 0.1% or less)

Since both Mg and Ca have the effect | action which improves hot workability, you may contain 1 type, or 2 or more types of these as needed. However, when it contains Mg, since the weldability will fall when the content exceeds 0.1%, when it contains Mg, the content shall be 0.1% or less. Mg content becomes like this. Preferably it is 0.0005 to 0.1%. In the case of containing Ca, if the content exceeds 0.1%, the weldability is lowered. When Ca is included, the content is made 0.1% or less. Ca content becomes like this. Preferably it is 0.0005 to 0.1%.

Fifth group (in mass%, Y: 0.15% or less, La: 0.15% or less, Ce: 0.15% or less and Nd: 0.15% or less)

Since Y, La, Ce, and Nd all have the effect | action which improves oxidation resistance, you may contain 1 type, or 2 or more types of these as needed. However, when it contains these elements, when the content exceeds 0.15%, workability will fall, respectively, When it contains, the content shall be 0.15% or less. Preferably it is 0.0005 to 0.15%.

The metal material which has the function of suppressing the surface reaction of the carburizing gas and the metal according to the present invention is problematic in metal dusting, carburizing and caulking, and therefore, the metal material is a requirement specified in (f) or (g) above. You just need to satisfy

You may shape | mold the metal material which concerns on this invention to necessary shapes, such as a thick plate, a thin plate, a seamless pipe | tube, a welded pipe, a forging, and a wire rod, by means, such as melt | dissolution, casting, hot working, cold working, and welding. Moreover, you may shape | mold in required shape according to methods, such as powder metallurgy and centrifugal casting. The surface of the metal material after the final heat treatment may be subjected to surface treatment such as pickling, shot blasting, shot peening, mechanical cutting, grinder polishing and electropolishing. Moreover, you may shape | mold the metal material which concerns on this invention to irregular shape, such as one or two or more protrusion shape, on the surface. In addition, the metal material according to the present invention may be molded into a required shape in combination with various carbon steels, stainless steels, Ni-based alloys, Co-based alloys, Cu alloys, and the like. In this case, there is no restriction on the joining method of the metal material and the various steels or alloys according to the present invention. For example, the joining or the “caulking” mechanical joining, or the thermal joining such as welding or diffusion treatment may be used. It is also possible.

The present invention will be described in more detail with reference to the following Examples, but the present invention is not limited to these Examples.

(Example 1)

The metal material of the chemical composition shown in Table 1 was solvent-processed using the high frequency heating vacuum furnace, and hot forging and hot rolling were produced, and the metal plate of 6 mm of plate | board thickness was produced. The metal plate was subjected to a solid solution heat treatment under conditions of 1160 to 1230 ° C for 5 minutes, and a part of the metal plate was cut to prepare a test piece.

From the metal material of Table 1, the test piece of width 15mm x length 20mm was cut out. The test piece is kept isothermally maintained at 650 ° C. in a 45% CO-42.5% H ₂ -6.5% CO ₂ -6% H ₂ O gas atmosphere by volume ratio, and is taken out after 200 hours and formed on the surface of the test piece. ) Was judged from both sides of visual observation and optical microscope observation. This result is put together in Table 2 and shown.

From Table 2, the pit generate | occur | produced after the elapse of 200 hours among the metal materials of numbers 24-33 which chemical composition deviates from the conditions prescribed | regulated by this invention. Therefore, metal dust resistance is inferior in the synthesis gas environment containing CO. On the other hand, the pit does not generate | occur | produce all the metal materials prescribed | regulated by this invention, and it is excellent in metal dust resistance.

(Example 2)

The metal material of the chemical composition shown in Table 1 was melted using the high frequency heating vacuum furnace, and hot forging and hot rolling were produced, and the metal plate of 6 mm of plate | board thickness was produced. The metal plate was subjected to a solid solution heat treatment under conditions of 1160 to 1230 ° C. for 5 minutes, and a part of the metal plate was cut to prepare a test piece. From the metal material of Table 1, the test piece of width 15mm x length 20mm was cut out. The test piece is isothermally maintained at 650 ° C. in a 30% C ₃ H ₈ -70% H ₂ gas atmosphere by volume ratio, and taken out after 10 hours, and the presence or absence of a pit generated on the surface of the test piece is visually and optically microscope. Judging from observation. This result is put together in Table 2 and shown.

From Table 2, among the metal materials of numbers 24-33 whose chemical composition deviates from the conditions prescribed | regulated by this invention, the metal materials of numbers 24, 26-28, and 31-33 generate | occur | produce a 10-hour test. In the hydrocarbon gas environment, the metal dust resistance is inferior. On the other hand, the metal material prescribed | regulated by this invention does not generate | occur | produce a pit at all, and is excellent in metal dust resistance.

(Example 3)

The metal material of the chemical composition shown in Table 1 was solvent-processed using the high frequency heating vacuum furnace, and hot forging and hot rolling were performed, and two metal plates of 12 mm of thickness, 50 mm of width, and 100 mm of length were produced, respectively. The metal plate was subjected to the solid solution heat treatment under the condition of 1200 ° C. for 5 minutes, and a part of the metal plate was cut to prepare a test piece.

Next, after giving a V-shaped groove with an angle of 30 ° and a root thickness of 1.0 mm on one side in the longitudinal direction of the test piece, the thickness was obtained by using "DNiCrMo-3" specified in JIS Z3224 (1999) as a coated arc welding rod. Four circumferences were restrained welded on the commercially available metal plate of "SM400C" prescribed | regulated to JISG3106 (2004) which is 25 mm, width 150 mm, and length 150 mm. Thereafter, using the "YNiCrMo-3" TIG welding wire specified in JIS Z3334 (1999), multi-layer welding was performed in the groove by TIG welding under the condition of 6 kJ / cm. After the above-mentioned welding construction, 10 test specimens for observing the microstructure of the seam are collected from each test body, and the mirror is polished after mirror polishing the cross section. It observed by doubling. The results are summarized in Table 2.

From Table 2, it turns out that the HAZ crack is recognized by the metal material of No. 25 which C content does not satisfy No. 24 and Formula (1) which deviate from the conditions prescribed | regulated by this invention. Moreover, although C content enters the conditions prescribed | regulated by this invention, it turns out that the HAZ crack suppression effect is small in the metal material of Nos. 28-31 whose content of Cu, Si, and S deviates from a prescription | regulation. On the other hand, in the metal material prescribed | regulated by this invention, neither HAZ crack has generate | occur | produced and it is excellent in weldability.

(Industrial availability)

Provided is a metal material having an effect of suppressing the surface reaction of a carburizing gas and a metal, and excellent in metal dusting resistance, carburizing resistance, and coking resistance and improving weldability. It can be used for cracking furnaces in petroleum refining, petrochemical plants, etc., reforming furnaces, heating furnaces, welding structural members such as heat exchangers, and the durability and operation efficiency of the apparatus can be greatly improved.

Claims (3)

In mass%, C: 0.08 to 0.4%, Si: 0.6 to 2.0%, Mn: 0.05 to 2.5%, P: 0.04% or less, S: 0.015% or less, Cr: 22 to 30%, Ni: 20% or more 30 Less than%, Cu: 0.5 to 10.0%, Al: 0.01 to 1%, Ti: 0.01 to 1%, N: 0.15% or less, O (oxygen): 0.02% or less, and the balance consists of Fe and impurities And a carburized metal material characterized by satisfying the following formula (1).
C? 0.062 x Si + 0.033 x Cu-0.004 x Cr + 0.043. (One)
Here, the element symbol in (1) formula shows content in the mass% of the element. In mass%, C: 0.08 to 0.4%, Si: 0.6 to 2.0%, Mn: 0.05 to 2.5%, P: 0.04% or less, S: 0.015% or less, Cr: 18 to 30%, Ni: 20% or more 30 Less than%, Cu: 0.5 to 10.0%, Al: 0.01 to 1%, Ti: 0.01 to 1%, N: 0.15% or less, O (oxygen): 0.02% or less, and the balance consists of Fe and impurities And a carburized metal material characterized by satisfying the following formula (1).
C? 0.062 x Si + 0.033 x Cu-0.004 x Cr + 0.043. (One)
Here, the element symbol in (1) formula shows content in the mass% of the element. The method according to claim 1 or 2,
The carburizing-resistant metal material further containing at least 1 sort (s) of the component chosen from the at least 1 group from the 1st group to the 4th group shown below.
1st group: in mass%, Co: 10% or less,
Second group: by mass%, Mo: 2.5% or less and W: 5% or less,
Third group: in mass%, B: 0.1% or less, V: 0.5% or less, Zr: 0.1% or less, Nb: 2% or less and Hf: 0.5% or less,
Fourth group:% by mass, Mg: 0.1% or less and Ca: 0.1% or less.