JP2018171640A - Two-phase stainless steel wire material for weld rod and two-phase stainless steel wire for weld rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-phase stainless steel wire material for weld rod which causes no nozzle blocking during casting, and is excellent in hot workability and weld workability.SOLUTION: A two-phase stainless steel wire material for weld rod contains C:0.005-0.10%, Si:0.20-2.00%, Mn:0.50-5.50%, Ni:6.00-10.00%, Cr:21.00-26.00%, Mo:0.05-4.00%, P:0.040% or less, S:0.0025% or less, N:0.10-0.30%, Al:0.005-0.080%, Ca:0.0006-0.0025%, Mg:0.0005-0.0030%, B:0.0010- 0.0060%, and the balance Fe with impurities, and has a DF value of 30-60%, where a number ratio of Ca Al Mg-based oxides is 40% or more, a number ratio of Si Mn Cr Fe-based oxides is 20% or less, and a number ratio of an Mg oxide is 4 times or more of the Al Mg oxide (Al Mg oxide including O).SELECTED DRAWING: None

Description

  The present invention relates to a duplex stainless steel wire for a welding rod and a duplex stainless steel wire for a welding rod.

  The duplex stainless steel is a stainless steel which has toughness and corrosion resistance by adjusting Cr, Ni and Mo as main elements and adjusting the phase ratio of ferrite and austenite to about 50%. When welding duplex stainless steel, gas shielded arc welding is used. The gas shielded arc welding method is roughly classified into a non-consumable electrode type and a consumable electrode type. Among them, the gas metal arc (abbreviated as GMA) welding method, which is a consumable electrode type welding method, uses a welding wire as an electrode, and forms a weld metal with the molten wire and the molten base material. It is the method of welding by.

In the GMA welding method, in order to suppress generation of spatter during welding, a welding rod made of duplex stainless steel with a reduced Ca content may be used. However, when the Ca content in the steel is reduced, the inclusions are not reformed, and the spinel inclusions (MgO.Al ₂ O ₃ system) increase, and the molten steel is sent to the tundish during continuous casting of steel. There is a problem that the nozzle is easily blocked. Further, the number density of Ca-based inclusions is reduced by reducing the amount of Ca. Some Ca-based inclusions have the effect of immobilizing S (sulfur) in steel and detoxifying it. However, when the amount of Ca is reduced, the amount of inclusions that immobilize S is reduced and the amount of inclusions in steel is reduced. The solid solution S increases, which may cause cracks during hot rolling. For this reason, the welding rod which consists of a duplex stainless steel which prevents nozzle obstruction | occlusion, is excellent in hot workability, and was excellent also in welding workability is desired.

Patent Document 1 includes C, Si, Mn, P, S, Ni, Cr, Mo, N, Al, Mg, Ca, O, the balance being Fe and inevitable impurities, and non-metallic inclusions contained in the steel. _{things, MgO · Al 2 O 3,} Al 2 O 3, MgO, MnO-Al 2 O 3 based oxide, one or two of CaO concentration 40 mass% or less of _CaO-Al 2 _{O 3} based oxide The number ratio of CaO—Al ₂ O ₃ oxide to all nonmetallic inclusions is 40% or less, and the CaO concentration in all nonmetallic inclusions is 10 mass% or less, 60 ° C., in a 20% NaCl aqueous solution. A duplex stainless steel having a pitting potential Vc ′ ₁₀ of 600 mV (vs SCE) or more is described.

  Patent Document 2 discloses C, Si, Mn, P, S, Ni, Cr, Mo, V, sol. A highly corrosion-resistant duplex stainless steel made of Al, Ca, B, N, O and the balance Fe and having excellent hot workability with a γ phase ratio of 30 to 70% is described.

The duplex stainless steel described in Patent Document 1 has a low Ca content of 0.0005% by mass or less. When this steel material is used as a welding rod, spattering during welding is suppressed. Since this duplex stainless steel positively precipitates MgO inclusions and MgO-Al ₂ O ₃ inclusions, nozzle clogging tends to occur during the casting of the steel material, resulting in poor productivity. Further, in the duplex stainless steel described in Patent Document 1, the Ca component elutes from the CaO-containing inclusions into the aqueous solution to form a gap between the base metal and the inclusion, and this gap serves as a starting point. In view of the occurrence of corrosion and deterioration of corrosion resistance, the Ca concentration contained in the steel is reduced to 0.0005% by mass or less, and no study is made on weldability.

  Further, the high corrosion resistance duplex stainless steel described in Patent Document 2 includes steel having a high Ca concentration. Therefore, when this stainless steel is welded as a welding rod, there is a problem that spatter is often generated.

Japanese Patent No. 4824640 Japanese Patent Publication No. 7-17987

  The present invention has been made in view of the above circumstances, and there is no risk of nozzle clogging during casting, excellent hot workability, and further excellent workability during welding. An object is to provide a duplex stainless steel wire for a wire rod and a welding rod.

In steel containing a relatively large amount of Ca, the modification of inclusions proceeds in the steelmaking process, and the generation of spinel inclusions (MgO.Al ₂ O ₃ system) is suppressed, and nozzle clogging during casting is prevented. However, since it contains a large amount of Ca, spatter is generated during welding and welding workability is reduced.
On the other hand, when the amount of Ca in steel is reduced, nozzle clogging occurs, and Ca / Al, which is effective for fixing S (sulfur), is accompanied by an increase in spinel inclusions (MgO.Al ₂ O ₃ system). -Mg-based oxides decrease, the amount of solute S in steel increases, and hot workability decreases.
Furthermore, as the number ratio of Si, Mn, Cr, and Fe-based oxides that easily absorb S increases, solid solution S decreases. It is easily reduced and reduced by welding heat input to release solute S into the steel, thereby reducing hot workability.

  The present inventors who have found the above phenomenon intensively studied in order to improve welding workability, productivity and hot workability, and the Ca content is in the range of 0.0006 to 0.0025%, and in the steel. The number ratio of Ca, Al, Mg-based oxides, the number ratio of Si, Mn, Cr, Fe-based oxides, and the number ratio of Mg oxides and the number of Al / Mg oxides We succeeded in improving welding workability, productivity and hot workability by making the ratio with the ratio within a predetermined range. The gist of the present invention is as follows.

[1] The chemical component is mass%,
C: 0.005-0.10%,
Si: 0.20 to 2.00%
Mn: 0.50 to 5.50%,
Ni: 6.00 to 10.00%,
Cr: 21.00 to 26.00%,
Mo: 0.05 to 4.00%
P: 0.040% or less,
S: 0.0025% or less,
N: 0.10 to 0.30%,
Al: 0.005 to 0.080%,
Ca: 0.0006 to 0.0025%,
Mg: 0.0005 to 0.0030%,
B: 0.0010 to 0.0060%
And the balance consists of Fe and impurities,
The DF value represented by the following formula is 30.0 to 60.0%,
Among inclusions with a particle size of 1.0 μm or more present in steel, the number ratio of Ca / Al / Mg-based oxide is 40% or more, and the number ratio of Si / Mn / Cr / Fe-based oxide is 20% or less. A duplex stainless steel wire rod for welding rods in which the number ratio of Mg oxide is at least four times the number ratio of Al · Mg oxide (including the case where the number ratio of Al · Mg oxide is 0).
DF value = 7.2 × ([Cr] +0.88 [Mo] +0.78 [Si] +2.2 [Ti] +2.3 [V]) − 8.9 × ([Ni] +0.03 [Mn] ] +0.72 [Cu] +22 [C] +21 [N]) − 44.9
However, the element symbol in the above formula is the content (% by mass) of the element, and 0 is substituted when the element is not included.
[2] Furthermore, in mass%,
V: 1.00% or less,
Ti: 0.005% or less,
Cu: The duplex stainless steel wire for welding rods according to [1], containing one or more of 0.50% or less.
[3] Furthermore, in mass%,
REM: 0.0100% or less,
Ta: 0.0010 to 0.1000%
The duplex stainless steel wire for welding rods according to [1] or [2], comprising one or two of the above.
[4] The chemical component is mass%,
C: 0.005-0.10%,
Si: 0.20 to 2.00%
Mn: 0.50 to 5.50%,
Ni: 6.00 to 10.00%,
Cr: 21.00 to 26.00%,
Mo: 0.05 to 4.00%
P: 0.040% or less,
S: 0.0025% or less,
N: 0.10 to 0.30%,
Al: 0.005 to 0.080%,
Ca: 0.0006 to 0.0025%,
Mg: 0.0005 to 0.0030%,
B: 0.0010 to 0.0060%
And the balance consists of Fe and impurities,
The DF value represented by the following formula is 30.0 to 60.0%,
Among inclusions with a particle size of 1.0 μm or more present in steel, the number ratio of Ca / Al / Mg-based oxide is 40% or more, and the number ratio of Si / Mn / Cr / Fe-based oxide is 20% or less. A duplex stainless steel wire for welding rods in which the number ratio of Mg oxide is four times or more of the number ratio of Al · Mg oxide (including the case where the number ratio of Al · Mg oxide is 0).
DF value = 7.2 × ([Cr] +0.88 [Mo] +0.78 [Si] +2.2 [Ti] +2.3 [V]) − 8.9 × ([Ni] +0.03 [Mn] ] +0.72 [Cu] +22 [C] +21 [N]) − 44.9
However, the element symbol in the above formula is the content (% by mass) of the element, and 0 is substituted when the element is not included.
[5] Furthermore, in mass%,
V: 1.00% or less,
Ti: 0.005% or less,
Cu: The duplex stainless steel wire for welding rods according to [4], containing one or more of 0.50% or less.
[6] Furthermore, in mass%,
REM: 0.0100% or less,
Ta: 0.0010 to 0.1000%
The duplex stainless steel wire for welding rods according to [4] or [5], comprising one or two of the above.
In the above description, the case where the number ratio of Al / Mg oxide is 0 includes that the number ratio of Al / Mg oxide is 0% and the number ratio of Mg oxide is more than 0%. Means applicable.

  ADVANTAGE OF THE INVENTION According to this invention, the duplex stainless steel wire for welding rods excellent in both weldability and hot workability, and the duplex stainless steel wire for welding rods can be provided.

Hereinafter, a duplex stainless steel wire for a welding rod (hereinafter may be referred to as a wire) and a duplex stainless steel wire for a welding rod (hereinafter may be referred to as a steel wire) according to embodiments of the present invention will be described. .
The wire and steel wire of the present embodiment have a chemical composition of mass%, C: 0.005 to 0.10%, Si: 0.20 to 2.00%, Mn: 0.50 to 5.50%, Ni: 6.00 to 10.00%, Cr: 21.00 to 26.00%, Mo: 0.05 to 4.00%, P: 0.040% or less, S: 0.0025% or less, N : 0.10-0.30%, Al: 0.005-0.080%, Ca: 0.0006-0.0025%, Mg: 0.0005-0.0030%, B: 0.0010-0 .0060% is contained, the balance is Fe and impurities, the DF value represented by the following formula is 30.0 to 60.0%, and among inclusions present in steel, Ca · Al · Mg The number ratio of the system oxide is 40% or more, the number ratio of the Si / Mn / Cr / Fe system oxide is 20% or less, and the number of Mg oxides Ratio is more than four times the number ratio of Al · Mg oxide (number ratio of Al · Mg oxides comprises 0), a wire rod and steel wire.

DF value = 7.2 × ([Cr] +0.88 [Mo] +0.78 [Si] +2.2 [Ti] +2.3 [V]) − 8.9 × ([Ni] +0.03 [Mn] ] +0.72 [Cu] +22 [C] +21 [N]) − 44.9
However, the element symbol in the above formula is the content (% by mass) of the element, and 0 is substituted when the element is not included.

  Moreover, the wire rod and steel wire of this embodiment are further mass%, and V: 1.00% or less, Ti: 0.005% or less, Cu: 0.50% or less, 1 type or 2 types or more. Further, it may include one or two of REM: 0.0100% or less and Ta: 0.0010 to 0.1000%.

  Hereinafter, the chemical components of the duplex stainless steel wire for the welding rod and the duplex stainless steel wire for the welding rod will be described. In the following description, “%” means “mass%” unless otherwise specified.

C: 0.005-0.10%
C is an inevitable element present in steel and is also a strong austenitizing element. If its content exceeds 0.10%, it combines with Cr during welding and welding reheating to form carbides, so that the toughness and corrosion resistance of the weld metal deteriorate. Therefore, the C content is 0.10% or less. Preferably it is 0.025% or less. On the other hand, if it is attempted to reduce excessively, the manufacturing cost increases, and if the amount of C, which is a strong austenitizing element, is small, the DF value is significantly reduced, so the lower limit is preferably made 0.005% or more. . A more preferred lower limit is 0.010% or more.

Si: 0.20 to 2.00%
Si is an element that acts as a deoxidizer during the melting of duplex stainless steel, but it must be controlled to 2.00% or less from the viewpoint of ensuring hot workability. Moreover, in order to reduce Si extremely, since the cost at the time of refining is caused, a minimum is made 0.20% or more. From the viewpoint that it can be remarkably improved, the content is preferably 0.20 to 0.80%, more preferably 0.20 to 0.60%.

Mn: 0.50 to 5.50%
Mn is a deoxidizer and has the effect of improving hot workability. It is an element effective for fixing S as MnS and preventing the occurrence of red hot brittleness due to the formation of FeS. In order to achieve this, 0.50% or more is necessary. However, if it is contained in a large amount, the refractory melting loss during melting is increased and the corrosion resistance is deteriorated, so the content is made 5.50% or less. If it is less than 0.50%, the cost in the refining process is increased, so the lower limit is preferably 0.50% or more. More preferably, Mn is 0.80 to 5.00%.

Ni: 6.00 to 10.00%
Ni is an element that increases the γ phase, and further improves the corrosion resistance and toughness of the weld metal. It also has the effect of suppressing hot working cracks. In order to acquire these effects, it is desirable to contain 6.00% or more. On the other hand, Ni is an expensive element, and adding excessively leads to an increase in cost, so the upper limit is made 10.00% or less. Preferably, it is 7.00 to 9.00%.

Cr: 21.00 to 26.00%
Cr is a basic element of stainless steel and contributes to improving the corrosion resistance of the weld metal. In order to ensure the high corrosion resistance of the duplex stainless steel, the lower limit is made 21.00% or more. On the other hand, Cr promotes the generation of the σ phase in the weld and leads to a decrease in the toughness of the weld. Therefore, the addition amount is made 26.00% or less. Preferably it is 21.00-25.50%, More preferably, it is 21.00-25.00%.

Mo: 0.05 to 4.00%
Mo is not only an element effective for improving corrosion resistance, but also has an effect of strengthening solid solution, and is contained in an amount of 0.05% or more. However, if it exceeds 4.00%, the hot workability deteriorates, so the upper limit is made 4.00% or less. Preferably it is 0.10 to 4.00%.

P: 0.040% or less P is an element inevitably contained in steel, and is limited to 0.040% or less in order to deteriorate the hot workability of steel. Desirably, it is 0.030% or less.

S: 0.0025% or less S is an element contained as an unavoidable impurity, and decreases hot workability, easily causes cracking defects during hot rolling, and deteriorates corrosion resistance. 0025% or less. Desirably, it is 0.0010% or less.

N: 0.10 to 0.30%
N is an element having an effect of contributing to stabilization of austenite, and at the same time, is an element effective for improving corrosion resistance and strength, and therefore needs to be 0.10% or more. However, if it is contained in a large amount, a problem of surface flaws due to hot workability occurs, so the upper limit is made 0.30% or less. Preferably it is 0.12-0.30%, More preferably, it is 0.14-0.30%.

Al: 0.005-0.080%
Al is an element having an effect as a deoxidizing agent, and when acting as a deoxidizing agent, 0.005% or more is contained. However, if Al is contained excessively, harmful spinel oxides (MgO.Al ₂ O ₃ inclusions) are produced in large quantities and induce nozzle clogging during casting. More preferably, it is 0.060% or less. More preferably, it is 0.050% or less.

Ca: 0.0006 to 0.0025%
Since Ca can fix S and improve hot workability, in order to acquire the effect, it is made to contain 0.0006% or more. However, if contained in a large amount, harmful spinel oxides (MgO.Al ₂ O ₃ inclusions) are produced in large amounts and induce nozzle clogging during casting, so the upper limit is made 0.0025% or less. More preferably, it is 0.0010 to 0.0020%.

Mg: 0.0005 to 0.0030%
Mg is an element that improves hot workability, and contributes to an increase in Ca · Al · Mg-based oxides and Mg-based oxides, so 0.0005% or more is contained. On the other hand, if the Mg content exceeds 0.0030%, the hot workability is decreased, so the upper limit is made 0.0030% or less.

B: 0.0010 to 0.0060%
B is an element that improves hot workability and contains 0.0010% or more. On the other hand, if the content exceeds 0.0060%, the corrosion resistance deteriorates, so the upper limit is made 0.0060% or less. Desirably, it is 0.0015 to 0.0025%.

  The balance of the chemical component is Fe and impurities. Here, the impurity is a component that is mixed due to various factors in the manufacturing process including raw materials such as ore and scrap when industrially manufacturing steel, and does not adversely affect the present invention. It means what is allowed in the range. However, in the present invention, it is necessary to define an upper limit for P and S among impurities as described above.

  Moreover, the duplex stainless steel wire for welding rods and duplex stainless steel wire for welding rods of this embodiment are further in mass%, V: 1.00% or less, Ti: 0.005% or less, Cu: 0.00. One or more of 50% or less may be included. Furthermore, you may include 1 type or 2 types of REM: 0.0100% or less and Ta: 0.0010-0.1000%. When these elements are not included, the lower limit of these elements is 0%.

V: 1.00% or less Ti: 0.005% or less V and Ti may be contained for adjusting the ferrite phase ratio (DF value adjustment). Ti may be mixed as raw material scrap. However, if V and Ti are contained excessively, the toughness of the weld metal after welding is lowered, so the upper limit of V is set to 1.00% or less and the upper limit of Ti is set to 0.005% or less.

Cu: 0.50% or less Cu, like V and Ti, may be contained for adjusting the ferrite phase ratio (DF value adjustment). Moreover, Cu may mix as raw material scrap origin. However, if Cu is excessively contained, hot workability deteriorates, so the upper limit of Cu is 0.50% or less.

REM: 0.0100% or less Since REM (rare earth metal) has a high affinity with S, it can act as an S-fixing element to improve hot workability. However, excessive inclusion of REM causes nozzle clogging, so the upper limit is made 0.0100% or less. Note that REM refers to a total of 17 elements composed of Sc, Y, and lanthanoid, and the content of REM means the total content of these 17 elements.

Ta: 0.0010 to 0.1000%
Since Ta has a high affinity with S, it acts as an S-fixing element and is expected to improve hot workability. Therefore, it is preferable to contain 0.0010% or more. However, excessive addition causes a decrease in toughness, so the upper limit is made 0.10% or less.

DF value: 30.0-60.0%
Moreover, it is necessary to adjust content of the chemical component of the steel mentioned above so that it may become the range of 30.0-60.0% by the DF value represented by a following formula. The DF value is a numerical value for estimating the amount of ferrite phase in the steel, and the following equation is a regression of the relationship between the duplex stainless steel according to the present invention produced by changing various component amounts and the ferrite phase amount. It is what I asked for. If the DF value is less than 30.0%, the hot workability deteriorates, so the lower limit is made 30.0%. On the other hand, when the DF value exceeds 60.0%, the hot workability is deteriorated. Preferably, it is 45.0 to 55.0% of range.

DF value = 7.2 × ([Cr] +0.88 [Mo] +0.78 [Si] +2.2 [Ti] +2.3 [V]) − 8.9 × ([Ni] +0.03 [Mn] ] +0.72 [Cu] +22 [C] +21 [N]) − 44.9
However, the element symbol in the above formula is the content (% by mass) of the element, and 0 is substituted when the element is not included.

Next, the inclusions included in the wire rod and steel wire of the present embodiment will be described.
The structure of the wire rod and steel wire of the present embodiment includes various types and sizes of inclusions. In particular, among the inclusions having a particle size of 1.0 μm or more, the number of Ca · Al · Mg-based oxides. It is preferable that the ratio is 40% or more, the number ratio of Si / Mn / Cr / Fe-based oxide is 20% or less, and the number ratio of Mg oxide is four times or more of the number ratio of Al / Mg oxide.
The reason why the inclusion particle size is 1.0 μm or more is because inclusions having a relatively large particle size affect nozzle clogging during casting, hot workability, and welding workability.

Ca · Al · Mg-based oxides are inclusions containing at least 90% by mass of Ca, Al, and Mg, excluding O (oxygen). Ca, Al, and Mg are included in the form of, for example, CaO, Al ₂ O ₃ , and MgO, respectively. When the amount of precipitation of Ca · Al · Mg-based oxide increases, the generation of spinel inclusions (MgO · Al ₂ O ₃ -based) is suppressed, and nozzle clogging during steel casting is suppressed. Further, Ca · Al · Mg-based oxides have a property of fixing S in steel, and reduce the solid solution S to improve hot workability. Of the inclusions contained in the structure, the number ratio of the Ca · Al · Mg oxide is preferably 40% or more, more preferably 60% or more, and even more preferably 70% or more. . If the number ratio of the Ca.Al.Mg based oxide is less than 40%, the number of spinel inclusions (MgO.Al ₂ O ₃ based) increases, and it becomes impossible to prevent nozzle clogging during steel casting. Moreover, hot workability falls.

The Si.Mn.Cr.Fe-based oxide is an inclusion containing 75% by mass or more of Si, Mn, Cr, and Fe in total, excluding O (oxygen). Si, Mn, Cr, and Fe are included in the form of, for example, SiO ₂ , MnO, CrO, and FeO. Si / Mn / Cr / Fe-based oxides have the property of fixing solute S, but on the other hand, they are easily reduced by heating or the like. For this reason, when receiving welding heat input, S fixed by the Si / Mn / Cr / Fe-based oxide is released into the steel. Thereby, the solid solution S in steel increases and hot workability is reduced. Therefore, it is better that the Si / Mn / Cr / Fe-based oxide is less. Therefore, among the inclusions contained in the structure, the number ratio of Si / Mn / Cr / Fe-based oxides is preferably 20% or less, more preferably 10% or less, and 5% or less. More preferably. When the number ratio of Si / Mn / Cr / Fe-based oxide exceeds 20%, hot workability deteriorates.

In the wire rod and steel wire of this embodiment, the number ratio of Mg oxide is four times or more the number ratio of Al · Mg oxide (including the case where the number ratio of Al · Mg oxide is 0). It is preferable. The case where the number ratio of Al.Mg oxide is 0 means that the number ratio of Al.Mg oxide is 0%, and the case where the number ratio of Mg oxide exceeds 0% corresponds to the steel of the present invention. Means that. Mg oxide is an inclusion containing 80% by mass or more of Mg except for O (oxygen). Mg is mainly contained in the form of MgO. Further, Al · Mg oxide is a spinel inclusion, contains O, and contains 80 mass% or more of Mg and Al, and the ratio of Al to Mg [Al] / [Mg] is 1.5. Inclusions that are ~ 2.5. Al is included in the form of Al ₂ O ₃ and Mg is included in the form of MgO. Similar to Ca / Al / Mg-based oxides, Mg oxide suppresses the formation of spinel inclusions (Al / Mg oxides) by increasing the amount of precipitation and prevents nozzle clogging during steel casting. Become so. Also, hot workability is improved. Therefore, in this embodiment, the number ratio of Mg oxide is set to four times or more of the number ratio of Al · Mg oxide. If it is less than 4 times, nozzle clogging cannot be prevented and hot workability deteriorates, which is not preferable.

  In addition to the above, there are various inclusions in the structure of the wire rod and steel wire of the present embodiment, but these are not particularly defined in the present invention.

Hereinafter, a method for measuring inclusions will be described. Observe an arbitrary horizontal cross-section in the wire drawing direction of the wire or steel wire, randomly select 20 inclusions with a particle size of 1.0 μm or more, and use them as a population, and inclusions included in the population Is analyzed by SEM-EDS to identify the type and number of inclusions. From the results, the numbers of Ca.Al.Mg based oxide, Si.Mn.Cr.Fe based oxide, Mg oxide and Al.Mg oxide are obtained, and the number ratio is further obtained. For example, when four Ca · Al · Mg-based oxides are found from 20 populations, the number ratio of Ca · Al · Mg-based oxides is 4/20 × 100 = 20%.
However, MgO and MgO.Al ₂ O ₃ may exist alone or in a Ca.Al.Mg-based oxide. Therefore, when MgO or MgO.Al ₂ O ₃ having a particle diameter of 1.0 μm or more is present in the Ca · Al · Mg-based oxide, MgO is converted into Ca · Al · Mg-based oxide and Mg oxide, respectively. Counting, MgO.Al ₂ O ₃ is counted as Ca · Al · Mg oxide and Al · Mg oxide.

  Next, the manufacturing method of the wire rod of this embodiment is demonstrated. In primary refining, deoxidation treatment is performed with Si or Al. After making O into 0.0050% or less, Ca is added in the secondary refining. At this time, the addition form of Ca is not particularly limited, but it may be added in the form of metallic Ca or Ca alloy. Thereby, the composition of inclusions can be adjusted within the scope of the present invention.

Molten steel whose composition of inclusions is adjusted is poured into a tundish by a casting nozzle and cast into a slab by casting with a mold. The wire rod of this embodiment is manufactured by hot rolling the slab. Moreover, for example, after performing the primary wire drawing on the wire, a strand heat treatment at 1000 to 1100 ° C. is performed, and the secondary wire drawing is performed, thereby manufacturing the steel wire of the present embodiment.
However, the production method of the present invention is not limited to this, and can be appropriately set within a range where the effects of the present invention can be obtained.

  Examples will be described below. In addition, the conditions of an Example are one example of conditions employ | adopted in order to confirm the feasibility and effect of this invention, and this invention is not limited to this one example of conditions. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

  Molten steel having chemical components shown in Table 1 was poured into a tundish from a casting nozzle, cast into a slab by casting with a mold, and the slab was hot-rolled to produce a wire having a wire diameter of 5.5 mm. Furthermore, after the primary wire drawing was performed on the obtained wire, a strand heat treatment at 1000 to 1100 ° C. was performed, and the secondary wire drawing was performed to produce a steel wire having a wire diameter of 1.0 mm. . In addition, adjustment of the precipitation amount of inclusions is performed by performing deoxidation treatment with Si or Al in the primary refining of molten steel. After adjusting O, it adjusted by adding Ca in secondary refining. The hot rolling was performed under the conditions of heating the cast slab to 1100 ° C., rolling start temperature 1080 ° C., rolling end temperature 1050 ° C., and total area reduction 99.9%. And the nozzle obstruction | occlusion property at the time of casting, hot workability, and the welding workability | operativity at the time of welding a steel wire as a welding rod were evaluated. The results are shown in Table 2.

The nozzle blockage at the time of casting was evaluated according to the following evaluation criteria by confirming the presence or absence of nozzle clogging.
○: No nozzle clogging ×: Continuous casting impossible due to nozzle clogging tendency

The hot workability was evaluated according to the following evaluation criteria by confirming the presence or absence of surface defects on the wire after hot rolling.
○: No wrinkles ×: Surface wrinkles with a depth of 0.15 mm or more

Welding workability was evaluated by the following method.
Inside a copper collection box, on a duplex stainless steel plate (NSSC2120, manufactured by Nippon Steel & Sumikin Stainless Steel Co., Ltd.), with a bead-on plate, welding current 150A, voltage 24V, welding speed 30cm / min, shielding gas 100% A weld bead was produced for 1 minute using a welding rod made of a steel wire to be tested under the conditions of CO ₂ (20 l / min) and no preheating. The presence or absence of spatter scattered in the box during the production of the weld bead was evaluated. The evaluation criteria are as follows.

○: Spatter is not generated ×: Spatter is generated

In addition, regarding the existence ratio of inclusions, a wire is used as an evaluation sample, an arbitrary horizontal section in the wire drawing direction is observed, and 20 inclusions having a particle diameter of 1.0 μm or more are randomly selected. The type and number of inclusions were identified by analyzing each inclusion with SEM-EDS. From the results, the number of Ca.Al.Mg-based oxide, Si.Mn.Cr.Fe-based oxide, Mg oxide and Al.Mg oxide was determined, and the number ratio was further determined. The MgO and MgO · _Al 2 _{O 3,} when Ca · Al · Mg-based oxide particle size 1.0μm or more MgO or MgO · _Al 2 _{O 3} in the present, MgO is Ca · Al · Mg counting each as a system oxide and Mg oxide, MgO · _Al 2 _{O 3} was counted as Ca · Al · Mg-based oxides and Al · Mg oxides. Further, when the number ratio of Al · Mg oxide is 0% and the number ratio of Mg oxide exceeds 0%, it corresponds to the steel of the present invention. “Mg oxide / Al · Mg oxide” in Table 2 represents the ratio of the number ratio of Mg oxide to the number ratio of Al · Mg oxide.
The results are shown in Table 2.

As shown in Table 1 and Table 2, test no. In Nos. 1 to 8 and 17 to 19, the number ratio of chemical components and inclusions satisfied the scope of the present invention, and the nozzle closing property, hot workability, and welding workability were all good.
Test No. In No. 9, the DF value was less than 30.0%, and the hot workability and welding workability deteriorated.
Test No. No. 10, the DF value exceeded 60.0%, and the hot workability deteriorated.
Test No. No. 11 had a Ca / Al / Mg oxide number ratio of less than 40%, and nozzle clogging did not occur, but hot workability deteriorated.
Test No. In No. 12, the number ratio of Si / Mn / Cr / Fe-based oxide exceeded 20%, and nozzle clogging did not occur, but hot workability deteriorated.
Test No. In No. 13, the number ratio of Mg oxide was less than four times the number ratio of Al · Mg oxide, and nozzle clogging occurred.
Test No. In No. 14, the amount of S exceeded 0.0025%, and hot workability deteriorated.
Test No. No. 15 had a Ca content of less than 0.0006%, and the number ratio of Mg oxide was less than four times the number ratio of Al · Mg oxide, resulting in nozzle clogging.
Test No. In No. 16, the Ca content exceeded 0.0025%, and the welding workability deteriorated.

  As described above, the chemical composition satisfies a predetermined range, the DF value is 30.0 to 60.0%, the number ratio of Ca / Al / Mg-based oxide is 40% or more, Si / Mn / Cr The number ratio of Fe-based oxide is 20% or less, and the number ratio of Mg oxide is four times or more of the number ratio of Al / Mg oxide (including the case where the number ratio of Al / Mg oxide is 0). It turns out that a wire and a steel wire are excellent in welding workability, productivity, and hot workability.

Claims (6)

Chemical composition is mass%,
C: 0.005-0.10%,
Si: 0.20 to 2.00%
Mn: 0.50 to 5.50%,
Ni: 6.00 to 10.00%,
Cr: 21.00 to 26.00%,
Mo: 0.05 to 4.00%
P: 0.040% or less,
S: 0.0025% or less,
N: 0.10 to 0.30%,
Al: 0.005 to 0.080%,
Ca: 0.0006 to 0.0025%,
Mg: 0.0005 to 0.0030%,
B: 0.0010 to 0.0060%
And the balance consists of Fe and impurities,
The DF value represented by the following formula is 30 to 60%,
Among inclusions with a particle size of 1.0 μm or more present in steel, the number ratio of Ca / Al / Mg-based oxide is 40% or more, and the number ratio of Si / Mn / Cr / Fe-based oxide is 20% or less. A duplex stainless steel wire rod for welding rods in which the number ratio of Mg oxide is at least four times the number ratio of Al · Mg oxide (including the case where the number ratio of Al · Mg oxide is 0).
DF value = 7.2 × ([Cr] +0.88 [Mo] +0.78 [Si] +2.2 [Ti] +2.3 [V]) − 8.9 × ([Ni] +0.03 [Mn] ] +0.72 [Cu] +22 [C] +21 [N]) − 44.9
However, the element symbol in the above formula is the content (% by mass) of the element, and 0 is substituted when the element is not included. Furthermore, in mass%,
V: 1.00% or less,
Ti: 0.005% or less,
The duplex stainless steel wire for welding rods according to claim 1, comprising one or more of Cu: 0.50% or less. Furthermore, in mass%,
REM: 0.0100% or less,
Ta: 0.0010 to 0.1000%,
The duplex stainless steel wire for welding rods according to claim 1 or 2, comprising one or two of the above. Chemical composition is mass%,
C: 0.005-0.10%,
Si: 0.20 to 2.00%
Mn: 0.50 to 5.50%,
Ni: 6.00 to 10.00%,
Cr: 21.00 to 26.00%,
Mo: 0.05 to 4.00%
P: 0.040% or less,
S: 0.0025% or less,
N: 0.10 to 0.30%,
Al: 0.005 to 0.080%,
Ca: 0.0006 to 0.0025%,
Mg: 0.0005 to 0.0030%,
B: 0.0010 to 0.0060%
And the balance consists of Fe and impurities,
The DF value represented by the following formula is 30 to 60%,
Among inclusions with a particle size of 1.0 μm or more present in steel, the number ratio of Ca / Al / Mg-based oxide is 40% or more, and the number ratio of Si / Mn / Cr / Fe-based oxide is 20% or less. A duplex stainless steel wire for welding rods in which the number ratio of Mg oxide is four times or more of the number ratio of Al · Mg oxide (including the case where the number ratio of Al · Mg oxide is 0).
DF value = 7.2 × ([Cr] +0.88 [Mo] +0.78 [Si] +2.2 [Ti] +2.3 [V]) − 8.9 × ([Ni] +0.03 [Mn] ] +0.72 [Cu] +22 [C] +21 [N]) − 44.9
However, the element symbol in the above formula is the content (% by mass) of the element, and 0 is substituted when the element is not included. Furthermore, in mass%,
V: 1.00% or less,
Ti: 0.005% or less,
The duplex stainless steel wire for welding rods according to claim 4, comprising one or more of Cu: 0.50% or less. Furthermore, in mass%,
REM: 0.0100% or less,
Ta: 0.0010 to 0.1000%
The duplex stainless steel wire for welding rods according to claim 4 or 5, comprising one or two of the above.