JP5899007B2 - Flux-cored wire for hardfacing arc welding - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is used for hardfacing welding, and is suitable for obtaining a weld metal having excellent wear resistance and crack resistance not only at room temperature but also in a high temperature environment, and ensuring good welding workability. The present invention relates to a flux-cored wire for hardfacing arc welding.

  Various parts of industrial machines such as iron and steel making facilities and civil engineering machines are required to have wear resistance, heat resistance, corrosion resistance, impact resistance, and the like. In particular, the surface of a part used for hot working is exposed to high-temperature gas and combustion gas, and the material is formed into a necessary shape, and damage due to metal contact occurs. Therefore, from the viewpoint of preventing damage at high temperatures, wear resistance and heat resistance at high temperatures are required.

  In addition, in order to safely operate and maintain the above-mentioned equipment such as industrial machines, if such high temperature damage occurs, the equipment should be replaced completely or partially It is necessary to replace parts that are worn or peeled off. However, if these damaged parts to be replaced are discarded and a replacement product is newly produced, the depreciation and production costs become enormous, resulting in an increase in cost and an increase in production labor. Therefore, conventionally, a hardfacing welding method has been widely adopted as a repairing means for damaged parts that have been worn out or peeled off.

  In the hardfacing welding method as the repairing means, conventionally, a coated arc welding rod has been used, and the hardfacing welding is performed on the surface of the component to form a high quality overlaying layer, thereby extending the life. In recent years, overlay welding using a submerged arc welding method and a gas shielded arc welding method has become common from the viewpoint of improving the efficiency of welding.

  Under such circumstances, especially high-efficiency hardfacing welding is possible, it has excellent wear resistance in high-temperature environments, and in addition, it has excellent welding workability. Development is desired. However, the martensitic or high Cr iron-based overlay welding material applied to conventional applications has a problem that the wear resistance and crack resistance at high temperatures cannot be satisfied.

  Further, as a conventional technique of hardfacing welding, a flux-cored wire for hardfacing that limits the amounts of C, Si, Mn, Cr, W, V, Mo, and B is disclosed (for example, see Patent Document 1). ). According to the disclosed technique of this Patent Document 1, with the aim of improving the strength of the weld metal and also improving the crack resistance, among these elements described above, the contents of Mo and B, among others, are optimized, and welding is performed. The metal structure is a composite structure composed of martensite and boride of steel.

  However, the flux-cored wire has a problem that the crystal grains become coarse and wear resistance becomes insufficient under a high temperature environment. Further, since B is added, there is a problem that a low melting point compound is generated in the grain boundary and crack resistance is lowered.

  Moreover, the flux-cored wire for hardening buildup which limits content of each component of C, Si, Mn, Ni, Cr, and Mn / Si is disclosed (for example, refer patent document 2). According to the technology disclosed in Patent Document 2, a stable hardness of the deposited metal is obtained by adjusting the amount of Cr and C and adding Ni, and by adjusting the amount of Si and Mn and adding Ti, a good bead shape is obtained. Is to be obtained. Further, the disclosed technique of Patent Document 2 has found that an appropriate amount of an alkali metal compound or the like is added to extremely stabilize the arc and reduce the amount of spatter generated.

  However, with this flux-cored wire, the amount of C and Ni is low, so the amount of crystallization of the austenite phase is small, and since Mo and W are not contained, the heat resistance and wear resistance at high temperatures deteriorate. there were.

JP-A-11-197877 JP 2010-253516 A

  Therefore, the present invention has been devised in view of the above-mentioned problems, and the object of the present invention is used for hardfacing welding, and is resistant to wear and cracking not only at room temperature but also at high temperature. An object of the present invention is to provide a flux-cored wire for hardfacing arc welding in which a weld metal having excellent properties is obtained and welding workability is good.

In order to solve the above-described problems, a flux-cored wire for hardfacing arc welding according to the present invention is a flux-cored wire for hardfacing arc welding in which a stainless steel outer shell is filled with a flux. %, The total of stainless steel skin and flux, C: 0.15-0.60%, Si: 0.3-1.0%, Mn: 1.5-4.5%, Ni: 7.0 -10.0%, Cr: 13.0-20.0%, Mo: 3.0-6.0%, W: 3.0-6.0%, In the flux, TiO ₂ : 0.5 to 4.0%, SiO ₂ : 0.1 to 1.5%, total of one or more of Al ₂ O ₃ and ZrO ₂ : 0.05 to 0.20% , F-converted value of fluorine compound: 0.1 to 1.5%, C, Si, Mn, Ni, C The content (% by mass) of each component of r, Mo, and W is 0.9 to 1.5 in terms of A value of the following formula, and the others are Fe component of stainless steel outer skin, Fe component from iron alloy, and It is an inevitable impurity.

  A = (Cr + Mo + 1.5Si + 0.7W) / (Ni + 30C + 0.5Mn) (formula)

  According to the flux-cored wire for hardfacing arc welding according to the present invention, a weld metal with excellent wear resistance and crack resistance can be obtained not only at room temperature but also in a high temperature environment, and welding workability is good. A flux-cored wire for arc welding can be provided.

  In order to solve the above-mentioned problems, the present inventors have made trials of flux-cored wires having various component compositions and examined them in detail. As a result, it has been found that the wear resistance at high temperatures is improved by adding Mo and W.

  On the other hand, when held at a high temperature for a long time, it became clear that an extremely hard and brittle σ phase was precipitated in the ferrite, resulting in a variation in hardness and a decrease in wear resistance. Therefore, it has been newly found that by optimizing the amount of addition of Mo, which is a ferrite-forming element and promotes precipitation of the σ phase, it is possible to reduce the σ phase while keeping the amount of ferrite low.

  In addition, the present inventors have found that it is possible to adjust the amounts of C and Cr to generate W and Cr carbides and improve wear resistance.

Furthermore, the present inventors have conducted further studies because the ferrite content is decreased and crack resistance tends to be deteriorated. As a result, in order to improve the cracking resistance, by adjusting the amount of Ni crystallization and adjusting the ferrite crystallization amount, P affecting the cracking resistance is dissolved in the ferrite, It has been found that it is effective to reduce segregation of low melting point compounds by adding Mn. Further, it was found that the welding workability can be improved by adding appropriate amounts of TiO ₂ , SiO ₂ , Al ₂ O ₃ , ZrO ₂ and fluorine compounds.

  That is, the flux-cored wire for hardfacing arc welding to which the present invention is applied is a flux-cored wire for hardfacing arc welding in which a stainless steel sheath is filled with a flux, and is a mass% with respect to the total mass of the stainless steel sheath. And flux, C: 0.15 to 0.60%, Si: 0.3 to 1.0%, Mn: 1.5 to 4.5%, Ni: 7.0 to 10.0%, Cr: 13.0 to 20.0%, Mo: 3.0 to 6.0%, W: 3.0 to 6.0%, C, Si, Mn, Ni, Cr, Mo, W The content (% by mass) of each component is 0.9 to 1.5 in the A value of the following formula, and the others are Fe component of stainless steel skin, Fe component from iron alloy, metal oxide, fluorine Hardening arc welding flux characterized by being a compound and inevitable impurities Ri is a wire.

  A = (Cr + Mo + 1.5Si + 0.7W) / (Ni + 30C + 0.5Mn) (formula)

  The flux-cored wire for hardfacing arc welding to which the present invention consisting of the above-described component composition is applied can be achieved by a synergistic effect due to the individual and coexistence of each component composition of the stainless steel outer sheath and the filling flux. The reasons for the addition and limitation of each component composition are described below. In addition, content of each component composition is shown by the mass% with respect to the wire total mass. In addition, the content of each component composition is the total amount of the stainless steel skin and the flux.

[C: 0.15-0.60%]
C is added from stainless steel skin, ferromanganese, ferrosilicon manganese, graphite, and the like, and has the effect of generating carbides between Cr and W and increasing the hardness of the deposited metal. If C is less than 0.15%, the formation of carbides between Cr and W is insufficient, and the hardness at normal temperature cannot be obtained. On the other hand, when C exceeds 0.60%, carbides between Cr and W are coarsened, and the hardness at high temperature varies. Therefore, C is 0.15 to 0.60%.

[Si: 0.3-1.0%]
Si has a deoxidizing action and is added from stainless steel shell, metal silicon, ferrosilicon, ferrosilicon manganese, and the like, and has an effect of improving bead shape and slag encapsulation. If Si is less than 0.3%, the amount of slag formed by the deoxidation reaction during welding is reduced, and the slag encapsulation is impaired. On the other hand, if Si exceeds 1.0%, the amount of slag becomes excessive and the bead shape deteriorates. Therefore, Si is made 0.3 to 1.0%.

[Mn: 1.5 to 4.5%]
Mn has a deoxidizing action similar to Si, and is added from stainless steel skin, metal manganese, ferromanganese, ferrosilicon manganese, etc., and reduces arc stability and spatter generation while segregating low melting point compounds. It has the effect of reducing and improving crack resistance. If Mn is less than 1.5%, the low melting point compound is segregated at the austenite grain boundary, so that the crack resistance is deteriorated. On the other hand, if Mn exceeds 4.5%, droplet transfer is hindered by the deoxidation reaction that occurs during welding, the arc becomes unstable, and the amount of spatter generated increases. Therefore, Mn is 1.5 to 4.5%.

[Ni: 7.0 to 10.0%]
Ni is an element that is added from a stainless steel shell, metallic nickel, ferronickel, or the like and stabilizes the austenite phase, and thus has the effect of adjusting the ferrite content and improving crack resistance. When Ni is less than 7.0%, the amount of austenite crystallized decreases and the amount of ferrite increases, so that the formation of carbides between Cr and W precipitated from austenite is entirely suppressed, and a sufficiently high temperature is achieved. Hardness cannot be obtained. On the other hand, when Ni exceeds 10.0%, the amount of ferrite crystallized decreases, segregation of the low melting point compound is promoted, and crack resistance deteriorates. Therefore, Ni is set to 7.0 to 10.0%.

[Cr: 13.0 to 20.0%]
Cr is added from a stainless steel shell, metallic chromium, ferrochromium, and the like, and is an element that stabilizes the ferrite phase, and also produces Cr carbide and has the effect of increasing the hardness of the deposited metal. If Cr is less than 13.0%, the formation of Cr carbide is suppressed and sufficient hardness at room temperature cannot be obtained. On the other hand, if the Cr content exceeds 20.0%, the production of Cr carbide increases and the hardness at room temperature becomes excessive, resulting in a decrease in ductility and separation of the weld overlay. Therefore, Cr is 13.0 to 20.0%.

[Mo: 3.0-6.0%]
Mo is added from a stainless steel skin, metal molybdenum, ferromolybdenum, or the like, has the effect of promoting the formation of Cr and W carbides, increasing the hardness at high temperature, and improving the secondary curability. If Mo is less than 3.0%, sufficient hardness at high temperature cannot be obtained. On the other hand, if Mo exceeds 6.0%, an extremely hard and brittle σ phase is precipitated from the ferrite, and the hardness at high temperature varies, so the wear resistance decreases. Therefore, Mo is set to 3.0 to 6.0%. The secondary curability here contributes to improvement of wear resistance by dispersing Mo carbides in austenite at 500 ° C. or higher.

[W: 3.0-6.0%]
W is added from metallic tungsten, tungsten carbide, etc., and promotes the formation of W carbide to increase the hardness and improve the wear resistance, and also reduces the precipitation of the σ phase. If W is less than 3.0%, sufficient hardness at normal temperature cannot be obtained. On the other hand, if it exceeds 6.0%, carbides including Cr and W are coarsened, so that the hardness at normal temperature varies and the wear resistance decreases. Therefore, W is set to 3.0 to 6.0%.

[A value: 0.9 to 1.5]
By adjusting the C, Si, Mn, Ni, Cr, Mo, W to 0.9 to 1.5 in the A value of the following formula, the balance between the ferrite phase and the austenite phase is adjusted, and crack resistance and σ phase are adjusted. Has the effect of suppressing the precipitation of. If the A value is less than 0.9, the solid solubility of P and S decreases as the ferrite crystallization amount decreases, so that the crack resistance deteriorates. On the other hand, when the A value exceeds 1.5, the amount of ferrite crystallized increases, so that when held at a high temperature for a long time, the σ phase is precipitated from the ferrite and the hardness at high temperature varies. Accordingly, the A value is set to 0.9 to 1.5.

  A = (Cr + Mo + 1.5Si + 0.7W) / (Ni + 30C + 0.5Mn) (formula)

[TiO _2: 0.5~4.0%]
TiO ₂ is added from rutile, titanium oxide, sodium titanate, titanium slag, illuminite or the like. These have the effect of encapsulating the entire bead uniformly. Moreover, there exists an effect which maintains an arc and stabilizes droplet transfer. If the TiO ₂ content is less than 0.5%, the viscosity of the slag is increased, so that the droplet transfer is inhibited and the arc stability is deteriorated. On the other hand, when TiO ₂ exceeds 4.0%, the arc is continued and droplet transfer is performed smoothly, but the amount of slag generated during welding is increased and the slag encapsulation is deteriorated. Therefore, TiO ₂ is set to 0.5 to 4.0%.

[SiO ₂ : 0.1 to 1.5%]
SiO ₂ is added from silica sand, zircon sand or the like and acts as a slag forming agent, and has the effect of adjusting the physical properties of the slag with a small amount. If the SiO ₂ content is less than 0.1%, the formation of fragile and amorphous slag is impaired, and the slag releasability deteriorates. On the other hand, if SiO ₂ exceeds 1.5%, the arc becomes rough and the amount of spatter generated increases. Thus, SiO ₂ is 0.1 to 1.5%.

[Total of one or more of Al ₂ O ₃ and ZrO ₂ : 0.05 to 0.20%]
Al ₂ O ₃ is added from alumina, ZrO ₂ is added from zircon sand and zirconium oxide, etc. The total of one or more of Al ₂ O ₃ and ZrO ₂ is 0.05% or more, improving the slag viscosity and improving the bead shape. Acts as a slag forming agent. On the other hand, if the total of one or more of Al ₂ O ₃ and ZrO ₂ exceeds 0.20%, the viscosity of the slag increases and the droplets grow excessively, resulting in an increase in the amount of spatter generated. Therefore, the total of one or more of Al ₂ O ₃ and ZrO ₂ is 0.05 to 0.20%.

[F conversion value of fluorine compound: 0.1 to 1.5%]
F is added from sodium fluoride, potassium silicofluoride, cryolite, aluminum fluoride, lithium fluoride, fluorite, etc., and improves the stability of the arc. If it is less than%, the arc becomes unstable. On the other hand, if the F-converted value of the fluorine compound exceeds 1.5%, the melting point of the slag decreases, the slag solidifies faster than the molten metal, and the bead shape becomes uneven. Therefore, the F conversion value of the fluorine compound is set to 0.1 to 1.5%.

  Others are the Fe component of the stainless steel skin, the Fe component from the iron alloy, and inevitable impurities. From the viewpoint of crack resistance, P is preferably 0.040% or less and S is preferably 0.030% or less.

  As mentioned above, although the reason for limitation of the component composition of the flux-cored wire for hardfacing arc welding of the present invention has been described, when referring to the method for producing the flux-cored wire, for example, when forming a stainless steel skin from a strip steel into a tubular shape The filled flux that has been blended, stirred, and dried is filled into a U-shaped groove, then formed into a round shape, and drawn to a predetermined wire diameter. At this time, a seamless type flux-cored wire can be obtained by welding the formed outer seam. When the stainless steel sheath is a pipe, the pipe can be vibrated, filled with flux, and drawn to a predetermined wire diameter. In either case, even if the manufacturing method is used, the wire diameter can be manufactured up to 0.8 to 3.6 mm.

  The flux can be granulated by adding a sticking agent (potassium silicate and sodium silicate aqueous solution) so that supply and filling can be performed smoothly.

  Hereinafter, the present invention will be described in detail by way of examples.

  Using the austenitic stainless steel outer skin having chemical components shown in Table 1, flux-cored wires for hardfacing arc welding having various component compositions shown in Table 2 were produced.

  Incidentally, Table 2 shows the mass% with respect to the total mass of the wire in the case where fluxes having the respective component compositions of the austenitic stainless steel skins of the hoop numbers W1 to W3 shown in Table 1 are added. That is, the mass% of the sum total of the stainless steel outer layer and the flux of each chemical component with respect to the total mass of the flux-cored wire is shown. Table 2 shows the flux filling rate, which is the ratio of the mass of the flux to the total mass of the stainless steel shell and the flux of each chemical component. The wire diameter was 2.0 mm.

  Welding workability evaluation is based on JIS Z 3114 using SM490A steel plate having the components shown in Table 3, and under the welding conditions shown in Table 4, three-layer overlay welding is performed in a downward welding posture. Welding workability was evaluated by eye welding. As for welding workability, arc stability, spatter, slag encapsulation, and bead shape were subjected to a visual test. Moreover, the Vickers hardness was measured based on JISZ3114, JISZ2244, and JISZ2252, using the test piece which evaluated welding workability | operativity. As for Vickers hardness, the average of 10 points is 250 to 350 at normal temperature (test temperature: 20 ° C.), and the average of 10 points is good to be 200 to 300 at high temperature (test temperature: 600 ° C.). . In addition, the variation range of the Vickers hardness measured at each test temperature was such that the difference between the maximum value and the minimum value was 50 or less.

  As for crack resistance, a C-type jig restraint butt weld cracking test was performed in accordance with JIS Z 3155. In the C-type jig restraint butt weld cracking test, a SM490A steel plate having the components shown in Table 3 was subjected to two-layer buttering to form a groove. Two test bead lengths of about 80 mm were welded under the welding conditions shown in Table 4 with the root interval of the test plate being 2 mm. The evaluation was good when the average crack rate was 5% or less. The results are summarized in Table 5.

表２及び表５中のワイヤＮｏ．１〜８が本願発明例、ワイヤＮｏ．９〜１８は比較例である。本願発明であるワイヤＮｏ．１〜８は、Ｃ、Ｓｉ、Ｍｎ、Ｎｉ、Ｃｒ、Ｍｏ、Ｗ、Ａ値、各酸化物及びＦ換算値が適正であるので、常温硬さ及び高温硬さが良好であり、いずれの硬さのばらつきが認められず、耐割れ性及び溶接作業性も良好であり、極めて満足な結果であった。

The wire Nos. 1 to 8 are examples of the present invention, wire Nos. 9 to 18 are comparative examples. Wire No. which is the present invention. 1 to 8, C, Si, Mn, Ni, Cr, Mo, W, A value, each oxide and F conversion value are appropriate, so that normal temperature hardness and high temperature hardness are good, There was no variation in thickness, and the crack resistance and welding workability were also good, which was a very satisfactory result.

In the comparative example, the wire No. No. 9 had a large amount of C, so the variation in high-temperature hardness was large. Moreover, since the A value was low, the cracking rate was high. Further, since the amount of TiO ₂ is small, the arc is unstable and the total amount of Al ₂ O ₃ and ZrO ₂ is large, so that the amount of spatter generated is large.

Wire No. No. 10 has a high room temperature hardness because of the large amount of Cr. Moreover, since the A value was high, the high-temperature hardness variation was large. Further, since TiO ₂ is large, slag encapsulated is poor, since the sum of the Al ₂ O ₃ and ZrO ₂ is less, the bead shape was also poor.

Wire No. No. 11 was poor in slag encapsulation because it contained less Si. Moreover, since there was little Cr, the normal temperature hardness was low. In addition, since the SiO ₂ is large, the amount of occurrence of spatter were many.

  Wire No. No. 12 had a poor bead shape due to the large amount of Si. Moreover, since there was little Mn, the crack rate was high.

  Wire No. No. 13 had a large amount of Mn, so the arc was unstable and the amount of spatter generated was large. Moreover, since there was much Mo, the dispersion | variation in high temperature hardness was large.

Wire No. No. 14 had a low Ni hardness, so its high temperature hardness was low. Moreover, since there was much W, the dispersion | variation in normal temperature hardness was large. Further, since SiO ₂ is small, the slag removability is poor.

  Wire No. No. 15 had a low C hardness, so the room temperature hardness was low. Moreover, since there was much Ni, the crack rate was high. Furthermore, since the F-converted value of the fluorine compound is small, the arc was unstable.

  Wire No. Since No. 16 had less W, the room temperature hardness was low, and because Mo was less, the high temperature hardness was low. Further, since the F-converted value of the fluorine compound is large, the bead shape was bad.

Claims (1)

In the flux-cored wire for hardfacing arc welding by filling the stainless steel outer shell with flux,
It is the mass% with respect to the total mass of the wire.
C: 0.15-0.60%,
Si: 0.3 to 1.0%,
Mn: 1.5 to 4.5%,
Ni: 7.0 to 10.0%,
Cr: 13.0-20.0%,
Mo: 3.0-6.0%,
W: 3.0 to 6.0%,
In mass% with respect to the total mass of the wire,
TiO _2: 0.5~4.0%,
SiO ₂ : 0.1 to 1.5%,
Total of one or more of Al ₂ O ₃ and ZrO ₂ : 0.05-0.20%,
F converted value of fluorine compound: 0.1 to 1.5%,
The content (mass%) of each component of C, Si, Mn, Ni, Cr, Mo, and W is 0.9 to 1.5 in terms of the A value of the following formula, and the other is Fe of stainless steel skin. A flux-cored wire for hardfacing arc welding, which is a component, an Fe component from an iron alloy, and inevitable impurities.
A = (Cr + Mo + 1.5Si + 0.7W) / (Ni + 30C + 0.5Mn) (formula)