JP5300180B2 - Method of forming hardfacing layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a hardfaced layer, which suppresses occurrence of cracks in the hardfaced layer. <P>SOLUTION: The method for forming a hardfaced layer comprises: a step of forming a molten pool 8 on a base material 4 by melting a welding wire 7 as a filler material; a step of feeding hard particles 2, which contain first particles consisting of materials having specific gravity smaller than that of the filler material, to the molten pool 8; and a step of obtaining a hardfaced layer 3, which is formed on the base material 4 by solidifying the molten pool 8 and contains the hard particles 2 in an unmolten state. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a method for forming a hardfacing layer.

Conventionally, it has been practiced to improve the wear resistance of a base material by forming a hardened overlay layer by performing overlay welding on a member (base material) that requires wear resistance. In the formation of the hardfacing layer, the filler metal is melted by welding to generate a molten pool on the base material, and hard particles are dispersed in the molten pool (see Patent Document 1). Thereby, a hardfacing layer in which hard particles are mixed in an unmelted state can be obtained, and wear resistance can be improved.
JP-A-8-47774

  When the hardfacing layer is formed as described above, in the cooling process, the shrinkage amount of the hardfacing layer is large relative to the shrinkage amount of the base material. Works. And since a hardfacing layer has low elongation and toughness, when it receives such a stress, there exists a possibility that the crack may generate | occur | produce on the surface of a hardfacing layer. In order to prevent the occurrence of such cracks, preheating and post-heating are often performed, but this is one factor that reduces productivity.

  An object of the present invention is to provide a method of forming a hardened layer that can suppress the occurrence of cracks in the hardened layer.

The method of forming a hardfacing layer according to the first aspect of the present invention includes a step of melting a filler material to form a molten pool on a base material, and melting hard particles including first particles made of a material having a specific gravity smaller than that of the filler material. The process of supplying to the pond, and the hard pool is solidified in the state where the hard particles are concentrated on the upper part of the molten pool. And a step of obtaining a build-up layer. The hard particles are made of a material having a smaller coefficient of thermal expansion than the filler material. Then, in the step of supplying the hard particles to the molten pool, the hard particles are dropped vertically below the arc of the molten pool.

  In this cured overlay layer forming method, the first particles contained in the hard particles supplied to the molten pool are made of a material having a specific gravity smaller than that of the filler material constituting the molten pool. For this reason, many unmelted first particles can be distributed in the vicinity of the surface of the hardfacing layer obtained by solidifying the molten pool. Since cracks often occur from the surface of the hardfacing layer, it is possible to suppress the occurrence of cracks from the surface of the hardfacing layer by distributing a large number of first particles near the surface of the hardfacing layer. it can. Thereby, in this hardening build-up layer formation method, generation | occurrence | production of the crack in a hardening build-up layer can be suppressed.

  Further, in this cured overlay layer forming method, the hard particles are made of a material having a smaller thermal expansion coefficient than that of the filler material, so that the thermal expansion coefficient of the entire cured overlay layer is reduced by the composite side of the thermal expansion coefficient. be able to. For this reason, the shrinkage | contraction amount at the time of cooling of a hardfacing layer can be reduced, and generation | occurrence | production of a crack can be suppressed more.

  The hardened layer forming method of the second invention is the hardened layer forming method of the first invention, wherein the hard particles further include second particles made of a material having a specific gravity equal to or higher than the specific gravity of the filler material.

  In this cured build-up layer forming method, second particles made of a material having a specific gravity equal to or higher than the specific gravity of the filler material are supplied to the molten pool. For this reason, many first particles can be distributed in the vicinity of the surface of the hardfacing layer, and many second particles can be distributed in a portion lower than the layer in which the first particles are distributed.

The method for forming a hardfacing layer according to the third invention is the method for forming a hardfacing layer according to the first or second invention , wherein the filler material is mainly a mild steel, Ni-based or Cu-based metal. Ingredients.

  In this hardfacing layer forming method, the filler material has a high ductility because it contains mild steel, Ni-based, or Cu-based metal as a main component. For this reason, generation | occurrence | production of the crack in a hardfacing layer can be suppressed more.

The hardened layer forming method according to a fourth aspect of the present invention is the hardened layer forming method according to any one of the first to third aspects, wherein the hard particles include carbide or carbonitride.

  Since carbides and carbonitrides have good wettability with the melted filler material, this cured overlay layer forming method forms a cured overlay layer in which hard particles and the filler material are firmly bonded. be able to.

The hardened layer forming method of the fifth invention is the hardened layer forming method of any one of the first to fourth inventions, wherein the hard particles are carbide, carbonitride, or one or more of these. Are made of particles obtained by binding Fe, Co, and Ni metals.

  Since carbides and carbonitrides have good wettability with the melted filler material, this cured overlay layer forming method forms a cured overlay layer in which hard particles and the filler material are firmly bonded. be able to.

  In the hardfacing layer forming method according to the present invention, the first particles included in the hard particles supplied to the molten pool are made of a material having a specific gravity smaller than that of the filler material constituting the molten pool. For this reason, many 1st particle | grains of a non-molten state can be distributed in the surface vicinity of the hardfacing layer obtained by solidifying a molten pool. Since cracks often occur from the surface of the hardfacing layer, the occurrence of cracks from the surface of the hardfacing layer can be suppressed by distributing a large amount of the first particles near the surface of the hardfacing layer. . Thereby, in this hardening build-up layer formation method, generation | occurrence | production of the crack in a hardening build-up layer can be suppressed.

<First Embodiment>
A welding system 1 used in the method of forming a hardfacing layer according to the present invention is shown in FIG. The welding system 1 forms a hardfacing layer 3 containing hard particles 2 in an unmelted state on a base material 4 by arc welding. The base material 4 is, for example, a component of a construction machine such as bucket tooth that requires wear resistance, and is made of a metal such as carbon steel, low alloy steel such as NiCrMo steel or CrMo steel, or high manganese cast steel. It is. Further, it can be used as a base material 4 made of a Ni-based alloy such as Inconel or Hastelloy, or a Cu-based alloy such as brass or bronze. The welding system 1 includes a torch 5 and a hard particle supply nozzle 6.

  A welding wire 7 is supplied to the torch 5 as a filler material. The welding wire 7 is mainly composed of mild steel, Ni-based, or Cu-based metal. The welding wire 7 is fed out from a coil (not shown) and supplied to the torch 5, and protrudes from the tip of the torch 5 by a predetermined length L1 (projection length). The welding wire 7 is melted by an arc and supplied as a filler material, whereby a molten pool 8 is generated on the base material 4. The torch 5 is inclined at an angle θ (torch angle) with respect to the surface of the base material 4 and moves at a predetermined speed along the surface of the base material 4 (see arrow A1 in FIG. 1).

  The hard particle supply nozzle 6 is disposed in the vicinity of the torch 5 outside the torch 5 and is disposed above the molten pool 8 formed by melting the welding wire 7. The hard particle supply nozzle 6 moves with the torch 5 while weaving with a predetermined width back and forth along the traveling direction of the torch 5 (see arrow A1 in FIG. 1) (see arrows A2 and A3 in FIG. 1). The hard particles 2 are supplied directly under the arc of the molten pool 8 by dropping by gravity from the moving hard particle supply nozzle 6. The distance from the hard particle supply nozzle 6 to the arc generation portion of the molten pool 8 is L2. Further, a water cooling pipe 9 is disposed on the outer periphery of the hard particle supply nozzle 6 to cool the hard particle supply nozzle 6.

  The hard particles 2 supplied from the hard particle supply nozzle 6 are composed of first particles made of a material having a specific gravity smaller than that of the filler material constituting the welding wire 7 and a coefficient of thermal expansion smaller than that of the filler material. For example, when steel is used as the filler material, the first particles include carbides such as TiC, TiCN, ZrC, and Cr3C2, carbonitrides, or at least one of these Fe-based, Co-based, and Ni-based materials. It consists of particles bonded with a metal. The first particles have a hardness necessary as an additive component of the hardfacing layer 3, for example, a hardness of 500 to 2000 Hv, preferably 1000 to 1800 Hv. Moreover, the particle size of the first particles is 0.5 to 5 mm, preferably 0.5 to 2.5 mm, and the addition amount of the first particles is 5 to 55% by volume with respect to the hardfacing layer 3, Preferably it is 15-45 volume%.

  Next, FIG. 2 shows a flow of a method for forming a hardfacing layer using the welding system 1.

  First, in the first step S1, arc welding is performed. Here, by generating an arc, the welding wire 7 is melted and supplied as a filler material, and a molten pool 8 is generated on the base material 4. In the hardfacing layer forming method according to the present invention, the overlay welding for forming the surfacing layer of mild steel or the like before the formation of the hardfacing layer is not performed.

  Next, in the second step S <b> 2, the hard particles 2 fall from the hard particle supply nozzle 6 and are supplied to the molten pool 8. The second step S2 is performed in parallel with the first step S1, and the hard particles 2 are supplied to the liquid molten pool 8 before solidification.

  In the third step S3, the molten pool 8 is solidified to obtain the hardfacing layer 3 formed on the base material 4 and containing the hard particles 2 in an unmelted state. Here, in the part after the torch 5 and the hard particle supply nozzle 6 move, the molten pool 8 naturally solidifies to form the hardfacing layer 3. Since the hard particles 2 supplied to the molten pool 8 in the second step have a specific gravity smaller than that of the filler material, the hard particles 2 are concentrated and distributed near the surface in the formed hardfacing layer 3.

  While the torch 5 and the hard particle supply nozzle 6 are moved, the hardened layer 3 is formed so as to cover a predetermined region of the base material 4 by repeatedly performing these first to third steps.

  When the hardfacing layer 3 is formed by such a method of forming the hardfacing layer, the molten pool 8 is solidified in a state where the hard particles 2 having a specific gravity smaller than that of the filler material are concentrated on the upper portion of the molten pool 8. Thereby, the hardfacing layer 3 with many hard particles 2 distributed near the surface can be obtained, and it can suppress that the surface of the hardfacing layer 3 cracks at the time of cooling. Moreover, it can suppress that a crack arises on the surface of the hardfacing layer 3 also by using the ductile material as mentioned above as a filler material.

  Hereinafter, specific examples of the method for forming the hardfacing layer according to the first embodiment will be described. In addition, the table | surface which compared the conditions in each Example is shown in FIG.

In the welding system 1 and the cured overlay layer forming method described above, the cured overlay layer 3 is formed under the following conditions.
[Types of base material 4 and welding wire 7]
Base material 4: SH30 (NiCrMo steel)
Welding wire 7: JFE Welding Rod Co., Ltd. (50 kg class mild steel, specific gravity 7.8), φ1.2 mm
The protruding length L1 of the welding wire 7 is 25 mm, and the torch angle θ is 60 °.
[Welding conditions]
Welding current: 350A
Welding voltage: 33V
Weld heat input: 15.4 kJ / cm
Welding speed (moving speed of torch 5): 45 cm / min
In addition, 30 liters of CO2 is supplied as shielding gas per minute.
[Types of hard particles 2]
Hard particles 2: TiC-Ni (specific gravity 7.5 g / cm3)
Hard particle 2 particle size: 0.71 to 2.36 mm
Supply amount of hard particles 2: 158.5 g / min
Total particle supply volume: 21.1 cm3 / min
Hard particle 2 content: 38.5%
In addition, the content rate of the hard particle | grains 2 shows the ratio of the cross-sectional area of the hard particle 2 in the total cross-sectional area of the hardfacing layer 3, and does not consider the melt-mixing to the hardfacing layer 3 of the hard particle 2. Apparent content.
[Movement condition of hard particle supply nozzle 6]
Weaving waveform: sin wave Weaving frequency: 3.0 Hz
Weaving width: 9.4mm
Distance between hard particle supply nozzle 6 and arc generation part L2: 25 mm
By forming the hardfacing layer 3 under the above-described conditions, it is possible to obtain the hardfacing layer 3 in which the hard particles 2 are distributed in the vicinity of the surface, and on the surface of the hardfacing layer 3 during cooling. It can suppress that a crack arises.

  A material made of SCMnH11 (high Mn steel) is used as the base material 4, and the hardfacing layer 3 is formed in the same manner as in Example 1 for other conditions. Also in this case, similarly to Example 1, the hardfacing layer 3 in which the hard particles 2 are distributed in the vicinity of the surface can be obtained.

Second Embodiment
In the second step in the first embodiment, the timing for supplying the hard particles 2 may be when the molten pool 8 is in a semi-solidified state. In this case, the hard particles 2 may include particles made of a material having a specific gravity equal to or higher than that of the filler material. For example, when steel is used as the filler material, NbC is a material having substantially the same specific gravity. Moreover, as what has a big specific gravity, there exists a thing which consists of a particle | grain which couple | bonded Mo2C, TaC, WC, W2C, or one or more of these with Fe type, Co type, and Ni type metals.

  The configuration of the welding system 1 and other processes are the same as in the first embodiment.

  Hereinafter, specific examples of the method for forming the hardfacing layer according to the second embodiment will be described.

Hard particles 2: WC-Co (specific gravity 14.5 g / cm3)
Hard particle 2 particle size: 0.71 to 2.36 mm
Supply amount of hard particles 2: 306.5 g / min
Total particle supply volume: 21.1 cm3 / min
Hard particle 2 content: 38.5%
The moving condition of the hard particle supply nozzle 6 is substantially the same as that of the first embodiment, but the weaving width is 9.8 mm. Other conditions are the same as those in the first embodiment, but the hard particles 2 are supplied from the hard particle supply nozzle 6 when the molten pool 8 is in a semi-solid state.

  In this case, since the hard particles 2 are supplied to the semi-solidified molten pool 8, even the hard particles 2 having a specific gravity larger than that of the filler metal are difficult to settle. For this reason, the molten pool 8 is solidified in a state where the hard particles 2 are concentrated on the upper portion of the molten pool 8. Thereby, the hardfacing layer 3 with many hard particles 2 distributed near the surface can be obtained, and it can suppress that the surface of the hardfacing layer 3 cracks at the time of cooling.

  The base material 4 is made of SCMnH11 (high Mn steel). Other conditions are the same as in the third embodiment.

  Also in this case, similarly to Example 3, it is possible to obtain the hardfacing layer 3 in which the hard particles 2 are distributed in the vicinity of the surface, and to suppress the surface of the hardfacing layer 3 from being cracked during cooling. Can do.

<Third Embodiment>
In the second step in the first embodiment, not only the first particles smaller than the specific gravity of the filler material but also hard particles 2 further including second particles made of a material having a specific gravity equal to or higher than the specific gravity of the filler material are hardened. You may supply from the particle supply nozzle 6. FIG. Here, the second particles are the same as those exemplified as the hard particles in the second embodiment. The second particles are supplied in a state of being mixed with the first particles as a powder separate from the first particles. The material exemplified as the first particles and the material exemplified as the second particles are Fe-based, Co Particles bonded with a system or Ni-based metal may be supplied as hard particles.

  The configuration of the welding system 1 and other processes are the same as in the first embodiment.

  Hereinafter, specific examples of the method of forming the hardfacing layer according to the third embodiment will be described.

Hard particle 2: Mixing of TiC-Ni and WC-Co (TiC: 38 vol% (24 wt%), WC-Co: 62 vol% (76 wt%))
Hard particle 2 particle size: 0.71 to 2.36 mm
Supply amount of first particles (TiC-Ni): 49.5 g / min
Supply amount of second particles (WC-Co): 163.0 g / min
Total particle supply volume: 17.8 cm 3 / min
Hard particle 2 content: 37.1%
The welding conditions and the moving conditions of the hard particle supply nozzle 6 are substantially the same as in Example 1, but the welding speed is 42 cm / min, the welding heat input is 15.6 kJ / cm, and the weaving width is 8.0 mm. About other conditions, it is the same as that of Example 1, and both 1st particle | grains and 2nd particle | grains are supplied to the molten pool 8 of a liquid state.

  When the hardfacing layer 3 is formed under the above-described conditions, the first particles having a specific gravity smaller than that of the filler material are concentrated on the upper portion of the molten pool 8, and the second particle having a specific gravity larger than that of the filler material. The molten pool 8 is solidified with the particles concentrated in the lower part of the molten pool 8. Thereby, the hardfacing layer 3 with many 1st particles distributed near the surface can be obtained, and it can suppress that a crack arises on the surface of the hardening layer 3 at the time of cooling. Moreover, since the hard particles 2 can be distributed not only on the surface of the hardfacing layer 3 but also on the lower portion by the second particles, the hard particles 2 can be dispersed in the hardfacing layer 3 and stable. Abrasion resistance can be obtained.

  The base material 4 is made of SCMnH11 (high Mn steel). Other conditions are the same as in the fifth embodiment.

  Also in this case, similarly to Example 5, it is possible to obtain the hardfacing layer 3 in which many first particles are distributed near the surface and many second particles are distributed in the lower part.

  INDUSTRIAL APPLICATION This invention has the effect which can suppress generation | occurrence | production of the crack in a hardening buildup layer, and is useful as a hardening buildup layer formation method.

The figure which shows the structure of the welding system used with the hardfacing layer forming method which concerns on this invention. The figure which shows the flow of the hardfacing layer forming method which concerns on this invention. The figure which shows the table | surface which compared the conditions of each Example.

Claims (5)

Melting the filler material to generate a molten pool on the base material;
Supplying hard particles containing first particles made of a material having a specific gravity smaller than that of the filler material to the molten pool;
When the molten pool is solidified in a state where the hard particles are concentrated on the upper part of the molten pool, the hard particles are formed on the base material and contain the hard particles in an unmelted state, and the hard particles are distributed in a large amount on the surface. Obtaining an overlay layer;
With
The hard particles are made of a material having a smaller coefficient of thermal expansion than the filler material,
In the step of supplying the hard particles to the molten pool, the hard particles are dropped vertically downward directly under the arc of the molten pool.
A method for forming a hardfacing layer. The hard particles further include second particles made of a material having a specific gravity equal to or higher than the specific gravity of the filler material.
The cured built-up layer forming method according to claim 1. The filler material is mainly composed of mild steel, Ni-based, or Cu-based metal,
The method for forming a hardfacing layer according to claim 1 . The hard particles include carbide or carbonitride,
The method for forming a hardfacing layer according to any one of claims 1 to 3 . The hard particles are composed of carbides, carbonitrides, or particles obtained by bonding one or more of these with Fe-based, Co-based, or Ni-based metals.
The method for forming a hardfacing layer according to any one of claims 1 to 4 .

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