JPS63242490A - Composite filler metal for build-up welding - Google Patents

Abstract

PURPOSE:To easily obtain the titled composite flux by forming mixed sintered crystal of matrix metallic powder with dispersed ceramics powder and specifying its density in the range of a specific ratio at the time of having no void and performing the combined build-up welding with the high adherent strength and an uniform distributing state of ceramics. CONSTITUTION:The composite filler metal for the build-up welding of this invention is the mixed sintered crystal of the matrix metallic powder of Cr-Ni- Fe, etc., with the dispersed ceramics powder such as Al2O3, etc., and its density is 55-98% when there is no void. Then, since said composite filler metal has low sintered density <=98%, its bond is weak and it can be welded at a low current and the heat input to a molten pool can be reduced. Moreover, when the heat input is reduced, the melting temperature becomes low and the viscosity of molten metal becomes high. As a result, a dispersed state of ceramics at a build-up zone can be uniformized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a composite welding material for welding to obtain a composite overlay in which ceramics are dispersed in a metal matrix, and in particular, it relates to a welding composite welding material for obtaining a composite overlay in which ceramics are dispersed in a metal matrix. The present invention relates to a composite thermal material that can obtain the following properties.

[Conventional technology]

Composite materials in which ceramics are dispersed in a metal matrix combine the features of both metals and ceramics.

Applying such composite materials to the sliding surfaces of various machines and the surfaces of roll materials is extremely effective in improving the abrasion resistance and heat resistance of the surfaces. Thermal spraying is a well-known method for applying the surface of this composite material. When applying a composite material surface using the thermal spraying method, a matrix metal powder and a dispersed ceramic powder are mixed and supplied, heated and melted by plasma or the like, and then collided with the material surface at high speed. This creates a composite film in which ceramics are dispersed in a metal matrix.

The dispersed ceramic Nox used is aluminum oxide (
A A! Os ), TiO2, Chromium oxide (Cr z Os ), Tungsten carbide (
WC), titanium carbide (TiC), chromium carbide (CrnC)
m), niobium carbide (NbC), molybdenum carbide (Mo
□C), zirconium carbide (ZrC), etc., matrix metals include Cr-Fe series, Cr-Ni-Fe series, C
These include r-Go type, Cr-Ni type, etc.

However, the surface coating of a composite material formed by thermal spraying has a weak adhesion strength, and furthermore, it is not possible to obtain a large coating thickness. Therefore, there is a risk that the coating may peel off during use, and the lifespan against wear is also short. Another problem is that thermal spraying requires a dedicated and expensive thermal spraying machine, making it difficult to perform the process easily.

For this reason, recently, a method to easily generate a thick surface film with high adhesion strength has been developed.
A method of composite overlaying using a composite filler rod by tungsten inert gas arc welding (TIG) was proposed. (Unexamined Japanese Patent Publication No. 186190/1986) This method is
First, ceramic powder is uniformly mixed with metal powder and sintered to create a composite filler rod. TIG welding is then performed using this filler rod under normal welding conditions.

The resulting overlay has high adhesion strength and is resistant to mechanical shock, which is fundamentally superior to composite coatings produced by thermal spraying.

[Problem that the invention seeks to solve]

However, this method also has the following problems.

Since ceramic has a lower specific gravity than metal as a matrix material, the ceramic transferred from thermal spraying during welding receives buoyancy in the molten pool and tends to float. As a result, in the case of downward welding, the ceramic is biased toward the surface side of the built-up portion, and the ceramic concentration in that portion becomes high. Such uneven distribution of ceramics causes variations in the properties of the built-up portion in the thickness direction. In other words, the surface tends to become brittle due to the high ceramic concentration;
Because the ceramic concentration is low inside, the desired characteristics tend not to be obtained.

The present invention aims to solve these problems and provide a composite thermal spraying method that can easily obtain a composite overlay with high adhesion strength and a uniform ceramic distribution state by welding.

[Means for solving problems]

The non-uniformity of ceramic dispersion in weld overlay using composite thermal spraying is basically due to the difference in specific gravity between the ceramic 7x and the matrix metal, but the degree of this is greatly influenced by the viscosity of the molten matrix metal and the time until solidification. be done. That is, if the viscosity of the matrix metal is high or the solidification time is short, the floating of the ceramic in the molten pool tends to be hindered, and the floating speed becomes slow. Under such conditions, the molten metal solidifies due to heat taken from the surroundings before the ceramic floats. For this reason, the higher the viscosity of the molten pool and the shorter the time until solidification, the more uniform the ceramic dispersion becomes.

On the other hand, when the component system is constant, the viscosity and solidification time of the molten metal are expressed as a function of temperature, and the temperature is controlled by the amount of heat input during welding.

For this reason, one way to make the dispersion state of ceramics uniform in the built-up portion is to suppress welding heat input as much as possible.

From this point of view, the present inventor conducted various experiments and research on thermal spraying that makes it possible to lower welding heat input, and as a result, by optimizing the density conditions of composite thermal spraying as powder sintered crystals. We have discovered that it is possible to weld with low heat input, and that it is also possible to obtain a built-up part with highly uniform ceramic dispersion by manual heat welding.

That is, the gist of the present invention is a composite thermal spraying product for overlay, which is a mixed sintered product of matrix metal powder and dispersed ceramic powder, and has a density of 55 to 98% of that without pores. .

The composite thermal spraying of the present invention has a low sintered density of 98% or less, so the bond is weak, and low current welding is possible. The temperature decreases and the molten metal viscosity increases. As a result, the dispersion state of the ceramics in the built-up portion becomes uniform. Furthermore, in this case, since the molten metal temperature is lower, the cooling time is also shortened, which also contributes to uniformity of ceramic dispersion.

In the present invention, the density of the hot material is limited to 55 to 98% for the following reasons. If the density is less than 55%, the strength of the hot material (rod) will be insufficient and handling will be difficult, so it is preferably 80% or more. If it is 80% or more, the rod has sufficient strength and can be handled as easily as a normal welding rod. In particular, with regard to composite welding rods for coated arc overlay, since force is applied to the rod at the start of welding or when short-circuiting,
It is desirable to ensure sufficient strength with a density of 80% or more.

Moreover, when it exceeds 98%, a welding current comparable to that when the density is 100% is required, and the effect of reducing welding heat input is not significant.

The composite hot material of the present invention is used as a welding rod for TIG build-up or a welding rod for covered arc build-up.For TIG build-up, it is used in the form of a sintered rod, and for covered arc build-up, it is used as a sintered rod. It is used with a flux coating applied to the outer periphery.

The composite thermal material of the present invention exhibits remarkable effects particularly when used as a coated arc welding rod. During shielded arc welding, the molten metal is transferred to the base metal by the arc flow from the tip of the rod toward the base metal, but with a low-density welding rod, the bond between the powders is weaker, and the force of the heating and arc flow transfers the molten metal to the base metal. transition is likely to occur. In other words, a low-density product can be overlaid with less heat input than a high-density product, and as a result, a dispersion overlay with extremely uniform ceramic dispersion can be obtained.

The composite thermal material of the present invention is produced by, for example, adding a paraffin-based, resin-based, or cellulose-based binder to metal powder and dispersed ceramic powder, compression molding, and sintering while controlling temperature and time to achieve a predetermined product density. A method of hot compression molding (hot press molding) using a hot mold (such as a graphite mold), a method of adding a cellulose binder and extrusion molding from an extrusion mold, and then changing the temperature and time. Manufacturing methods such as controlling and sintering to obtain a predetermined product density can be applied. The rod obtained by this method usually has a rod diameter of about 1.2 to 8 mm, and can be used as a filler rod for TIG, or by applying flux to the outer periphery.
Can be used as a coated arc welding rod.

As the matrix metal constituting the composite thermal material, Cr-Ni-
Fe-based, Cr-Fe-based, Cr-M.

-Co series, Cr-W-Co series, 5i-Cr-pJi series,
Cr-Ni type, etc. are suitable. Dispersed ceramic materials include aluminum oxide (Aj!tOs), titanium oxide (TiOt), chromium oxide (crzoco), yttrium oxide (YzOs), and silicon oxide (SiC).
), chromium carbide (CrnCm), molybdenum carbide (M
o□C), niobium carbide (NbC), zirconium carbide (
ZrC), titanium nitride (TiN), boron nitride (BN)
, silicon nitride (S is Na ), etc. are used.

The particle size of the dispersed ceramic material is 0.001 to 0.05
It is best to set it to about 1■. The finer the powder, the more uniform the ceramics dispersion is possible, and the greater the effect of ceramics dispersion, such as improving wear resistance, improving high temperature hardness, and improving sliding properties, and the amount of ceramics blended is 0.0
The content is preferably 5 to 50% by weight, and particularly for coated arc welding rods, 0.05 to 40% by weight is preferable because if the electric resistance of the rod itself becomes too high, welding defects will occur.

As for the welding conditions, the welding current varies depending on the product density, but compared to one with a density of 100%, welding current with a density of 55%
~98%, about 60-95%, density 80-98%
It is best to set it at about 75 to 95%.

〔Example〕

Sprayed powder (matrix metal) of a Co-based alloy having the components shown in Table 1 with a particle size of 59 μm or less and a particle size of 1.5 μm.
of aluminum oxide powder (ceramics powder) at a weight ratio of 90:10, 2% by weight of cellulose binder and 10% by weight of water were added and kneaded, and this was mixed using a 3fi diameter nozzle. The extruded material was then extruded at a pressure of 150° C. in an inert atmosphere at 1275° C. to obtain a sintered rod with a rod diameter of 2.5 m and a density of 87%. This wire was used as a wire, and a lime titania-based flux was applied to the outer periphery to obtain a coated arc welding rod (Example 1 of the present invention).

In addition, zirconium oxide (ZrO7) powder with a particle size of 1.5 was used instead of aluminum oxide powder, and the other conditions were exactly the same as above.
A coated arc welding rod was obtained (Invention 2).

In addition, as a comparative example, the one of Example 1 of the present invention was further subjected to isothermal pressurization at 1250°C using a ceramic mold, and the diameter was 2.45 mm.
A product with a density of 100% mm was manufactured.

Overlay welding was performed using these three types of welding rods.

Overlay welding was performed by underlaying 5US308 on the 545C base material, preheating it to 200°C, and then performing downward arc welding under the conditions shown in Table 2.

Figure 1 shows the cross-sectional shape of the bead obtained by two-layer stacking.

The analysis results of the density distribution (weight ratio) of the ceramics in the surface layer a, center portion b, and bottom portion C in FIG. 1 were as shown in Table 3.

Although the ceramic concentration is slightly low in the bottom part C due to dilution with the base material, it can be seen that the ceramics are uniformly dispersed in the center part b and the surface part a.

Moreover, when comparing Example 1 and Example 2, Zr0t has a larger unit weight and is closer to the matrix metal, so A 1 t
It is more uniformly dispersed than Os. On the other hand, the overlay part using a 100% density welding rod used as a comparative example had a deep weld penetration depth D due to the influence of heat input.
The concentration of ceramics was high in the surface layer a, and was low in the center, indicating that the dispersion state was non-uniform.

〔Effect of the invention〕

As is clear from the above explanation, the composite hot material for overlaying of the present invention can be applied with a lower welding current than hot materials made by normal manufacturing methods, and a large amount of heat can be transferred to the base metal and molten pool. It is possible to form a uniform ceramic dispersion build-up layer by lowering the It is highly effective in improving properties, extends the life of overlay parts, reduces maintenance man-hours, and makes a great contribution to the field of surface modification by overlay.

Table 1 Table 2 *Single f1 (g/cc) Table 3

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the cross-sectional shape of a bead obtained in an experiment conducted as an example.

Claims (4)

[Claims] (1) A mixed sintered product of matrix metal powder and dispersed ceramic powder, with a density of 55 ~
A composite welding material for overlay welding, characterized in that it is 98%. (2) The composite melt material for overlay welding according to claim 1, which is a filler rod for TIG overlay. (3) The composite melt material for overlay welding according to claim 1, which has a flux coating layer on the outer periphery and is a welding rod for covered arc overlay. (4) The composite welding material for overlay welding according to claim 2 or 3, which is used for hard overlay to improve wear resistance at room temperature or high temperature.