JPH11277246A - Wear resistant cladding layer by welding and cladding material by welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always guarantee high wear resistance by universally preparing the hardness of a fixed level or more even in any section of cladding by welding at the time of forming high hard cladding layer on a base material by PTA welding or the like. SOLUTION: This layer is composed of a micro structure mainly consisting of a base of Ni or Fe and a ternary multiple compound or precepitation of W, Cr and B. For example, when a powder plasma arc welding method is used, powder of tungsten carbide and chromium boride of 40-80 weight % is incorporated in powder of Ni or Fe, and moreover although the weight % of tungsten carbide in composite powder is always larger than that of chromium boride, chromium boride itself of 10-30 weight % is definitely incorporated. Whereby, extremely high hardness for the cladding layer by welding is obtained and moreover the difference of hardness in the vertical direction within the layer is always controlled to a slight difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasion-resistant material, particularly to a weld overlay having only a portion corresponding to a wear surface hardened, and a material thereof.

[0002]

2. Description of the Related Art Conventionally, a surface treatment or a weld overlay has been applied to the surface of a base material in order to impart a specific property such as abrasion resistance to a specific surface of a specific member of an apparatus or a machine. As is well known, many methods have been put into practical use for welding overlaying, but arc welding using a flux-cored composite wire which is sufficient with a simple apparatus is often used. This is achieved by inserting C into a hollow tubular shell made of flexible mild steel, stainless steel, etc.
In this method, a flux-cored composite wire obtained by mixing and filling required additive components such as r, C, Si, and Mn as a powder is flexibly supplied to the surface of the base material and welded.

On the other hand, surface coating by thermal spraying is widely performed. This is a method in which a metal or ceramic is melted and small particles are jetted at a high speed to coat the surface of the object. The equipment and operation are relatively simple and can be applied to large base materials.
The droplet sprayed from the thermal spray gun flies in the air, collides with the surface of the thermal sprayed body and is crushed, and at the same time is rapidly cooled and solidified. In this way, flat small particles are deposited to form a thermal sprayed coating, but the surface is partially oxidized, and a small gap is left between the particles.

[0004] A number of prior art techniques have been proposed for strengthening coatings to improve wear resistance by thermal spraying. For example, W
Japanese Patent Application Laid-Open No. 9-268361, in which a cermet is formed by combining a Co-based double boride and a Co-Cr-Mo-based alloy phase, or each of the carbide cermet particles and a boride is previously combined integrally by mechanical alloying or CVD. Japanese Patent Application Laid-Open No. 6-116702, which attempts to prevent the two components from separating during the thermal spraying operation, and furthermore, in the powder thermal spraying in which the three components of W, Cr, and Ni are combined, its wear resistance, hardness,
Japanese Patent Publication No. Sho 52-26 wherein tungsten carbide is uniformly and finely distributed by adding boron of 3% or less to improve weldability.
No. 725 and so on.

[0005] Powder plasma arc welding (hereinafter referred to as "PT
A welding). The principle of this method is that, as shown in FIG.
The molten metal is supplied into the molten metal 4 and transferred to a molten pool while melting the powder to form a weld overlay layer 15. Carbide, oxide, boride powder, etc. other than metal powder can be freely mixed and added to the weld metal. There are advantages. Further, it is considered that the penetration is shallower than that of the conventional welding method, the welding bead is smooth, and the welding bead is suitable for welding. Generally, argon gas is used for the plasma gas 11, the shield gas 12, and the powder supply gas 13. The raw material powder P usually used for PTA welding is a metal powder such as Fe, Ni, or Cr. In order to further harden the weld overlay, tungsten carbide is added in an amount of 30 to 70% by weight ( (Hereinafter, simply expressed as%). From the viewpoint of the feeding property and the welding efficiency, usually, a powder having a particle size of 45 to 200 μm is frequently used.

[0006] A number of conventional techniques have also been proposed for PTA welding. Japanese Patent No. 2703713 to prevent powder scattering by limiting the particle size and shape of the powder, and Japanese Patent Application Laid-Open No. 7-195177.
No. 2,703,735 in which pinholes are prevented by adding 0.5 to 20 ppm of hydrogen, Patent No. 2668055, which is limited to shovels and screws,
-266209 and so on.

[0007]

Among the prior arts described above, in the case of thermal spraying, as described above, droplets are sprayed onto the surface of the base material by a spray gun to form a thin thermal spray coating on which flat small particles are deposited. Therefore, voids tend to remain between the particles of the coating, and there is a limit in the density. In addition, there is a limit in blending a metal powder that has a surface that is easily oxidized and has a strong affinity for oxygen. In any case, the particles are deposited independently of each other, and even if the hardness is improved as a simple substance, it is difficult to expect a drastic increase in the hardness due to the formation of a compound. Since the particles and the substrate are not metallurgically related, they are merely a physical attachment of the powder to the irregularities on the surface of the substrate, so a high degree of integral bonding cannot be expected, and simply static abrasion resistance Despite its suitability for use, there is a high risk of abrasion and peeling for dynamic abrasion wear, etc., and its film thickness is at most several hundred microns, so its use as a surface treatment for wear-resistant parts is limited. Is done.

On the other hand, PTA welding has a smooth weld bead and good wear resistance, and is suitable for forming a wear-resistant surface which faces various abrasive wear. However, today, which requires higher wear resistance, it is not always possible to cope with the dispersion hardening of high-hardness tungsten carbide, which is a known means. That is, the conventional technique of compounding a large amount of tungsten carbide based on Ni or Fe as a welding powder by PTA welding, as Table 1 suggests, has a problem due to the difference in density (specific gravity difference) between the base metal and the additive compound. Surface.

[0009]

[Table 1]

Since Vickers hardness Hv (hereinafter simply referred to as hardness) of Ni serving as a base is about 120 and Fe is about 100, W ₂ C 3000 and WC are 1800.
It is foreseeable that if the tungsten carbide is evenly distributed in the matrix, the hardness of the entire weld overlay, and hence the wear resistance, will be dramatically improved. All of the prior art stands at this origin, and there is no doubt that the wear resistance is enhanced by the weld overlay with the addition of tungsten carbide. However, with respect to Ni powder, W ₂ C was 30, 50, 7
When PTA welding is performed with powders having different mixing ratios of 0%, and divided horizontally at the top and bottom of the weld overlay, and the hardness is measured for each fault, a surprisingly serious problem is encountered.

FIG. 7 shows a typical example of 30% Ni + 70% W.
_It shows the measurement results of the hardness of each fault of ₂ C. The average hardness of the first row slightly dissolved in the base material SS400 is 11
In contrast to this, the average hardness of each row decreases extremely to 974, 699, and 534, and the average hardness of each of the four rows further increases to 861. Stayed.

FIG. 8 shows, in addition to the measured values, an additional 50%
30% and W_TwoChange the amount of C to separate the top and bottom of the weld overlay.
5 is a table showing a correlation with an average hardness of a horizontal section to be cut.
, W The hardness as a whole increases with the addition of 2C.
At the same time, the variation in hardness in the weld overlay increases further.
The tendency of great badness increased, and R (minimum value of average hardness / flatness)
The maximum value of the average hardness) decreases rapidly and the wear resistance of the
This suggests that the balance is being lost.

It is understood that the cause of the great difference in hardness is due to the difference in specific gravity of the components. Looking at the density (g / cm ³ ) in Table 1, Ni as the base was 8.
90, while Fe is 7.86, W ₂ C is 17.86.
20, WC is 15.77, and if there is such a big difference,
Even within the short melting time of PTA welding, most of the tungsten carbide having a remarkably high melting point and large mass settles in the molten pool in an undissolved state, and it is natural that the molten tungsten carbide also settles. I can say.

In the formation of the weld overlay by the PTA welding method, one of the prior arts is a means of replacing the conventional addition of a large amount of tungsten carbide for increasing the hardness with the addition of chromium boride. It is well known that chromium boride also has properties similar to tungsten carbide and behaves almost metallurgically. In this case, chromium boride has a low density unlike tungsten carbide, and 5.6 in CrB ₂ .
0 g / cm ^{3, which} is smaller than the base Ni density,
There is little concern about immediate settling in the molten pool. But,
To 80% Ni 20% of the a CrB ₂ were individually blended, the hardness distribution in the maximum 734 as shown in FIG. 9, although what small variations in the hardness of only the buttered welding layer 668 and the density is small at the lowest , The total average hardness is about 700, indicating only the limit of single addition.

According to the present invention, when a high hardness overlay is formed on a base material by PTA welding or the like, a hardness of a certain level or more is universally provided at any part of the weld overlay, and a high level of wear resistance is always obtained. It is an object of the present invention to provide a weld overlay that guarantees weldability, or a unique welding material that forms the weld overlay.

[0016]

The wear-resistant weld overlay according to the present invention comprises a microstructure mainly composed of a matrix of Ni or Fe and a ternary compound of W, Cr and B or a precipitate. In addition, it is characterized in that it has an extremely high hardness which is almost close to both upper and lower portions in the layer. Specifically, at any position in the weld overlay, the hardness exceeds at least 700 and the minimum / maximum average hardness of each fault plane measured horizontally at each depth from the surface of the overlay. A configuration in which the ratio R is always concentrated in a narrow range exceeding 0.80 regardless of the depth is a desirable embodiment.

As a welding material for forming the weld overlay layer, a powder material used in the powder plasma arc welding method may be composed of Ni or Fe powder and tungsten carbide and chromium boride powder in total of 40 to 80 powder. By weight, the tungsten carbide in the composite powder always occupies a larger percentage than the chromium boride. However, since the chromium boride itself always contains 10 to 30% by weight, the weld overlay is extremely high. Produces high hardness and suppresses the ratio R of the minimum / maximum average hardness of each fault plane measured horizontally at each depth from the surface of the overlay to a narrow range that always exceeds 0.80 regardless of the depth Is a requirement. For the flux cored wire for welding used in the arc welding method, nickel or mild steel, or stainless steel, in the outer shell formed into a hollow tubular plate material selected from either,
Tungsten carbide and chromium boride powder together with shielding gas generating agent, slag forming agent, and deoxidizing agent are charged in a total of 40 to 80% based on the total weight including the hull, but tungsten carbide is always higher than chromium boride. Large weight%
And the chromium boride itself must contain at least 10 to 30%.

Table 1 shows the melting point, hardness and density of chromium boride. The hardness of CrB ₂ is extremely high at 2100,
B also shows a numerical value according to this, and since its density is lower than that of Ni or Fe, which is the base, it is effective for hardening the upper part of the weld overlay without settling in the molten pool. It is possible to harden the entire weld overlay as compared with a single addition. In addition, this is a consideration of a single element level. As a result of observing the structure of the weld metal, part or half of tungsten carbide is melted by heat of a welding arc, and most or most of chromium boride is melted. After cooling and solidification in the weld metal, compounds or precipitates containing a large amount of three components of W, Cr and B are observed. This compound or precipitate is considered to be very hard and has good wear resistance, and the problem is solved.

In order to form a weld overlay which satisfies this requirement, the total of 80% or less of tungsten carbide and chromium boride as the spray powder in the PTA welding method is 80% or less. If it exceeds, the weld overlay becomes brittle, and many large cracks opened on the surface are generated, and it is confirmed that when subjected to external force such as vibration or impact, there is a great risk of peeling and falling off. However, the sum of tungsten carbide and chromium boride must be greater than 40%.
This is a general rule that it has been empirically obtained that the conventional tungsten carbide is added to the Ni or Fe welding pool to improve the hardness of the build-up layer, and that the tungsten carbide is set in the range of 30 to 70%. Also, the hardness measurement in Comparative Example 1 revealed the result confirming this.
Even if 10% chromium boride is added to 30% or less tungsten carbide, it is hard to expect that the hardness required by the present application can be obtained. In addition, tungsten carbide is always higher in the mixing ratio than chromium boride, and the chromium boride itself is 10 to 10%.
Must contain 30%. Unless this requirement is satisfied, all the hardness in one weld overlay is 700 or more, and the hardness variation R (minimum average hardness / maximum average hardness) in each horizontal section is 0.80. Cannot be guaranteed. If the welding method is an arc welding method, it is replaced by filling a total of 40 to 80% of tungsten carbide + chromium boride with respect to the total weight including the outer surface of the welding flux cored wire, but other conditions are as follows. There is no change.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The components shown in Table 1 were combined as shown in Table 2 and powders having a particle diameter of 45 to 200 .mu. Were applied and welded.

[0021]

[Table 2]

The welding conditions are welding current 170A, welding voltage 2
3 V, welding speed 70 mm / min (however, for the abrasion test sample, the welding speed was reduced to 40 mm / min and waving was performed), and P was put on a 25 mm thick SS400 steel plate.
TA welding was performed.

[0023] In Table 2, Comparative Examples 1 to 3 are prior arts containing tungsten carbide alone as already described in FIG.
Comparative Example 4 is a prior art in which chromium boride alone was blended as described in FIG. Comparative Examples 1 and 2 have no measurement points having a hardness exceeding 700, and Comparative Example 3 has a total average hardness of 861. However, the average minimum hardness (534) of each fault is the average maximum hardness (110).
7) is only 0.48. In Comparative Example 4, the ratio is 0.94 because the density is small, and the variation is small, but the total average is about 700, which is data indicating the limit of single addition.

In Comparative Example 5, a large number of large cracks were observed in the weld overlay to predict the peeling, and the limit (80%) of the total amount of tungsten carbide and chromium boride was specified. Comparative Example 6 is a high-Cr cast iron, which is a typical wear-resistant material, and it is well known that a wear-resistance magnification of 3.7 is not sufficient, and that the entire product is brittle and severely restricts use conditions. It is.

FIG. 2 shows 30% Ni + 50% W ₂ C + 20% CrB ₂ (Example 2 in Table 2) as a typical example of the hardness distribution according to the embodiment of the present invention. As shown in the figure, the ratio R between the minimum (1103) and the maximum (1338) of the average hardness of each row divided into four was 0.82, and the minimum value of the individual hardness was 1012. Similarly, FIG. 1 summarizes the measurement results of Examples 1 to 4, and shows the average hardness and the minimum / maximum average hardness, that is, R, of each of the four divided faults. Filled black is the Fe-based embodiment, showing substantially similar values.

The abrasion test was performed using ASTM G as shown in FIG.
Disk Rotary Pressure Abrasion Tester 2 manufactured according to Standard 65
Measured using 0. In the figure, 120r. p. The test piece S is pressed with a load of 8.8 kgf against the circumference of the rubber wheel 21 rotating at a speed of m.
The wear resistance of each test piece was compared by a pressure abrasion test in which 300 g / min of No. 6 silica sand was added from the sand hopper 22 as a grinding powder between the surfaces. The wear resistance ratio in Table 2 is obtained by converting the numerical value measured on a fault plane obtained by cutting the weld overlay of each test piece horizontally at two locations above and below assuming that the SS material is 1.0, and increasing the CrB ₂ %. In addition, it has been proved that the wear resistance is also greatly increased. In addition, when the upper and lower wear resistance ratios are compared for each test piece, a ratio almost equal to the minimum / maximum hardness ratio is obtained, indicating a small variation consistent with the variation in hardness. In contrast, in the comparative example, a large decrease in hardness is directly consistent with a decrease in the abrasion resistance ratio, indicating data further confirming the superiority of the material of the present invention.

The feature of the present invention is that the hardened layer is hardened in a well-balanced manner by a high approximate hardness over the entire cross section regardless of the upper and lower portions of the weld overlay. One of the reasons is as follows. With the proper addition ratio of the combination of tungsten carbide and chromium boride, the hardness of the upper part of the weld overlay is reduced by the precipitation of tungsten carbide having a higher density than the base Ni or Fe in the molten pool. Chromium boride having a low density compensates. However, this alone cannot explain why tungsten carbide or chromium boride achieves a much higher maximum hardness than when added alone. The reason is only possible if a ternary compound or precipitate of W, Cr and B newly generated by the coexistence of tungsten carbide and chromium boride is assumed.

FIG. 4 shows the uppermost portion of the welding layer according to the second embodiment of the present invention.
In other words, the X-ray analysis (electron beam micro-analyzer EP
MA) shows the microstructure of the portion subjected to MA), and the straight line crossing the center shows the scanning line of the measurement X-ray. FIG. 5 is a calibration diagram showing a part of the X-ray analysis. Cr, W, and C were analyzed under the conditions of an acceleration current of 15 KV, a sample current of 5 × 10 ⁻⁸ A, and a beam diameter of 2 μm.
The density of each component of B was detected by the level of the calibration curve, and the phases of the three components were identified by comparing the level of the three components with the position of the corresponding microstructure. That is, the peaks (A1, A2,
A3) is in good agreement with the light gray structure (A1, A2, A3) in FIG. 4, and this phase is the region of high hardness of the dense ternary compound or precipitate of W, Cr, B, and FIG. Valley (B1,
B2) matches well with the dark gray structure (B1, B2) in FIG. 4, and this phase is presumed to be a low hardness matrix region corresponding to the matrix of Ni + Fe (transition from the base material). The greatest feature of the present invention is that the ternary compound or the precipitate occupies the majority of the tissue in any fault plane. Although the specific molecular structure and crystal structure cannot be specified at this time, there is no doubt that the three-component synergistic action forms a highly leveled phase with high hardness throughout the entire region.

For flux-cored wires, it is a requirement that, basically following the principles of the prior art, only certain proportions of tungsten carbide and chromium boride be adhering to specific standards. For example, rutile (TiO ₂ ), alumina (Al ₂ O ₃ ) or the like as a slag forming material, rutile (TiO ₂ ), Na, K or the like as an arc stabilizer, Fe—Si or the like as a deoxidizing agent, As a gas generating component, CaF ₂ or the like is typical. In a gas shield type, the shielding gas generating component may be small, and in a self-shield type, it is naturally required to mix a large amount. It is particularly necessary in the case of the present invention to control the filling rate of each flux component in the outer shell, and the mixing ratio of tungsten carbide and chromium boride as additive components is a predetermined ratio with respect to the total weight including the outer shell. It is an important condition in the embodiment to densely fill so as to fall within the range.

[0030]

As described above, according to the present invention, the average hardness of each of the horizontal sections divided at the top and bottom of the weld overlay is concentrated in a very narrow range, and the hardness at any fault is tungsten carbide or borane. The level is clearly higher than that of the prior art in which chromium oxide is added in a substantially total amount by itself, and the synergistic metallurgical effect is remarkably remarkable. Moreover, the present invention limits not only the hardness, and therefore the wear resistance, but also the weldability and the durability during use to within an acceptable range. The weld overlay is beautiful and smooth and has the fineness peculiar to the PTA welding method. A bead has not only high hardness but also an element that projects a subtle positive effect on abrasion resistance.

[Brief description of the drawings]

FIG. 1 shows hardness (Hv) -CrB showing an embodiment of the present invention.
₂ is a weight percent relationship diagram.

FIG. 2 is a distribution diagram of hardness (Hv) at each part of a section of a weld overlay shown in a representative example of an embodiment of the present invention.

FIG. 3 is a basic structural view of a wear tester used in the present invention.

FIG. 4 is a microscopic structure of the upper surface of a sample subjected to X-ray analysis.

FIG. 5 is a diagram showing variations in the contents of Cr, W, and B, which are calibrated by X-ray analysis.

FIG. 6 is a front view showing the principle of the PTA welding method.

FIG. 7 shows hardness (Hv) at each part of a section of a weld overlay of Comparative Example 3 of the prior art.

FIG. 8 is a graph showing the relationship between hardness (Hv) and tungsten carbide weight% in Comparative Examples 1 to 3 of the prior art.

9 shows the hardness (Hv) at each part of the cross section of the weld overlay of another comparative example 4. FIG.

[Explanation of symbols]

 10 Powder plasma arc welding machine (PTA welding machine) 11 Plasma gas 12 Shielding gas 13 Supply gas 14 Plasma arc 15 Weld overlay 20 Abrasion tester 21 Rubber foil 22 Sand popper S Test piece

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B23K 35/30 340 B23K 35/30 340L 35/368 35/368 E // C22C 29/02 C22C 29/02 C

Claims (4)

[Claims] 1. A wear-resistant weld overlay comprising a Ni or Fe matrix and a microstructure mainly composed of a ternary compound of W, Cr and B or a precipitate, and whichever part of the upper or lower part of the layer is formed. A wear-resistant weld overlay, characterized by having a very high hardness that is substantially similar to that of the above. 2. The method according to claim 1, wherein the Vickers hardness (Hv) exceeds 700 at any position in the weld overlay, and each of the fault planes is divided horizontally at every depth from the surface of the overlay. A wear-resistant weld overlay, wherein the ratio R of the minimum value / maximum value of the average hardness always exceeds 0.80 regardless of the depth. 3. A wear-resistant welding overlay material, which is a powder material used in a powder plasma arc welding method,
A composite powder containing a total of 40 to 80% by weight of tungsten carbide and chromium boride powder in Ni or Fe powder,
Tungsten carbide in the composite powder always occupies a larger percentage by weight than chromium boride, but the chromium boride itself always contains 10 to 30% by weight. Material for weld overlay. 4. A wear-resistant welding overlay material, which is a flux-cored wire for welding used in an arc welding method, wherein a plate material selected from nickel, mild steel, or stainless steel is formed into a hollow tubular shape. A flux cored wire filled with tungsten carbide and chromium boride powder together with a shielding gas generating agent, a slag forming agent, and a deoxidizing agent in the outer shell that has been coated, based on the total weight of the flux cored wire including the outer shell. The total content of tungsten carbide and chromium boride is 40 to 80% by weight, and tungsten carbide always accounts for more than chromium boride, but chromium boride itself always contains 10 to 30% by weight. Wear-resistant welding overlay material used for arc welding.