JP2013000814A - Zinc-base alloy shot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zinc-base alloy shot which is used for surface processing to remove burr from or grind and clean an aluminum die casting product or magnesium die casting product by shot blast, has superior cost performance, does not deteriorate erosion resistance and is in accordance with surface hardness of a product to be processed.SOLUTION: The zinc-base alloy shot of three component system contains 1.800 to 6.000 mass% Cu and 0.0010 to 0.5000 mass% Fe as additional elements, where Vickers hardness is 80 to 110 HV, and purity of Cu to be an additional element is ≥99.9 mass%. The zinc-base alloy shot is used for shot blast of aluminum alloy die castings or magnesium alloy die castings.

Description

The present invention relates to shots for shot blasting for the purpose of deburring and polishing nonferrous metal parts, sand removal of cast products, and the like.

More specifically, the present invention relates to light alloy die casting and casting products made of light alloys such as aluminum-based alloys or magnesium-based alloys, scale removal, metal product coating and seizing removal of release agents, or oxide films and hot water. The present invention relates to a zinc-based alloy shot used for projection processing and spraying processing used for wrinkle removal.

Conventionally, because of surface treatment for deburring and polishing of products, die casting products used for automobile parts, etc., are often shot blasts that project small spheres called shots onto products at high speed. Yes.

Shot materials such as aluminum-based alloys, stainless steel, and zinc-based alloys have been generally used as shot materials used for this shot blasting.

Zinc-based alloy shots have lower dust explosion sensitivity due to shot crushing than aluminum-based alloy shots and stainless steel shots. For this reason, in recent years, many shots have been used as shots for shot blasting of non-ferrous metal die-cast products (for example, Patent Documents 1 and 2).

JP-A-9-70758 Japanese Patent Laid-Open No. 2002-224963

However, since the shot described in Patent Document 1 has a hardness of 50 HV to 60 HV, there is a problem that productivity of deburring and polishing is low. Further, if the Cu content exceeds 2.00% by weight, the absolute number of solid solutions increases too much, and the toughness is significantly impaired compared to zinc and becomes brittle. (Patent Document 1, paragraph 0009).

On the other hand, the shot described in Patent Document 2 has a hardness of more than 60 HV to 150 HV. Here, too soft shots have low deburring and cleaning productivity. On the other hand, a shot that is too hard has a short life and causes problems such as scratching the product to be processed. That is, when the Vickers hardness is lower than 60 HV in the zinc-based alloy shot, the deburring ability and the scouring ability are not sufficient, and when exceeding 150 HV, cracking and wear of the zinc-based alloy shot during deburring and scouring The amount of shot consumption increased.

By the way, the shot described in Patent Document 2 has a Cu content in zinc of 1.8 to 13.0%. However, since Cu is more expensive than Zn, there is a problem that if the Cu content is too high, the price of the shot becomes high. Moreover, according to the zinc base alloy shot, the darkening after the projection with respect to a to-be-processed product had arisen. For this reason, although darkening was reduced by adding Cu to a zinc base alloy shot, the property does not want to be lowered even when Cu is reduced.

The present invention has been made in view of these problems. The present invention is a zinc-based alloy shot used for surface treatment for deburring and polishing aluminum die-cast products and magne-die cast products by shot blasting, and has good cost performance and does not reduce corrosion resistance. An object is to provide a zinc-based alloy shot according to hardness.

As a result of intensive studies to solve the problems of these zinc-based alloy shots, the inventors of the present invention add a small amount of Fe as a secondary additive element together with Cu as a main additive element in a zinc-based alloy. Thus, the present inventors have found that there is an alloy composition that can produce a blackened zinc-based alloy shot having a Vickers hardness of 80 to 110 HV when adjusted to a specific alloy composition, and has arrived at the present invention.

That is, in the said patent documents 1, 2, examination of the relationship between Cu and Fe was inadequate. The present invention has been conceived by earnestly examining this relationship. In zinc-copper-iron ternary zinc-based alloy of the present invention, Fe has the effect of increasing hardness in cooperation with Cu by adding a very small amount, and also inhibits corrosion and reduces discoloration. There is an effect of. If the Fe content is too low, it is difficult to obtain these effects. However, when the Fe content is high, as in the case where the Cu content is high, although the mechanical strength and Vickers hardness are improved, the present invention has been conceived on the basis that the toughness and impact resistance tend to decrease. is there.

The zinc-based alloy shot of the present invention is a ternary zinc-based alloy shot containing Cu: 1.800 to 6.000 mass% and Fe: 0.0010 to 0.5000 mass% as additive elements, and The Vickers hardness is 80 to 110 HV. The shot hardness (hereinafter, “Vickers hardness” is simply called “hardness” unless otherwise specified) refers to the hardness when not used. In the present invention, “%” indicating the alloy composition means “% by mass” unless otherwise specified.

According to the present invention, the hardness is optimum, and the corrosion resistance is not lowered even when used for surface treatment for deburring or blasting by shot blasting for aluminum die cast products and magne die cast products which are processed products. The zinc-based alloy shot according to the surface hardness of the product to be treated could be provided. Cost performance was also good. That is, according to the present invention, it is possible to provide a shot that is excellent in erasing and deburring of an aluminum die cast product having a Vickers hardness of 90 HV to 110 HV and a magneto die cast product having a Vickers hardness of 85 HV to 105 HV.

The zinc-based alloy shot of the present invention does not contain Ni, Mn, or the like that is subject to the PRTR system, and is desirable from the viewpoint of environmental protection and work safety.

Furthermore, the zinc-based alloy shot of the present invention can relatively reduce the Cu content when preparing shots of the same hardness.

It is a ternary phase diagram showing the alloy composition range of the present invention. It is a flowchart which shows an example of the manufacturing method of the zinc base alloy shot of this invention. It is a figure explaining the manufacturing apparatus of the zinc base alloy shot of this invention. It is a graph which shows the relationship between the zinc base alloy shot of this invention, and Vickers hardness. It is a graph which shows the corrosion rate of the zinc base alloy shot of this invention.

Hereinafter, the zinc-based alloy shot of the present invention will be described in detail. FIG. 1 schematically shows a composition range (blackened portion) of the present invention in a phase diagram of a ternary alloy composition of a zinc-based alloy shot. The zinc-based alloy shot of the present invention contains Fe as a secondary additive element, with Cu being the main additive element, for the purpose of optimal adjustment of hardness.

The chemical component composition of the zinc-based alloy shot of the present invention is appropriately selected from the balance of shot hardness (or scouring ability) and granulation / brittleness / corrosion resistance.

In zinc-copper-iron ternary zinc-based alloys of the present invention, Cu has the effect of increasing the mechanical strength and hardness of the zinc-based alloy. If the Cu content is too low, it is difficult to obtain these effects. . However, when the Cu content is high, the mechanical strength and hardness are improved, but the toughness (impact resistance) tends to decrease.

Further, in the zinc-copper-iron ternary zinc-based alloy of the present invention, when the alloy composition is adjusted by addition of Fe, it is the same as when other elements are mixed in the zinc-copper binary alloy. In addition, there was a case where a granular material could not be formed because the dispersed flow could not be performed. Therefore, the influence of Fe will be described in detail below.

The method for producing a zinc-based alloy shot according to the present embodiment includes a melting step for dissolving zinc, copper and iron, a granulating step for dripping the molten metal into a cooling medium such as water and granulating, and a granulated product. It has a recovery step for solidifying and depositing and collecting in a cooling medium, a drying step for drying the recovered material, and a classification step for classifying the granular material including shots that have undergone drying (see FIG. 2). And since the said molten metal is rapidly cooled by dripping the melted molten metal which adjusted the composition in a cooling medium, it becomes a fine and uniform structure | tissue compared with a general casting material.

(1) In the granulated zinc-copper binary alloy, the dripping nozzle is clogged when Fe enters, which is an inhibitory element in production. For example, when it exceeds 0.02%, clogging starts to occur, and when it exceeds about 0.05%, the frequency of clogging increases. Clogging reduces productivity in manufacturing.

FIG. 3 shows an apparatus for producing a zinc-based alloy shot according to the present invention. In FIG. 3, the manufacturing apparatus uses a molten metal holding container 1 provided with a nozzle 1 a for dropping molten metal at the bottom. In addition, a cooling tank 3 into which a cooling medium 2 such as water is charged is provided below the nozzle 1a. The cooling tank 3 is provided with a cooling tower (not shown) as a cooling means. Then, the molten metal L in the molten metal holding container 1 is dropped from the dropping nozzle 1a so as to reach the dropping nozzle 1a and the cooling medium 2 in a non-oxidizing atmosphere (for example, in contact with nitrogen gas). Furthermore, with cooling due to contact with the cooling medium 2, it is spheroidized under the influence of surface tension. Thereby, the grain 4 of a zinc base alloy is manufactured.

In order to reduce the clogging of the dropping nozzle and produce a shot with an appropriate particle size, the molten metal melt is dropped from a nozzle having a diameter of 0.1 mm to 1.0 mm into a cooling medium such as water. Is preferred. If the diameter is smaller than 0.1 mm, clogging is likely to occur, and if the diameter is larger than 1.0 mm, the shot diameter becomes too large.

(2) Brittle resistance Fe improves the hardness of the zinc-based alloy, but makes the shot brittle even with slight addition. In zinc-based alloys, when Fe is added in an amount greater than 0.006%, the brittleness resistance begins to deteriorate. Further, the limit addition amount of Fe is about 0.5%.

(3) Corrosion resistance Furthermore, in zinc-copper binary alloy, what added Fe to 0.02-0.7% has strong corrosion resistance.

(4) Particle size The average particle size (median diameter) of the zinc-based alloy shot in the present invention is preferably in the range of 0.1 to 3.0 mm. Although it varies depending on the strength of the product to be treated and the purpose of treatment, it is difficult to obtain sufficient deburring ability and polishing ability if the average particle size is too small. On the other hand, if the average particle size is excessive, the product to be treated will be scratched by surface treatment (deburring and polishing), or processed to a satin finish more than necessary, and the specified surface roughness cannot be maintained. Or

(5) Relationship between hardness and product to be treated The relationship between the zinc-based alloy shot of the present invention and the Vickers hardness of the product to be treated is described below. Since the Vickers hardness of the zinc-based alloy shot of the present invention is 80 to 110 HV, the surface of the aluminum alloy or magnesium alloy (Vickers hardness 85 to 110) product can be processed smoothly and without damaging the surface. . On the other hand, when a zinc-based alloy shot having a Vickers hardness of over 110 HV is used, the surface may be scratched or processed into a satin finish more than necessary, and the predetermined surface roughness may not be maintained.

(6) Inevitable impurities A zinc-based alloy shot is obtained by classifying the grains 4 of the zinc-based alloy so as to have a predetermined size. In the zinc-based alloy shot of the present invention, it is desirable that the total content of inevitable impurities other than Zn, Cu, and Fe contained therein is as small as possible. When the content of inevitable impurities increases, the toughness tends to decrease and cracks are likely to occur. In addition, the service life is reduced. When a raw material such as Zn or Cu (hereinafter sometimes referred to as “metal”) contains Fe as an impurity, the Fe can be used as all or part of the auxiliary additive element of the present invention. Specifically, the non-essential elements other than the three components contained in the zinc-based alloy shot are at least one of Pb, Cd, Sn, Si, Ti, As, Sb, Bi, S, Mn, Al, Mg, and Be. It is preferable that the total content of these non-essential elements is 0.0100 to 0.0300 mass%, more preferably 0.0100 to 0.0200 mass%.

(7) Raw material As a raw material of Zn which is a base element, for example, JIS
H2107 ordinary zinc bullion (99.97% or more), pure zinc bullion (99.995% or more), special zinc bullion (99.99% or more) and the like can be mentioned. Incidentally, the Fe content of ordinary zinc bullion is 0.005% or less.

As a raw material of Cu, for example, electrolytic copper ingot (99.96% or more) of JISH2121 can be cited.

Moreover, as a raw material of Fe, for example, various steel ingots, steel slabs, and steel materials specified in JIS G 0203 can be used as appropriate.

(8) Composition In the present invention, to obtain a Vickers hardness of about 80 to 110 HV, as described above, the same Cu with a Cu content of 1.800 to 6.000% is used. However, it is preferably a ternary zinc-based alloy shot containing Cu: 2.200 to 4.500 mass% and Fe: 0.0030 to 0.0450 mass% as additive elements, and has a Vickers hardness of It may be 80-100HV. More preferably, Cu: 2.200 to 3.000% by mass and Vickers hardness of 85 to 97 HV. Thereby, in order to obtain shots having the same hardness, the Cu content can be greatly reduced, and a reduction in shot toughness can be suppressed. This is considered because the hardness of the shot is remarkably increased by the inclusion of Fe and Cu.

In the zinc-based alloy shot of the present invention, since the corrosion of the shot is suppressed by the addition of Fe, the corrosive material is not transferred to the surface of the product to be treated when colliding with the product to be treated. When applied to the surface treatment of a product to be treated made of an alloy, suppression of blackening of the product to be treated can be expected, and the effect becomes remarkable.

When used for shot blasting, a very large external force is applied to the zinc-based alloy shot. By making the structure fine and uniform, mechanical properties such as impact resistance and tensile strength are improved. Can be suitably used. The case where it manufactures using the above-mentioned manufacturing method is demonstrated concretely below (refer FIG. 2).

First, raw materials such as ingots of the base element (Zn) and additive elements (Cu and Fe) are weighed and put into a crucible so as to have a set alloy composition ratio. Next, the crucible is heated by resistance heating or combustion gas, whereby the charged ingot mixture is melted to obtain a molten metal. The melting and heating temperature at this time varies depending on the alloy composition and production scale, but is usually set appropriately in the range of 550 to 700 ° C. The melting point of each element is as follows. Zn: 419.6 ° C, Cu: 1083.4 ° C, Fe: 1535 ° C

Next, the molten metal is put into a molten metal holding container. The molten metal holding container is provided with a resistance heating device as a heating means, and can be held so that the molten metal is not cooled more than necessary when manufacturing a zinc-based alloy shot. The molten metal holding temperature at this time is appropriately set in the range of 450 to 650 ° C., although it varies depending on the alloy composition and production scale.

A dripping nozzle for dripping molten metal is provided at the bottom of the molten metal holding container. A cooling medium such as water is inserted into a lower portion of the nozzle, and a cooling tank provided with a cooling tower as a cooling means is disposed. Yes. The cooling medium may be oil. When the molten metal in the molten metal holding container is dropped from the dropping nozzle, it comes into contact with the nitrogen gas in a non-oxidizing atmosphere from the dropping nozzle to the cooling medium, and further, with cooling due to contact with the cooling medium. Spheroidized under the influence of surface tension.

Note that the temperature of the cooling medium rises when the molten molten metal comes into contact with the cooling medium, and thus the rapid cooling of the molten molten metal is hindered. Therefore, the cooling medium is maintained at a set temperature by a cooling tower as a cooling means. For example, in the case of water, the set cooling temperature is usually 60 ° C. or lower. If the temperature exceeds 60 ° C., the water in contact with the molten melt will boil and the interface will be in a vaporized state, making it difficult to exhibit a rapid cooling effect.

At the bottom of the cooling medium, zinc-based alloy granules are deposited. This is recovered and dried, for example, with a rotary dryer, and then classified with a vibrating sieve to obtain a zinc-based alloy shot. The classification is performed so as to obtain a predetermined particle size according to the intended use of the zinc-based alloy shot.

In addition, the manufacturing method of a zinc base alloy shot is not limited to the dripping granulation method like this Embodiment. For example, known methods such as a gas atomizing method, a centrifugal atomizing method, and a water atomizing method can be appropriately selected according to the shape, particle size, and the like of the target zinc-based alloy shot.

Hereinafter, an evaluation test performed for confirming the effect of the present invention will be described. Each zinc-based alloy shot was manufactured using the drop granulation method shown in FIGS. Each shot thus produced was classified to prepare a shot for projection of each sample having an average particle diameter (median diameter) of 1.0 mm. Then, the shots of each sample were evaluated by performing the tests of the following items. The results are shown in Table 1.

(1) Hardness FIG. 4 is a graph showing the relationship between the added amount of Fe and the hardness (Vickers hardness) of the zinc-based alloy shot of the present invention. According to this graph, it can be seen that even if the Cu content is as low as 2.5%, even if a small amount of Fe is added, it is easy to obtain a shot with high hardness. The Vickers hardness was measured as follows. For each sample (1 mmφ shot), 10 shots were embedded in resin and fixed, and then the shot was polished in half to prepare a test piece. And about each test piece, based on JISZ2244, Vickers hardness was measured before use (shot). The measurement is an arithmetic average of n = 10. Here, in the zinc-based alloy shot of the present invention, when the Fe content is 0.0200 to 0.0300 mass%, a relatively high shot can be obtained. Also, a shot with particularly good corrosion resistance can be obtained. In addition, in the zinc-based alloy shot of the present invention, when the Fe is 0.0030 to 0.0180 mass% and the Vickers hardness is 85 to 93 HV, a zinc-based alloy shot having particularly excellent hardness and granulation properties is obtained. Obtainable. Furthermore, in the zinc-based alloy shot of the present invention, when the Fe content is 0.0030 to 0.0060 mass%, a zinc-based alloy shot that is particularly excellent in hardness, granulation properties, and brittleness resistance can be obtained.

(2) Shot blast evaluation test 100 kg of shots (average particle diameter: 1.0 mm) of each sample prepared in the above were applied at a projection speed of 60 m / s with “The Ervin Test Machine (Ervin)” (steel material (Rockwell hardness)). The target was 65 HRC (specified in JIS G0202, JIS Z2245)), and was projected (shot) 5000 times.

(3) Shot life For each sample, shots were classified with a sieve for each number of projections, and the residual rate remaining on the sieve was measured. As a result, it was found that the lifetime tends to decrease as the Fe content increases. In addition, the rate of decrease is about 100% when the Fe content is 0.005%. When the Fe content is 0.2%, about 90% or more can be secured. Further, the Fe content is 0.05. It was confirmed that there was no problem in practical use.

(4) Corrosion test Ten cylindrical samples (φ2 × 10 mm) formed from an alloy having the same composition as each sample were embedded horizontally in 10 pieces of resin, fixed, and then cut in half in the axial direction to prepare test pieces. . And about each test piece, the neutral salt spray test was done according to JISZ2371. And the corrosion rate (white rust: ZnO) of the alloy exposed surface was visually measured using a precision ruler (vernier caliper), and obtained by the following formula. The color of rust was white.

Corrosion rate (%) = 100 × total corrosion area (mm ² ) / total sample surface area (mm ² ) From FIG. 5 showing the results of the corrosion test, only a slight amount of Fe (0.0030 to 0.0050%) is contained. It can be seen that the corrosion rate is significantly reduced.

As described above, according to the shot blast evaluation test and the corrosion test, the zinc-based alloy shot of the present invention containing the secondary additive element Fe together with the primary additive element Cu is shot blasted according to the aluminum die cast product or the magne die cast product that is the product to be processed. The optimum Vickers hardness used for surface treatment for deburring and polishing was achieved. In addition, it was possible to provide a zinc-based alloy shot that has good cost performance and does not reduce corrosion resistance. In addition, it has been proved that the shot life is practically sufficient.

DESCRIPTION OF SYMBOLS 1 ... Molten metal holding container 1a ... Nozzle 2 ... Cooling medium 3 ... Cooling tank 4 ... Zinc base alloy shot L ... Molten metal

Claims (12)

It is a ternary zinc-based alloy shot containing Cu: 1.800 to 6.000 mass% and Fe: 0.0010 to 0.5000 mass% as additive elements, and has a Vickers hardness of 80 to 110 HV. Zinc-based alloy shot characterized by that. It is a ternary zinc-based alloy shot containing Cu: 2.200 to 4.500 mass% and Fe: 0.0030 to 0.0450 mass% as additive elements, and has a Vickers hardness of 80 to 100 HV. Zinc-based alloy shot characterized by that. The zinc-based alloy shot according to claim 1, wherein Cu: 2.200 to 3.000 mass% and Vickers hardness is 85 to 97 HV. The zinc-based alloy shot according to any one of claims 1 to 3, wherein a purity of Cu as the additive element is 99.9% by mass or more. The zinc-based alloy shot according to any one of claims 1 to 3, wherein Fe: 0.0200 to 0.0300 mass%. Non-essential elements other than the three components contained in the zinc-based alloy shot were selected from the group consisting of Pb, Cd, Sn, Si, Ti, As, Sb, Bi, S, Mn, Al, Mg, and Be. The zinc-based alloy shot according to any one of claims 1 to 5, wherein the total content of at least one kind is 0.0100 to 0.3000 mass%. The zinc-based alloy shot according to claim 6, wherein the total content of the non-essential elements is 0.0100 to 0.0200 mass%. The zinc-based alloy shot according to any one of claims 1 to 3, wherein Fe: 0.0030 to 0.0180 mass% and Vickers hardness is 85 to 93HV. The zinc-based alloy shot according to claim 8, wherein Fe: 0.0030 to 0.0060 mass%. 10. The zinc-based alloy shot according to claim 1, wherein the zinc-based alloy shot is used for shot blasting of an aluminum alloy die casting or a magnesium alloy die casting. The zinc-based alloy shot according to claim 10, wherein the average particle diameter of the particles is 0.1 to 3 mm. It is a manufacturing method of the zinc base alloy shot of Claim 11, Comprising: The process which dripped the molten metal from the nozzle of diameter 0.1mm-1.0mm in a cooling medium, In this cooling medium, solidification and deposition A method for producing a zinc-based alloy shot, characterized by classifying and producing a granular material that has undergone the step of drying and the step of drying the solidified and deposited material.