JPH0244881B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is useful as a pre-treatment such as removing scale from the metal surface and preparing the substrate when plating, thermal spraying, painting, etc. are applied to shot materials, especially metal surfaces. The present invention relates to a metal powder suitable for use in hydraulically accelerated shot blasting.

(Prior Art) When a metal surface is subjected to plating, thermal spraying, painting, etc., it is necessary to process the metal surface into a matte finish as a pretreatment in order to improve adhesion. One of these processing methods is the shot blasting method, and in order to improve adhesion, the shot surface of the shot material has a complicated uneven shape, for example, a concave slope with finer unevenness, etc. It is preferable to have an overhang shape. In order to form such an uneven shape on a metal surface, it is better to use a polygonal shot material rather than a spherical shot material.
For this reason, polygonal metal-based steel grit, mineral-based silica sand, zirconia, carborundum (SiC) Fe--Si powder, etc. are known as shot materials for conventional hydraulically accelerated shot blasting.

(Problems to be Solved by the Invention) However, the polygonal shot materials conventionally used have the following drawbacks. In other words, when performing surface treatment on thin coatings, water pressure is used to accelerate shot materials with fine particle sizes of several tens of microns, but steel grit is oxidized by water and oxidized iron powder is deposited on the metal surface. There was a problem that it adhered and impaired coating properties. In addition, mineral shot materials are easily crushed,
The number of times that it can be used repeatedly is small; for example, silica sand is said to have a lifespan of 1/30 to 1/60 that of steel grit. Additionally, mineral shot materials have a problem in that their specific gravity is low and the grinding effect per unit number is low.

The present invention solves the above-mentioned problems of conventional shot materials, and is particularly suitable for hydraulic accelerated shot blasting for pre-treatment, such as scale removal and substrate preparation, when surface treatments such as coating metal surfaces are carried out. The object of the present invention is to provide a metal powder for shot that can be used.

(Means for solving the problem) The metal powder for shot according to the present invention has a
Cr: 10 to 24%, C: 2% or less, Si: 27% or less,
Polygonal mechanically pulverized powder containing 3.7% or more of C% + 0.37Si%, residual Fe and unavoidable impurities, with an under-sieve particle size of 210 microns, and a specific gravity of 6 or more. It is characterized by

Further, according to the present invention, the metal powder for hydraulic accelerated shots includes Cr: 18 to 24% by weight, C:
2% or less, Si: 27% or less, C% + 0.37Si% 3.7
Composition consisting of residual Fe and unavoidable impurities, or by weight Cr: 10-18%, C: 0.45%
Hereinafter, it is preferable to have a composition including Si: 20 to 27%, with residual Fe and unavoidable impurities.

The present invention first focuses on corrosion resistance, and the Fe-Cr
based on a series alloy. However, the Cr content
Fe-Cr alloys with a content of 18% or less are highly ductile and are difficult to make into powder by mechanical crushing. Therefore,
Advantageous elements C and Si were added to embrittle this alloy. Addition of C and Si improves the crushability and makes it possible to produce powder by mechanical pulverization, but when the amounts of C and Si added are small, polygonal powder cannot be obtained. For example, C: 1%,
The powder is obtained by mechanically pulverizing alloy flakes consisting of Si: 2%, Cr: 18%, residual Fe and unavoidable impurities.
As shown in the micrograph of FIG. 12, it is not polygonal. Therefore, the shapes of the powders obtained by varying the amounts of C and Si added and performing mechanical pulverization for a certain period of time were determined. As a result, as shown in Figure 1,
When Cr: 10 to 24% by weight, the total amount of C and Si,
That is, it has been found that when C%+0.37Si% is less than 3.7%, the powder does not have a polygonal shape, and when it is 3.7% or more, the powder becomes polygonal. In other words, in order to obtain powder with a polygonal shape, C and
The amount added with Si is shown by diagonal lines in Figure 1.C%+
It is necessary that 0.37Si% be in the range of 3.7% or more.

Next, as a shot material, the higher the specific gravity, the
Grinding effect increases. Therefore, C, Si, Cr, and Fe are used to increase the specific gravity of conventional mineral shot materials.
The components of were determined by calculation. The specific gravity of each element is C: 2.25, Si: 2.33, Cr: 7.19, Fe: 7.87,
In order to make the specific gravity of the alloy consisting of these components 6 or more, which is greater than the specific gravity of the mineral shot material, it is sufficient that it satisfies the following formula.

1/100 (2.25 x C% + 2.33 x Si% + 7.19 x Cr% + 7.87 x Fe%) > 6 Therefore, since Fe% = 100 - (C% + Si% + Cr%), Substituting into the above formula and rearranging, C%=0.99Si%≦33.3−12.1Cr% Here, from 10%≦Cr≦24%… When Cr=24% C%+0.99Si%≦30.4 Cr=10% When C%+0.99Si%≦32.1 Therefore, if the Cr content is 10 to 24% and the specific gravity is 6 or more, Si and C are shown with diagonal lines in Figure 2. C%+0.99Si%≦ It is necessary to have a component range of 30.4.

Next, the range of ingredients from the viewpoint of the lifespan as a shot material will be explained.

Mineral shot materials are highly friable, quickly become finer during work, and have a short lifespan. Therefore, in the present invention
The lifespan of Te-Si shot material (Fe-45%Si) was set as the limit. Therefore, when metal chips with a size of 1 to 2 mm are crushed with a vibrating crusher for a certain period of time, the ratio of pulverization to 63 microns or less is the same as that of the Fe-Si shot material: 10%≦Cr<24%. 0%<C
<2%, Si=27%.

Therefore, in order to ensure a longer life than the Fe-Si shot material mentioned above, it is necessary to
The upper limit of the amount of Si added must be 27%.

For the above reasons, the metal powder for shots according to the present invention contains Cr: 10 to 24% by weight, C: 2% by weight or less, shown with diagonal lines in FIG. 4, and Si: 27% by weight.
Hereinafter, C weight % + 0.37Si weight % must contain C and Si in a range of 3.7 weight % or more, thereby forming a polygonal shape, having an appropriate specific gravity, and Fe-Si shot material ( Fe−45%Si) or more.

Furthermore, the range of ingredients required from the viewpoint of corrosion resistance when the metal powder for shot according to the present invention is used in hydraulically accelerated shot blasting using tap water containing [Cl] ^- ions will be explained.

Tap water contains several tens of ppm of [Cl] ^- ions, and therefore needs to have corrosion resistance in such an environment. There, [Cl] ^- ion
As a result of testing by immersing a sample in a 1000 ppm NaCl aqueous solution for one week, it was found that when it contained Cr: 18-24%, it was indicated by diagonal lines in Figure 5: C: 2% or less, Si: 4 In the range of % or more, also Cr: 10~18%
If it includes C: shown with diagonal lines in Figure 6
It was confirmed that it does not rust in the range of 0.45% or less and Si: 20% or more, and has sufficient corrosion resistance in tap water.

Therefore, when the metal powder for hydraulic accelerated shots according to the present invention contains Cr: 18 to 24%,
C shown with diagonal lines in Figure 7: 2% or less, Si: 27
% or less, C%+0.37Si% is 3.7% or more
It is necessary to contain and Si, and also Cr:
When it contains 10 to 18%, it is necessary to contain C and Si in the range of C: 0.45% or less and Si: 20 to 27%, which are indicated by hatching in FIG.

Next, a method for manufacturing shot metal powder according to the present invention will be explained.

Molten metal having the above composition is melted, and this is made into, for example,
As described in the specification of Japanese Patent Application No. 59-60384 ``Flat-shaped metal chips, their manufacturing method, and their manufacturing apparatus'', they are housed in the melting tank 1 of the apparatus shown in FIG. The tip of a bowl-shaped protrusion 3 provided on the outer periphery of a rotating drum 2 made of high-temperature copper with a diameter of about 300 mm is inserted into the molten metal 4, and the temperature of the molten metal is adjusted by a heating element 5, and a level adjustment block is also installed. 6 is raised and lowered into the molten metal 4 to adjust the molten metal level, and the rotating drum 2 is rotated at a rotation speed of about 200 to 300 rpm to at least partially solidify the molten metal adhering to the tip of the protrusion 3. By peeling it off from the protrusion, a bowl-shaped metal chip 7 as shown in FIG. 10 having a thickness of about 0.3 mm is manufactured, for example.

The bowl-shaped metal chip 7 manufactured in this way is placed between the striking ring 9 and the cylindrical block 10 in the vessel 8 of the hard high manganese steel disk mill shown in FIG. 11, and the lid 11 is attached. , the bowl-shaped metal chips are crushed by the impact force generated by the collision between the ring 9 and the cylindrical block 10 in the vessel 8, and passed through a 210-micron sieve. The metal powder for shot according to the present invention can be obtained on the sieve by passing it through a micron sieve.

The metal powder according to the present invention is not limited to the above-mentioned manufacturing method, but can be produced by manufacturing metal chips using other suitable methods and equipment, or by mechanically pulverizing with a rotary ball mill or other pulverizing equipment. It can be made into powder.

Example 1 SUS430 scrap material, Fe-Si, Fe-Cr, carbon powder C = 1.1%, Si = 9.5%, Cr = 19%, remainder
The composition was adjusted to become Fe, and 500kg was melted in a high-frequency induction furnace. This molten metal was made into bowl-shaped metal chips having a diameter of 1 to 2 mm and a thickness of 0.3 mm using the apparatus shown in FIG. Next, 20g of this metal chip
was ground for 30 seconds using a disc mill with a diameter of about 150 mm as shown in FIG. 11 to produce a powder.

This powder was sieved, and the metal powder remaining between 63 to 88 micrometer sieve meshes had a polygonal shape as shown in the micrograph of FIG. 13. Furthermore, when this powder was sieved through a 63-micron sieve, the incidence under the sieve was 36%. Compared to the comparative example of Fe-Si shot material (Fe-45%Si) produced in the same way, the under-sieve occurrence rate was 89% when the metal powder was sieved with a 63-micron mesh. It can be seen that it has a low value and a long life. Further, the specific gravity of the metal powder according to this example was determined to be 7.12, and the specific gravity of the metal powder according to the above comparative example was 7.12.
It is larger than the powder of the base material. Furthermore, 1 g of [Cl] ^-ion was immersed in 10 c.c. of NaCl aqueous solution containing 1000 ppm.
As a result of examining the corrosion resistance, no rusting occurred even after 7 weeks.

Example 2 SUS430 scrap material, Fe-Si, Fe-Cr, carbon powder C: 0.4%, Si: 26%, Cr: 15%, remainder
The composition was adjusted to become Fe, and 500
Kg dissolves. Furthermore, a metal chip having a diameter of 1 to 2 mm and a thickness of 0.3 mm is prepared in the same manner as in Example 1.
Further, 20 g of the above metal chips were ground for 30 seconds in a disc mill similar to that used in Example 1 to produce powder. This powder was sieved, and the material remaining between 63 and 88 micrometer sieve meshes had a polygonal shape as shown in the micrograph of FIG. 14. Also, when this powder was sieved through a 63 micron sieve, the occurrence rate under the sieve was 80%, and the occurrence rate of Fe-45%Si made in the same way was 89%.
It can be seen that it is less fragile and has a longer lifespan compared to the conventional method. The specific gravity of this powder is 6.33, and the Fe-
Larger than Si shot material. Furthermore, when 1 g of the material was immersed in 10 c.c. of NaCl aqueous solution (1000 ppm of Cl ^- ions) to examine its corrosion resistance, no rusting occurred even after one week.

(Effects of the Invention) The metal powder for shot according to the present invention has an under-sieve particle size of 210 microns and a polygonal shape. It is suitable for processing and has a longer lifespan than conventional mineral shot materials.
Also, because of its high specific gravity, it has an excellent grinding effect, and has the advantage that it has better corrosion resistance than conventional steel shot materials, and can be used in hydraulic acceleration shot systems.

[Brief explanation of drawings]

Figure 1 is a graph showing the weight % range of C and Si for Fe-Cr alloy powder containing 10 to 24 wt% Cr to have a polygonal shape, and Figure 2 is a graph containing 10 to 24 wt% Cr. A graph showing the weight percent range of C and Si for the specific gravity of Fe-Cr alloy powder to be 6 or more. Shot material (Fe-45%Si)
Weight% of C and Si to have longer lifespan
4 is a graph showing the weight percent range of C and Si in the metal powder for shots according to the present invention, and FIG. 5 is a graph showing the weight percent range of C and Si in the shot metal powder according to the present invention.
C for the alloy powder to have corrosion resistance in tap water
Figure 6 is a graph showing the weight percent range of Si and Si.
A graph showing the weight percent range of C and Si for the Fe-Cr alloy powder containing 10 to 18 weight percent Cr to have corrosion resistance in tap water. :18~24% by weight
Weight percent of C and Si in shot metal powder containing
A graph showing the range, FIG. 8 is a graph showing the weight % range of C and Si in a shot metal powder containing 10 to 18 weight % Cr that can be used in the hydraulic acceleration shot method according to the present invention, and FIG. 10 is a perspective view of a metal chip manufactured by the apparatus shown in FIG. Longitudinal cross-sectional view of the disc mill used, 1st
Figure 2 is a micrograph showing the shape of Fe-Cr metal powder outside the composition range of the present invention, Figures 13 and 14.
The figure is a micrograph showing the shape of the metal powder of the present invention. DESCRIPTION OF SYMBOLS 1... Melting tank, 2... Rotating drum, 3... Protrusion, 4... Molten metal, 5... Heating element, 6... Level adjustment block, 7... Metal chip, 8... Disc mill vessel, 9 ...Blow ring, 10...
Cylindrical block, 11...lid.

Claims (1)

[Claims] 1. Cr: 10 to 24%, C: 2% or less, by weight;
Si: 27% or less, containing 3.7% or more of C% + 0.37Si%, a polygonal mechanically pulverized powder having a composition consisting of residual Fe and inevitable impurities, and having an under-sieve particle size of 210 microns, A metal powder for shots, characterized by having a specific gravity of 6 or more. 2 By weight, Cr: 18-24%, C: 2% or less,
Si: 27% or less, containing 3.7% or more of C% + 0.37Si%, having a composition consisting of residual Fe and inevitable impurities, and having excellent corrosion resistance against tap water. The metal powder for shot according to item 1. 3 By weight, Cr: 10-18%, C: 0.45% or less,
2. The metal powder for shots according to claim 1, which contains Si: 20 to 27%, has a composition consisting of residual Fe and unavoidable impurities, and has excellent corrosion resistance against tap water.