AMS-2431-7.pdf

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AEROSPACE

MATERIAL

SPECIFICATION

AMS2431/7 REV. B

Issued 1988-04 Reaffirmed 1994-04 Revised 2013-02

Superseding AMS2431/7A

Peening Media Ceramic Shot

RATIONALE

AMS2431/7B results from a Five Year Review and update of this specification and adds coverage for AZB100 ceramic shot.

1. SCOPE

1.1 Purpose

The complete requirements for procuring the product shall consist of this document and the latest issue of the basic specification, AMS2431.

1.2 Application

Ceramic shot conforming to this specification is typically intended for use in peening of metal surfaces to impart compressive stresses to these surfaces thereby increasing resistance to fatigue and stress-corrosion cracking. Generally, ceramic shot may be used where ferrous contamination of the part is undesirable or very hard parts (over 60 HRC) are to be peened for maximum residual compressive stress.

2. APPLICABLE DOCUMENTS

See AMS2431.

3. TECHNICAL REQUIREMENTS

3.1 Ceramic shot shall conform to AMS2431 and the requirements specified herein.

3.2 Composition shall be high quality zirconium oxide and silica. The percentage variation by weight ranges of the main constituents of ceramic shot shall be:

TABLE 1 - COMPOSITION

Constituent min max Zirconium Oxide 60 70 Silica 28 33 Alumina -- 10 Other Constituents, total -- 3

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SAE AMS2431/7B Page 2 of 6

3.2.1 Hardness

Hardness shall be measured by the manufacturer at least on mother production batches. User should measure hardness at his discretion or when a counter analysis is required.

For AZB850 to AZB150, at least 90% of the readings shall fall within the range of 643 to 785 HV (58 to 63 HRC, for reference only).

For AZB100, the mean value of the readings shall fall within the same range of 643 to 785 HV.

3.2.2 Density shall be between 3.60 and 3.95 g/cc, measured at 70°F (21°C) by a pycnometric method.

3.2.3 Magnetic particles shall not exceed 0.1% by weight of the original sample.

3.2.4 Surface Discolorations

Not more than 15% of the shot shall show foreign discolorations. A particle shall be considered objectionable for foreign discoloration when more than 25% of its surface area is discolored.

3.2.5 Coatings

Foreign materials are not permitted.

3.3 Workmanship

3.3.1 Shape

Ceramic shot shall be spherical to ellipsoid in shape. Table 2 shows the maximum percentage of ceramic shot having a sphericity lower than 0.5 and the minimum percentage of ceramic shot having a sphericity of 0.8 and above (true spheres).

See Section 8 for definition of sphericity.

Maximum number of permissible broken or angular beads is shown on column 11 of Table 2. This number shall never exceed 3% of the actual count. See Section 8 for definition of roundness.

3.3.2 Satellites

Maximum allowable number of shot with satellites shall be Table 3. See Section 8 for definition of satellites.

3.4 Size shall conform to the requirements of Table 2.

3.5 Test Methods and Procedures

3.5.1 Size Classification

Sieve analysis shall be determined in accordance with ASTM D 1214. Screens shall be in accordance with U.S. Standard Series described in ASTM E 11.

3.5.2 Composition shall be measured by the manufacturer at least on mother production batches by x-ray fluorescence or by other method acceptable to purchaser. User should measure composition at his discretion or when a counter analysis is required.

3.5.3 Hardness shall be determined by a Vickers diamond pyramid penetrator using 1000 gram load in accordance with ASTM E 384 or ASTM C 1327. To avoid fracture of beads, the loads shall be as follows: 200 gram load for AZB100, 500 gram load for AZB150, AZB210 and AZB300 and 1000 gram load for AZB425, AZB600 and

AZB850.

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SAE AMS2431/7B Page 3 of 6

3.5.4 Contamination

3.5.4.1 Magnetic Particle

Content shall be determined by slowly sprinkling approximately 1500 gram of the sample ceramic shot on an inclined aluminum tray that is 0.062 inch (1.57 mm) deep by 6 inches (152 mm) wide by 12 inches (305 mm) long. The tray shall be supported by a nonmagnetic frame so that it is inclined with a 6 inch (152 mm) rise from end to end, (30 degrees from horizontal). Four 1 × 1 × 6 inches (25 × 25 × 152 mm) bar magnets are positioned against the under surface and crosswise to the inclined tray about the middle of its length. Thickness of tray at magnet location shall not exceed

0.062 inch (1.57 mm). Magnets shall be not less than 10 000 Gauss each and arranged so that the magnetic north and south poles alternate. The magnetic particles (iron) that accumulate on the tray as the beads roll down shall be brushed into a preweighed dish. The procedure shall be repeated with the same 1500 gram sample until all visible magnetic particles are collected. The dish shall be reweighed and the magnetic particle content calculated as a percentage of the total original sample.

3.5.4.2 Surface discolorations shall be determined microscopically using magnification as per 4.1.5.

3.5.5 Shape

A visual count shall be made of three fields of at least 100 shot each on the sample prepared as per 4.1.5.

3.5.6 Density

Sixty grams of shot, carefully weighed to the nearest 0.1 gram, and previously dried, shall be placed in a 100 mL graduated cylinder containing approximately 50 mL of reagent water. The resultant volume minus initial volume represents the volume of the shot.

60gDensity Shot Volume

TABLE 2 – CERAMIC SHOT FOR PEENING – SIZES AND SPHERICITY

Designation

Nominal Sizes, Millimeters

Nominal Sizes, Inch

Nominal Sizes, Mesh

Sieve Size, Millimeters Maximum

0.5% Retained

Sieve Size, Millimeters Maximum

5% Retained

Sieve Size, Millimeters Maximum

10% Passing

Sieve Size, Millimeters Maximum

3% Passing

Minimum % of Shot

W/Sphericity

0.8 and Above (True

Spheres)

Maximum Number of Shot with Sphericity Below 0.5 per Square Centimeter

Number Broken or Angular Beads

Acceptable per Square Centimeter

AZB850 0.85/1.18 0.033/0.047 16/20 1.400 1.180 0.850 0.710 65 4 2

AZB600 0.6/0.85 0.024/0.033 20/30 1.000 0.850 0.600 0.425 65 8 4

AZB425 0.425/0.6 0.017/0.024 30/40 0.710 0.600 0.425 0.300 70 14 8

AZB300 0.300/0.425 0.012/0.017 40/50 0.500 0.425 0.300 0.250 70 27 15

AZB210 0.212/0.300 0.008/0.012 50/70 0.355 0.300 0.212 0.180 80 55 20

AZB150 0.150/0.212 0.006/0.008 70/100 0.250 0.212 0.150 0.125 80 300 65

AZB100 0.100/0.150 0.004/0.006 100/140 0.180 0.150 0.106 0.063 80 600 90

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SAE AMS2431/7B Page 4 of 6

TABLE 3 – CERAMIC SHOT WITH SATELLITES

Designation

Maximum Number of Shot with Satellites per

Square Centimeter

Maximum Number of Shot with 3 or More

Satellites per Square Centimeter

AZB850 8 3

AZB600 13 6

AZB425 38 12

AZB300 66 21

AZB210 125 40

AZB150 174 50

AZB100 348 100

4. QUALITY ASSURANCE PROVISIONS

See AMS2431 and the following:

4.1 Sampling

Samples for testing shall be representative of each production batch. Any 25 kg container from each production batch is representative of the production batch. The sampling method is to select randomly a 25 kg container from each production batch and blend the contents. Test samples can then be obtained by successive passes through a sample splitter until the test samples quantity 150 < Q < 300 g is obtained. Two samples of approximately 200 grams each shall be split to the following test quantities.

4.1.1 Composition

Not less than two samples from each shipment.

4.1.2 Hardness

At least 10 micro-hardness readings shall be made with no more than 1 impression from any one shot.

4.1.3 Specific Gravity

Two 60 gram samples for specific gravity determination.

4.1.4 Size

Two representative samples of 60 grams minimum weight.

4.1.5 Shape

Sphericity, roundness and satellites are measured by an actual counting of a one layer field of ceramic beads, using minimum area to be counted as follows:

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SAE AMS2431/7B Page 5 of 6

TABLE 4 – MINIMUM MAGNIFICATION & AREA VALUES FOR SHAPE CONTROL OF APPROXIMATELY 300 BEADS

Shot Size Minimum

Magnification* 300 Shot Area in cm2 AZB850 20x 3.47 AZB600 20x 2.00 AZB425 20x 1.02 AZB300 32x 0.43 AZB210 32x 0.22 AZB150 64x 0.11 AZB100 64x 0.05

* Magnification = Optical lens × digital (camera for instance) × software (if applicable)

The measurements shall be made using a binocular magnifying glass or microscope with the minimum magnification in order to clearly see the surface of each shot (See Table 4). A 30 × 30mm sample strip is made of a double side piece of adhesive tape mounted on a substrate; plastic or glass for example. The product to be analyzed shall be taken from a 50 g representative sample of the batch. Part of this sample shall be then transferred onto a sample strip by pouring the sample onto the strip, or dipping the strip into the sample container. This shall be done until the strip is fully covered with a single layer of beads. Three different fields chosen at random on each strip with at least 100 shots in each field shall be used to make the measurements. The results for 100 shots in each of the 3 fields shall be added and then divided by the corresponding area in Table 4 to give the results per square centimeter. These results shall be compared to Table 2 and Table 3.

4.1.5.1 A mechanical method of inspection for shape is permitted provided that it can be correlated to the optical method and is acceptable to purchaser.

5. PREPARATION FOR DELIVERY

See AMS2431 and the following:

5.1 Packaging and Identification

Shot shall be packaged in 25 kg units.

6. ACKNOWLEDGMENT

See AMS2431.

7. REJECTIONS

See AMS2431.

8. NOTES

See AMS2431 and the following:

8.1 Definitions

8.1.1 Batches:

A mother production batch is greater in quantity than a production batch (i.e. multiple of production batches). A production batch is 1000 kgs.

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SAE AMS2431/7B Page 6 of 6

8.1.2 Sphericity (Ref. 3.3.1):

It refers to the aspect ratio of short to long axes of the hypothetical ellipse that would contain the actual image of the ceramic bead as seen through a microscope.

Example of shot with sphericity below 0.5:

8.1.3 Roundness (Ref. 3.3.1):

It refers to the relative angularity of grain corners, the ceramic shot having round and smooth surfaces. Scored, broken or angular particles are those that would present sharp or angular surfaces when impacted, causing metal removal or unsatisfactory or irregular finishes.

8.1.4 Satellites (Ref. 3.3.2):

Satellites are particles attached to the surface of a bead.

D = Bead diameter d = Satellite diameter

A satellite is counted if all of the following conditions apply:

d ≤ 0.25 D d ≥ 0.5 mm in the magnified view

PREPARED BY AMS COMMITTEE “B”

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