What a Forging Macroetch Report Must Identify Before It Can Support a Purchase
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A macroetch photograph does not prove that an entire forged track link is sound. It documents what was observed on one identified specimen and one examined section. Before using the image in a purchase decision, trace it back to the parent forging, the manufacturing stage, the section plane and location, the examined extent, and the criterion used to interpret it. If that chain is missing, the photograph is an unbounded illustration—not evidence of the whole part.
Macroetch is useful for low-magnification review of gross structure, relative homogeneity, structural or compositional variation, and some discontinuities. It is not a microscopic grain-size measurement, a whole-part mechanical test or a service-life prediction.
Start with the image-to-forging relationship
A macrograph should be read as evidence of a defined section, not as a portrait of every location in a forging. A link-shaped forging can contain different section thicknesses, transitions, bores and load-bearing areas. An image from one cut face may be relevant to a particular concern, but it does not automatically represent other regions.
Ask these questions before accepting a macroetch record:
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What exact part number, drawing revision, heat or lot does the specimen represent?
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Is the specimen a production part, a test coupon or another related sample?
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At what manufacturing stage was the section taken?
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Where was the section located on the parent forging?
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What plane was cut and what direction does the image show?
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Does the photograph show the complete section face or only a local area?
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Which areas of the parent forging were not represented by the specimen?
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What criterion or purchaser-producer agreement was used to interpret the observation?
ASTM E381-22 describes macroetch testing as a low-magnification method for showing relative homogeneity, gross structural or compositional variation, and discontinuities in steel products. Its public scope also states that producer and purchaser agreement can address the manufacturing stage and the number and location of sections. The standard's public description does not make a macrograph a whole-part acceptance certificate. The relevant section plan and acceptance source still have to be identified for the order.
Use a macrograph-to-drawing section map
Place the macrograph beside a simple map or drawing extract that connects the observed face to its source. The map does not need to reveal proprietary dimensions, but it must make the relationship traceable.
| Record field | What the report should identify | What remains limited without it |
|---|---|---|
| Parent forging identity | Part number, drawing revision, heat, lot or other traceable production reference | Whether the image relates to the quoted forging |
| Specimen identity | Specimen or coupon number, and its relationship to the parent forging | Whether the photographed piece was taken from the stated production item |
| Manufacturing state | The stage at which the sample was taken, such as a stated pre- or post-process condition | Whether the image represents the condition required by the purchase specification |
| Section location | Drawing zone, section number or a marked location map | Whether the observation represents the critical area of the forging |
| Section plane and orientation | Cut plane, viewing direction and orientation relative to the forging | What structural direction or geometry the image actually shows |
| Examined extent | Full section face or a defined local region | Whether an unshown portion of the cut face was reviewed |
| Excluded region | Areas outside the section or not visible in the image | What the report does not represent |
| Invoked criterion | The agreed specification, drawing note or purchaser-producer criterion | How the observation was evaluated and by whom |
For a single image, an annotated drawing extract can be clearer than a long checklist. For several sections, use one row per specimen and section. The point is to make every image claim traceable to a physical location and a stated manufacturing condition.
Distinguish a report review from destructive sampling
Macroetch examination normally requires sectioning a specimen. That makes the examination destructive for the piece that is cut. Reviewing a macroetch report already supplied by a producer is not destructive to the buyer's retained item, but it does not remove the sampling boundary.
A report may refer to a representative coupon, a production piece or a section taken from a forging. These are not interchangeable descriptions. The purchase record should state which one applies and why it represents the specified material or location. If the supplier calls an image “representative” but cannot identify the parent forging, section location and stage, the representation claim is missing.
Do not treat the image's visual quality as evidence that the sample plan was adequate. A sharp, high-contrast macrograph can still show the wrong location, the wrong manufacturing stage or only a small portion of the relevant section.
Keep macrostructure separate from grain size and performance
Macroetch is a low-magnification observation. It does not establish microscopic average grain size. A report that needs to support a grain-size requirement must identify the separate specimen and method applicable to that requirement.
Macroetch also does not prove fatigue life, strength, toughness or overall forging quality. Those conclusions require their own specified tests, samples, methods and acceptance criteria. A macrostructural observation can be part of a broader evidence package, but it should retain its own scope.
For a separate question about microscopic inclusions, see what steel cleanliness reports can prove. That article addresses a different type of microstructural evidence and does not expand a macrograph's coverage.
Resolve missing representation before relying on the image
If the macrograph-to-drawing map is complete, label the result as a traceable macrostructural observation of the stated specimen and section. If the map has missing or conflicting fields, label the representation claim accordingly and return it to the drawing or quality owner.
For an item-specific inquiry, KTSU's link and chain collection provides the public product family. Attach the identified drawing zones, the manufacturing state to be represented and the requested evidence extent, then ask what documentation is available for the quoted item. KTSU is not represented here as performing macroetch examination or providing an ASTM certificate. The record is ready to support procurement only when the photograph, specimen, section plane, parent forging and interpretation criterion are traceably connected.