# Duplex Pipe Inspection: Why Chemistry Alone Is Not Enough

Canonical: https://jundapipe.com/en-CA/blog/duplex-pipe-heat-treatment-inspection

Build a duplex pipe inspection request around heat treatment, sampling and applicable A923 methods, with a traceability review table.

A duplex pipe inspection request should connect material identity, heat treatment, sampling and acceptance criteria. Chemical composition and mechanical results are necessary evidence where specified, but they do not alone demonstrate the absence of detrimental intermetallic phases. [ASTM A923-25, scope 1.4](https://store.astm.org/a0923-25.html)

Define the examination package before manufacture. A generic request for “all tests” leaves the method, sampling and pass criteria unresolved.

## What do the A923 methods examine?

[ASTM A923-25](https://store.astm.org/a0923-25.html) addresses detection of detrimental intermetallic phases in certain duplex grades. Its public scope identifies three methods:

| Method | Published examination type                                  | Procurement detail to establish                                 |
| ------ | ----------------------------------------------------------- | --------------------------------------------------------------- |
| A      | Sodium hydroxide etch test for structure classification     | Applicable grade, specimen location and interpretation criteria |
| B      | Charpy impact test for structure classification             | Applicable temperature, orientation and acceptance requirements |
| C      | Ferric chloride corrosion test for structure classification | Applicable grade, test conditions and acceptance criteria       |

The public scope does not establish that every method applies to every duplex grade. Consult the full standard and project requirements before selecting the method. Passing one test should not be presented as proof of immunity to every corrosion or toughness problem.

## Why do sampling location and thermal history matter?

A923 explains that formation of detrimental phases depends on temperature and cooling history, and that the specimen must represent the region most likely to develop them. For material receiving common heat treatment, the slowest-cooling region can be relevant. [Sampling basis](https://store.astm.org/a0923-25.html)

Ask how the specimen relates to the heat-treatment batch, dimensions and delivered material. A report from a convenient sample is not automatically representative of another lot or a different section size.

Create a traceability chain: material heat → production or heat-treatment lot → sample identity and location → test report → released pieces. Any break in that chain should be resolved before the result is relied upon.

## How should the inspection plan be written?

List the governing product standard, exact grade, condition, required examinations, sampling basis, acceptance criteria, witness requirements and document references. [ASTM A790/A790M-24](https://store.astm.org/a0790_a0790m-24.html) provides for supplementary requirements where greater testing is desired; the order must identify the relevant additions.

Keep testing responsibilities explicit. State who selects and identifies specimens, who performs the test and who reviews the result. If third-party witnessing is required, agree the stage and notification procedure before production reaches it.

## What does a capability page prove?

Junda publishes solution heat treatment and testing capabilities, including metallographic examination, within its [production information](https://jundapipe.com/production-environment). This establishes published capability information; it is not a report for a specific S32750 shipment, an A923 qualification or a guarantee that every listed examination is included in every order.

For the [S32750 enquiry](https://jundapipe.com/products/s32750-super-duplex-steel-pipe), submit the inspection plan through the [contact page](https://jundapipe.com/contact). Request confirmation of the proposed scope and documents. Keep any additional metallurgical requirements separate from the [PREN calculation](https://jundapipe.com/blog/pren-calculation-stainless-steel), which addresses composition screening only.