# 347 vs 347H Stainless Steel Pipe: What Changes in the Order?

Canonical: https://jundapipe.com/en-GB/blog/347-vs-347h-stainless-steel-pipe

Understand why 347 and 347H need separate purchase requirements, and review creep duty, product form and certificates before substitution.

347 and 347H should not be treated as interchangeable purchase descriptions. The H designation introduces requirements relevant to elevated-temperature strength. Before accepting a substitution, check the product standard, material designation, supplied condition and design-code requirements for the actual service.

[ASTM A312/A312M-25, scope 1.2](https://store.astm.org/a0312_a0312m-25.html) identifies TP347H as a modification of TP347 intended for temperatures where creep and stress rupture properties are important. This explains why an offer for “347/347H” needs documentary detail rather than acceptance based on the combined label.

## What is common to the material family?

[IMOA’s austenitic reference table](https://www.imoa.info/molybdenum-uses/molybdenum-grade-stainless-steels/austenitic-stainless-steel.php) identifies 347 as UNS S34700 and lists niobium in its composition. This provides general material context. It does not establish the composition or condition of a pipe supplied under a particular product specification.

The same distinction applies to a supplier’s equivalence chart: it may help locate candidate designations, but it cannot establish that one heat meets every requirement of two grades. Request the actual ordered grade and the certificate’s explicit statement.

## Which differences matter to procurement?

| Review item         | What to establish                                                  | Why it matters                                                   |
| ------------------- | ------------------------------------------------------------------ | ---------------------------------------------------------------- |
| Service duty        | Temperature, duration, cycling and pressure                        | Determines whether time-dependent strength is part of the design |
| Product standard    | Pipe or tube specification and edition                             | Requirements depend on the product form                          |
| Grade and condition | Exact designation, heat treatment and relevant material properties | A shortened label can omit requirements                          |
| Dual designation    | Evidence that the supplied material meets both claimed grades      | Overlap in a chemistry result alone is insufficient              |
| Design acceptance   | Approval under the project code and material specification         | Supplier agreement does not replace design approval              |

This table is a review method, not a set of acceptance limits. Obtain those limits from the selected standard and project specification.

## Does the same rule apply to heat-exchanger tubes?

Check the tube specification independently. [ASTM A213/A213M-25, scope 1.2](https://store.astm.org/a0213_a0213m-25.html) states that H grades have requirements different from similar grades without H, providing higher creep-rupture strength. Its scope concerns seamless boiler, superheater and heat-exchanger tubes.

A pipe certified to one standard cannot be assumed to meet a tube specification simply because the material name resembles it. Confirm the required dimensions, wall basis, tests and material condition. The [A312/A269/A213 comparison](https://jundapipe.com/blog/astm-a312-a269-a213-selection) provides a scope-level starting point.

## How should a proposed substitution be handled?

Ask the supplier to identify the proposed grade and list every deviation from the order. Send that list, the material certificate and supporting technical data to the responsible engineer. Record the acceptance or rejection against the specific line item; do not silently change the description on the purchase order.

Junda lists [347H seamless stainless steel pipe](https://jundapipe.com/products/347h-seamless-stainless-steel-pipe). Its current catalogue does not separately establish a 347 supply entry or JIS equivalence. [Catalogue source](https://jundapipe.com/products) For either requirement, send the exact specification through the [contact page](https://jundapipe.com/contact) and obtain written confirmation of what can be offered.