# Type 310 stainless steel

High-chromium, high-nickel austenitic stainless: 310/310S/310H identity, heat-service boundaries and qualification.

Reviewed: 2026-11-01

Tags: materials, stainless-steel, heat-resistant

## Identity and grade boundaries

Sandmeyer's Alloy 310 guide gives **950°C maximum in oxidizing gas above 2 g/m³ sulfur**. At or below **2 g/m³**, it gives **1050°C continuous and 1100°C peak**. These are atmosphere-specific oxidation screening temperatures. A loaded component needs a separate creep and design assessment. [Sandmeyer high-temperature corrosion table](https://www.sandmeyersteel.com/wp-content/uploads/310-Spec-Sheet.pdf#page=1)

Type 310 is an austenitic stainless steel, UNS S31000. ATI's product listing gives chromium 24–26%, nickel 19–22% and carbon at most 0.25% by mass. High chromium and nickel distinguish this family from common 18-8 stainless steels, but the name does not specify product form, heat treatment, grain size or a construction-code qualification. [ATI, Type 310 product page](https://www.atimaterials.com/Products/Pages/ati-310.aspx)

Keep the suffix when recording material. ATI's chemistry table distinguishes **310, S31000**, with 0.25% maximum carbon; **310S, S31008**, with 0.08% maximum; and **310H, S31009**, with 0.04–0.10% carbon. A heat may satisfy overlapping chemistry ranges, but dual certification must be demonstrated against all applicable requirements rather than inferred from carbon alone. [ATI, 309/309S/310/310S technical data sheet, chemistry table](https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/austenitic/ati_309_309s_310_310s_tds_en3_2_v1.pdf#page=1)

Sandmeyer describes 310S as a lower-carbon fabrication variant and 310H as a modification for enhanced creep resistance. These are selection distinctions, not permission to replace one with another. Retain the exact UNS designation, ordered specification and required final condition in every material record. [Sandmeyer, Alloy 310/310S/310H specification sheet](https://www.sandmeyersteel.com/wp-content/uploads/310-Spec-Sheet.pdf#page=1)

## Product form and mechanical data

ATI offers plate, sheet and strip. Its Type 310 product page lists the following mechanical values under the plate entry:

| Quantity | Listed value |
| --- | ---: |
| Tensile strength, minimum | 515 MPa |
| Yield strength, minimum | 205 MPa |
| Elongation, minimum | 40% |
| Hardness, maximum | 95 HRB |

The listing is not a high-temperature design table. Confirm the required condition, test basis, thickness and governing specification before using it for acceptance. [ATI, Type 310 plate listing](https://www.atimaterials.com/Products/Pages/ati-310.aspx)

## Oxidation is one service constraint

A named example is Outokumpu **Therma 310S/4845**, EN 1.4845/UNS S31008. Its Therma bulletin gives a 1050°C maximum service-temperature guide and describes good oxidation resistance in mildly cyclic conditions. This is a 310S producer example, not a guaranteed limit for generic S31000 equipment. [Outokumpu, Therma range data sheet, grade description and table 2](https://otke-cdn.outokumpu.com/-/media/files/products/therma/outokumpu_therma_range_datasheet.pdf#page=1)

For selection, describe gas composition, oxygen potential, sulfur/carbon/nitrogen activity, deposits, gas velocity and thermal cycling. Include actual metal temperature rather than only a furnace controller setpoint. Local hot spots, supports and welds need their own assessment. Published oxidation guidance is a screening input; it is not an allowable stress or an equipment life prediction.

## Creep, cycling and metallurgical change

Outokumpu's table 8 gives **mean 1,000-hour creep-rupture strengths** for Therma 310S/4845 of 80 MPa at 700°C and 35 MPa at 800°C. These are time-dependent rupture data, not safe working stresses. The same bulletin discusses sigma-phase effects on thermomechanical-fatigue behavior. [Outokumpu, Therma data sheet, table 8 and fatigue discussion](https://otke-cdn.outokumpu.com/-/media/files/products/therma/outokumpu_therma_range_datasheet.pdf#page=1)

A **comparison only** gives `80 − 35 = 45 MPa`, or `45 / 80 × 100 = 56.25%` lower mean rupture strength across those two test temperatures. This arithmetic must not be used to interpolate an allowable pressure or extrapolate service life. The design basis needs the applicable code, time horizon, weld factors, corrosion allowance and loading history.

Different failure mechanisms can govern different parts of one operating cycle. Assess sustained load at temperature, expansion restraint during heating/cooling, and handling or repair after service. A component that survived hot operation is not thereby qualified for cold straightening or another duty cycle.

## Fabrication and aqueous exposure

ATI notes rapid work hardening during forming/machining and the need to account for heat removal and dimensional tolerance. It states that these austenitic grades cannot be hardened through heat treatment; cold-worked strength is not stable at the elevated temperatures where they are commonly used. Its welding guidance supports common processes but still requires suitable filler and procedure selection. [ATI technical data sheet, fabrication and welding](https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/austenitic/ati_309_309s_310_310s_tds_en3_2_v1.pdf#page=1)

ATI also warns that 309/310 remain susceptible to chloride stress-corrosion cracking. Thus high nickel content or heat resistance should not be converted into a blanket wet-corrosion approval. Check shutdown condensates, wash fluids and contaminants separately from normal hot-gas operation. [ATI technical data sheet, aqueous corrosion](https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/austenitic/ati_309_309s_310_310s_tds_en3_2_v1.pdf#page=1)

Before fabrication, identify which operations require solution treatment, dimensional allowance or renewed inspection. For repair, retain prior service history and assess the material condition before welding or forming. Qualify the completed joint and final geometry rather than assigning unmodified parent-stock properties to the assembly.

## Ordering and source editions

An actionable purchase definition includes exact grade/UNS; form and dimensions; specification edition; supplied/final condition; required grain-size or creep-related controls; inspection certificate and joining requirements. Capture the service atmosphere, temperature/time profile and design basis alongside the material choice.

ATI's PDF is printed **version 1, February 17, 2014**. Outokumpu's bulletin is printed **1565EN:5, November 2022**. Sandmeyer's PDF carries **Alloy 310 06/2014** and **rev 02/2023 PDF link** markings. These source identifiers do not establish the latest contractual specification edition. Confirm current supply and required certification with the producer.

See also [grades, tempers and conditions](../grades-tempers-and-conditions.md).