---
title: "A4 (316) Stainless Steel Spiral-Wound Metal Gasket"
description: "A4 (316) Stainless Steel Spiral-Wound Metal Gasket (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80): superior, including marine and chloride"
url: https://engineeringhardware.com/guide/material/a4-stainless-steel-cad-svg-090-gasket/
source: Engineering Hardware & Fasteners
---

# A4 (316) Stainless Steel Spiral-Wound Metal Gasket

Washers · GB/T 4622 / ASME B16.20

Mechanical properties, corrosion behaviour and the full dimensional range for this grade.

A4 Stainless Steel Spiral-Wound Metal Gasket are supplied to ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80. Corrosion behaviour is superior, including marine and chloride environments, the material is largely non-magnetic, and the usable service range is approx. -200 °C to +400 °C, subject to the property class and the joint. In practice this grade is specified for marine, coastal and chemical applications.

- **Grade:** ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80
- **Corrosion resistance:** Superior, including marine and chloride environments
- **Magnetic response:** Largely non-magnetic
- **Service temperature:** approx. -200 °C to +400 °C, subject to the property class and the joint

Property values are typical for the grade. Certified mechanical test data is available on request for production orders.

![A4 (316) Stainless Steel Spiral-Wound Metal Gasket reference image](https://engineeringhardware.com/wp-content/uploads/2026/06/Spiral-Wound-Metal-Gasket-—-GB-T-4622-ASME-B16.20-Series-090-—-GB-T-4622-ASME-B16.20.webp)

A4 Stainless Steel Spiral-Wound Metal Gasket are supplied to GB/T 4622 / ASME B16.20. The grade provides superior, including marine and chloride environments and is largely non-magnetic; the practical service range is approx. -200 °C to +400 °C, subject to the property class and the joint. Property data, grade comparison and the full size table follow.

## Why Choose A4 Stainless Steel for Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090)

Specified for marine, coastal and chemical applications. For spiral-wound metal gasket — gb/t 4622 / asme b16.20 (series 090), this matters when superior, including marine and chloride environments is the primary requirement.

## Mechanical & Physical Properties

| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
| --- | --- |
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |

## Corrosion Behavior in Service

A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.

## Galvanic & Galling Considerations

For stainless spiral-wound metal gasket — gb/t 4622 / asme b16.20 (series 090) the compatibility question is galvanic rather than galling: joined to aluminum or galvanized steel in wet service, stainless drives corrosion of the less-noble metal. Isolate with a coating, sleeve or non-conductive washer where the joint sees moisture. Note also that stainless is softer than hardened carbon steel, so where the part carries a wear or shear duty, check the load against the grade before substituting.

## Using Stainless Fasteners in Aluminum

Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.

## Sizes of Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) Available in A4 Stainless Steel

| Nominal pipe size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Reference standard |
| --- | --- | --- | --- | --- |
| DN15 | 22 | 42 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN20 | 27 | 49 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN25 | 34 | 59 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN32 | 43 | 69 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN40 | 49 | 75 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN50 | 61 | 87 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN65 | 77 | 109 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN80 | 89 | 121 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN100 | 115 | 149 | 4.5 | GB/T 4622 / ASME B16.20 |
| DN150 | 169 | 205 | 4.5 | GB/T 4622 / ASME B16.20 |

Dimensions are independent of the material: the table above lists the sizes supplied, and on this page every one of them is quoted in A4 Stainless Steel. The catalogue's default material column has been omitted here so it cannot be read as contradicting that.

Custom manufacturing · Made to drawing

## Need this washer in a grade that is not listed?

A4 Stainless Steel is one of the grades the catalog describes. Bearing area is usually the reason for a special washer: a larger outside diameter to spread load into a softer material, or a thicker section to resist dishing. Made by stamping or punching.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

[Custom washer manufacturing](https://engineeringhardware.com/custom/washers/)[Send a drawing](https://engineeringhardware.com/custom/washers/#rfq)

## Technical Drawing

Dimensioned line drawing of DN15 Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) to GB/T 4622 / ASME B16.20. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Inner diameter d1 (mm):** 22
- **Outer diameter d2 (mm):** 42
- **Thickness t (mm):** 4.5
- **Winding material:** 304SS + flexible graphite

## Dimensions & Specifications (GB/T 4622 / ASME B16.20)

| Nominal pipe size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Winding material | Reference standard |
| --- | --- | --- | --- | --- | --- |
| DN15 | 22 | 42 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN20 | 27 | 49 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN25 | 34 | 59 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN32 | 43 | 69 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN40 | 49 | 75 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN50 | 61 | 87 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN65 | 77 | 109 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN80 | 89 | 121 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN100 | 115 | 149 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |
| DN150 | 169 | 205 | 4.5 | 304SS + flexible graphite | GB/T 4622 / ASME B16.20 |

## Applications & Industries

Spiral-Wound Metal Gasket are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from DN15 to DN150 (size designation).

### Industries that specify Spiral-Wound Metal Gasket

- **Rotating & vibrating plant:** Spring, tooth and wedge types that maintain or lock bolt tension.
- **Steel fabrication:** Spreading load under a head or nut and protecting the surface finish.
- **Machine building & OEM:** Setting bearing area on soft alloy, plastic and oversized holes.
- **Timber & construction:** Large-diameter washers that stop pull-through in softer material.

### Typical applications

- maintaining bolt tension in a joint that settles
- spreading clamp load over a soft or oversized bearing face
- protecting a painted or plated surface under a turned nut

### Service conditions to specify against

- **Marine and coastal:** Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- **Hardness matters:** Under a high-strength bolt a soft washer embeds into the joint and preload is lost — specify a hardened washer for structural bolting.

[Full application guide: where Spiral-Wound Metal Gasket are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/cad-svg-090-gasket/)

Inside the plant

## Manufactured in our own plant

This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.

1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift.
2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g.
3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1.
4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227.

## Frequently Asked Questions

### Can A4 Stainless Steel replace plated alloy steel structurally?

Only at the standard strength classes — A2-70 / A4-80 are roughly equivalent to class 7 steel; A4-100 reaches class 8.8. For class 10.9 or 12.9 strength, plated alloy steel is required.

### Are A4 Stainless Steel Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) magnetic?

A4 Stainless Steel Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) are largely non-magnetic.

### What corrosion resistance do A4 Stainless Steel Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) offer?

A4 Stainless Steel Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) provide superior, including marine and chloride environments with a service range of approx. -200 °C to +400 °C, subject to the property class and the joint.

### Should I choose A4 Stainless Steel or A2 (304) for Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090)?

For Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090), A4 Stainless Steel suits general indoor and outdoor use; A2 (304) is preferred for marine, coastal and chemical environments. Choose by corrosion exposure first.

### How do I request a quotation?

Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.

## Related Pages

[View the full Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) page](https://engineeringhardware.com/fastener/cad-svg-090-gasket/)

### More Spiral-Wound Metal Gasket — GB/T 4622 / ASME B16.20 (Series 090) Guides