ASTM Standards for Steel Plates for Pressure Vessels

Introduction to ASTM A20-85

Standard designation A20-85 establishes common requirements that apply to rolled steel plates for pressure vessels under numerous ASTM specifications. These requirements govern unless otherwise specified in individual material specifications. The standard also includes supplementary requirements for additional testing or inspection when desired by the purchaser.

Appendix X2 of the standard describes the production and characteristics of coiled products that may be used for pressure vessel plates. In case of conflicting requirements, the individual material specification takes precedence over this general specification.

Purchasers may specify additional requirements that don't contradict the provisions of this general specification or individual material specifications. Such additional requirements must be included in the order information and are subject to negotiation with the supplier.

Generally, all materials covered by these specifications are intended to be suitable for fusion welding.

ASTM Specifications for Pressure Vessel Plates

The following table lists the ASTM specifications covered by standard designation A20-85:

Table 1. ASTM Specifications for Pressure Vessel Plates

Manufacturing Processes for Pressure Vessel Plates

Unless otherwise specified in the material specification, steel for pressure vessel plates may be manufactured using various processes including open-hearth, basic-oxygen, electric-furnace, vacuum arc remelt (VAR), or electroslag remelt (ESR).

The steel may be cast in ingots or strand cast. When multiple heats are consecutively strand cast, they must be melted to the same steelmaking composition range. The heat number assigned to the cast product (slab) may remain unchanged until all of the steel in the slab is from the following heat.

For plates produced from strand-cast slabs, the reduction ratio of thickness from slab to plate must be a minimum of 3 to 1. Plates can be produced either as discrete cut lengths of flat product or from coils. Plates produced from coil refers to plates that have been leveled or flattened and cut to length from a coiled product and are furnished without heat treatment. Plates that undergo heat treatment (annealing, normalizing, normalizing-and-tempering, or quenching-and-tempering) after decoiling are considered discrete cut lengths of flat products.

Heat Treatment Requirements and Options

Heat treatment of pressure vessel plates may be performed by the manufacturer, processor, or fabricator unless otherwise specified in the material specification. When the material specification requires heat treatment to be performed by the purchaser or their agent, and the material is to be supplied in a condition other than that required by the material specification, this must be stated in the order.

When plates are ordered without the required heat treatment, the responsibility for conforming to the heat treatment requirements of the material specification falls to the purchaser. The heat treatment must be performed as specified in the material specification, though the purchaser may specify alternative heat treatment methods provided they don't conflict with the material specification requirements.

When normalizing is performed by the fabricator, it may be accomplished during the heating process for hot forming. The temperature for hot forming should not significantly exceed the normalizing temperature.

If no heat treatment is required, the manufacturer or processor may optionally heat treat the plates by normalizing and then stress relieving to meet the material specification. With purchaser approval, cooling rates faster than those obtained by cooling in air are permissible to improve toughness, provided the plates are subsequently tempered in the temperature range from 595 to 705°C.