Understanding the Australian Boiler and Pressure Vessel Grades and Terminology

XLERPLATE® steel's boiler and pressure vessel range are plate products specially designed using a fully killed, fine grained carbon-manganese steel. These products are manufactured to the Australian Boiler and Pressure Vessel Standard, AS 1548:2008, the standard has a number of options in terms of available grades and the supply conditions for those grades. This document sets out to explain the grade designations and supply conditions that are available under the standard and considerations associated with each of the available supply conditions.

Grade Designation

All grades in the Australian Boiler and Pressure Vessel Standard AS 1548:2008 have grade names in the following form:

Australian Boiler and Pressure Vessel Standard AS 1548:2008 have grade names designation

Supply Conditions

There are four supply conditions available consisting of Normalised Rolling (NR), Normalised (N), NRA Designated Grades (NRA) and Thermo-mechanical Controlled Rolling (T). These supply conditions are explained further below.

Normalised Rolling (NR)

A rolling process in which the final deformation (rolling pass) is carried out in a certain temperature range that produces a material condition equivalent to that obtained after normalising.

Normalised (N)

The heat treatment process undertaken after rolling where the XLERPLATE® steel is heated between 870 – 930°C. Normalised grades may be replaced by Normalised Rolled grades with agreement between the purchaser and the manufacturer.

NRA Designated Grades (NRA)

Grades with an NRA supply condition are supplied with the plate rolled in a Normalised Rolled condition, but with tests carried out on normalised and stress relived test samples. The fabricator MUST normalise or hot form grades with an NRA designation to ensure that the steel meets the required properties. Failure to carry out normalising or hot forming of the steel supplied may mean the XLERPLATE® fails to meet the requirements of the Standard.

Thermo-mechanical Controlled Rolling (T)

A rolling process in which a significant amount of deformation (rolling) takes place at temperatures below the normalising range, leading to a fine grained structure. TMCR is used to achieve improve strength and toughness with relatively low CEQ chemistries. TMCR is not suitable for hot forming at temperatures >620°C as this may adversely affect the properties of T grade steels. The T grades are not generally suitable for hot forming.

Considerations Associated with the Supply Condition Options

Supply Condition	Advantages	Disadvantages
Normalised Rolled (NR)	Lowest cost option Widest range of available sizes Shortest lead time	Some low temperature impact tested grades (e.g. L50) may not be available.
Normalised (N)	Best toughness Wide range of low temperature impact tested grades available	Most expensive option Limited size range due to limitations with additional heat treatment process Longer lead time due to additional heat treatment process
NRA Designated (NRA)	Suitable for hot forming applications, such as dished ends Customer knows what properties are obtained after hot forming	Requires the customer to carry out hot forming (or normalising) in a very controlled manner to ensure the correct properties are obtained
Thermo-mechanical Controlled Rolled (T)	Good toughness can be achieved at relatively low cost (compared to normalised plate). Wide range of low temperature impact tested grades available.	Not suitable for applications requiring hot forming or normalising.