HIC re-test after normalizing ?

[Itsnotgoinganywhere]

I have a plate that is purchased as tested and HIC resistant, but manufacturing process requires normalizing after forming, would this still be acceptable, or is HIC test required after the heat treatment? MR0175 does not spell this out (from what I can tell anyway) and we do not have further client instructions.

 

[SJones]

It is down to the end user. Table footnote b of Table B.3 in ISO 15156-2 states "the samples being taken to represent the general performance of an order should be agreed between the producer and the equipment user." The same footnote requires compliance with sub-subclause 8.3.2 of ISO 15156-1 which states that "the test samples shall be representative of the commercial product."

Some end users believe that a HIC test at the plate mill covers them for a manufactured product irrespective of what treatment the plate has received in the process. My personal take on "representative of the commercial product" is in the final supply condition after all forming and heat treatment.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[MagBen]

From a technical point of view, it is probably acceptable. The sample for HIC test is normally stressed. After normalzing, HIC resistance could be even better.

 

[ParickT]

It would be highly suggestable to do a HIC test in the expected equipment condition before putting in service.
Plate mills do that by testing specimens in as-delivered heat-treat condition PLUS any simulated expectable condition (e.g. exepcted PWHT of equipment, heat treat of formed pieces etc...).
The reason is that heat treat can dramatically change the microstructure and stress concentrations of your steel, giving rise to variable responses towards HIC resistance in testing.
Generally, a final stress relief in the PWHT range is best to achieve optimized resistance of an oterhwise purposefully elaborated steel intended for HIC resistance (otherwise it is random).

 

[MagBen]

The main purposes of normalization are to mkae a more homogeneous/finer micro structure, to eliminates internal stresses, strains caused by previous cold work suhc as rolling, forming, machining etc., to increase toughness/soften the material, ALL of which increase HIC resistance.
However, this was my hypothetical statement. If your normlization was for PWHT, for subsequent hardening, and if the application is very critical, you' d better do a HIC test again.

 

[ParickT]

The final real heat treatment on an appropriately made steel must be made in the PWHT / tempering range (about 610°C) for the steel to fully develop its HIC resistance. Noramlization temperature treatment before that, either before or after forming according to various rules and choices, is necessary, but not sufficient.