Re: [MW:9204] Materials

Dear Akhil,

Steel mentioned below is known as Carbon Steel (C-Mn-Si) so I would like to give you a general idea of normalizing and as-rolling.

If you refer Fe-C diagram, there are 2 points lower critical transformation AC1(750 deg) and upper critical transformation AC3(900 deg), Plate rolling process for Plate supplied in Normalizing condition is similar to As-rolled condition, however normalizing is subjected to additional heat treatment.

With As-Rolled plate, ther is only moderate strength and toughness requirement, generally the finish rolling temperature of As-rolled plate will be above the AC1 Temperature. 

Normalizing is usually specified where there is some high temperature forming during process fabrication and just above the AC3 temperature and held for a period of time. Since the heating is done to A3 temp., a fine grained Austenite is developes, After heating the plate is cooled in still air, as the plate cools, a fine grained ferrite/pearlite mixture takes place of Austenite.

Normalizing is usually specified where mechanical properties are not achievable by As-Rolled process alone.Your choice depends upon MDMT(if design temp. is low) and Heavy wall thickness.

Normalized rolling produes more fine grained structure than normalizing alone and is better for structure steel and pressure vessel application and mechanical properties.This is achieved by deformation in two steps both above the recrystallization stop temperature. The first step, called roughing, is carried out at high temperatures in order to minimize the rolling forces.After a certain holding time the final deformation takes place at a specified temperature at least heated above the AC1 temp and cooled in still air.

For query no. 3, you can accept it if CE (carbon equivalent is appropriate) doesn't exceed then secified. Sometimes added to inhance mechanical properties.

hope this will be usefull and respond to other query Asap.

Regards
Manpreet Singh


On Wed, 12 Jan 2011 11:01:16 +0530 akcme wrote
>Dear All,
>
>
>1. What will happen when Mo content of SA 516 Gr. 70 become ZERO?? As
>per SA 20 only maximum level restriction is mentioned when that
>specific material content become zero is it acceptable as per Code??
>
>2. What is the difference between Normalized Rolled and Normalized and
>supply condition as "as rolled"?
>
>3. If Nb content of SA 516 Gr.70 is higher than what is mentioned in
>SA 20 Table 1. and our customer is ready to accept it as per Table 1
>Note D, Do we need to mention it in Technical Delivery Condition?
>
>4. For Super Duplex, what exactly meant by Finish Nr. 1?? If our
>requirement is White pickled steel, can I accept it just with the word
>Finish Nr. 1??
>
>5. Is there any specific Normalizing temperature and the duration to
>be followed for SA 516 Gr. 70 in Code??
>
>
>
>Regards
>
>Akhil
>
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