[MW:5478] RE: 5437] Hardness of Untempered Martensite

Dear Babu,

Untempered Martensite is brittle in nature, which will have high hardness level. Martensite will be formed in carbon and low alloy steel, when the cooling rate is higher than the critical cooling rate. For example, quenching the steel into water/oil from austenitizing temperature range will produce martensite (brittle) structure at room temperature. In order to convert brittle martensite to less brittle and also to retain toughness, tempering process shall follow after quenching

During quenching, some % of austenite may retain to room temperature due to some of the alloying elements (austenitic stabilizing elements such as Mn, Ni, C) and cooling rate. This austenite may try to convert as secondary martensite when tempering treatment is carried out. Hence this martensite is called “untempered martensite” which is brittle in nature. This may contribute to the overall brittleness to the material/ structure.

Microstrural analysis can reveal the untempered martensite in the steel micro-structure.

Regards,

L. Prabhu kumar,

Sr. Principal Engineer,

Equipments & Materials Dept.,

Saipem India Projects Limited,

Nungambakkam High Road, Chennai - 600 034, India.

Tel:+91 44 43906588, Ext.: 588, Fax:+91 44 66840345,

Mobile Ph. No.: +91 9003010978.

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Kathalingam Babu
Sent: Tuesday, June 08, 2010 6:21 AM
To: materials-welding@googlegroups.com
Subject: [MW:5437] Hardness of Untempered Martensite

Any body have the idea on hardness for the untempered Martensite ?

What will be the morphology of micro?

Thanks & Regards,

K.Babu
Singapore

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