What is Difference between Marine Steel ABS Grade A and Mild Steel Q235B

The mild steel Q235B is also widely used for ship building nowadays to instead marine steel ASTM A131/A131M grade A plates. It is important to know their difference, so that you can make a better choice and decision.

First, let us check their chemical composition and mechanical properties:
Q235B and ABS Grade A Chemical composition %

Q235B and ABS Grade A Mechanical properties

In general, the ABS Grade A ship building plates and Q235B mild steel plates almost have no big difference in chemical composition and mechanical properties. That is why a lot of clients can also accept to use Q235B carbon steel if they have no strict requirement for classification socirty certificate. Under such condition, the Q235B has advantages as: fast delivery and lower price also.

But if the user require classification society certificate, Q235B will not work anymore. It must be marine material ABS Grade A. Show you a ABS Gr.A classification society certificate, and you will understand it:

Please check the certificate No. In top right corner and ABS stamp as well as signature in lower right corner. You can take the certificate No. and check with ABS classification society in any country about authenticity of the marine grade plates mentioned in the Mill Test Certificate/ ABS classification society certificate.

The main marine grade steel of BBN steel are grade A, B, D, E, AH32, DH32, EH32, FH32, AH36, DH36, EH36, FH36, AH40, DH40, EH40, FH40, etc. And our cooperated classification societies are ABS, LR, BV, VL (DNV GL), RMRS, RINA, KR, NK, CCS.