Debasis SA 333 : Grades 3, 4 & 7 given in your querry : Three gardes given by you have these basic elemental constitution Grade 3: C: 0.19 max Ni - 3.18-3.82 Mn- 0.31-0.64 Grade 4: C: 0.12 Ni: 0.47-.0.98 Mn: 0.29-1.06 Grade 7: C: 0.19 max Ni: 2.03-2.57 Mn: 0.90 max. Grade 4 manufacture is seamless process. For the seam less process reheat and cotnrol hot working is needed at not less than 845 o C. For other grades normalizing at not less than 815 o C and cool in air is needed. NDT temperture and Kic for each of the above grades would vary by simple variations in thermomechanical treatment. Second because of concentation of fabrication defects (i..e, blow holes inclusions etc) is extremely sensitive to mill practice . Since it is microstructure and defect concentration that primarily determine toughness rather than composition, a large variation in toughness can be produced in a given steel simply by varying thermomechnaical treatment and fabricatin practices. Commercial steels are sold in "hot rolled" condition and the rolling treatments have a considerable effect on impact properties. Rolling to a lower finishing temperature (controlled rolling - for ex: for grade 7) lowers the impact-transition temperature. Another effect is the effect of alloying elements like Mn and Ni in these grades. If the Carbon content is high (>0.15%) a high Mn content may have a detrimental effect on impact properties - because of the high hardenability causes the austenite to transform to upper bainite structure rather than ferrite or pearlite. Ni like Mn is able to improve toughness . The magnitude of this effect is dependent on carbon content and heat treatment. The principal benefit of Ni addition to commercial steels > 0.1% C is from substantial grain-size refinement and reduction of free nitrogen content after normalzing. The reasons for this behavior are not clear at present. It may be related to the fact that Ni is an austenite stabilizer and consequently lowers the transition at which austenite decompostion takes place . A detailed understanding of the fracture of steel requires, therefore, an understanding of both the physical metallurgical aspects (ex: what microstructure will result from a given heat treatment) as well as understanding of how this particular microstructure affects the toughness of a structure of given geometry. Trust this helps you to answer your query. C.V.Srinivasan Nishi Engineers Pvt Ltd India Sept 13,2005 E-mail:nishi@vsnl.com >SA 333 material is used for low temp. service. In different >grade "Ni" plays an important role in rendering low >temperature impact notch toughness. But to mention Grade 3 >having Ni=3.18-3.82 and Grade 4 having Ni = 0.47-0.98 but >both having minimum Impact Test temperature of -100C. Also >to mention Grade 7 which is having rather high side Ni = >2.03-2.57 compared to Grade 7 is having low side minimum >impact test temp. of - 75C. > >A discussion input invited for this aspect of "low Ni vs. >higher Impact Strength " / please >regards >DM

Gopal SA 333 - Grade 6 is C-Mn grade with Mn content can go upto 1.35 Max but normally kept at 0.30-1.00%. Impact test for this grade is max: -45 o C unlike for other grades with Ni where impact test is from - 75 to 100 o C. HIgher Mn restricts the impact strength with higher carbon in Grade 6. Trust this is of help toyou >What about Gr.6?