Stainless Steel World Magazine October 2024 | Page 40

but low in a longitudinal direction . Furthermore , the microstructure is free from continuous networks of Cr 2 N precipitates . Average austenite spacing and ferrite content of forged and rolled bar - The average austenite spacing values with standard deviation “ s ” obtained and ferrite content for the half radius of the longitudinal microstructure were listed in Table 2 . The average austenite spacing values for the rolled specimen are lower for all rolled specimens with low scatter ( below ± 0.06 μm ), as shown in Table 2 . The average ferrite content of Ø140 and Ø180 bar produced by the rolling process is slightly higher than that of the forged one with low scatter ( below ± 0.03 ). However , the average ferrite content of the Ø160 forged bar is somewhat higher than the one produced by the forging process . Tensile properties - The tensile results of the transverse ( T ) and longitudinal ( L ) directions in two different processes were listed in Table 3 . As shown in Table 3 , the yield and ultimate strength results for the rolled specimen of each final diameter in the longitudinal direction are somewhat high and similar for all rolled specimens . In addition , the variation in the yield strength for the rolled versus forged specimen in the longitudinal direction are relatively small , though greater in the final diameter Ø140 . For the diameters Ø160 and Ø180 mm , there were no big differences in yield strength between rolled and forged bar in the longitudinal direction . Besides , the variation in the ultimate tensile strength for the rolled and forged specimens is very small , though greater in the final diameter Ø160 and Ø180 mm and the same as in the diameter Ø140 . Furthermore , the yield strength results of the rolled specimens of each final diameter in the transverse direction are similar for all rolled Ø140 and Ø160 specimens , but in the rolled diameter Ø180 mm is slightly lower . However , the ultimate tensile strength of the rolled specimen in the transverse direction is rather similar to the forged specimen . Furthermore , the variation in the tensile strength for the rolled versus forged bar in the transverse direction are very small , though somewhat greater in the final diameter Ø160 . It is worth noting that

no or very small variation in the tensile strength is observed between the longitudinal and transverse directions . As shown in Table 3 , the elongation results in the rolled specimens of each final diameter are very close in the longitudinal and transverse direction and also similar to forged bar . Impact toughness - Results of the impact toughness testing of rolled versus forged bars in the longitudinal and in the transverse direction were shown in Table 4 . The toughness average and single values for the rolled specimens of each final diameter in the longitudinal direction are greater than the forged specimens and similar for all rolled specimens . In addition , the toughness results for the rolled specimens in the transverse direction are somewhat greater than the forged specimens and similar for all rolled specimens . It is worth noting that the variation in the average impact toughness values for the rolled versus forged specimens in both directions is significantly higher , though somewhat greater in the final diameter of Ø180 mm . Hardness - The results of hardness testing of an as-rolled and as-forged

Route Rolling Forging

Ø140 29.61 ± 0.04 51.9 ± 0.01 43.7 ± 0.04 47.4 ± 0.02

Ø160 32.01 ± 0.06 50.3 ± 0.01 42.8 ± 0.08 51.3 ± 0.0

Ø180 30.81 ± 0.05 49.9 ± 0.01 42.5 ± 0.05 47.3 ± 0.03

Table 2 . Average austenite spacing values and ferrite content by different hot-working process

Ø140

Ø160

Ø180

Table 3 . Tensile properties of rolled and forged bars

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