Stainless Steel World Magazine October 2024 | Page 38

In order to study the influence of the rolling and forging process on the microstructures , the tensile , impact toughness , and hardness of Sanmac 2205 three different diameter solid bars for each process were investigated . The rolled and forged bars were produced by Alleima Tube AB . The results showed that the average ferrite content for the rolled and the forged specimens were virtually the same . Additionally , the tensile results for the rolled specimens were higher than those after forging . However , variations in the tensile properties for the rolled versus forged specimens were very small . Moreover , Rockwell hardness values for the specimens after rolling were slightly higher than those after forging .

By Dr Munir Al-Saadi , R & D Senior Engineer , Alleima Tube AB ( formerly Sandvik Materials Technology ), Sandviken , Sweden

Introduction Sanmac 2205 is widely used in production flow lines for extracting oil and gas from sour wells , in refineries and in process solutions contaminated with chlorides [ 1 ] . It has shown enhanced mechanical and corrosion properties , making it an attractive and economical choice for various applications . Sanmac 2205 bar is mainly produced by EAF melting , AOD process , LF Refining , Continuous Casting ( CC ), Hot-rolling , Solution Annealing , Straightening , and Peeling to a final rolled-bar diameter . However , there is interest in producing material by forging . Compared with forging , rolling is the more beneficial process . It is several times higher in productivity and 1.5 times higher in dimensional precision , thus lowering material loss during peeling and after final rolling . As the total cost of rolling is lower than forging , replacing forging with rolling for Sanmac 2205 is desirable to reduce the cost of production .

Rolling and forging are both hightemperature compressed deformation processes . However , there are significant differences in equipment shape and movement , deformation zone geometry and metal flow pattern . Therefore , the type of hot working process might have an effect on microstructure isotropy and impact strength . In the present work , the CC blooms in the form of 365x265 mm are processed with rolling and forging to manufacture solid bars of three different diameters ( Ø140 , Ø160 , and Ø180 mm ) per each process .

Experimental procedure and material processing The chemical composition of the rolled and forged bar used in this study is shown in Table 1 , along with the chemical requirement of ASTM A182 grade 51 ( UNS S31803 ) for reference . Transverse and longitudinal samples for microstructural test , tensile testing , and impact testing were extracted from a location at half radius and at a distance approximately 2½ times the outer diameter of a bar (~ 500 mm ) from a heat-treated end surface . The microstructural samples were machined , prepared , and etched for examination using a Light Optic Microscope ( LOM ). Etchant 13a and Etchant 220 according to ASTM E407 [ 5 ] were used . Austenite spacing was measured on longitudinal samples using specification DNV-RP-F112 [ 6 ] . Furthermore , the ferrite content of each test specimen and location were measured using a ferritscope at halfradius of the bar . Tensile tests were made at room temperature according to ASTM A370 [ 7 ] and performed on a set of three specimens for each location and direction . In addition , the tensile equipment was used according to ASTM E8 / E8M-13a and conformed to Practice ASTM E4 . Impact toughness tests were made at a temperature of ~ -50 ° C and the impact machine was used according

538239 60992 Ø140 0.019 0.40 0.80 0.026 0.0029 22.42 5.41 3.07 0.174

Rolled bar 538986

Forged bar 539872

0.016 0.56 0.74 0.023 0.0040 22.26 5.44 3.13 0.173

0.016 0.40 0.84 0.021 0.011 22.36 5.41 3.08 0.171

Table 1 . Chemical composition , wt . %

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