Chapter 10 Phase Diagrams: The Road Map to Phases and Structures 219 Goodheart-Willcox Publisher Figure 10-28. This table shows the mechanical properties of UNS G10800 steel processed to different microstructures. All tempering is done for one hour at the stated temperature. Mechanical Properties of UNS G10800 (AISI 1080) Steel Processed to Different Microstructures Process used Microstructure developed Process/ temper temperature, °F (°C) Yield strength, ksi (MPa) Ultimate tensile strength, ksi (MPa) Percent elongation Reduction in area, % As-rolled Pearlite partly recrystallized 85 (566) 140 (965) 12 17 Normalized (air cool) Fine pearlite 1650 (900) 76 (524) 146 (1010) 11 21 Annealed (slow cool) Medium pearlite 1450 (790) 55 (376) 89 (615) 25 45 Quench & temper Tempered martensite 400 (205) 142 (979) 190 (1310) 12 35 Quench & temper Tempered martensite 600 (315) 142 (979) 189 (1303) 12 35 Quench & temper Tempered martensite 800 (425) 138 (951) 187 (1289) 13 36 Quench & temper Tempered martensite 1000 (540) 117 (807) 164 (1131) 16 40 Quench & temper Tempered martensite 1200 (650) 82 (600) 129 (889) 21 50 An important feature of the microstructures discussed is the different sizes of the components. Pearlite structures vary with the cooling rate. Bainite structures are smaller than fine pearlite. The cementite particles in fully tempered martensite are yet smaller than bainite, and smaller than pearlite by orders of magnitude. Smaller particles inhibit dislocation motion better, resulting in higher yield strength. Figure 10-28 summarizes typical strengths and elongations available for a UNS G10800 steel processed by the different methods described in this chapter. The magic of steel is that all these different sets of properties are attainable simply through changes in the processing. If you want to produce consistent parts, then you need to know which small changes in the process cycle create the most change in microstructure, and thus changes in properties. These sensitive steps need the closest attention from technicians and operators. The technician who understands the sequence of process to microstructure to property is also in position to recognize whether a specific process cycle is on track or is leading to an undesirable outcome. Copyright Goodheart-Willcox Co., Inc.