The effects of titanium additions on AF1410 ultra-high-strength steel

Abstract

The mechanical properties and microstructure of two heats of AF1410 steel were compared. The first heat, heat 811, contained a titanium addition of 0.02 wt pct, while the second heat, heat 91, contained no titanium, manganese, or other strong sulfide formers. The sulfur in heat 811 was gettered as titanium carbosulfide, while in heat 91 the sulfides were chromium sulfide. The toughness of heat 811 was found to be much enhanced compared to heat 91, with Charpy impact energies of 176 J and 79 J and K IC fracture toughness values of and , respectively. This significant difference in fracture toughness is attributed to the fact that titanium carbosulfide particles are more resistant to void nucleation than the chromium sulfide particles, which appear to nucleate voids at the onset of plastic strain. In addition to altering the sulfide particle type, the titanium addition also results in the presence of undissolved MC carbides in the titanium-modified steel in addition to the M 2 C carbides found in heat 91. These carbides act as grain growth inhibitors, resulting in a finer prior austenite grain size and martensite packet size in heat 811. 170 MPa.m 1 / 2 235 MPa.m 1 / 2

Mechanical Property of Ultrafine Elongated Grain Structure Steel Processed by Warm Tempforming and Its Application to Ultra-High-Strength Bolt

“…Charpy absorbed energy, vE, at room temperature for various steels; ultrafine grain ferritic steel, 30) JIS-low-alloy, 31) AISI/SAE-low-alloy, 32) 0.34%C-2%Si-1%Cr-3%Ni, 33) ausformed 0.2%C-3%Ni-3%Mo, 34) HY130, 35) HY180, 25) AF1410, 26) high-purity 18%Ni, 27) 18%Ni (250), 28) and 18%Ni (350) 29) maraging steels. Data for 0.4%C-2%Si-1%Cr-1%Mo steels that were quenched and tempered at a temperature of 500°C (QT) and tempformed at a temperature of 500°C with an equivalent strain, εeq, of 1.75 (TF), 5) are also shown.…”

“…Figure 1 plots the Charpy V-notch impact absorbed energy, vE, as a function of yield strength, σ ys , at room temperature for various steels. 23,24) High-alloy steels, [25][26][27][28][29] which are typified by maraging steels, have been developed through 1) reducing the amounts of inclusions and impurity elements such as P and S, 2) minimizing the amount of C, 3) adding alloying elements such as Ni, and 4) refining…”

Mechanical Property of Ultrafine Elongated Grain Structure Steel Processed by Warm Tempforming and Its Application to Ultra-High-Strength Bolt

“…σ ys vE 23 . Relation between yield strength, σ ys , and V-notch Charpy absorbed energy, vE, at room temperature for various steels; ultrafine grain ferritic steel 30) , JIS-low-alloy 31) , AISI/SAE-low-alloy 32) , 0.34%C-2%Si-1%Cr-3%Ni 33) , ausformed 0.2%C-3%Ni-3%Mo 34) , HY130 35) , HY180 25) , AF1410 26) , high-purity 18%Ni 27) , 18%Ni (250) 28) , and 18%Ni (350) 29) maraging steels. Data for 0.4%C-2%Si-1%Cr-1%Mo steels that were quenched and tempered at 500°C (QT) and tempfromed at 500°C with an equivalent strain, ε eq , of 1.75 (TF) 5) are also shown.…”

Ultrahigh Charpy impact toughness (~450J) achieved in high strength ferrite/martensite laminated steels

“…High alloy steels exhibit much higher impact toughness than low alloy steels. For example, the impact energy of high alloyed precipitated hardening steels (austenite steel and nanobainite steel) could be about 200J at strength level of 1.5 GPa and about 50J at 2.0 GPa at RT 9 10 11 , due to the existence of austenite and addition of Ni and Co. These high alloy steels are much more expensive than low alloy steels, which restricts their application and drives the research and development of low alloy steels with high strength and high toughness.…”