Development of Ultra High Strength Steel by Electroslag Refining and Thermomechanical Treatment

Abstract

Development of low alloy ultra high strength steel with yield strength in excess of 1600 MPa and elongation of 10 % with good fracture toughness is the primary objective of this investigation. The alloys were prepared through electroslag refining (ESR) followed by thermomechanical treatment (TMT). The base alloy was prepared with 0.23 % C, 1.09 % Mn, 5.7 % Cr, 1.18 % Mo, 0.40 % V, 0.19 % Si, 0.011 % S, 0.015 % P, 0.02 % Al and 0.013 % N. Other alloy was developed by inoculation of about 0.06 % titanium in which other elements are kept intentionally similar with the base alloy. The ESR ingots further underwent for TMT to convert it into plates. The specimens of TMT plates of the base alloy displayed tensile strength, yield strength, % elongation and fracture toughness of 1792, 1580 MPa, 7.6 % and 70 MPaHm, respectively while titanium inoculated alloy showed tensile strength of 1885 MPa, yield strength of 1700 MPa, elongation of 8.4 % and fracture toughness of 84 MPaHm. It was observed that the mechanical properties of the titanium inoculated alloy were substantially improved compared to base alloy. Optical, SEM, TEM and EDAX investigations confirmed that the microstructures of the base alloy and titanium inoculated alloy consisted of predominantly bcc lath martensites. TEM and corresponding EDAX studies revealed that the inter lath martensite spacing in the titanium inoculated alloy was finer than the base alloy and also confirmed a homogeneous precipitate of 20-30 nm titanium carbonitrides in titanium inoculated alloy. The improvement of mechanical properties in titanium alloy may be due to refinement of prior austenite grains, inter lath martensite spacing as well as precipitation hardening.

Tensile Fracture Behavior of 316L Austenitic Stainless Steel Manufactured by Hot Isostatic Pressing

“…These formulae have been used to successfully probe the effects of alloying element concentration (often nitrogen) on the hardness, yield strength, and tensile strength of austenitic stainless steel. [32][33][34][35][36][37] These formulae were employed herein to calculate theoretical yield strength and UTS values for the different heats, and these are compared with the experimental values in Table III. Since nitrogen and carbon have the highest weighting in both equations, the chemical concentrations (wt pct) of these elements have also been tabulated, along with the total wt pct of carbon + nitrogen.…”

Reduction of Residual Stress for High‐Strength Low‐Alloy Steel Strip Based on Finite Element Analysis

“…is condition decreases the size of austenite grains, whereas the ferrite grains are refined despite the little consumption of alloying elements [3,4]. Furthermore, cooling the plate evenly is difficult because of the large flow of cooling water.…”