The Structure And Properties of a Thermo‐mechanically Processed Low Carbon High Strength Steel

Abstract

Research efforts were given towards development of low carbon high strength steels since recent past. The present study deals with the development of a low carbon high strength steel alloyed with Mn, Ni, Mo, Cu and microalloyed with Ti and Nb. The steel was subjected to three stage controlled rolling operation followed by accelerated cooling. The structure and properties of the steel at various processing conditions were evaluated. Microstructural observation reveals predominantly lath martensite along with twinned martensite structure at all processing conditions. High strength values at higher finish rolling temperatures have been obtained due to fine martensitic structure along with tiny precipitates of microalloying carbide and carbonitride. The strength value increases marginally at lower finishing temperature due to comparatively finer lath size of martensite and increased precipitation density of carbides, carbonitrides along with Cu particles. The variation in impact toughness properties at different finish rolling temperatures is found to be negligible at ambient and subambient temperatures. The formation of stable and large TiNmCN particles during casting have impaired the impact toughness values at ambient and at -40°C temperatures.Keywords: high strength steel, thermo-mechanical processing, twinned martensite, microalloying precipitate, toughness steel research into 77 (2006) No. 4

Use of the Aging Effect to Change the Local Properties of Structure Components

“…19(a). The dominant martensite morphology of low carbon steel grades like DP steels is of lath type, which is characterised by a high dislocation density [42][43], leading to a strong contrast in the TEM micrograph as can be seen in Fig. 19(b).…”

Ageing behavior of a Cu-bearing ultrahigh strength steel

“…Recently, a development of a new category low carbon microalloyed ultrahigh strength type steels has been reported by the present author [12][13][14][15]. These are copper bearing steels and ultrahigh strength properties have been achieved by newer alloy design and controlled thermomechanical processing.…”

Local Laser Heat Treatment in Dual-Phase Steels

“…The bright grains can be clearly identified as the ferrite phase, while the dark ones are attributed to martensite (Figure 7(a)). The dominant martensite morphology of low carbon steel grades such as DP steels is of lath type, which is characterized by a high dislocation density, [34,35] leading to a strong contrast in the TEM micrograph, as can be seen in Figure 7(b). The most affected areas of ferrite were in the vicinity of martensite crystals (Figure 7(b)).…”