Showing papers on "Microalloyed steel published in 1989"

Microstructural trapping effects on hydrogen induced cracking of a microalloyed steel

Abstract: The susceptibility of a Ti microalloyed HSLA steel to internal hydrogen induced cracking has been correlated with the hydrogen trapping character of the microstructure. Both of these properties are influenced by aging reactions which determine the type and extent of carbide precipitation as well as metalloid segregation to grain boundarie. In turn, crack path susceptibility and total trapping character determine in large part the threshold and steady-state cracking propensities. Thus, metalloid segregation concurrent with potent irreversible trap (TiC) precipitation results in low inherent toughness, but no appreciables drop in threshold stress intensity. Conversely, cementite precipitates formed at lower aging temperatures provide potent crack initiation sites in the absence of deep trapping, resulting in a lower threshold for cracking.

HAZ fracture toughness of titanium containing steels

Abstract: Steels containing various combinations of microalloying elements (Nb, V, and Ti) were welded at heat inputs from 3 to 6 kJ mm−1. It was shown by detailed crack tip opening displacement fracture toughness testing of coarse grained heat affected zone (HAZ) regions in single pass weld deposits that the poorest toughness properties were exhibited by steel containing a combination of Nb, V, and Ti. Steel microalloyed with only titanium had the best HAZ fracture toughness at all heat input levels. Detailed microstructural analysis, grain size measurement, hardness, and precipitation in HAZ regions were evaluated to explain the fracture toughness properties observed.MST/887

Microalloyed steel and process for preparing a railroad joint bar

Abstract: A microalloyed, fully killed steel has a composition, in weight percent, of from about 0.20 to about 0.45 percent carbon, from about 0.90 to about 1.70 percent manganese, from about 0.10 to about 0.35 percent silicon, from about 0.01 to about 0.04 percent aluminum, from about 0.05 to about 0.20 percent vanadium, from about 0.008 to about 0.024 percent nitrogen, balance iron. The steel is particularly useful when hot rolled to a railway joint bar section, and air cooled. The resulting joint bar meets AREA specifications in the as-rolled condition, without the need for a reheat and oil quench heat treatment after rolling.

Influence of manganese and sulphur on hot ductility of steels heated directly to temperature

Abstract: The hot ductility of normalised microalloyed steels having a variation in Mn and S content has been examined over the temperature range 700–1000°C after heating directly to the test temperature. Ductility troughs were generally found in the austenite and these became more severe on increasing the S content or decreasing the Mn content. The improvement in hot ductility on increasing the Mn content was found to be a result of grain refinement. Increasing the S content was also accompanied by grain refinement, but any improvement in the ductility associated with this refinement was offset by the detrimental effect of having a greater volume fraction of MnS inclusions at the γ boundaries, thereby promoting grain boundary sliding and cavitation. The hot ductility in the hot rolled state before normalising was also examined. Behaviour was found to be similar, but hot ductility was lower than after normalising owing to a coarser grain size.MST/1010

Carbon Equivalence and Weldability of Microalloyed Steels

Abstract: : This effort sought to determine the validity of carbon equivalent formulae to predict weldability of low carbon microalloyed steels. The HAZ of a range of steels was characterized (HSLA 80-130, HY 130, DQ and AC types) and Yuriokas formula was found to be the most accurate in predicting HAZ hardness. The CE1 carbon equivalent formula was also found to most accurately predict hardenability except that the effect of copper is not linear above 0.5%. The hydrogen sensitivity was evaluated by the Implant, Battelle and UT-Mod Hydrogen Sensitivity tests at two hydrogen levels. The lower critical stress in the implant test was used to define the critical preheat temperatures for steels evaluated. The HLSA 80 type materials may require a preheat of 150 F under highly restrained conditions with hydrogen present. HLSA 130 was found to be superior to HY 130 in regard to hydrogen cracking sensitivity. The high strength steels can be ranked in the order of increasing preheat cracking as: HSLA 100-- HSLA 130--DQ 125--HY 130 DQ 80 and AC 50 steels responded well to testing at high hydrogen levels (20ppm) and ambient temperature preheat. A soft zone was found in the HAZ of the HSLA, DQ and AC steels which was a function of weld heat input. The soft zone in the copper bearing HLSA steel could be eliminated by PWHT. A probe study showed that the HSLA steel is similar to A 1710 grades with regard to PWHT/Reheat cracking and that the HAZ toughness decrease is also similar to the A 710 grades.

State-of-The-Art of Controlled Rolling

Abstract: A discussion of published research of controlled rolling of steels is presented. Simulation of controlled rolling and industrial practice are reviewed. Some general conclusions are drawn.