In the last two decades, the significant market demands for microalloyed steels have led to enormous efforts as regards the optimization of their properties. Following a national research program, the present work was scheduled to deal with a special grade of V-microalloyed steel. This grade was examined after a series of successive isothermal heat treatment to produce a variety of phase combinations (e.g., ferritic-martensitic, ferritic-martensitic-bainitic and ferritic-bainitic microstructures). Tensile and impact tests were performed to gain knowledge about the mechanical properties. The resulting microstructures were evaluated by means of SEM and optical microscopy. The results indicated that the corresponding tensile behaviour of the steels was strongly affected by microstructure and heat treatment parameters. Furthermore, the related ultimate tensile strength and impact values were broadly varied (750 to 1200 MPa and 5 J to 40 J, respectively) by the steels´ microstructure and chemical composition. The corresponding fracture surfaces were found to vary with the steel´s microstructure.

The influence of accelerated cooling and coiling temperature is studied in a microalloyed steel grade in order to investigate the strengthening owing to phase transformation in the presence of microalloying elements. A Nb-V microalloyed steel grade was deformed in the austenitic range followed by controlled quenching to simulate rolling and runout table cooling conditions. Cooling rate was varied from 100 to 150 °C/sec, while coiling temperatures were varied between 475 to 625 °C, with 25 °C step. Decrease in transformation temperature in conjunction with accelerated cooling resulted in non-equiaxed ferrite structures with array of phase morphologies. Intermediate transformation temperatures produced increase in strength concurrent with observed peak broadening in X-ray diffraction. In addition, microstructural modelling is done using Quench properties module of JMatPro under experimental conditions.

Dry sliding adhesive wear behaviour of as-cast and austempered ductile iron (ADI) samples alloyed with manganese and copper was investigated in a pin-on-disc wear testing machine. As-cast samples suffered a rapid and continuous wear, while the austempered samples exhibited improved wear resistance on increasing the austempering temperature and time. ADI samples with higher copper plus manganese contents inherently possessed higher hardness due to presence of martensite in the ausferrite matrix. The wear conditions used in the present
study further promoted the formation of martensite under wear load and contributed much improved wear performance. In ADIs containing manganese only, wear process involved a mixed mechanism of oxidation and delamination. On combined alloying with copper and manganese, wear resistance increased considerably showing only mild oxidation and practically no delamination. The combinedly alloyed austempered samples exhibited even better wear resistance than that of cast and heat treated high manganese steel. Thus, the addition of manganese and copper in the experimental ductile irons assisted austempering by virtue of their synergistic effect on hardenability of Fe-C alloys and improving wear resistance through subsequent work hardening of the wear surface.

Steel enjoys an unsurpassed wide range of properties: first of all its stiffness-strength-formability relationship contributes to featuring steel a high potential as versatile light-weight construction material. In this respect it pays to use steel, its price cannot be undercut without accepting compromises. This is topped by additional gains comprising high availability, reliability, excellent manufacturability and recyclability. Steel enjoys great popularity amongst designers, most of them are very familiar with it. In intermaterial competition, steel may not win in every single discipline, but steel is the undisputed champion in multi-discipline jobs. This makes steel an indispensable material.

High nitrogen steels are commonly known for their excellent mechanical properties, i.e. strength and corrosion resistance. A state-of-the-art production routine is P-ESR melting (pressurised electro slag remelting). It is possible to manufacture both, austenitic as well as martensitic steels suitable for forging and hot rolling. Some basic knowledge of the material peculiarities is mandatory to avoid any potential issues during plastic deformation. The following paper provides an overview of the manufacturing of HNS as well as some properties to be considered for plastic deformation.

news in steel

Quick and successful turnaround for an effective rolling process

Following the successful commissioning of the upgraded bar mill at its Basauri location, Spanish company SIDENOR ACEROS ESPECIALES, S.L. has issued the final acceptance certificate (FAC) to SMS group (www.sms-group.com).

SSAB Form Tube Plus – new precision steel tubes with superior properties

SSAB Form Tube Plus is a completely new family of precision steel tubes that provides a unique combination of bendability, dimensional accuracy and superior surface quality suitable for high-gloss painting and chrome plating.

Profiling aluminum vacuum brazing furnaces

Fluke Process Instruments provides a dedicated temperature profiler for aluminum vacuum brazing furnaces. The Datapaq Furnace Tracker system automatically generates CQI-9 and AMS 2750E reports.

Daehan Sinpyeong upgrades rolling mill with new quenching and HSD® lines

South-Korean Daehan Steel Co. Ltd. is modernizing a bar mill . The rolling mill in Daehan´s Sinpyeong works located in the Busan area is designed to produce 130 tons per hour of rebar in diameters from 16 to 32 millimeters up to grade SD 500.