Los aceros de plasticidad inducida por transformacion (TRIP) pertenecen a la familia de Aceros Avanzados de Alta Resistencia. La microestructura de estos aceros consiste en particulas de austenita retenida en una fase primaria de ferrita, existiendo tambien martensita y bainita en distintas cantidades. Cuando son sometidos a esfuerzos, la austenita retenida se transforma gradualmente en martensita. Este efecto, sumado a la distribucion de tensiones y deformaciones entre las fases, hace que los aceros TRIP presenten en general una elevada resistencia mecanica y buena conformabilidad, propiedades que en general son opuestas. Ademas presentan una alta tasa de endurecimiento por deformacion, haciendo a dichos aceros TRIP interesantes para diversas aplicaciones en ingenieria. El objetivo del presente trabajo es estudiar la obtencion de aceros TRIP a partir de un acero convencional disponible en el mercado, y con cierto contenido de silicio. Se trataron termicamente muestras a distintas temperaturas y tiempos, a fin de obtener aceros TRIP de distinto grado. Sobre cada muestra de acero TRIP obtenida, se caracterizo la microestructura, se evaluo el contenido de austenita retenida mediante difraccion de rayos X, y se determinaron las propiedades mecanicas mediante ensayos de traccion y microdureza. Se obtuvieron aceros TRIP con diferentes fracciones de ferrita, martensita, bainita y austenita retenida. Se establecieron relaciones entre dichas fracciones, las propiedades mecanicas resultantes y los parametros de tratamiento termico.

Dual-Phase steels (DP) are constituted by a ferrite matrix with a martensite fraction, giving a good combination of strength, ductility, capacity of energy absorption and strain hardening. Mechanical properties arecontrolled by martensite and ferrite fractions, martensite carbon content, grain sizes and strength of both phases. The carbon content affects the martensite hardness and the hardenability. This work studied the effect of carbon content on microstructure and mechanical properties of DP steels. Samples of steels with different carbon content were heat treated at different intercritical temperatures, obtaining DP steels with different fractionsof martensite. Microstructural characterization, microhardness and tensile test were made for each condition. Increasing carbon content and martensite fraction hardness and strength were increased. The best properties combination was reach for steels with a carbon content of 0.1 to 0.15% and 50% of martensite.Stress relationships obtained were from 1.55 to 2.25.

The objective of this work was to evaluate the influence of martensite fraction on the wear mode and the energy dissipation by friction of dual phase (DP) steel tested under reciprocating sliding conditions. For this purpose, a Ti-Nb microalloyed steel was heat treated in a conventional furnace at temperatures between 780 and 880°C (intercritical annealing temperature) for 3 min to obtain DP microstructures with volume fractions of martensite between 25 and 90%. Wear tests were carried out in both DP and as-received samples, using a reciprocating tribometer with ball-on-flat geometry, at two constant applied loads, 2.5 and 4 N. The wear damage of each sample was measured through volume loss and the dissipated energy during the test. The obtained results evidenced a significant influence of the contact load over the wear mode, because at low load the DP wear was reduced with increased hardness but just up to 75% of martensite. At high load, the sliding process promotes an oxide mixture in the ferritic microstructure that acts as a factor in wear reduction.

Dual Phase steels (DP) are part of the Advanced High Strength Steels (AHSS) family and consist in a ferritic matrix with a fraction of dispersed martensite between 5 and 50%, which gives the material a good combination of strength and ductility, with a significant capacity to absorb energy. Steel wires called in Argentina ATR500N, are used to manufacture steel welded framework, wires mesh and lattice girders for reinforcement of concrete structures and their mechanical requirements have defined in this country by the IRAM-IAS U500 526 standard. The current manufacturing process uses a wire rod of low carbon steel, hardened by cold working, producing a low ductility and low yield strength to tensile strength ratio product, although meet the requirements of the standard. The objective of the present work is to develop DP steels for ATR500N product, starting from the raw material used today and compare their mechanical properties to the commercial product. Several grades of DP steels were obtained and characterized microstructural and mechanically. Expressions of technological interest were developed, relating properties with fraction of martensite. Certain DP steels were slightly hardened by cold working and compared with the commercial ATR500N product. The DP steels developed fully satisfy the requirements of the standard and, in addition, a significantly higher elongation, hardening exponent and yield strength to tensile strength ratio. These characteristics are interesting for earth-quake resistant applications. A new manufacturing route could be developed for ATR500N product.

Dual Phase steels (DP) have been used recently as an interesting option for structural elements, specialy in automotive industry, due to weight reduce requirements. Welding of these materials becomes particularly important considering their application as structural elements and the related manufacturing methods. In particular resistance spot welding (RSW) and gas metal arc welding (GMAW) are widely used in the automotive manufacturing. The plasma arc welding (PAW) has the charateristic, within arc welding processes, to involve the highest energy density, being this parameter interesting to certain applications on automative industry (tailor welded blanks). The objective of this work is to study the microstructural evolution and properties of welded DP steels by mean of RSW, GMAW and PAW. In this regard four DP steels, with tensile strength of 550, 700 y 850 MPa and thickness of 1 and 1.3 mm, were welded by mean of mentioned welding processes. Microstructures were charaterized and mechanical properties for each weld joint were determined. For the three processes good quality welded joints were obtained. It was observed on heat affected zone (HAZ) a softened zone whose hardness is below to initial base metal hardness. This softening is related to the dissolution of the martensitic phase due to thermal cycle introduced by welding. Arc welds were the most affected.