Barbosa C.A.,Villares Metals SA |
Goldenstein H.,University of Sao Paulo
Journal of ASTM International | Year: 2011
Recent literature has shown several papers dealing with cryogenic treatments of tool steels. Most of them see an improvement in wear resistance supposedly due to microstructural modifications that occur at cryogenic temperatures. Cryogenic treatments are supposed to modify the way secondary carbides precipitate, obtaining a finer and more homogeneous distribution. Specimens of an AISI D2 tool steel were submitted to different thermal cycles, including cryogenic treatment, and the volumetric fraction of micrometric carbides was determined. The samples were analyzed by scanning electron microscopy and the image analysis was carried out with Image J software. The present work also discusses what is understood about secondary carbides and the modifications that occur with micrometric (from the austenite-carbide field) and nanometric (from the temper of martensite) secondary carbides. No difference was found between the micrometric carbide with and without cryogenic treatment, while some indications were found that the nanometric carbides are refined and more homogeneously distributed after cryogenic treatment. Copyright © 2011 by ASTM International.
Mesquita R.A.,Nove de Julho University |
Barbosa C.A.,Villares Metals SA |
Morales E.V.,Santa Clara University |
Kestenbach H.-J.,Federal University of São Carlos
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2011
The formation of secondary carbides during tempering of H11 hot work steels at 898 K (625 °C) was studied by transmission electron microscopy (TEM) and related to the previously established effects of Si content on mechanical properties. Lower Si contents (0.05 and 0.3 pct Si) and higher Si contents (1.0 and 2.0 pct Si) were observed to yield different carbide phases and different particle distributions. Cementite particles stabilized by Cr, Mo, and V in the lower Si steels were found to be responsible for similar precipitation hardening effects in comparison to the M2C alloy carbides in the higher Si steels. The much higher toughness of the lower Si steels was suggested to be due to a finer and more homogeneous distribution of Cr-rich M7C 3 carbides in the interlath and interpackage regions of the quenched and tempered martensite microstructure. The present effects of Si content on the formation of alloy carbides in H11 hot work steels were found to be the result of the retarding effect of Si on the initial formation of cementite, well known from the early tempering stages in low alloy steels. © 2010 The Minerals, Metals & Materials Society and ASM International.
Villares Metals SA, Barbosa and Mesquita | Date: 2012-09-26
STEEL WITH HIGH TEMPERING RESISTANCE, characterized by a composition of alloying elements consisting essentially of, in percent by mass, C between 0.20 and 0.50, Si lower than 1.0, P lower than 0.030, Cr between 3.0 and 4.0, Mo between 1.5 and 4.0, V between 0.1 and 2.0, Co lower than 1.5, being the remaining composed of Fe and inevitable deleterious substances. The steel is produced by processes involving ingot casting and hot/cold forming, or used with the cast structure; or by processes involving atomization or dispersion of the molten metal, such as powder metallurgy, powder injection or spray forming.
Jaimes R.F.V.V.,University do Grande |
Afonso M.L.C.d.A.,Technological and Nuclear Institute of Portugal |
Rogero S.O.,Brazilian Nuclear Energy Research Institute (IPEN) |
Agostinho S.M.L.,University of Sao Paulo |
Barbosa C.A.,Villares Metals SA
Materials Letters | Year: 2010
Nickel, a component of stainless steels (SS) applied in orthopedic implants may cause allergic processes in human tissues. P558 nickel free SS was studied to verify its viability as a substitute for stainless steel containing nickel. Its performance is compared to ISO 5832-9 and F138 most used nowadays grades in implants fabrications, in minimum essential medium, MEM, at 37 °C. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and "in vitro" cytotoxicity were used as techniques. From the electrochemical point of view P558 SS is comparable to ISO 5832-9 SS in MEM. It remains passivated until the transpassivation potential, above which generalized corrosion occurs. F138 presents pitting corrosion at 370 mV/SCE. The cytotoxicity results showed that P558, ISO 5832-9 and F138 do not present cytotoxic character. Therefore, these results suggest that P558 SS can be applied in orthopedic implants. © 2010 Elsevier B.V. All rights reserved.
Development of UNS S 32760 super-duplex stainless steel produced in large diameter rolled bars [Desenvolvimento do aço inoxidável super-duplex UNS S 32760 produzido em barras laminadas de grande diâmetro]
Barbosa C.A.,Villares Metals SA |
Sokolowski A.,Villares Metals SA
Revista Escola de Minas | Year: 2013
Nowadays super-duplex stainless is an important material for the Oil and Gas industries, especially for off-shore production. In deep water exploitation the reliability of production system is very important. Corrosion resistance for pitting of the high alloyed duplex stainless steels with high Mo and N content has to be achieved even in large diameters bars. Therefore, the present work deals with an improved super-duplex stainless steel for the production of large diameter rolled 6bars up to 152.40 mm (6 inches). Among the main improvements, the corrosion resistance evaluated both by the chemical method according to the ASTM G-48 method, as well as electrochemical methods, was achieved. During the production of such large dimensions, the precipitation of inter-metallics and nitrides after cooling from high temperatures was studied by changing the chemical composition using Thermo-Calc and evaluating the new proposed chemical compositions. Several alloy compositions were laboratory scale cast, and the austenite/ferrite balance as well as PREN pitting resistance equivalent number content was correlated to the microstructure and the corrosion properties obtained. It was thus possible to determine the ideal chemical composition and define the new processing parameters to produce the UNS S32760 grade (4501) according to the Norsok standard. The new material properties produced in a production full scale heat are also presented.
Farina A.B.,Villares Metals SA |
Liberto R.C.N.,Villares Metals SA |
Barbosa C.A.,Villares Metals SA
SAE Technical Papers | Year: 2013
UNS N07751 and UNS N07080 alloys are commonly applied for automotive valve production for high performance internal combustion engines. These alloys present high hot resistance to mechanical strength, oxidation, corrosion, creep and microstructural stability. However, these alloys present low wear resistance and high cost due to the high nickel contents. In this work it is presented the development of two new nickel intermediate alloys for application in automotive high performance valves that are alternatives to the alloys UNS N07751 and UNS N07080. The new developed alloys are based on a high nickel chromium austenitic matrix with dispersion of and phases and containing different NbC contents. Due to the nickel content reduction in the developed alloys in comparison with the current used alloys, the new alloys present an economical advantage for substitution of these traditional Ni-based alloys, once the new alloys present similar to better properties than UNS N07751 and UNS N07080 alloys. Copyright © 2013 SAE International.
Villares Metals SA | Date: 2013-01-16
The present invention relates to a steel for extrusion tools characterized for lower cost and tempering resistance higher than that of conventional steel H13, whose chemical composition, in percentage by mass, comprises the following: Carbon between 0.40 and 0.60, Silicon below 1.0, Phosphorus below 0.030; Chromium between 2.5 and 4.5; Molybdenum between 0.5 and 0.7, considering that molybdenum can be replaced by tungsten in a ratio = 2W/1Mo; Vanadium between 0.10 and 1.0; Manganese below 1.0; the remainder consisting essentially of Fe and inevitable deleterious substances. As an option to provide high hardness after nitriding, the Al content of the steel of the present invention can bye 1.0; for high toughness purposes, however, this Al content should be kept below 0.10.
Villares Metals SA | Date: 2010-04-08
1BAINITIC STEEL FOR MOULDS, with a composition of alloy elements that consist, in mass percentage, of Carbon between 0.05 and 1.0; Manganese between 0.5 and 3.0; Phosphorous, Boron, Titanium and Vanadium given by the ratio NU=[Ti+P+10B+(V0.10)], being the values of NU between 0.02 and 0.30, with titanium always above 0.005, boron always below 0.010 and Vanadium may be partially or totally replaced with Niobium, in the proportion of two parts in mass of niobium for one part of Vanadium; Nickel, Molybdenum and Chromium given by the ratio G=[0.13Ni+0.60Mo+0.26Cr], with values of G above 0.10 and below 1.0; Sulphur up to 0.10; Silicon between 0.05 and 3.0; Nitrogen below 0.10; Calcium with contents up to 0.02; Aluminum below 0.5, Cobalt lower than 2.0, the remaining being substantially Iron and impurities that cannot be avoided in the elaboration process; for its production the final hardness may be obtained by calm air cooling, directly after hot conformation or by previous heating in furnace, even in blocks with section up to 1000 mm; the values of hardness, in Vickers scale, are defined by the equation: HV=(450140) % C+(21045), for values between 280 and 450 HV (30 to 45 HRC); for applications of high toughness, the steel of present invention may also be produced with quick cooling, from temperatures above 900 C., in water or oil mediums.
Villares Metals SA | Date: 2013-02-13
1 BAINITIC STEEL FOR MOULDS, with a composition of alloy elements that consist, in mass percentage, of Carbon between 0.05 and 1.0; Manganese between 0.5 and 3.0; Phosphorous, Boron, Titanium and Vanadium given by the ratio NU = [Ti + P + 10 B + (V-0.10)], being the values of NU between 0.02 and 0.30, with titanium always above 0.005, boron always below 0.010 and Vanadium may be partially or totally replaced with Niobium, in the proportion of two parts in mass of niobium for one part of Vanadium; Nickel, Molybdenum and Chromium given by the ratio G = [0.13 Ni + 0,60 Mo + 0.26 Cr], with values of G above 0.10 and below 1.0; Sulphur up to 0.10; Silicon between 0.05 and 3.0; Nitrogen below 0.10; Calcium with contents up to 0.02; Aluminum below 0.5, Cobalt lower than 2.0, the remaining being substantially Iron and impurities that cannot be avoided in the elaboration process; for its production the final hardness may be obtained by calm air cooling, directly after hot conformation or by previous heating in furnace, even in blocks with section up to 1000 mm; the values of hardness, in Vickers scale, are defined by the equation: HV = (450 140) %C + (210 45), for values between 280 and 450 HV (30 to 45 HRC); for applications of high toughness, the steel of present invention may also be produced with quick cooling, from temperatures above 900C, in water or oil mediums.
Villares Metals SA | Date: 2012-09-26
STAINLESS MOLD STEEL WITH LOWER DELTA-FERRITE CONTENT, characterized by a composition of alloying elements consisting essentially of, in percentage by mass, Carbon between 0.01 and 0.20; Nitrogen between 0.01 and 0.07; Manganese between 2.0 and 4.0; Nickel between 0.01 and 1.0; Chromium between 11.0 and 13.0; Molybdenum + Tungsten lower than 1.0; Copper between 0.01 and 1.5; Vanadium between 0.01 and 1.0; Sulfur between 0.01 and 0.20; Calcium at maximum 0.01; Aluminum lower than 0.05; Silicon lower than 1.0; the remainder consisting essentially of Fe and inevitable impurities to the preparation process.