Abstract: O aço de alta resistência 22MnB5 é utilizado com revestimento de alumínio-silício com o objetivo de melhorar a resistência a corrosão e desgaste em peças que favorecem o fenômeno corrosivo. Uma alternativa para a substituição do revestimento alumínio-silício é uma composição química do revestimento utilizando zinco-níquel. Neste trabalho foi estudado o processo de perda de massa nos meios corrosivos (ácido, neutro e alcalino). Foram utilizadas três variáveis: revestimento zinco-níquel como recebido, revestimento zinco-níquel estampado e zinco puro. Foi constatado que em meios ácidos (pH’s de 0 a 1) o processo de corrosão foi muito intenso para todos os materiais, do pH 3 ao 13 a perda de massa foi insignificante, havendo a proteção do material pela camada passiva. O revestimento estampado se mostrou com maior tendência a perda de massa enquanto que o revestimento como recebido se mostrou bem resistente.

Palavras-Chave: steels; gravimetric analysis; nickel; zinc; surface coating; silicon; aluminium; mass loss

COSTA, P.D.O.L.; ROSSI, J.L.; COSTA, I.; COUTO, C.P. Análise gravimétrica do revestimento de zinco-níquel de um aço 22MnB5 E zinco puro. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 23., 04-08 de novembro, 2018, Foz do Iguaçu, PR. Anais... 2018. p. 4920-4925. Disponível em: http://repositorio.ipen.br/handle/123456789/29558. Acesso em: $DATA.

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Abstract: Targeting the reduction of stamped sheet metal thicknesses, higher mechanical properties and better crash performance arise the hot stamping process as viable alternative. This is achieved by heating up a steel blank to approximately 900 ºC for the austenitization, soon after it is transferred to the hot stamping press, to be conformed and cooled, aiming a martensitic microstructure, After that, the finished part presents a tension strength about 1500 MPa. At the blank moving between furnace and press, oxidation occurs on the sheet metal surface, and Al-Si coating has been used as a good surface protection, which works against the oxidation process through a protection barrier. For corrosion analysis and a behavior evaluation of the coating subjected to climatic agents, the most trustful way is by means of the utilization of the natural weathering test, in the present case in an urban environment. It was used samples of 22MnB5 steel plates after different heat treatment conditions, achieving, in this way, weathering results based in technical standards obtained by means of light microscopy techniques.

OLIVEIRA, B.G.; CUNHA, L.F.; ABBADE, L.; COLOSIO, M.A.; ROSSI, J.L.; COUTO, C.P.; LARA, J.C.; LIMA, V.F. Characterization of Al-Si coating on press hardening steel (PHS) submitted to a natural weathering test. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 23., 04-08 de novembro, 2018, Foz do Iguaçu, PR. Resumo... 2018. p. 4947-4947. Disponível em: http://repositorio.ipen.br/handle/123456789/29561. Acesso em: $DATA.

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Abstract: The hot stamping process consists to heat the steel blank at total austenitization temperatures and to transfer it into the press tooling for forming and fast cooling to fully martensitic transformation. This transference from furnace to press stage might promote some steel oxidation. The application of coatings avoids this phenomenon. The AlSi coating, a patented process, has been the most applied on steel. Hence, alternative coatings like ZnNi are under development. It is known that this furnace heating causes chemical elements diffusion that results in intermetallics formation in the coating and in the substrate. This study has the objective of analyse the diffusion profiles of chemical elements present in the substrate and coatings of AlSi and ZnNi using glow discharge optical emission spectroscopy technique (GDOES). The results showed that the diffusion of the elements Zn and Fe is the responsible for the formation of Zn-Fe phases for those samples coated using ZnNi, besides that in the AlSi sample the diffusion of Al and Fe elements control the formation of phases which consist in Al-Fe.

Palavras-Chave: steels; aluminium oxides; silicon alloys; coatings; intermetallic compounds; glow discharges; emission spectroscopy; metals; corrosion protection; hardening; presses

COUTO, C.P.; POLITANO, R.; COSTA, P.; ROSSI, J.L. Diffusion analyses using gdoes technique of chemical elements present on 22MNB5 steel and ALSI and ZNNI coatings. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIENCIA DOS MATERIAIS, 22., 06-10 de novembro, 2016, Natal, RN. Abstract... 2016. p. 5494. Disponível em: http://repositorio.ipen.br/handle/123456789/27276. Acesso em: $DATA.

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Abstract: Studies on residual stress effect in resistance spot welding (RSW) have not been widely explored for the new ultra-high strength steels (UHSS), such as, press-hardened steel (PHS) used for the automotive industry application. The number of PHS parts has been widely increasing in the vehicle structure, due to its ultra-high tensile strength achieved after the hot stamping process, which can reach 1500 MPa. This outstanding steel properties is function of steel grade and is a guaranty for lightweight and safety. Weldability is one of major issues to allow the large product application in the automotive industry however, the numbers of papers and works with focus on PHS weldability is still small. The residual stresses in spot welded joints play an important role in affecting the durability of the joint. It is well known that the residual stresses may reduce the mechanical properties of the welding joint and contribute to hydrogen embrittlement effect. This paper has undertaken an experimental survey of residual stress on 22MnB5 - PHS steel, using X-ray diffraction technique, before any heat treatment, i.e., without hot stamping, with variation of the main welding parameters. In general, it was found that the residual stress results showed a great influence of the resistance spot welding parameters. The residual stress measures showed levels up to 300 MPa in PHS material, which can impair the material usage.

LARA, J.A.C.; COUTO, C.P.; NIZES, A.D.C.; ABBADE, L.; GONSALEZ, B.; COLOSIO, M.A.; ROSSI, J.L. Effect of resistance spot welding parameters on the residual stress of automotive ultra high strength steel. In: SENAFOR, 37th; INTERNATIONAL FORGING CONFERENCE, 21th; NATIONAL SHEET METAL FORMING CONFERENCE, 20th; INTERNATIONAL SHEET METAL FORMING CONFERENCE, 7th; BRDDRG CONGRESS, 4th; INTERNATIONAL CONFERENCE ON MATERIALS AND PROCESSES FOR RENEWABLE ENERGIES – BRAZIL/RS, 7th; INTERNATIONAL CONFERENCE ON SURFACE ENGINEERING IN MATERIAL FORMING, October 04-06, 2017, Porto Alegre, RS. Proceedings... 2017. Disponível em: http://repositorio.ipen.br/handle/123456789/34075. Acesso em: $DATA.

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Abstract: The carmakers and all their production chain must achieve worldwide targets of lightweight, safety and reduced fuel consumption. The use of ultra high strength steel, such as press-hardened steels (PHS), in vehicle structures has been contributing with this. This type of steel is widely used in hot stamping process, which consists in heating the steel blank to the total austenitization temperature, and then transferring it from the furnace into the die where the steel is deformed and quenched at the same time, with a minimum cooling rate of 27 K/s. The boron-manganese PHS steel comprises perlite and ferrite microstructure, and its tensile strength is around 600 MPa in the annealed condition. Thus, after the hot stamping process the PHS microstructure completely changes to martensite and the tensile strength increases to 1500 MPa or more. The transferring step is a critical one, due to the contact of the hot steel blank with the atmospheric air; as consequence, it causes the steel oxidation. To avoid that, the steel is protected with metallic coatings. The hot-dip AlSi is the most currently used coating for this application, however, in order to keep up with the high PHS demand, alternative coatings, like zinc-base is under investigation. This work had the objective of evaluating the corrosion resistance of PHS, 22MnB5 grade, coated with electroplated ZnNi before and after hot stamping, using scanning vibrating electrode technique (SVET). The corrosion-localized techniques are more suitable, once the results showed that after hot stamping the coating layer changes completely, as a result of chemical elements diffusion. Thus, different phases of Zn-Fe-Ni are formed and random distributed which impacts the corrosion resistance of the steel.

Palavras-Chave: corrosion resistance; surface coating; steels; ferrite; scanning electron microscopy; perlite; hardening; pressing; zinc; nickel; coatings

COUTO, C.P.; COSTA, I.; VIVEIROS, B.G. de; ALENCAR, M.C.; PANOSSIAN, Z.; ROSSI, J.L.; COLOSIO, M.A. The use of scanning vibrating electrode technique to evaluate the effect of hot stamping on corrosion resistance of press hardened steel 22MnB5 metallic coated with electroplated ZnNi. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 23., 04-08 de novembro, 2018, Foz do Iguaçu, PR. Resumo... 2018. p. 5149-5149. Disponível em: http://repositorio.ipen.br/handle/123456789/29567. Acesso em: $DATA.

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Abstract: The development of components ecologically correct is something more and more necessary. The first developement of valve seat inserts (VSI) take in account the use of cobalt and lead in its chemical composition. Such elements are avoided in the current applications due to its high cost and toxicological effects, respectively. In the present work was used VSI developed with a new chemical composition. The aim of this work were to air quench and characterize such components. The studied VSI were obtained with AISI M3:2 high-speed steel admixed with iron powder and another additives such as manganese sulphide, graphite, zinc stearate and carbides. All the air quenched VSI were double tempered, for one hour each, at seven equidistant temperature from 100 °C until 700 °C. The air quenched components had its mechanical and physical properties determined by means of its apparent density, apparent hardness and crush radial strength. The chemical composition was measured through the gases analyses and energy dispersive X-ray fluorescence spectrometry techniques. Microstructural and phase characterizations were performed with the support of optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Regarding the VSI required properties, the best results were obtained with the components air quenched and double tempered at 600 °C.

GOMES, M.P.; SANTOS, I.P.; REIS, L.A.M.; COUTO, C.P.; BETINI, E.G.; MUCSI, C.S.; COLOSIO, M.A.; ROSSI, J.L. Valve seat insert: air quenching and characterization of components obtained with AISI M3:2 high-speed steel. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 23., 04-08 de novembro, 2018, Foz do Iguaçu, PR. Resumo... 2018. p. 6228-6228. Disponível em: http://repositorio.ipen.br/handle/123456789/29600. Acesso em: $DATA.

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