Desenvolvimento de procedimentos para o reparo por solda do aço AISI P 20 utilizado em matrizes de injeção termoplástica
Carregando...
Data
2019-02-28
Autores
Ferraz, Nilson Aneas
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Matrizes de injeção de termoplásticos são de elevado custo, o que requer atenção em sua fabricação e utilização. Durante a fabricação de uma matriz e ao longo de sua vida útil, erros processuais, tais como usinagem em lugar não exigido pelo projeto ou quebras de fechamentos das matrizes, podem inutilizá-la. Para o reparo dos moldes, geralmente é utilizado o processo de soldagem TIG (Tungsten Inert Gas). Contudo, processos de soldagem em geral deixam marcas e ondulações no aço reparado que refletem na qualidade da resina termoplástica a ser injetada. Visando recuperar moldes de aço inutilizados, buscou-se realizar reparos de solda em que tais descontinuidades não apareçam. Este trabalho tem como objetivos apresentar as análises das alterações macro e microestruturais provenientes de reparos de solda aplicados no aço AISI P20 utilizado na fabricação de moldes. Para tanto, foram aplicadas duas condições de reparos: 1°) sendo as amostras “a”, “b” e “c”, soldagem com metal de adição dissimilar (AWS A5.18 ER 80s-b2) com e sem as aplicações de tratamentos térmicos pós-solda de recozimento, têmpera e revenimento, respectivamente, e 2°) sendo as amostras “d” e “e”, soldagem com metal de adição da mesma composição química (AISI P20) com tratamentos térmicos pós-solda de recozimento, têmpera e revenimento, respectivamente. Após, com os melhores resultados dos itens apontados anteriormente, foi feito em uma amostra de maior dimensão um reparo de solda seguido dos tratamentos térmicos e texturização fotoquímica, a fim se saber se haveria a possibilidade da presença de marcas de solda. Os resultados indicaram que a utilização dos tratamentos térmicos de recozimento, têmpera e revenimento alteraram a microestrutura das regiões soldadas, porém não deixaram marcas ou ondulações do metal de solda e da zona afetada pelo calor, aproximando a dureza dessas regiões à do metal-base. Com isso, pode-se concluir que os objetivos foram alcançados, pois achou-se entre as quatro condições mencionadas uma que apresentou uma solda onde não foi possível encontrar vestígios da mesma, mesmo com o ataque fotoquímico.
Thermoplastic injection molds are of high cost, which requires attention in their manufacture and use. During the fabrication of a die and over its useful life, procedural errors such as machining in place not required by the design or breakages of die closures may render it unusable. For the repair of the molds, the TIG (Tungsten Inert Gas) welding process is usually used. However, welding processes generally leave marks and undulations on the repaired steel which reflect on the quality of the thermoplastic resin to be injected. To recover unused steel molds, we sought to carry out weld repairs in which such discontinuities do not appear. The objective of this work is to present the macro and microstructural alterations from weld repairs applied to AISI P20 steel used in the manufacture of molds. In order to do this, two repair conditions were applied: 1) with samples "a", "b" and "c", welding with dissimilar addition metal (AWS A5.18 ER 80s-b2) with and without the applications of annealing, tempering and annealing, respectively, and 2 °), the samples being "d" and "e", welding with addition metal of the same chemical composition (AISI P20) with heat treatments after annealing of annealing, tempering and tempering, respectively. Then, with the best results of the previously mentioned items, a weld repair was done in a larger sample followed by thermal treatments and photochemical texturization, to know if there would be the possibility of the presence of weld marks. The results indicated that the annealing, tempering and tempering treatments altered the microstructure of the welded regions but did not leave marks or undulations of the weld metal and the zone affected by the heat, approaching the hardness of these regions to that of the base metal. With this, it can be concluded that the objectives were reached, as it was found among the four mentioned conditions one that presented a weld where it was not possible to find traces of it, even with the photochemical attack.
Thermoplastic injection molds are of high cost, which requires attention in their manufacture and use. During the fabrication of a die and over its useful life, procedural errors such as machining in place not required by the design or breakages of die closures may render it unusable. For the repair of the molds, the TIG (Tungsten Inert Gas) welding process is usually used. However, welding processes generally leave marks and undulations on the repaired steel which reflect on the quality of the thermoplastic resin to be injected. To recover unused steel molds, we sought to carry out weld repairs in which such discontinuities do not appear. The objective of this work is to present the macro and microstructural alterations from weld repairs applied to AISI P20 steel used in the manufacture of molds. In order to do this, two repair conditions were applied: 1) with samples "a", "b" and "c", welding with dissimilar addition metal (AWS A5.18 ER 80s-b2) with and without the applications of annealing, tempering and annealing, respectively, and 2 °), the samples being "d" and "e", welding with addition metal of the same chemical composition (AISI P20) with heat treatments after annealing of annealing, tempering and tempering, respectively. Then, with the best results of the previously mentioned items, a weld repair was done in a larger sample followed by thermal treatments and photochemical texturization, to know if there would be the possibility of the presence of weld marks. The results indicated that the annealing, tempering and tempering treatments altered the microstructure of the welded regions but did not leave marks or undulations of the weld metal and the zone affected by the heat, approaching the hardness of these regions to that of the base metal. With this, it can be concluded that the objectives were reached, as it was found among the four mentioned conditions one that presented a weld where it was not possible to find traces of it, even with the photochemical attack.
Descrição
Palavras-chave
Reparo, Aço aisi p20, Matrizes de injeção de termoplásticos, TIG, Repair, AISI p20 steel, Thermoplastic Injection plastic molds, TIG, Aço de alta resistência, Termoplásticos, Soldagem