{"id":24965,"date":"2026-11-04T13:06:41","date_gmt":"2026-11-04T05:06:41","guid":{"rendered":"https:\/\/aobosteel.com\/?page_id=24965"},"modified":"2026-11-04T13:17:50","modified_gmt":"2026-11-04T05:17:50","slug":"4340-steel-properties","status":"publish","type":"page","link":"https:\/\/aobosteel.com\/pt\/4340-steel-properties\/","title":{"rendered":"A\u00e7o 4340: Propriedades, Dureza e Tratamento T\u00e9rmico"},"content":{"rendered":"<h1 id=\"h-4340-steel-properties\" class=\"wp-block-heading has-large-font-size\">A\u00e7o 4340: Propriedades, Dureza e Tratamento T\u00e9rmico<\/h1>\n\n\n\n<h2 id=\"h-what-is-4340-steel\" class=\"wp-block-heading\">O que \u00e9 o A\u00e7o 4340?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">O 4340 \u00e9 um a\u00e7o liga n\u00edquel-cromo-molibd\u00eanio de m\u00e9dio carbono (AISI\/SAE 4340). Pertence aos a\u00e7os estruturais de ultra-alta resist\u00eancia e \u00e9 valorizado pela temperabilidade profunda, alta tenacidade em alta resist\u00eancia e forte desempenho em fadiga. Pe\u00e7as t\u00edpicas s\u00e3o trens de pouso de aeronaves, eixos e semi-eixos de servi\u00e7o pesado, engrenagens, virabrequins e outros componentes que suportam alta tens\u00e3o em se\u00e7\u00f5es espessas.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">O n\u00edquel \u00e9 o que o diferencia de um a\u00e7o cromo-molibd\u00eanio como o 4140. Entre 1,65 e 2,00 por cento, o n\u00edquel eleva a tenacidade, atua com o cromo e o molibd\u00eanio para aprofundar a temperabilidade na se\u00e7\u00e3o e mant\u00e9m propriedades de impacto \u00fateis em baixa temperatura.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Um ponto \u00e9 importante para a sele\u00e7\u00e3o de material: o 4340 \u00e9 um a\u00e7o estrutural liga, n\u00e3o um a\u00e7o ferramenta. Ele n\u00e3o \u00e9 projetado para a resist\u00eancia ao desgaste ou dureza a quente que o trabalho de matrizes e corte exige. Se voc\u00ea est\u00e1 escolhendo material para uma matriz, pun\u00e7\u00e3o ou ferramenta de trabalho a quente, a compara\u00e7\u00e3o com a\u00e7os ferramenta mais abaixo \u00e9 a relevante.<\/p>\n\n\n\n<div class=\"wp-block-buttons is-layout-flex wp-block-buttons-is-layout-flex\">\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link wp-element-button\" href=\"https:\/\/aobosteel.com\/wp-content\/uploads\/2026\/11\/AISI-4340-Reference-Card.pdf\" download>Baixar a ficha do 4340, 412 KB<\/a><\/div>\n<\/div>\n\n\n\n<h2 id=\"h-4340-at-a-glance\" class=\"wp-block-heading\">4340 em Resumo<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Propriedade<\/td><td>4340 T\u00edpico<\/td><td>O que isso significa na pr\u00e1tica<\/td><\/tr><tr><td>Steel type<\/td><td>A\u00e7o liga n\u00edquel-cromo-molibd\u00eanio<\/td><td>Ultra-alta resist\u00eancia em se\u00e7\u00f5es pesadas<\/td><\/tr><tr><td>Dureza recozida<\/td><td>217 HB<\/td><td>A condi\u00e7\u00e3o da barra \u00e9 normalmente usinada<\/td><\/tr><tr><td>Dureza ap\u00f3s t\u00eampera<\/td><td>58 HRC a 13 mm, 53 HRC a 100 mm<\/td><td>Mant\u00e9m a dureza profundamente na se\u00e7\u00e3o<\/td><\/tr><tr><td>Dureza de trabalho<\/td><td>24 a 53 HRC ap\u00f3s revenimento<\/td><td>A temperatura de revenimento define o n\u00edvel<\/td><\/tr><tr><td>T\u00eampera total<\/td><td>T\u00eampera em \u00f3leo at\u00e9 75 mm, em \u00e1gua para se\u00e7\u00f5es maiores<\/td><td>A t\u00eampera em \u00e1gua aumenta o risco de trincas<\/td><\/tr><tr><td>Usinabilidade<\/td><td>Cerca de 50 por cento do AISI 1212 a 187 a 241 HB<\/td><td>Menor que o 4140 por causa do n\u00edquel<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 id=\"h-chemical-composition\" class=\"wp-block-heading\">Composi\u00e7\u00e3o Qu\u00edmica<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Elemento<\/td><td>AISI 4340<\/td><td>JIS SNCM 439<\/td><td>GB 40CrNiMoA<\/td><\/tr><tr><td>Carbon (C)<\/td><td>0.38\u20130.43<\/td><td>0.36\u20130.43<\/td><td>0.37\u20130.44<\/td><\/tr><tr><td>Mangan\u00eas (Mn)<\/td><td>0.60\u20130.80<\/td><td>0.60\u20130.90<\/td><td>0.50\u20130.80<\/td><\/tr><tr><td>Sil\u00edcio (Si)<\/td><td>0.15\u20130.35<\/td><td>0.15\u20130.35<\/td><td>0.17\u20130.37<\/td><\/tr><tr><td>N\u00edquel (Ni)<\/td><td>1.65\u20132.00<\/td><td>1.60\u20132.00<\/td><td>1.25\u20131.65<\/td><\/tr><tr><td>Cromo (Cr)<\/td><td>0.70\u20130.90<\/td><td>0.60\u20131.00<\/td><td>0.60\u20130.90<\/td><\/tr><tr><td>Molibd\u00eanio (Mo)<\/td><td>0.20\u20130.30<\/td><td>0.15\u20130.30<\/td><td>0.15\u20130.25<\/td><\/tr><tr><td>F\u00f3sforo (P)<\/td><td>0,035 m\u00e1x.<\/td><td>0,030 m\u00e1ximo<\/td><td>0,035 m\u00e1x.<\/td><\/tr><tr><td>Enxofre (S)<\/td><td>0,040 m\u00e1ximo<\/td><td>0,030 m\u00e1ximo<\/td><td>0,035 m\u00e1x.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Valores em porcentagem. O grau de forno el\u00e9trico E4340 usa as mesmas faixas com residuais mais restritos, f\u00f3sforo e enxofre a 0,025 m\u00e1x cada, e mangan\u00eas a 0,65 a 0,85. \u00c9 a vers\u00e3o especificada onde inclus\u00f5es e vida em fadiga importam, como forjados aeroespaciais.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A faixa de n\u00edquel \u00e9 o n\u00famero a verificar quando um cliente pede 4340 e a usina oferece 40CrNiMoA. Com 1,25 a 1,65 por cento de n\u00edquel, o grau chin\u00eas fica no limite inferior da faixa do 4340, ent\u00e3o uma se\u00e7\u00e3o pesada pode n\u00e3o atingir a dureza que o desenho pressup\u00f5e, mesmo que cada elemento esteja dentro de sua pr\u00f3pria faixa.<\/p>\n\n\n\n<h2 id=\"h-tempering-response\" class=\"wp-block-heading\">Resposta ao Revenimento e Propriedades Mec\u00e2nicas<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">O 4340 atinge resist\u00eancia muito alta mantendo tenacidade utiliz\u00e1vel, e esse equil\u00edbrio \u00e9 sua propriedade definidora. A tabela abaixo \u00e9 a resposta padr\u00e3o ao revenimento para o 4340 temperado em \u00f3leo, mantido na temperatura por pelo menos duas horas.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Revenimento<\/td><td>Resist\u00eancia, MPa (tra\u00e7\u00e3o \/ escoamento)<\/td><td>Dureza HB (HRC)<\/td><td>Impacto Izod, J<\/td><\/tr><tr><td>205 \u00b0C<\/td><td>1980 \/ 1860<\/td><td>520 (53)<\/td><td>20<\/td><\/tr><tr><td>315 \u00b0C<\/td><td>1760 \/ 1620<\/td><td>490 (50)<\/td><td>14<\/td><\/tr><tr><td>425 \u00b0C<\/td><td>1500 \/ 1365<\/td><td>440 (46)<\/td><td>16<\/td><\/tr><tr><td>540 \u00b0C<\/td><td>1240 \/ 1160<\/td><td>360 (39)<\/td><td>47<\/td><\/tr><tr><td>650 \u00b0C<\/td><td>1020 \/ 860<\/td><td>290 (31)<\/td><td>100<\/td><\/tr><tr><td>705 \u00b0C<\/td><td>860 \/ 740<\/td><td>250 (24)<\/td><td>102<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Leia a coluna de impacto, n\u00e3o apenas a dureza. Entre 205 \u00b0C e 540 \u00b0C a dureza cai cerca de 160 HB enquanto a energia absorvida mais que dobra, raz\u00e3o pela qual o 4340 \u00e9 especificado onde uma pe\u00e7a deve suportar choque em alta resist\u00eancia.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Dois efeitos de fragiliza\u00e7\u00e3o importam ao revenir o 4340:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Fragiliza\u00e7\u00e3o por martensita revenida<\/strong> \u2014 queda de propriedades na faixa de 230 a 370 \u00b0C, onde a tenacidade ao impacto cai enquanto a dureza ainda parece saud\u00e1vel.<\/li>\n\n<li><strong>Fragiliza\u00e7\u00e3o por revenido revers\u00edvel<\/strong> \u2014 resfriamento lento atrav\u00e9s de aproximadamente 375 a 575 \u00b0C ap\u00f3s revenimento a alta temperatura permite a segrega\u00e7\u00e3o de f\u00f3sforo nos contornos de gr\u00e3o austen\u00edtico pr\u00e9vios. Resfriamento r\u00e1pido e revenimento duplo limitam isso; o molibd\u00eanio no 4340 reduz, mas n\u00e3o elimina, a sensibilidade.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Devido ao segundo efeito, o revenimento abaixo de 455 \u00b0C n\u00e3o \u00e9 recomendado para o 4340 onde a pe\u00e7a sofre carregamento de impacto ou fadiga. Onde a resist\u00eancia m\u00e1xima \u00e9 o requisito, como em alguns componentes de aeronaves, a janela de baixa temperatura \u00e9 usada com revenimento duplo e um processo qualificado.<\/p>\n\n\n\n<h2 id=\"h-hardenability\" class=\"wp-block-heading\">Temperabilidade e Tamanho da Se\u00e7\u00e3o<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A temperabilidade profunda \u00e9 a raz\u00e3o pela qual os engenheiros recorrem ao 4340 em vez de a\u00e7os liga mais simples. A t\u00eampera em \u00f3leo endurece se\u00e7\u00f5es redondas at\u00e9 75 mm de di\u00e2metro; se\u00e7\u00f5es maiores precisam de t\u00eampera em \u00e1gua, o que aumenta o risco de trincas. Graus mais simples como o 4140 endurecem bem em barras pequenas, mas amolecem no n\u00facleo de se\u00e7\u00f5es pesadas.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Di\u00e2metro da barra, temperada em \u00f3leo<\/td><td>Dureza superficial HRC<\/td><td>Dureza HB<\/td><\/tr><tr><td>13 mm (0.5 in)<\/td><td>58<\/td><td>614<\/td><\/tr><tr><td>25 mm (1 in)<\/td><td>57<\/td><td>596<\/td><\/tr><tr><td>50 mm (2 in)<\/td><td>56<\/td><td>577<\/td><\/tr><tr><td>100 mm (4 in)<\/td><td>53<\/td><td>528<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">A perda nessa faixa \u00e9 de cerca de 5 HRC. Fa\u00e7a a mesma compara\u00e7\u00e3o no 4140 e a queda fica mais pr\u00f3xima de 8 HRC, com o n\u00facleo caindo muito mais r\u00e1pido ap\u00f3s 75 mm, que \u00e9 a diferen\u00e7a pr\u00e1tica entre os dois graus.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ap\u00f3s o revenimento, a vantagem se mant\u00e9m. Temperadas em \u00f3leo e revenidas a 425 \u00b0C, barras de 4340 de 13, 38 e 75 mm mant\u00eam 1460, 1450 e 1420 MPa. Temperadas em \u00e1gua e revenidas a 650 \u00b0C, barras de 75, 100 e 150 mm mant\u00eam 1055, 1035 e 1000 MPa a 340, 330 e 322 HB.<\/p>\n\n\n\n<h2 id=\"h-equivalent-grades\" class=\"wp-block-heading\">graus equivalentes<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Padr\u00e3o<\/td><td>Grau<\/td><td>Composi\u00e7\u00e3o qu\u00edmica, C \/ Mn \/ Si \/ Cr \/ Ni \/ Mo<\/td><\/tr><tr><td>ASTM A29\/A29M-03<\/td><td>4340 (G43400)<\/td><td>0.38\u20130.43 \/ 0.60\u20130.80 \/ 0.15\u20130.35 \/ 0.70\u20130.90 \/ 1.65\u20132.00 \/ 0.20\u20130.30<\/td><\/tr><tr><td>ASTM A29\/A29M-03<\/td><td>E4340 (G43406)<\/td><td>0.38\u20130.43 \/ 0.65\u20130.85 \/ 0.15\u20130.35 \/ 0.70\u20130.90 \/ 1.65\u20132.00 \/ 0.20\u20130.30<\/td><\/tr><tr><td>SAE J404 JUN00<\/td><td>4340 (G43400)<\/td><td>0.38\u20130.43 \/ 0.60\u20130.80 \/ 0.15\u20130.35 \/ 0.70\u20130.90 \/ 1.65\u20132.00 \/ 0.20\u20130.30<\/td><\/tr><tr><td>JIS G4053:2003<\/td><td>SNCM 439<\/td><td>0.36\u20130.43 \/ 0.60\u20130.90 \/ 0.15\u20130.35 \/ 0.60\u20131.00 \/ 1.60\u20132.00 \/ 0.15\u20130.30<\/td><\/tr><tr><td>GB (China)<\/td><td>40CrNiMoA<\/td><td>0.37\u20130.44 \/ 0.50\u20130.80 \/ 0.17\u20130.37 \/ 0.60\u20130.90 \/ 1.25\u20131.65 \/ 0.15\u20130.25<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">DIN 1.6565 (40NiCrMo6) e BS 817M40 (EN24) pertencem \u00e0 mesma fam\u00edlia e s\u00e3o as designa\u00e7\u00f5es mais frequentemente citadas ao lado do 4340 na Europa. S\u00e3o graus aproximados, n\u00e3o pe\u00e7as intercambi\u00e1veis: a faixa de n\u00edquel, o limite de enxofre e a faixa de temperabilidade variam entre normas, e um grau que atende \u00e0 composi\u00e7\u00e3o qu\u00edmica ainda pode n\u00e3o atingir a dureza na se\u00e7\u00e3o considerada no desenho.<\/p>\n\n\n\n<h2 id=\"h-heat-treatment\" class=\"wp-block-heading\">o tratamento t\u00e9rmico<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Etapa<\/td><td>Temperatura e observa\u00e7\u00e3o<\/td><\/tr><tr><td>Normalizando<\/td><td>870\u2013925 \u00b0C, manter por no m\u00ednimo 1 h ou 15\u201320 min por 25 mm, resfriar ao ar<\/td><\/tr><tr><td>Recozimento<\/td><td>830\u2013860 \u00b0C, manter, resfriar no forno a cerca de 15 \u00b0C\/h at\u00e9 480 \u00b0C, resfriar ao ar<\/td><\/tr><tr><td>Endurecimento<\/td><td>800\u2013845 \u00b0C, manter 15 min por 25 mm, temperar em \u00f3leo morno a 25\u201360 \u00b0C<\/td><\/tr><tr><td>Revenimento<\/td><td>455\u2013650 \u00b0C por no m\u00ednimo 2 h, resfriar ao ar; recomenda-se revenimento duplo<\/td><\/tr><tr><td>Al\u00edvio do estresse<\/td><td>650\u2013675 \u00b0C ap\u00f3s usinagem e antes do endurecimento, nunca acima da temperatura de revenimento depois<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Dois pontos pr\u00e1ticos que diferem do 4140 e custam caro quando ignorados. Primeiro, a faixa de austenitiza\u00e7\u00e3o \u00e9 mais baixa, 800\u2013845 \u00b0C contra 830\u2013870 \u00b0C, e o \u00f3leo deve ser morno, n\u00e3o frio. Segundo, o 4340 normalmente recebe revenimento duplo: o primeiro revenimento converte a austenita retida, o segundo restaura a tenacidade.<\/p>\n\n\n\n<h2 id=\"h-welding-4340\" class=\"wp-block-heading\">Soldagem do 4340<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">O 4340 n\u00e3o \u00e9 um a\u00e7o de soldagem pr\u00e9-qualificado. Um procedimento de soldagem deve ser elaborado e qualificado para a junta.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Pr\u00e9-aquecer acima da temperatura de in\u00edcio da martensita, <strong>290 \u00b0C (550 \u00b0F)<\/strong>, para que a zona afetada pelo calor se transforme em bainita em vez de martensita n\u00e3o revenida.<\/li>\n\n<li>Manter o pr\u00e9-aquecimento como temperatura entre passes e reaquecer a pe\u00e7a se ela cair abaixo.<\/li>\n\n<li>Um processo de baixo hidrog\u00eanio e consum\u00edveis de baixo hidrog\u00eanio s\u00e3o obrigat\u00f3rios.<\/li>\n\n<li>P\u00f3s-aquecimento n\u00e3o superior a 28 \u00b0C (50 \u00b0F) abaixo da temperatura de revenimento aplicada \u00e0 pe\u00e7a.<\/li>\n<\/ul>\n\n\n\n<h2 id=\"h-machining-4340\" class=\"wp-block-heading\">Usinagem do 4340<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">No estado recozido, com 187 a 241 HB, o 4340 \u00e9 usinado a cerca de <strong>50%<\/strong> da taxa do AISI 1212 tomado como 100%. Isso \u00e9 mais lento que o 4140 a 65%, e o n\u00edquel \u00e9 o motivo. No estado temperado e revenido, com 255 a 363 HB, o \u00edndice cai ainda mais: espere velocidades menores, mais desgaste de ferramenta e uma fixa\u00e7\u00e3o mais r\u00edgida, mas nenhuma distor\u00e7\u00e3o de um tratamento t\u00e9rmico posterior.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Pe\u00e7as comumente usinadas em 4340 incluem pinos de pist\u00e3o, rolamentos, engrenagens, mandris de m\u00e1quinas-ferramenta, blocos de matrizes e hastes de ferramentas de corte, al\u00e9m dos usos estruturais listados abaixo.<\/p>\n\n\n\n<h2 id=\"h-toughness\" class=\"wp-block-heading\">Tenacidade e tenacidade \u00e0 fratura<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A tenacidade \u00e9 a propriedade pela qual o 4340 \u00e9 efetivamente adquirido, e ela \u00e9 diretamente contraposta \u00e0 dureza. A tabela abaixo mostra o mesmo a\u00e7o em tr\u00eas durezas de trabalho, com a tenacidade \u00e0 fratura em deforma\u00e7\u00e3o plana medida em conjunto com a energia de impacto.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Dureza, HB<\/td><td>Resist\u00eancia, MPa<\/td><td>Charpy V-notch, J<\/td><td>K1c, MPa&middot;m&frac12;<\/td><\/tr><tr><td>550<\/td><td>2040<\/td><td>19<\/td><td>53<\/td><\/tr><tr><td>430<\/td><td>1520<\/td><td>30<\/td><td>75<\/td><\/tr><tr><td>380<\/td><td>1290<\/td><td>42<\/td><td>110<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Leia a linha da esquerda para a direita: de 380 HB a 550 HB o a\u00e7o ganha cerca de 60 por cento de resist\u00eancia e perde metade da tenacidade \u00e0 fratura, de 110 para 53 MPa\u00b7m\u00bd. Os valores de resist\u00eancia dessa tabela s\u00e3o estimados a partir da dureza, ent\u00e3o trate-os como uma correspond\u00eancia e n\u00e3o como dados medidos. Quando um desenho exige 4340 a 550 HB, exige uma pe\u00e7a que tolera pouco dano, e o projeto precisa considerar isso.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Um grau relacionado que vale conhecer: o 300M \u00e9 um 4340 modificado com sil\u00edcio, com cerca de 1,6 por cento de sil\u00edcio, teor ligeiramente maior de carbono e molibd\u00eanio e uma pequena adi\u00e7\u00e3o de van\u00e1dio. O sil\u00edcio permite uma temperatura de revenimento mais alta com a mesma resist\u00eancia, o que melhora a tenacidade. Ele tamb\u00e9m \u00e9 mais propenso \u00e0 descarboneta\u00e7\u00e3o durante o tratamento t\u00e9rmico, portanto a prote\u00e7\u00e3o da superf\u00edcie \u00e9 mais importante do que no 4340 comum.<\/p>\n\n\n\n<h2 id=\"h-4340-vs-4140\" class=\"wp-block-heading\">4340 versus 4140<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">O 4140 e o 4340 compartilham a base cromo-molibd\u00eanio, e a diferen\u00e7a \u00e9 o n\u00edquel. O 4140 praticamente n\u00e3o tem, o 4340 cont\u00e9m 1,65 a 2,00 por cento, e essa \u00fanica adi\u00e7\u00e3o \u00e9 o que os separa na an\u00e1lise de um desenho.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Propriedade<\/td><td>4340<\/td><td>4140<\/td><\/tr><tr><td>Endurecimento profundo<\/td><td>Excelente em se\u00e7\u00f5es pesadas<\/td><td>Moderado<\/td><\/tr><tr><td>T\u00eampera total<\/td><td>T\u00eampera em \u00f3leo at\u00e9 75 mm<\/td><td>Amolece no n\u00facleo acima de 75\u2013100 mm<\/td><\/tr><tr><td>Dureza a 100 mm<\/td><td>53 HRC conforme temperado<\/td><td>N\u00e3o endurece em toda a se\u00e7\u00e3o<\/td><\/tr><tr><td>Resist\u00eancia em alta for\u00e7a<\/td><td>Excelente<\/td><td>Bom<\/td><\/tr><tr><td>Resist\u00eancia a baixas temperaturas<\/td><td>Bom<\/td><td>Adequado<\/td><\/tr><tr><td>Custo relativo<\/td><td>Maior, por causa do n\u00edquel<\/td><td>Inferior<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Escolha o 4340 em vez do 4140 quando for necess\u00e1ria dureza plena em uma se\u00e7\u00e3o que o 4140 n\u00e3o consegue endurecer por completo, quando for exigida tenacidade m\u00e1xima em alta resist\u00eancia, quando a pe\u00e7a estiver sujeita a carregamento de fadiga, como componentes aeron\u00e1uticos e eixos de servi\u00e7o pesado, ou quando a tenacidade em baixa temperatura for importante. Para se\u00e7\u00f5es mais leves com resist\u00eancia moderada, o 4140 \u00e9 a resposta mais econ\u00f4mica.<\/p>\n\n\n\n<h2 id=\"h-4340-vs-tool-steel\" class=\"wp-block-heading\">4340 versus a\u00e7o-ferramenta<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Essa \u00e9 a distin\u00e7\u00e3o que atrai muitos compradores a esta p\u00e1gina, por isso vale a pena ser direto. O a\u00e7o 4340 n\u00e3o substitui o a\u00e7o ferramenta em trabalhos de corte e usinagem.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Exig\u00eancia<\/td><td>4340<\/td><td>A\u00e7o ferramenta (D2 \/ H13)<\/td><\/tr><tr><td>Resist\u00eancia ao desgaste<\/td><td>Baixo<\/td><td>Alto, devido ao volume de carboneto<\/td><\/tr><tr><td>Dureza quente<\/td><td>Pobre<\/td><td>Bom (H13)<\/td><\/tr><tr><td>reten\u00e7\u00e3o de borda<\/td><td>Pobre<\/td><td>Bom<\/td><\/tr><tr><td>Dureza m\u00e1xima pr\u00e1tica<\/td><td>~50\u201355 HRC<\/td><td>58\u201364 HRC<\/td><\/tr><tr><td>Resist\u00eancia estrutural com tenacidade<\/td><td>Excelente<\/td><td>Moderado<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">O 4340 leva vantagem quando a pe\u00e7a \u00e9 estrutural e precisa de resist\u00eancia e tenacidade extremas \u00e0 temperatura ambiente ou moderada. O a\u00e7o-ferramenta leva vantagem quando a pe\u00e7a precisa resistir ao desgaste, manter um fio de corte ou permanecer duro quando quente. Uma matriz de trabalho a frio exige D2 ou A2. Uma matriz de trabalho a quente ou ferramenta de extrus\u00e3o exige H13 ou H11. Usar 4340 nessas fun\u00e7\u00f5es produz desgaste prematuro e deforma\u00e7\u00e3o, n\u00e3o uma matriz mais barata.<\/p>\n\n\n\n<h2 id=\"h-applications\" class=\"wp-block-heading\">Aplica\u00e7\u00f5es comuns<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">O 4340 \u00e9 encontrado em trens de pouso e ferragens estruturais de aeronaves, eixos de helic\u00f3pteros e de transmiss\u00e3o, eixos e semieixos de servi\u00e7o pesado, engrenagens, virabrequins, parafusos de alta resist\u00eancia e canos de armas. Pe\u00e7as aeron\u00e1uticas cr\u00edticas quanto \u00e0 fadiga s\u00e3o frequentemente feitas de 4340 refundido a v\u00e1cuo, VAR ou ESR, para reduzir inclus\u00f5es e elevar a vida em fadiga, pois o a\u00e7o mais limpo resiste \u00e0 inicia\u00e7\u00e3o de trincas sob carga c\u00edclica.<\/p>\n\n\n\n<h2 id=\"h-standards-and-references\" class=\"wp-block-heading\">Normas e Refer\u00eancias<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">O 4340 \u00e9 coberto pela ASTM A29\/A29M e SAE J404 para barras, ASTM A322 para blocos e barras, e especifica\u00e7\u00f5es AMS para barras e forjados aeron\u00e1uticos. Os graus equivalentes est\u00e3o na JIS G4053 (SNCM439) e GB\/T 3077 (40CrNiMoA). As propriedades mec\u00e2nicas certificadas devem sempre estar vinculadas a uma norma declarada, a um tamanho de se\u00e7\u00e3o e a um local de ensaio.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Dados nesta p\u00e1gina:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Resposta ao revenimento, efeito de massa e pr\u00e1tica de tratamento t\u00e9rmico \u2014 ASM Handbook Vol. 4, Heat Treating, se\u00e7\u00e3o 4340.<\/li>\n\n<li>Faixas de dureza recozido, normalizado e revenido, dureza por tamanho de se\u00e7\u00e3o, \u00edndice de usinabilidade e pe\u00e7as t\u00edpicas \u2014 Cutting Data for Turning of Steel, cap\u00edtulo AISI 4340.<\/li>\n\n<li>Graus equivalentes e composi\u00e7\u00e3o qu\u00edmica \u2014 Handbook of Comparative World Steel Standards (ASTM DS 67B), tabela de a\u00e7os Ni-Cr-Mo.<\/li>\n\n<li>Composi\u00e7\u00e3o qu\u00edmica do GB 40CrNiMoA \u2014 \u901a\u7528\u94a2\u94c1\u6750\u6599 (manual chin\u00eas de materiais sider\u00fargicos).<\/li>\n\n<li>Pr\u00e1tica de soldagem \u2014 ASM Handbook Vol. 6, Welding, Brazing and Soldering.<\/li>\n\n<li>Ficha de refer\u00eancia do AISI 4340, PDF de 2 p\u00e1ginas, 412 KB. O PDF est\u00e1 em ingl\u00eas. As mesmas tabelas, para impress\u00e3o.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Leitura relacionada:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/aobosteel.com\/pt\/4140-steel-properties\/\">Propriedades e Tratamento T\u00e9rmico do A\u00e7o 4140<\/a><\/li>\n\n<li><a href=\"https:\/\/aobosteel.com\/pt\/4140-vs-h13\/\">A\u00e7o ferramenta 4140 vs H13<\/a><\/li>\n\n<li><a href=\"https:\/\/aobosteel.com\/pt\/d2-steel-vs-4140\/\">A\u00e7o ferramenta 4140 vs D2<\/a><\/li>\n\n<li><a href=\"https:\/\/aobosteel.com\/pt\/o-que-e-aco-para-ferramentas\/\">O que \u00e9 a\u00e7o para ferramentas?<\/a><\/li>\n\n<li><a href=\"https:\/\/aobosteel.com\/pt\/how-to-select-tool-steels\/\">Guia de Sele\u00e7\u00e3o de A\u00e7os para Ferramentas<\/a><\/li>\n\n<li><a href=\"https:\/\/aobosteel.com\/pt\/h13-tool-steel\/\">A\u00e7o ferramenta H13<\/a><\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p>4340 (40CrNiMoA \/ SNCM439) nickel-chromium-molybdenum steel: tempering response, hardness by section size, equivalent grades, welding and machinability.<\/p>","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"normal-width-container","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"disabled","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"class_list":["post-24965","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v28.8 (Yoast SEO v28.8) - 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