{"id":12,"date":"2026-03-12T08:23:00","date_gmt":"2026-03-12T07:23:00","guid":{"rendered":"https:\/\/www.matai.cz\/blog\/nerez-a2-vs-a4\/"},"modified":"2026-06-26T14:56:54","modified_gmt":"2026-06-26T12:56:54","slug":"nerez-a2-vs-a4","status":"publish","type":"post","link":"https:\/\/www.matai.cz\/blog\/nerez-a2-vs-a4\/","title":{"rendered":"Nerez A2 vs A4: rozd\u00edl mezi 304 a 316, korozn\u00ed odolnost a kdy zvolit kter\u00fd"},"content":{"rendered":"<p>U nerezov\u00e9ho spojovac\u00edho materi\u00e1lu naraz\u00edte nej\u010dast\u011bji na dv\u011b ozna\u010den\u00ed: <strong>A2<\/strong> a <strong>A4<\/strong>. Ob\u011b jsou austenitick\u00e9 nerezov\u00e9 oceli s v\u00fdbornou korozn\u00ed odolnost\u00ed, ale li\u0161\u00ed se chemick\u00fdm slo\u017een\u00edm a t\u00edm i vhodnost\u00ed pro r\u016fzn\u00e1 prost\u0159ed\u00ed. Tento \u010dl\u00e1nek vysv\u011btl\u00ed praktick\u00e9 rozd\u00edly mezi A2 a A4, jejich zna\u010den\u00ed a pom\u016f\u017ee v\u00e1m vybrat spr\u00e1vn\u00fd materi\u00e1l.<\/p>\n<h2>Co znamen\u00e1 A2 a A4<\/h2>\n<p>Ozna\u010den\u00ed A2 a A4 poch\u00e1z\u00ed z normy ISO 3506 pro nerezov\u00e9 spojovac\u00ed prvky. &bdquo;A&ldquo; znamen\u00e1 austenitickou nerezovou ocel.<\/p>\n<table border=\"1\" cellpadding=\"6\" cellspacing=\"0\">\n<thead>\n<tr>\n<th><\/th>\n<th>A2<\/th>\n<th>A4<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>EN materi\u00e1l<\/td>\n<td>1.4301 (pop\u0159. 1.4307)<\/td>\n<td>1.4401 (pop\u0159. 1.4404)<\/td>\n<\/tr>\n<tr>\n<td>AISI<\/td>\n<td>304<\/td>\n<td>316<\/td>\n<\/tr>\n<tr>\n<td>Lidov\u011b<\/td>\n<td>&bdquo;18\/8&ldquo;<\/td>\n<td>&bdquo;mari\u0148\u00e1k&ldquo; \/ marine grade<\/td>\n<\/tr>\n<tr>\n<td>Chrom<\/td>\n<td>cca 18 %<\/td>\n<td>cca 16-18 %<\/td>\n<\/tr>\n<tr>\n<td>Nikl<\/td>\n<td>cca 8-10 %<\/td>\n<td>cca 10-14 %<\/td>\n<\/tr>\n<tr>\n<td>Molybden<\/td>\n<td>&ndash;<\/td>\n<td>cca 2-3 %<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Kl\u00ed\u010dov\u00fd rozd\u00edl: molybden<\/h2>\n<p>Hlavn\u00ed rozd\u00edl je p\u0159\u00eddavek <strong>molybdenu (Mo)<\/strong> u oceli A4. Molybden v\u00fdrazn\u011b zvy\u0161uje odolnost proti <strong>bodov\u00e9 (pitting) a \u0161t\u011brbinov\u00e9 korozi<\/strong> v prost\u0159ed\u00ed s chloridy &ndash; tedy v slan\u00e9 vod\u011b, soln\u00e9m post\u0159iku, na cest\u00e1ch o\u0161et\u0159ovan\u00fdch posypovou sol\u00ed nebo u baz\u00e9nov\u00e9 chemie. Proto se A4 ozna\u010duje jako &bdquo;mo\u0159sk\u00e1&ldquo; nebo marine grade nerez.<\/p>\n<p>A2 nab\u00edz\u00ed velmi dobrou korozn\u00ed odolnost ve v\u011bt\u0161in\u011b vnit\u0159n\u00edch a b\u011b\u017en\u00fdch venkovn\u00edch prost\u0159ed\u00ed, ale v p\u0159\u00edm\u00e9m kontaktu s chloridy je n\u00e1chyln\u011bj\u0161\u00ed ke korozi ne\u017e A4.<\/p>\n<h2>Kdy zvolit A2 a kdy A4<\/h2>\n<p><strong>A2 (1.4301 \/ 304)<\/strong> &ndash; vhodn\u00e1 pro:<\/p>\n<ul>\n<li>vnit\u0159n\u00ed prost\u0159ed\u00ed, n\u00e1bytek, spot\u0159ebi\u010de,<\/li>\n<li>b\u011b\u017en\u00e9 venkovn\u00ed pou\u017eit\u00ed bez p\u0159\u00edm\u00e9ho kontaktu se sol\u00ed,<\/li>\n<li>obecn\u00e9 stroj\u00edrenstv\u00ed a stavebnictv\u00ed.<\/li>\n<\/ul>\n<p><strong>A4 (1.4401 \/ 316)<\/strong> &ndash; volte ji pro:<\/p>\n<ul>\n<li>p\u0159\u00edmo\u0159sk\u00e9 a pob\u0159e\u017en\u00ed prost\u0159ed\u00ed, slan\u00fd vzduch, mola, lod\u011b,<\/li>\n<li>baz\u00e9ny a aquaparky (chlor),<\/li>\n<li>chemick\u00fd pr\u016fmysl a prost\u0159ed\u00ed s agresivn\u00edmi l\u00e1tkami,<\/li>\n<li>silnice a mosty o\u0161et\u0159ovan\u00e9 posypovou sol\u00ed.<\/li>\n<\/ul>\n<p>Pro n\u00e1ro\u010dn\u00e1 prost\u0159ed\u00ed jsou ide\u00e1ln\u00ed nap\u0159\u00edklad <a href=\"\/p\/srouby-s-sestihrannou-hlavou-s-drikem-din-931-a4\/\">\u0161rouby z nerezu A4<\/a>, k nim\u017e dopln\u00edte odpov\u00eddaj\u00edc\u00ed <a href=\"\/p\/matice-sestihranne-0-8-d-din-934-a4\/\">matice z nerezu A4<\/a>. Pro b\u011b\u017en\u00e9 aplikace pln\u011b posta\u010d\u00ed <a href=\"\/p\/srouby-s-sestihrannou-hlavou-s-drazkou-din-933-a2\/\">spojovac\u00ed materi\u00e1l z nerezu A2<\/a>.<\/p>\n<h2>Cena<\/h2>\n<p>Vy\u0161\u0161\u00ed obsah niklu a molybdenu d\u011bl\u00e1 A4 dra\u017e\u0161\u00ed ne\u017e A2. Cenov\u00fd rozd\u00edl b\u00fdv\u00e1 citeln\u00fd, proto se A4 doporu\u010duje c\u00edlen\u011b tam, kde je jej\u00ed vy\u0161\u0161\u00ed korozn\u00ed odolnost skute\u010dn\u011b pot\u0159eba. Pro b\u011b\u017en\u00e9 pou\u017eit\u00ed je A2 ekonomi\u010dt\u011bj\u0161\u00ed volbou.<\/p>\n<h2>Magneti\u010dnost<\/h2>\n<p>Ob\u011b oceli jsou v \u017e\u00edhan\u00e9m stavu prakticky nemagnetick\u00e9 (austenitick\u00e1 struktura). Studen\u00fdm tv\u00e1\u0159en\u00edm &ndash; nap\u0159\u00edklad p\u0159i v\u00fdrob\u011b \u0161roub\u016f, matic nebo z\u00e1vito\u0159ez\u016f &ndash; v\u0161ak m\u016f\u017ee vzniknout slab\u00e1 magneti\u010dnost. M\u00edrn\u00e1 p\u0159ita\u017elivost k magnetu tedy neznamen\u00e1, \u017ee nejde o pravou nerez; je to b\u011b\u017en\u00fd jev u tv\u00e1\u0159en\u00e9ho austenitick\u00e9ho spojovac\u00edho materi\u00e1lu.<\/p>\n<h2>Zna\u010den\u00ed A2-70 a A4-80<\/h2>\n<p>Za p\u00edsmenem a \u010d\u00edslem materi\u00e1lu n\u00e1sleduje poml\u010dka a pevnostn\u00ed t\u0159\u00edda (dle ISO 3506):<\/p>\n<table border=\"1\" cellpadding=\"6\" cellspacing=\"0\">\n<thead>\n<tr>\n<th>Zna\u010den\u00ed<\/th>\n<th>Materi\u00e1l<\/th>\n<th>Min. pevnost v tahu Rm<\/th>\n<th>Min. mez kluzu Rp0,2<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>A2-70<\/td>\n<td>nerez 304<\/td>\n<td>700 MPa<\/td>\n<td>450 MPa<\/td>\n<\/tr>\n<tr>\n<td>A4-80<\/td>\n<td>nerez 316<\/td>\n<td>800 MPa<\/td>\n<td>600 MPa<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u010c\u00edslo (50\/70\/80) ozna\u010duje stav tv\u00e1\u0159en\u00ed: 50 = \u017e\u00edhan\u00fd stav, 70 = za studena ta\u017een\u00fd, 80 = siln\u011b za studena ta\u017een\u00fd. A2-70 a A4-80 jsou nejb\u011b\u017en\u011bj\u0161\u00ed pevnostn\u00ed t\u0159\u00eddy u \u0161roub\u016f. Na hlav\u011b \u0161roubu b\u00fdv\u00e1 vyra\u017eeno materi\u00e1lov\u00e9 i pevnostn\u00ed ozna\u010den\u00ed (nap\u0159. &bdquo;A2-70&ldquo;) a zna\u010dka v\u00fdrobce.<\/p>\n<h2>Historie zna\u010den\u00ed a glob\u00e1ln\u00ed ekvivalenty<\/h2>\n<p>Ozna\u010den\u00ed A2 a A4 je evropsk\u00fd syst\u00e9m zaveden\u00fd normou ISO 3506. V anglosask\u00e9m sv\u011bt\u011b se setk\u00e1te s jin\u00fdmi n\u00e1zvy pro tyt\u00e9\u017e oceli: A2 b\u00fdv\u00e1 ozna\u010dov\u00e1no jako &bdquo;18-8&ldquo; (18 % chromu, 8 % niklu) nebo AISI 304, A4 jako AISI 316 nebo &bdquo;marine grade&ldquo;. Je dobr\u00e9 tyto ekvivalenty zn\u00e1t, proto\u017ee dov\u00e1\u017een\u00fd materi\u00e1l a zahrani\u010dn\u00ed katalogy pou\u017e\u00edvaj\u00ed r\u016fzn\u00e1 zna\u010den\u00ed pro stejnou ocel. V Evrop\u011b i v \u010desk\u00e9m prost\u0159ed\u00ed je ale standardem pr\u00e1v\u011b dvojice A2 \/ A4 dopln\u011bn\u00e1 pevnostn\u00ed t\u0159\u00eddou (nap\u0159. A2-70).<\/p>\n<h2>Korozn\u00ed mechanismy: bodov\u00e1 a \u0161t\u011brbinov\u00e1 koroze<\/h2>\n<p>Korozn\u00ed odolnost nerezi je d\u00e1na tenkou pasivn\u00ed vrstvou oxidu chromu na povrchu. V p\u0159\u00edtomnosti chloridov\u00fdch iont\u016f (s\u016fl, chlor) se ale tato vrstva m\u016f\u017ee lok\u00e1ln\u011b naru\u0161it a vznik\u00e1 <strong>bodov\u00e1 koroze (pitting)<\/strong> &ndash; drobn\u00e9, ale hlubok\u00e9 d\u016flky. V \u00fazk\u00fdch sp\u00e1r\u00e1ch, pod podlo\u017ekami nebo v z\u00e1vitech, kam se h\u016f\u0159 dost\u00e1v\u00e1 kysl\u00edk, hroz\u00ed <strong>\u0161t\u011brbinov\u00e1 koroze<\/strong>. Pr\u00e1v\u011b proti t\u011bmto dv\u011bma mechanism\u016fm pom\u00e1h\u00e1 molybden v A4, kter\u00fd stabilizuje pasivn\u00ed vrstvu. Proto v chloridov\u00e9m prost\u0159ed\u00ed A2 \u010dasem &bdquo;rezav\u00ed&ldquo; (p\u0159esn\u011bji koroduje bodov\u011b), zat\u00edmco A4 vydr\u017e\u00ed mnohem d\u00e9le.<\/p>\n<p>Pozor i na tzv. galvanickou (kontaktn\u00ed) korozi: pokud spoj\u00edte nerez s m\u00e9n\u011b u\u0161lechtil\u00fdm kovem (nap\u0159. b\u011b\u017enou ocel nebo hlin\u00edk) ve vlhku, m\u00e9n\u011b u\u0161lechtil\u00fd kov koroduje rychleji. Ve spoji proto kombinujte materi\u00e1ly uv\u00e1\u017eliv\u011b a v n\u00e1ro\u010dn\u00e9m prost\u0159ed\u00ed pou\u017e\u00edvejte stejnorod\u00fd nerezov\u00fd spojovac\u00ed materi\u00e1l v\u010detn\u011b matic a podlo\u017eek.<\/p>\n<h2>Sva\u0159itelnost a varianty s n\u00edzk\u00fdm uhl\u00edkem<\/h2>\n<p>Pro sva\u0159ovan\u00e9 konstrukce existuj\u00ed n\u00edzkouhl\u00edkov\u00e9 varianty 1.4307 (304L, odpov\u00edd\u00e1 A2) a 1.4404 (316L, odpov\u00edd\u00e1 A4). Ni\u017e\u0161\u00ed obsah uhl\u00edku omezuje vznik karbid\u016f chromu p\u0159i sva\u0159ov\u00e1n\u00ed a t\u00edm i riziko mezikrystalov\u00e9 koroze v okol\u00ed svaru. U b\u011b\u017en\u00e9ho \u0161roubov\u00e9ho spoje, kde se nesva\u0159uje, tyto rozd\u00edly roli nehraj\u00ed a vysta\u010d\u00edte si se standardn\u00ed A2 nebo A4.<\/p>\n<h2>Praktick\u00e9 doporu\u010den\u00ed pro v\u00fdb\u011br<\/h2>\n<p>Jednoduch\u00e9 vod\u00edtko: je-li spoj trvale vystaven slan\u00e9 vod\u011b, chloru, posypov\u00e9 soli nebo chemik\u00e1li\u00edm, volte <strong>A4<\/strong>. Pro v\u0161echno ostatn\u00ed obvykle bohat\u011b sta\u010d\u00ed <strong>A2<\/strong>, kter\u00e1 je levn\u011bj\u0161\u00ed a snadno dostupn\u00e1. P\u0159i pochybnostech se vyplat\u00ed rad\u011bji p\u0159iplatit za A4 &ndash; v\u00fdm\u011bna zkorodovan\u00fdch spoj\u016f b\u00fdv\u00e1 dra\u017e\u0161\u00ed ne\u017e po\u010d\u00e1te\u010dn\u00ed \u00faspora.<\/p>\n<h2>Shrnut\u00ed<\/h2>\n<p>A2 (1.4301 \/ 304) je univerz\u00e1ln\u00ed nerez pro b\u011b\u017en\u00e1 prost\u0159ed\u00ed, A4 (1.4401 \/ 316) d\u00edky molybdenu odol\u00e1v\u00e1 chlorid\u016fm a hod\u00ed se k mo\u0159i, do baz\u00e9n\u016f a do chemicky agresivn\u00edho prost\u0159ed\u00ed. A4 je dra\u017e\u0161\u00ed &ndash; volte ji tam, kde se jej\u00ed vlastnosti vyplat\u00ed. Pevnostn\u011b se A2 dod\u00e1v\u00e1 nej\u010dast\u011bji jako A2-70 (Rm 700 MPa) a A4 jako A4-80 (Rm 800 MPa).<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Nerez A2 (1.4301\/304) vs A4 (1.4401\/316) se 2 % molybdenu. Korozn\u00ed odolnost, mo\u0159sk\u00e1 voda a chlor, cena, magneti\u010dnost a zna\u010den\u00ed A2-70\/A4-80.<\/p>\n","protected":false},"author":1,"featured_media":612,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_matai_meta_desc":"Nerez A2 (1.4301\/304) vs A4 (1.4401\/316) se 2 % molybdenu. Korozn\u00ed odolnost, mo\u0159sk\u00e1 voda a chlor, cena, magneti\u010dnost a zna\u010den\u00ed A2-70\/A4-80.","_matai_faq":"[{\"q\": \"Jak\u00fd je hlavn\u00ed rozd\u00edl mezi nerezem A2 a A4?\", \"a\": \"A4 obsahuje nav\u00edc cca 2-3 % molybdenu, d\u00edky \u010demu\u017e m\u00e1 v\u00fdrazn\u011b vy\u0161\u0161\u00ed odolnost proti bodov\u00e9 a \u0161t\u011brbinov\u00e9 korozi v prost\u0159ed\u00ed s chloridy (mo\u0159sk\u00e1 voda, chlor, posypov\u00e1 s\u016fl). A2 je vhodn\u00e1 pro b\u011b\u017en\u00e1 prost\u0159ed\u00ed.\"}, {\"q\": \"Kter\u00e9 ocele odpov\u00eddaj\u00ed A2 a A4?\", \"a\": \"A2 odpov\u00edd\u00e1 EN 1.4301 \/ AISI 304 (lidov\u011b 18\/8). A4 odpov\u00edd\u00e1 EN 1.4401 \/ AISI 316, tzv. marine grade nerez s molybdenem.\"}, {\"q\": \"Je nerez A4 nutn\u00e1 do baz\u00e9nu a k mo\u0159i?\", \"a\": \"Ano. V prost\u0159ed\u00ed s chlorem (baz\u00e9ny) a slanou vodou (pob\u0159e\u017e\u00ed) doporu\u010dujeme A4. A2 by zde mohla korodovat (pitting a \u0161t\u011brbinov\u00e1 koroze).\"}, {\"q\": \"Co znamen\u00e1 A2-70 a A4-80?\", \"a\": \"\u010c\u00edslo ud\u00e1v\u00e1 pevnostn\u00ed t\u0159\u00eddu dle ISO 3506. A2-70 m\u00e1 min. pevnost v tahu 700 MPa a mez kluzu 450 MPa, A4-80 m\u00e1 800 MPa a mez kluzu 600 MPa. \u010c\u00edslo souvis\u00ed se stupn\u011bm tv\u00e1\u0159en\u00ed za studena.\"}, {\"q\": \"Pro\u010d mi nerezov\u00fd \u0161roub trochu dr\u017e\u00ed na magnetu?\", \"a\": \"Studen\u00fdm tv\u00e1\u0159en\u00edm p\u0159i v\u00fdrob\u011b m\u016f\u017ee u austenitick\u00e9 nerezi vzniknout slab\u00e1 magneti\u010dnost. M\u00edrn\u00e1 p\u0159ita\u017elivost k magnetu neznamen\u00e1, \u017ee nejde o pravou nerez.\"}]","_matai_schema_type":"TechArticle","footnotes":""},"categories":[2],"tags":[],"class_list":["post-12","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-normy-a-materialy"],"_links":{"self":[{"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/posts\/12","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/comments?post=12"}],"version-history":[{"count":1,"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/posts\/12\/revisions"}],"predecessor-version":[{"id":215,"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/posts\/12\/revisions\/215"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/media\/612"}],"wp:attachment":[{"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/media?parent=12"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/categories?post=12"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.matai.cz\/blog\/wp-json\/wp\/v2\/tags?post=12"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}