{"id":2211,"date":"2021-07-28T02:22:41","date_gmt":"2021-07-28T02:22:41","guid":{"rendered":"https:\/\/wldstainless.com\/?p=2211"},"modified":"2021-07-28T02:24:47","modified_gmt":"2021-07-28T02:24:47","slug":"the-heat-treatments-of-u-stainless-steel-heat-exchanger","status":"publish","type":"post","link":"https:\/\/wldstainless.com\/cs\/the-heat-treatments-of-u-stainless-steel-heat-exchanger\/","title":{"rendered":"Topn\u00e9 o\u0161et\u0159en\u00ed u nerezov\u00e9ho tepeln\u00e9ho v\u00fdm\u011bn\u00edku"},"content":{"rendered":"

Kdy\u017e mluv\u00edme o tepeln\u00e9 \u00faprav\u011b austenitick\u00fdch U-tvarovan\u00fdch nerezov\u00fdch trubek, v\u011bt\u0161ina lid\u00ed si mysl\u00ed, \u017ee to nen\u00ed nutn\u00e9 kv\u016fli senzibilizaci a vysok\u00e9 teplot\u011b \u00faprav roztoku, co\u017e m\u016f\u017ee zp\u016fsobit deformaci trubky. Ve skute\u010dnosti je tepeln\u00e9 zpracov\u00e1n\u00ed austenitick\u00e9 nerezov\u00e9 oceli nevyhnuteln\u00e9; tepeln\u00fdm zpracov\u00e1n\u00edm nelze zm\u011bnit strukturu austenitick\u00fdch trubek, ale lze zm\u011bnit jejich zpracovatelnost.<\/p>\n

Nap\u0159\u00edklad kv\u016fli n\u00edzk\u00e9mu obsahu uhl\u00edku 304<\/a> Nerezov\u00e1 tepeln\u00e1 v\u00fdm\u011bnn\u00e1 trubka je p\u0159i normalizaci obt\u00ed\u017en\u00e1 na to, aby se hladkost povrchu fr\u00e9zovac\u00edho n\u00e1stroje vyhov\u011bla po\u017eadavk\u016fm a sn\u00ed\u017eila se tak \u017eivotnost n\u00e1stroje. N\u00edzkocelov\u00e1 martenzitov\u00e1 a \u017eelezn\u00e1 struktura kabelu z\u00edskan\u00e1 po ne\u00fapln\u00e9m uvoln\u011bn\u00ed mohou v\u00fdrazn\u011b zv\u00fd\u0161it tvrdost a hladkost povrchu a \u017eivotnost potrub\u00ed lze tak\u00e9 zv\u00fd\u0161it o 3 a\u017e 4 kr\u00e1t. Krom\u011b toho m\u00e1 oh\u00fdbac\u00ed \u010d\u00e1st tvaru U vlnit\u00e9 tepeln\u00e9 v\u00fdm\u011bnn\u00e9 trubky mal\u00fd polom\u011br oh\u00fdb\u00e1n\u00ed a z\u0159eteln\u00fd jev ztvrdnut\u00ed p\u0159i tepeln\u00e9 \u00faprav\u011b. Pro tepelnou \u00fapravu je nutn\u00e1 tepeln\u00e1 \u00faprava austenitick\u00e9 nerezov\u00e9 oceli a v porovn\u00e1n\u00ed s cel\u00fdm za\u0159\u00edzen\u00ed pro tepelnou \u00fapravu je tepeln\u00e1 \u00faprava austenitickou nerezovou ocel\u00ed vlnit\u00e9ho tvaru a pasivac\u00ed pomoc\u00ed p\u00e1len\u00ed mnohem jednodu\u0161\u0161\u00ed. V t\u00e9to pr\u00e1ci byla provedena \u0159ada test\u016f u tvarov\u00fdch trubek s r\u016fzn\u00fdmi specifikacemi, polom\u011brem oh\u00fdb\u00e1n\u00ed a podm\u00ednkami tepeln\u00e9 \u00fapravy a byla analyzov\u00e1na pot\u0159eba tepeln\u00e9 \u00faprav pro tvarov\u00e9 trubky z austenitick\u00e9 nerezov\u00e9 oceli.<\/p>\n

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Experiment\u00e1ln\u00ed materi\u00e1ly:<\/em><\/p>\n

304<\/a> Nerezov\u00e1 U-trubka<\/em><\/p>\n

Velikost: 19*2 mm, polom\u011br ohybu: 40, 15, 190, 265, 340 mm<\/em><\/p>\n

Rozm\u011bry: 25*2,5 mm Polom\u011br ohybu: 40, 115, 190, 265, 340 mm<\/em><\/p>\n

O\u0161et\u0159en\u00ed hork\u00fdm p\u00e1rem: nel\u00e9\u010deno, o\u0161et\u0159en\u00ed subsolidn\u00ed roztokovou, o\u0161et\u0159en\u00ed pevnou roztokovou<\/em><\/p>\n

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Testov\u00e1n\u00ed tvrdosti<\/h3>\n

Oh\u00fdbac\u00ed \u00fasek u-tvarovan\u00e9ho tepeln\u00fdch v\u00fdm\u011bn\u00edk\u016f bez tepeln\u00e9ho zpracov\u00e1n\u00ed a subsolida\u010dn\u00edho o\u0161et\u0159en\u00ed: s poklesem polom\u011bru oh\u00fdb\u00e1n\u00ed se hodnota tvrdosti zvy\u0161uje. Hodnota tvrdosti tepeln\u00fdch v\u00fdm\u011bn\u00edk\u016f po o\u0161et\u0159en\u00ed roztokem (v porovn\u00e1n\u00ed s hodnotou p\u0159ed oh\u00fdb\u00e1n\u00edm) se nijak v\u00fdznamn\u011b nem\u011bn\u00ed. To nazna\u010duje, \u017ee Austenitick\u00fd nerezov\u00fd ocelov\u00fd materi\u00e1l m\u00e1 v\u00fdrazn\u00fd tvrzen\u00fd efekt, a s n\u00e1r\u016fstem deformace se trend tvrzen\u00ed zvy\u0161uje.<\/p>\n

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Mikroskopick\u00e1 kontrola<\/h3>\n

Pro \u00faheln\u00fd oblouk se smr\u0161tiv\u00fdm polom\u011brem 40 mm: v mikrostruktu\u0159e bez tepeln\u00e9ho zpracov\u00e1n\u00ed se vyskytuje mnoho martenzitu a skloubov\u00fdch lini\u00ed, a rovinn\u00e1 forma austenitu v mikrostruktu\u0159e je zcela zmizela (p\u0159\u00edli\u0161 mnoho martenzitu by zkoli\u0161t\u011blo ocel). V\u011bt\u0161ina martenzitu v tk\u00e1ni o\u0161et\u0159en\u00e9 subsolutn\u00ed otopou byla transformov\u00e1na, ale mal\u00e9 mno\u017estv\u00ed martenzitu st\u00e1le existuje.<\/p>\n

Po \u00faprav\u011b roztaven\u00edm se zrn\u00e1 austenitu vyrovnaly a nebyl nalezen \u017e\u00e1dn\u00fd martenzit. V neoh\u0159\u00e1t\u00e9 mikrostruktu\u0159e u-tvarovan\u00fdch trubek s polom\u011brem ohybu R 115, 190, 265 a 340 mm se po oh\u00fdb\u00e1n\u00ed tak\u00e9 vyskytly p\u00e1sy skluzu a martenzit, ale obsah se postupn\u011b sni\u017eoval s n\u00e1r\u016fstem polom\u011bru ohybu. P\u0159i polom\u011bru R u-tvarovan\u00e9 trubky v\u011bt\u0161\u00ed ne\u017e nebo rovn\u00fd 265 mm \u00fa\u010dinek na mikrostrukturu p\u0159ed a po tepeln\u00e9 \u00faprav\u011b nen\u00ed v\u00fdznamn\u00fd. P\u0159i polom\u011bru R ni\u017e\u0161\u00edm ne\u017e 265 mm v mikrostruktu\u0159e neoh\u0159\u00e1t\u00fdch u-tvarovan\u00fdch trubek doch\u00e1z\u00ed k p\u0159\u00edtomnosti martenzitu a obsah martenzitu kles\u00e1 s n\u00e1r\u016fstem teploty tepeln\u00e9 \u00fapravy (subsolida\u010dn\u00ed a peletov\u00e1 \u00faprava).<\/p>\n

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Test intergranul\u00e1rn\u00ed korozivosti<\/h3>\n

Mikroskopick\u00fdm vy\u0161et\u0159en\u00edm bylo zji\u0161t\u011bno, \u017ee p\u0159\u00edtomnost martenzitu nem\u00e1 vliv na intergranul\u00e1rn\u00ed korozi. A\u010dkoli v absolutizovan\u00e9 mikrostruktu\u0159e existuje velk\u00e9 mno\u017estv\u00ed martenzitu, s distribuc\u00ed martenzitu nedoch\u00e1z\u00ed k tendenci intergranul\u00e1rn\u00ed koroze. N\u011bkter\u00e9 zrnit\u00e1 hranice se roz\u0161\u00ed\u0159ily p\u0159ed a po \u00faprav\u011b roztokem, a roz\u0161\u00ed\u0159en\u00ed rozd\u011blen\u00ed zrnit\u00fdch hranic bylo nez\u00e1visl\u00e9 na distribuci martenzitu. Na z\u00e1klad\u011b mikroskopick\u00e9ho vy\u0161et\u0159en\u00ed po zkou\u0161ce koroze bylo provedeno ohybov\u00e9 zkou\u0161en\u00ed u-tvar\u00fdch trubek v r\u016fzn\u00fdch stav\u00edch podle testovac\u00edho standardu. Po ohnut\u00ed o 180\u00b0 nebyla v trubk\u00e1ch nalezena \u017e\u00e1dn\u00e1 roztr\u017eenina intergranul\u00e1rn\u00ed koroze.<\/p>\n

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Teplota \u0159e\u0161en\u00ed \u00faprav<\/h3>\n

\u00da\u010dinok \u00faprav roztokom je ovplyvnen\u00fd n\u00edzkou teplotou roztoku a v\u00fdsledky anal\u00fdzy mikrostruktury a tvrdosti nemo\u017eno z\u00edska\u0165. Ak je teplota o nie\u010do vy\u0161\u0161ia, vo vn\u00fatri U-tvarov\u00e9ho segmentu sa m\u00f4\u017eu objavi\u0165 defekty, ako napr\u00edklad konk\u00e1vnos\u0165 alebo trhliny.<\/p>\n

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Z experimentu je zn\u00e1mo, \u017ee martenzitick\u00e1 transformace nerezov\u00e9 oceli po chladn\u00e9m zpracov\u00e1n\u00ed m\u00e1 mnohem v\u011bt\u0161\u00ed vliv na odolnost proti korozi ne\u017e na pevnost. Kdy\u017e je polom\u011br ohybu u-tvarovan\u00e9 trubice men\u0161\u00ed ne\u017e 115 mm, mikrostruktura u-tvarovan\u00e9 trubice p\u0159ed a po o\u0161et\u0159en\u00ed roztokem se v\u00fdrazn\u011b li\u0161\u00ed. Pro tento \u00fasek ohybu u-tvarovan\u00e9 trubice o mal\u00e9m polom\u011bru by m\u011bla b\u00fdt po chladn\u00e9m tvarov\u00e1n\u00ed prov\u00e1d\u011bna pevn\u00e1 roztokov\u00e1 \u00faprava. Pokud nen\u00ed po\u017eadov\u00e1no vy\u0161\u0161\u00ed odolnost proti intergranul\u00e1rn\u00ed korozi, doporu\u010duje se, aby se \u00fasek ohybu u-tvarovan\u00e9 trubice s polom\u011brem men\u0161\u00edm nebo rovn\u00fdm 265 mm o\u0161et\u0159il roztokovou \u00fapravou (pozn\u00e1mka: pro eliminaci zbytkov\u00e9ho nap\u011bt\u00ed). Pro u-tvarovan\u00e9 tepeln\u00e1 v\u00fdm\u011bnov\u00e1 trubice s velk\u00fdm polom\u011brem zak\u0159iven\u00ed se \u00fasek ohybu nelze o\u0161et\u0159it roztokem, s v\u00fdjimkou prost\u0159ed\u00ed citliv\u00e9ho na korozn\u00ed nap\u011bt\u00ed. Proto\u017ee je odpor tekutin k mal\u00e9 pr\u016fm\u011brnosti trubky vysok\u00fd, je obt\u00ed\u017en\u00e9 jej \u010distit a snadno se ucp\u00e1v\u00e1 konstrukce, zat\u00edmco odpor tekutin z nerezov\u00e9 oceli s velkou pr\u016fm\u011brnost\u00ed nen\u00ed tak vysok\u00fd jako u trubek mal\u00e9ho pr\u016fm\u011bru a je snadno \u010distiteln\u00fd, co\u017e je b\u011b\u017en\u011bj\u0161\u00ed pro visk\u00f3zn\u00ed nebo ne\u010dist\u00e9 tekutiny.<\/p>\n

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Spole\u010dnost WLD m\u016f\u017ee poskytnout 304\/316 nerezov\u00e9 tepeln\u00e1 v\u00fdm\u011bnn\u00e1 trubice o tlou\u0161\u0165ce od 10 mm do 114 mm a tlou\u0161\u0165ce od 0,6 mm do 3,0 mm. D\u00e9lka m\u016f\u017ee b\u00fdt p\u0159izp\u016fsobena podle va\u0161ich skute\u010dn\u00fdch pracovn\u00edch podm\u00ednek. Pokud ji pot\u0159ebujete, kontaktujte n\u00e1s pros\u00edm je\u0161t\u011b dnes.<\/em><\/p>","protected":false},"excerpt":{"rendered":"

When talking about the heat treatment of austenitic U-shaped stainless steel tubes, most people think it\u2019s not necessary because of sensitization and high solution treatment temperature, it is easy to cause deformation of the pipe. In fact, the heat treatment of Austenitic stainless steel is inevitable, heat treatment can not change the structure of stainless […]<\/p>\n","protected":false},"author":1,"featured_media":2212,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[],"class_list":["post-2211","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t