一、影響(xiang)不銹鋼組織的(de)兩大類合(he)金元素
形成鐵素(su)體的元素(su):Cr、Mo、Si、Al、W、Ti、Nb等。
形(xing)成(cheng)奧氏體(ti)的元素:C、N、Ni、Co、Mn、Cu等。
在一定溫度條件(jian)下(xia),不(bu)銹鋼的基(ji)體(ti)組(zu)織是由鋼中形成(cheng)鐵(tie)素(su)(su)體(ti)和形成(cheng)奧氏體(ti)的合金元素(su)(su)間的相互作用所決(jue)定的。
二、鉻當量與鎳當量
是指各合金元素形(xing)成(cheng)鐵素體組(zu)(zu)織(zhi)或形(xing)成(cheng)奧氏體組(zu)(zu)織(zhi)的能力的總和。
鉻(ge)當量= Cr + 1.5Mo + 1.5Si + 1.75Nb + 1.5Ti + 5.5Al + 0.75W , 各(ge)元素(su)(su)含量前的數(shu)字為該(gai)元素(su)(su)形成鐵素(su)(su)體(ti)的能力相當于鉻(ge)形成鐵素(su)(su)體(ti)能力的倍數(shu)。
鎳(nie)當量= Ni + Co + 30(C+N)+0.5Mn + 0.3 Cu ,各元素含量前的(de)數字為該元素形成(cheng)奧(ao)氏(shi)體的(de)能(neng)(neng)力(li)相當于鎳(nie)形成(cheng)奧(ao)氏(shi)體能(neng)(neng)力(li)的(de)倍數。
三、鉻當量與(yu)鎳當量對不銹鋼基體組織的(de)影響
圖2.1指出了自高溫冷卻后,鉻當量與鎳當量對不(bu)銹鋼(gang)基體組織的影響。從圖中可以根據不銹鋼化學成分中的鉻當量與鎳當量大致確定鋼的基體組織類型和組成。不銹鋼中的馬氏體不銹鋼和沉淀硬化不銹鋼系處于圖2.1中I 區和II區范圍內,而雙相不銹鋼則處于A+F區范圍內。
需要指出,各種(zhong)合金元(yuan)(yuan)(yuan)(yuan)素(su)(su)在(zai)鋼(gang)(包括不銹(xiu)鋼(gang))中相互作用(yong)(yong),在(zai)形(xing)成各種(zhong)基(ji)體(ti)組織(固(gu)溶(rong)(rong)(rong)(rong)(rong)體(ti))的(de)(de)同時,還可產生(sheng)不同程(cheng)(cheng)度(du)的(de)(de)固(gu)溶(rong)(rong)(rong)(rong)(rong)強化作用(yong)(yong),見(jian)圖(tu)2.2和圖(tu)2.3 。這主要是各種(zhong)合金元(yuan)(yuan)(yuan)(yuan)素(su)(su)(溶(rong)(rong)(rong)(rong)(rong)質(zhi))在(zai)基(ji)體(ti)組織(溶(rong)(rong)(rong)(rong)(rong)劑)中所處(chu)(chu)的(de)(de)位置導致溶(rong)(rong)(rong)(rong)(rong)劑晶格(ge)發生(sheng)不同程(cheng)(cheng)度(du)的(de)(de)畸變而(er)產生(sheng)的(de)(de)作用(yong)(yong)。根(gen)據(ju)溶(rong)(rong)(rong)(rong)(rong)質(zhi)元(yuan)(yuan)(yuan)(yuan)素(su)(su)在(zai)溶(rong)(rong)(rong)(rong)(rong)劑晶格(ge)中所處(chu)(chu)位置的(de)(de)不同,有間(jian)隙(xi)型(xing)元(yuan)(yuan)(yuan)(yuan)素(su)(su)和置換(huan)型(xing)元(yuan)(yuan)(yuan)(yuan)素(su)(su)之分(fen)。處(chu)(chu)在(zai)溶(rong)(rong)(rong)(rong)(rong)劑(Fe)晶格(ge)結點空隙(xi)處(chu)(chu)的(de)(de)元(yuan)(yuan)(yuan)(yuan)素(su)(su)(如C、N、B等),稱間(jian)隙(xi)型(xing)元(yuan)(yuan)(yuan)(yuan)素(su)(su);而(er)處(chu)(chu)在(zai)溶(rong)(rong)(rong)(rong)(rong)劑(Fe)晶格(ge)結點處(chu)(chu)的(de)(de)元(yuan)(yuan)(yuan)(yuan)素(su)(su)則(ze)稱為置換(huan)型(xing)元(yuan)(yuan)(yuan)(yuan)素(su)(su)(示意(yi)圖(tu)見(jian)圖(tu)2.4)。間(jian)隙(xi)型(xing)元(yuan)(yuan)(yuan)(yuan)素(su)(su)和置換(huan)型(xing)元(yuan)(yuan)(yuan)(yuan)素(su)(su)在(zai)鋼(gang)中所形(xing)成的(de)(de)固(gu)溶(rong)(rong)(rong)(rong)(rong)體(ti),又分(fen)別稱為間(jian)隙(xi)固(gu)溶(rong)(rong)(rong)(rong)(rong)體(ti)和置換(huan)固(gu)溶(rong)(rong)(rong)(rong)(rong)體(ti)。
由于(yu)碳(tan)、氮等間隙元(yuan)素(su)在鐵素(su)體中(zhong)的固(gu)(gu)溶(rong)度(du)很低,因(yin)此,鐵素(su)體不(bu)銹鋼主(zhu)要是(shi)置換固(gu)(gu)溶(rong)體;由于(yu)包(bao)括碳(tan)、氮在內的幾乎所有合(he)金元(yuan)素(su)在奧(ao)氏體中(zhong)均有相當的固(gu)(gu)溶(rong)度(du)(甚至可無限固(gu)(gu)溶(rong)),因(yin)此,奧(ao)氏體不(bu)銹鋼則常(chang)常(chang)是(shi)間隙元(yuan)素(su)固(gu)(gu)溶(rong)和置換元(yuan)素(su)固(gu)(gu)溶(rong)共存的固(gu)(gu)溶(rong)體。