45Mn2無縫鋼管力學性(xing)(xing)能是(shi)保證鋼(gang)材最終使用(yong)性(xing)(xing)能(機械性(xing)(xing)能)的(de)重要(yao)指標,它取決于鋼(gang)的(de)化學成分和熱(re)處理制度。在鋼(gang)管(guan)標準中,根據不(bu)同的(de)使用(yong)要(yao)求,規(gui)定了拉(la)伸性(xing)(xing)能(抗拉(la)強(qiang)度、屈服(fu)(fu)強(qiang)度或屈服(fu)(fu)點、伸長率)以及(ji)硬度、韌性(xing)(xing)指標,還有用(yong)戶要(yao)求的(de)高、低溫(wen)性(xing)(xing)能等。
①抗(kang)拉(la)(la)強(qiang)度(σb)試(shi)樣在(zai)拉(la)(la)伸過程中,在(zai)拉(la)(la)斷(duan)時所承(cheng)受的大力(Fb),除以(yi)試(shi)樣原橫(heng)截面積(So)所得的應力(σ),稱為(wei)抗(kang)拉(la)(la)強(qiang)度(σb),單位為(wei)N/mm2(MPa)。它表(biao)示金屬材料在(zai)拉(la)(la)力作用下(xia)抵抗(kang)破(po)壞的大能力。
②屈(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(σs)具(ju)有屈(qu)服(fu)(fu)(fu)(fu)現象的(de)(de)(de)金屬材料,試(shi)(shi)樣(yang)在拉(la)伸過(guo)程(cheng)中(zhong)力(li)(li)不增加(保持恒定)仍(reng)能繼續伸長時(shi)的(de)(de)(de)應(ying)力(li)(li),稱屈(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)。若力(li)(li)發(fa)生(sheng)下降(jiang)時(shi),則(ze)應(ying)區分上(shang)、下屈(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)。屈(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)的(de)(de)(de)單位為N/mm2(MPa)。上(shang)屈(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(σsu):試(shi)(shi)樣(yang)發(fa)生(sheng)屈(qu)服(fu)(fu)(fu)(fu)而(er)力(li)(li)下降(jiang)前的(de)(de)(de)大(da)應(ying)力(li)(li); 下屈(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(σsl):當不計初始瞬時(shi)效應(ying)時(shi),屈(qu)服(fu)(fu)(fu)(fu)階段中(zhong)的(de)(de)(de)小應(ying)力(li)(li)。屈(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)的(de)(de)(de)計算公(gong)式為:式中(zhong):Fs--試(shi)(shi)樣(yang)拉(la)伸過(guo)程(cheng)中(zhong)屈(qu)服(fu)(fu)(fu)(fu)力(li)(li)(恒定),N(牛頓)So--試(shi)(shi)樣(yang)原始橫截面積,mm2。
③斷后(hou)伸長(chang)(chang)率(σ)在拉伸試驗中,試樣(yang)拉斷后(hou)其標(biao)距(ju)(ju)(ju)所增(zeng)加的(de)長(chang)(chang)度(du)(du)與原(yuan)標(biao)距(ju)(ju)(ju)長(chang)(chang)度(du)(du)的(de)百分比,稱為(wei)伸長(chang)(chang)率。以σ表示,單位為(wei)%。計算公式為(wei):σ=(Lh-Lo)/L0*100%式中:Lh--試樣(yang)拉斷后(hou)的(de)標(biao)距(ju)(ju)(ju)長(chang)(chang)度(du)(du),mm; L0--試樣(yang)原(yuan)始(shi)標(biao)距(ju)(ju)(ju)長(chang)(chang)度(du)(du),mm。
④斷(duan)(duan)面收縮率(ψ)在拉(la)伸(shen)試驗中(zhong),試樣拉(la)斷(duan)(duan)后(hou)其縮徑(jing)處橫截(jie)面積(ji)的大縮減量與原始(shi)橫截(jie)面積(ji)的百分比(bi),稱為斷(duan)(duan)面收縮率。以ψ表示,單(dan)位為%。計算公式如下:式中(zhong):S0--試樣原始(shi)橫截(jie)面積(ji),mm2; S1--試樣拉(la)斷(duan)(duan)后(hou)縮徑(jing)處的最少橫截(jie)面積(ji),mm2。
⑤硬(ying)(ying)(ying)度(du)(du)(du)(du)指標(biao)金(jin)(jin)屬材(cai)料(liao)抵抗硬(ying)(ying)(ying)的(de)(de)物體壓(ya)陷(xian)表(biao)面(mian)的(de)(de)能力,稱為硬(ying)(ying)(ying)度(du)(du)(du)(du)。根據試(shi)驗(yan)方法和適用(yong)(yong)范圍不(bu)同,硬(ying)(ying)(ying)度(du)(du)(du)(du)又可分為布(bu)(bu)氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)、洛氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)、維氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)、肖氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)、顯微(wei)硬(ying)(ying)(ying)度(du)(du)(du)(du)和高(gao)溫硬(ying)(ying)(ying)度(du)(du)(du)(du)等。對于(yu)(yu)管(guan)材(cai)一(yi)般常用(yong)(yong)的(de)(de)有布(bu)(bu)氏(shi)(shi)(shi)、洛氏(shi)(shi)(shi)、維氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)三種。A、布(bu)(bu)氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)(HB)用(yong)(yong)一(yi)定直(zhi)(zhi)(zhi)徑(jing)(jing)的(de)(de)鋼球(qiu)(qiu)(qiu)或硬(ying)(ying)(ying)質合(he)金(jin)(jin)球(qiu)(qiu)(qiu),以(yi)(yi)規定的(de)(de)試(shi)驗(yan)力(F)壓(ya)入(ru)式(shi)(shi)樣表(biao)面(mian),經規定保(bao)持時間(jian)后卸除試(shi)驗(yan)力,測(ce)量試(shi)樣表(biao)面(mian)的(de)(de)壓(ya)痕(hen)直(zhi)(zhi)(zhi)徑(jing)(jing)(L)。布(bu)(bu)氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)值是以(yi)(yi)試(shi)驗(yan)力除以(yi)(yi)壓(ya)痕(hen)球(qiu)(qiu)(qiu)形表(biao)面(mian)積(ji)所得(de)的(de)(de)商。以(yi)(yi)HBS(鋼球(qiu)(qiu)(qiu))表(biao)示(shi),單位為N/mm2(MPa)。其計算公式(shi)(shi)為:式(shi)(shi)中:F--壓(ya)入(ru)金(jin)(jin)屬試(shi)樣表(biao)面(mian)的(de)(de)試(shi)驗(yan)力,N; D--試(shi)驗(yan)用(yong)(yong)鋼球(qiu)(qiu)(qiu)直(zhi)(zhi)(zhi)徑(jing)(jing),mm; d--壓(ya)痕(hen)平均直(zhi)(zhi)(zhi)徑(jing)(jing),mm。測(ce)定布(bu)(bu)氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)較準確可靠,但一(yi)般HBS只適用(yong)(yong)于(yu)(yu)450N/mm2(MPa)以(yi)(yi)下(xia)的(de)(de)金(jin)(jin)屬材(cai)料(liao),對于(yu)(yu)較硬(ying)(ying)(ying)的(de)(de)鋼或較薄的(de)(de)板(ban)材(cai)不(bu)適用(yong)(yong)。在鋼管(guan)標(biao)準中,布(bu)(bu)氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)用(yong)(yong)途(tu)最廣,往(wang)往(wang)以(yi)(yi)壓(ya)痕(hen)直(zhi)(zhi)(zhi)徑(jing)(jing)d來表(biao)示(shi)該材(cai)料(liao)的(de)(de)硬(ying)(ying)(ying)度(du)(du)(du)(du),既直(zhi)(zhi)(zhi)觀,又方便。舉例:120HBS10/1000/30:表(biao)示(shi)用(yong)(yong)直(zhi)(zhi)(zhi)徑(jing)(jing)10mm鋼球(qiu)(qiu)(qiu)在1000Kgf(9.807KN)試(shi)驗(yan)力作用(yong)(yong)下(xia),保(bao)持30s(秒)測(ce)得(de)的(de)(de)布(bu)(bu)氏(shi)(shi)(shi)硬(ying)(ying)(ying)度(du)(du)(du)(du)值為120N/ mm2(MPa)。