45Mn2無縫鋼管力學(xue)性能是保證鋼材最(zui)終使用性能(機械性能)的重要指標(biao)(biao),它取決于鋼的化(hua)學(xue)成分和(he)熱處理制度。在鋼管(guan)標(biao)(biao)準(zhun)中(zhong),根據不同(tong)的使用要求,規定了拉伸(shen)性能(抗拉強度、屈服(fu)強度或(huo)屈服(fu)點、伸(shen)長率)以及(ji)硬度、韌性指標(biao)(biao),還有用戶要求的高、低溫(wen)性能等。
①抗(kang)拉(la)強(qiang)度(σb)試樣在拉(la)伸(shen)過程中(zhong),在拉(la)斷時所承受的大力(Fb),除以(yi)試樣原橫截(jie)面積(So)所得的應(ying)力(σ),稱為抗(kang)拉(la)強(qiang)度(σb),單(dan)位為N/mm2(MPa)。它表示金屬材(cai)料在拉(la)力作用下抵抗(kang)破壞的大能力。
②屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)點(dian)(dian)(dian)(σs)具有屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)現(xian)象的金屬材料,試樣(yang)在拉伸(shen)過程(cheng)(cheng)中力(li)不增加(保持恒(heng)定(ding))仍(reng)能繼續伸(shen)長時(shi)的應(ying)(ying)力(li),稱屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)點(dian)(dian)(dian)。若力(li)發生(sheng)下(xia)(xia)降時(shi),則應(ying)(ying)區分上、下(xia)(xia)屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)點(dian)(dian)(dian)。屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)點(dian)(dian)(dian)的單位為N/mm2(MPa)。上屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)點(dian)(dian)(dian)(σsu):試樣(yang)發生(sheng)屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)而力(li)下(xia)(xia)降前的大(da)應(ying)(ying)力(li); 下(xia)(xia)屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)點(dian)(dian)(dian)(σsl):當(dang)不計初始(shi)瞬(shun)時(shi)效(xiao)應(ying)(ying)時(shi),屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)階段(duan)中的小應(ying)(ying)力(li)。屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)點(dian)(dian)(dian)的計算公式為:式中:Fs--試樣(yang)拉伸(shen)過程(cheng)(cheng)中屈(qu)(qu)(qu)(qu)服(fu)(fu)(fu)力(li)(恒(heng)定(ding)),N(牛頓)So--試樣(yang)原始(shi)橫截面積,mm2。
③斷(duan)(duan)后伸長(chang)率(lv)(σ)在拉伸試(shi)驗中(zhong),試(shi)樣(yang)拉斷(duan)(duan)后其(qi)標(biao)距所增加的長(chang)度與原標(biao)距長(chang)度的百(bai)分(fen)比,稱(cheng)為(wei)伸長(chang)率(lv)。以σ表示,單位為(wei)%。計(ji)算公式為(wei):σ=(Lh-Lo)/L0*100%式中(zhong):Lh--試(shi)樣(yang)拉斷(duan)(duan)后的標(biao)距長(chang)度,mm; L0--試(shi)樣(yang)原始標(biao)距長(chang)度,mm。
④斷(duan)(duan)面(mian)收(shou)縮(suo)率(ψ)在拉(la)伸試驗中,試樣拉(la)斷(duan)(duan)后其縮(suo)徑(jing)(jing)處橫截(jie)面(mian)積(ji)的(de)大縮(suo)減(jian)量與原始(shi)橫截(jie)面(mian)積(ji)的(de)百分比,稱為(wei)斷(duan)(duan)面(mian)收(shou)縮(suo)率。以ψ表示(shi),單位為(wei)%。計(ji)算公式如下:式中:S0--試樣原始(shi)橫截(jie)面(mian)積(ji),mm2; S1--試樣拉(la)斷(duan)(duan)后縮(suo)徑(jing)(jing)處的(de)最少(shao)橫截(jie)面(mian)積(ji),mm2。
⑤硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)指標金(jin)(jin)屬(shu)材(cai)料抵抗硬(ying)(ying)(ying)(ying)的(de)(de)物體壓(ya)(ya)陷表(biao)(biao)面(mian)(mian)的(de)(de)能力,稱為硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)。根(gen)據(ju)試(shi)驗(yan)方法和適用(yong)范圍(wei)不同,硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)又可(ke)分為布(bu)氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)、洛(luo)氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)、維氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)、肖氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)、顯微硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)和高溫硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)等。對(dui)于(yu)(yu)管(guan)材(cai)一般常(chang)用(yong)的(de)(de)有布(bu)氏(shi)(shi)、洛(luo)氏(shi)(shi)、維氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)三種。A、布(bu)氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)(HB)用(yong)一定直(zhi)徑(jing)(jing)的(de)(de)鋼(gang)(gang)(gang)球(qiu)或硬(ying)(ying)(ying)(ying)質合金(jin)(jin)球(qiu),以(yi)(yi)規(gui)定的(de)(de)試(shi)驗(yan)力(F)壓(ya)(ya)入式樣(yang)表(biao)(biao)面(mian)(mian),經規(gui)定保(bao)持時間后卸除(chu)試(shi)驗(yan)力,測(ce)量試(shi)樣(yang)表(biao)(biao)面(mian)(mian)的(de)(de)壓(ya)(ya)痕(hen)(hen)直(zhi)徑(jing)(jing)(L)。布(bu)氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)值是(shi)以(yi)(yi)試(shi)驗(yan)力除(chu)以(yi)(yi)壓(ya)(ya)痕(hen)(hen)球(qiu)形表(biao)(biao)面(mian)(mian)積所(suo)得的(de)(de)商(shang)。以(yi)(yi)HBS(鋼(gang)(gang)(gang)球(qiu))表(biao)(biao)示,單位為N/mm2(MPa)。其計算公(gong)式為:式中:F--壓(ya)(ya)入金(jin)(jin)屬(shu)試(shi)樣(yang)表(biao)(biao)面(mian)(mian)的(de)(de)試(shi)驗(yan)力,N; D--試(shi)驗(yan)用(yong)鋼(gang)(gang)(gang)球(qiu)直(zhi)徑(jing)(jing),mm; d--壓(ya)(ya)痕(hen)(hen)平均(jun)直(zhi)徑(jing)(jing),mm。測(ce)定布(bu)氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)較準確可(ke)靠,但(dan)一般HBS只(zhi)適用(yong)于(yu)(yu)450N/mm2(MPa)以(yi)(yi)下(xia)的(de)(de)金(jin)(jin)屬(shu)材(cai)料,對(dui)于(yu)(yu)較硬(ying)(ying)(ying)(ying)的(de)(de)鋼(gang)(gang)(gang)或較薄的(de)(de)板材(cai)不適用(yong)。在鋼(gang)(gang)(gang)管(guan)標準中,布(bu)氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)用(yong)途最(zui)廣,往(wang)往(wang)以(yi)(yi)壓(ya)(ya)痕(hen)(hen)直(zhi)徑(jing)(jing)d來表(biao)(biao)示該材(cai)料的(de)(de)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du),既直(zhi)觀,又方便。舉例:120HBS10/1000/30:表(biao)(biao)示用(yong)直(zhi)徑(jing)(jing)10mm鋼(gang)(gang)(gang)球(qiu)在1000Kgf(9.807KN)試(shi)驗(yan)力作用(yong)下(xia),保(bao)持30s(秒)測(ce)得的(de)(de)布(bu)氏(shi)(shi)硬(ying)(ying)(ying)(ying)度(du)(du)(du)(du)(du)(du)值為120N/ mm2(MPa)。