45Mn2無縫鋼管力學性(xing)能是保證(zheng)鋼(gang)材最終使用(yong)性(xing)能(機械(xie)性(xing)能)的重要(yao)指標,它取決于鋼(gang)的化學成分和熱處理(li)制度。在鋼(gang)管標準中,根據不(bu)同的使用(yong)要(yao)求,規定了(le)拉(la)伸性(xing)能(抗拉(la)強度、屈(qu)服強度或(huo)屈(qu)服點、伸長率(lv))以及(ji)硬度、韌性(xing)指標,還有用(yong)戶要(yao)求的高(gao)、低溫(wen)性(xing)能等。
①抗拉(la)強度(du)(σb)試樣在拉(la)伸過程中(zhong),在拉(la)斷時(shi)所(suo)承受的大力(li)(Fb),除以試樣原橫截面積(So)所(suo)得的應力(li)(σ),稱為(wei)抗拉(la)強度(du)(σb),單位為(wei)N/mm2(MPa)。它(ta)表(biao)示金屬材(cai)料在拉(la)力(li)作(zuo)用下抵抗破壞的大能力(li)。
②屈(qu)(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(dian)(dian)(σs)具有屈(qu)(qu)服(fu)(fu)(fu)(fu)現象的(de)金屬材(cai)料(liao),試樣在拉(la)伸過程中(zhong)(zhong)力不增加(保持恒定(ding))仍能繼(ji)續(xu)伸長時(shi)的(de)應(ying)力,稱屈(qu)(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(dian)(dian)。若力發(fa)生下(xia)降(jiang)時(shi),則應(ying)區分上、下(xia)屈(qu)(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(dian)(dian)。屈(qu)(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(dian)(dian)的(de)單位為N/mm2(MPa)。上屈(qu)(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(dian)(dian)(σsu):試樣發(fa)生屈(qu)(qu)服(fu)(fu)(fu)(fu)而力下(xia)降(jiang)前的(de)大應(ying)力; 下(xia)屈(qu)(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(dian)(dian)(σsl):當不計初始瞬時(shi)效應(ying)時(shi),屈(qu)(qu)服(fu)(fu)(fu)(fu)階(jie)段中(zhong)(zhong)的(de)小(xiao)應(ying)力。屈(qu)(qu)服(fu)(fu)(fu)(fu)點(dian)(dian)(dian)(dian)(dian)的(de)計算公式為:式中(zhong)(zhong):Fs--試樣拉(la)伸過程中(zhong)(zhong)屈(qu)(qu)服(fu)(fu)(fu)(fu)力(恒定(ding)),N(牛(niu)頓)So--試樣原始橫截(jie)面積,mm2。
③斷(duan)后(hou)伸(shen)長(chang)率(σ)在拉伸(shen)試(shi)驗(yan)中(zhong),試(shi)樣(yang)拉斷(duan)后(hou)其標距所(suo)增加的長(chang)度與原標距長(chang)度的百分比,稱為(wei)伸(shen)長(chang)率。以σ表示,單位為(wei)%。計算公式(shi)為(wei):σ=(Lh-Lo)/L0*100%式(shi)中(zhong):Lh--試(shi)樣(yang)拉斷(duan)后(hou)的標距長(chang)度,mm; L0--試(shi)樣(yang)原始標距長(chang)度,mm。
④斷面(mian)收(shou)縮(suo)率(ψ)在拉(la)伸試(shi)(shi)驗中(zhong),試(shi)(shi)樣(yang)拉(la)斷后(hou)其(qi)縮(suo)徑處(chu)(chu)橫截面(mian)積的(de)大縮(suo)減量與原(yuan)始(shi)橫截面(mian)積的(de)百(bai)分比,稱為(wei)斷面(mian)收(shou)縮(suo)率。以(yi)ψ表示,單位為(wei)%。計算公式如(ru)下:式中(zhong):S0--試(shi)(shi)樣(yang)原(yuan)始(shi)橫截面(mian)積,mm2; S1--試(shi)(shi)樣(yang)拉(la)斷后(hou)縮(suo)徑處(chu)(chu)的(de)最少(shao)橫截面(mian)積,mm2。
⑤硬(ying)度(du)指標金(jin)(jin)屬(shu)(shu)材(cai)(cai)料(liao)抵抗(kang)硬(ying)的(de)(de)物(wu)體壓(ya)(ya)陷表(biao)面(mian)(mian)的(de)(de)能(neng)力(li),稱為硬(ying)度(du)。根據試(shi)(shi)驗(yan)(yan)(yan)(yan)方(fang)法(fa)和(he)適(shi)用(yong)范圍不同,硬(ying)度(du)又(you)可分(fen)為布(bu)氏(shi)(shi)(shi)硬(ying)度(du)、洛氏(shi)(shi)(shi)硬(ying)度(du)、維氏(shi)(shi)(shi)硬(ying)度(du)、肖氏(shi)(shi)(shi)硬(ying)度(du)、顯(xian)微硬(ying)度(du)和(he)高溫硬(ying)度(du)等。對于管(guan)材(cai)(cai)一(yi)般常用(yong)的(de)(de)有布(bu)氏(shi)(shi)(shi)、洛氏(shi)(shi)(shi)、維氏(shi)(shi)(shi)硬(ying)度(du)三種。A、布(bu)氏(shi)(shi)(shi)硬(ying)度(du)(HB)用(yong)一(yi)定(ding)(ding)直(zhi)徑(jing)的(de)(de)鋼(gang)(gang)(gang)球(qiu)或硬(ying)質合金(jin)(jin)球(qiu),以(yi)(yi)規定(ding)(ding)的(de)(de)試(shi)(shi)驗(yan)(yan)(yan)(yan)力(li)(F)壓(ya)(ya)入式(shi)樣(yang)(yang)表(biao)面(mian)(mian),經規定(ding)(ding)保持(chi)(chi)時(shi)間后卸除試(shi)(shi)驗(yan)(yan)(yan)(yan)力(li),測(ce)(ce)量試(shi)(shi)樣(yang)(yang)表(biao)面(mian)(mian)的(de)(de)壓(ya)(ya)痕(hen)(hen)直(zhi)徑(jing)(L)。布(bu)氏(shi)(shi)(shi)硬(ying)度(du)值是以(yi)(yi)試(shi)(shi)驗(yan)(yan)(yan)(yan)力(li)除以(yi)(yi)壓(ya)(ya)痕(hen)(hen)球(qiu)形表(biao)面(mian)(mian)積(ji)所得的(de)(de)商(shang)。以(yi)(yi)HBS(鋼(gang)(gang)(gang)球(qiu))表(biao)示,單位為N/mm2(MPa)。其計算公式(shi)為:式(shi)中:F--壓(ya)(ya)入金(jin)(jin)屬(shu)(shu)試(shi)(shi)樣(yang)(yang)表(biao)面(mian)(mian)的(de)(de)試(shi)(shi)驗(yan)(yan)(yan)(yan)力(li),N; D--試(shi)(shi)驗(yan)(yan)(yan)(yan)用(yong)鋼(gang)(gang)(gang)球(qiu)直(zhi)徑(jing),mm; d--壓(ya)(ya)痕(hen)(hen)平均(jun)直(zhi)徑(jing),mm。測(ce)(ce)定(ding)(ding)布(bu)氏(shi)(shi)(shi)硬(ying)度(du)較準(zhun)確可靠,但一(yi)般HBS只(zhi)適(shi)用(yong)于450N/mm2(MPa)以(yi)(yi)下的(de)(de)金(jin)(jin)屬(shu)(shu)材(cai)(cai)料(liao),對于較硬(ying)的(de)(de)鋼(gang)(gang)(gang)或較薄(bo)的(de)(de)板材(cai)(cai)不適(shi)用(yong)。在鋼(gang)(gang)(gang)管(guan)標準(zhun)中,布(bu)氏(shi)(shi)(shi)硬(ying)度(du)用(yong)途最廣,往往以(yi)(yi)壓(ya)(ya)痕(hen)(hen)直(zhi)徑(jing)d來表(biao)示該材(cai)(cai)料(liao)的(de)(de)硬(ying)度(du),既直(zhi)觀(guan),又(you)方(fang)便。舉(ju)例:120HBS10/1000/30:表(biao)示用(yong)直(zhi)徑(jing)10mm鋼(gang)(gang)(gang)球(qiu)在1000Kgf(9.807KN)試(shi)(shi)驗(yan)(yan)(yan)(yan)力(li)作(zuo)用(yong)下,保持(chi)(chi)30s(秒)測(ce)(ce)得的(de)(de)布(bu)氏(shi)(shi)(shi)硬(ying)度(du)值為120N/ mm2(MPa)。