【摘要】：球墨鑄鐵屬于高強(qiáng)材料,具有接近于鋼材的綜合性能,且其生產(chǎn)成本較低,已用于制造對強(qiáng)度、韌性和耐磨性要求較高的零部件,在油氣管道、交通運(yùn)輸、農(nóng)機(jī)、船舶制造、礦石開采等領(lǐng)域具有廣闊的應(yīng)用前景。近年來,隨著社會節(jié)能環(huán)保意識的不斷增強(qiáng),材料的發(fā)展日益倡導(dǎo)輕重量、高效率和低成本,球墨鑄鐵的優(yōu)異特性使其有望取代灰鑄鐵和可鍛鑄鐵等工程材料,表現(xiàn)出巨大的發(fā)展?jié)摿�。但球墨鑄鐵的焊接性較差,成為限制其進(jìn)一步推廣應(yīng)用的首要因素。本課題采用ER50-6低合金鋼焊絲作為填充材料,在預(yù)熱150℃條件下,對新型鐵素體基球墨鑄鐵的CO2氣體保護(hù)焊(GMAW)展開研究。試驗使用金相顯微鏡(OM)、掃描電子顯微鏡(SEM)、維氏硬度計和萬能拉伸試驗機(jī)等手段研究接頭的組織和力學(xué)性能,并分析焊接工藝參數(shù)、顯微組織、裂紋形態(tài)以及力學(xué)性能之間的關(guān)系。采用雙面焊成形和單面焊雙面成形兩種方式焊接球墨鑄鐵,獲得的接頭焊縫中均出現(xiàn)明顯的氣孔,氣孔直徑一般小于0.5mm,試驗表明,焊接速度是影響氣孔產(chǎn)生的重要因素,適當(dāng)降低焊接速度可以有效的減少氣孔數(shù)量。接頭的宏觀裂紋一般出現(xiàn)在雙面焊成形的熔合區(qū),裂紋啟裂于焊趾部位,并沿著熔合區(qū)擴(kuò)展。裂紋形成的原因主要是接頭組織差異較大而產(chǎn)生過大的殘余應(yīng)力,并且熔合區(qū)主要為淬硬的萊氏體,對應(yīng)力的松弛能力較差。針對焊接熱輸入對焊縫、熔合區(qū)組織以及接頭顯微硬度的影響進(jìn)行了研究。試驗結(jié)果表明,淬硬組織一般出現(xiàn)在雙面焊接頭的后焊焊道,焊縫組織完全由竹葉狀的高碳馬氏體和少量的殘余奧氏體構(gòu)成,顯微硬度達(dá)到600～650HV500g。由于熱輸入較小,接頭冷卻速度快,在其熱影響區(qū)還會形成較窄的淬硬區(qū)。對于單面焊雙面成形接頭,焊縫組織主要為細(xì)小片層狀的托氏體,將熱輸入由8.6kJ/cm增加到18.2kJ/cm,可以看出托氏體的數(shù)量增加,片層間距也逐漸增大,焊縫的硬度由508HV500g降低到444HV500g。熔合區(qū)的萊氏體組織對熱輸入變化并不敏感,但增加熱輸入會使白口區(qū)寬度增大,因而從接頭的強(qiáng)韌性考慮要合理的控制焊接熱輸入。研究球墨鑄鐵焊接接頭的力學(xué)性能,結(jié)果顯示斷裂主要出現(xiàn)在熔合區(qū),單面焊雙面成形接頭的抗拉強(qiáng)度可以達(dá)到262MPa。使用掃描電鏡(SEM)對斷口形貌進(jìn)行觀察,無韌窩產(chǎn)生,斷口完全為脆性解理斷裂,裂紋沿著熔合區(qū)擴(kuò)展,并形成高低不平的解理臺階。
[Abstract]:Ductile iron is a kind of high strength material, it has close to the comprehensive properties of steel, and its production cost is relatively low. It has been used to manufacture parts which require higher strength, toughness and wear resistance, in oil and gas pipeline, transportation, agricultural machinery, ship manufacture, Ore mining and other fields have broad application prospects. In recent years, with the increasing awareness of energy saving and environmental protection in society, the development of materials increasingly advocates light weight, high efficiency and low cost. The excellent properties of ductile iron make it possible to replace engineering materials such as gray cast iron and malleable cast iron. Show great potential for development. However, the weldability of ductile iron is poor, which is the primary factor restricting its further application. In this paper, ER50-6 low alloy steel wire was used as filling material, and the CO2 gas shielded (GMAW) welding of new ferrite based ductile iron was studied under preheating condition of 150 鈩，

本文編號：2370664