【摘要】：球墨鑄鐵作為重要的金屬結構材料具有優(yōu)良的機械性能,一定程度上可與鋼媲美,且比鋼成本低廉,因此在軌道交通制造、船舶重工、風電裝備等領域應用較為廣泛。由于上述領域的各類設備大部分工作環(huán)境惡劣,有些需要在寒冷或者腐蝕嚴重的條件下經受頻繁的外力沖擊,這就對球墨鑄鐵的韌性和強度同時提出了更高的要求。以牌號QT400-18為代表的高強度高韌性球墨鑄鐵因其在強度和韌性平衡方面的優(yōu)越性,成為眾多船用柴油機的機體和缸蓋等關鍵鑄件的材質選擇,在實際生產中,大部分企業(yè)都依靠Si或者合金元素的固溶強化+高溫石墨化退火實現球墨鑄鐵鑄件兼具強度和韌性。本課題是由作者所在單位中車大連機車車輛有限公司鑄鍛分公司與大連理工大學合作進行的實踐型課題。中車大連機車車輛有限公司鑄鍛分公司生產的某中大型柴油機機體材質為QT400-18A,技術要求為抗拉強度Rm≥390MPa,屈服強度Rp0.2≥250MPa,伸長率A≥15%,布氏硬度140-180HBW,常溫下沖擊功平均值≥14J,單值≥11J。如果按照一般硅固溶強化+高溫退火的工藝方案生產,工藝流程長,退火時高溫下形成的氧化皮會使鑄件拋丸清理的時間成倍增加,造成人力和能源的浪費。為了縮短生產周期,節(jié)約成本,本課題通過重新選擇試塊位置和控制鐵液的化學成分(特別是Si和Cu的含量)得到鑄態(tài)下鑄件及其附鑄試塊均滿足其力學性能和金相組織的所有要求。本課題在P6型柴油機機體的生產過程中實施,采用兩臺5t中頻感應電爐聯合熔化,選用本溪高純生鐵和優(yōu)質碳素結構鋼為主要爐料,通過夾層覆蓋沖入法球化處理和多次孕育方式結合多次孕育技術,得到了鑄態(tài)組織為鐵素體+少量珠光體+球狀石墨+極少量硬化相的QT400-18高強度高韌性球墨鑄鐵機體。在此基礎上分別試驗了三種不同位置的附鑄試塊的力學性能和金相組織,通過對比分析,發(fā)現在鑄件端面平臺處的位置①(鑄型的下表面)冷卻條件與鑄件一致,且內部組織致密,無疏松和夾渣缺陷,各項性能指標穩(wěn)定。繼而采用該試塊位置,又分別研究了不同硅含量(Si1.8%,2.0%,2.2%,2.6%)和不同銅含量(Cu0.05%,0.10%,0.16%,0.25%)對附鑄試塊性能和組織的影響。試驗表明,當硅含量為1.8%時其鐵素體含量最低,強度和硬度最低,而23。C時沖擊值最高；當銅含量為0.25%時其珠光體含量最高,強度和硬度也最高,而23℃時沖擊值最低。依據該結果,將1.8%Si+0.2%Cu的方案應用于P6型柴油機機體的批量生產,鑄件合格,經濟效益顯著。位置①的6個試塊鑄態(tài)下珠光體含量在2%-10%,抗拉強度390MPa-410 MPa,屈服強度253MPa-266 MPa,伸長率20%-28%,布氏硬度140-150HBW,常溫下沖擊功平均值14J-16J,符合技術要求。
[Abstract]:As an important metal structure material, ductile iron has excellent mechanical properties, which is comparable to steel to a certain extent, and its cost is lower than that of steel. Therefore, it is widely used in the fields of rail transit manufacturing, ship heavy industry, wind power equipment and so on. Because most of the equipments in these fields have bad working conditions, some of them need to withstand frequent external force impact under cold or severe corrosion conditions, which requires higher toughness and strength of nodular cast iron at the same time. Because of its superiority in strength and toughness balance, high strength and high toughness ductile iron represented by brand QT400-18 has become the material choice of many key castings such as block and cylinder head of marine diesel engine. Most enterprises rely on solution strengthening and high temperature graphitization annealing of Si or alloy elements to realize ductile iron castings with both strength and toughness. This paper is a practical project carried out by the casting and forging branch of Dalian Locomotive and Rolling Stock Co., Ltd and Dalian University of Technology. The material of a medium-large diesel engine block produced by the casting and forging Branch of Dalian Locomotive and Rolling Stock Co., Ltd is QT400-18A, technical requirement: tensile strength Rmx390 MPa, yield strength Rp0.2 / 250 MPa, elongation A 鈮，

本文編號：2443109