【摘要】：球墨鑄鐵作為重要的金屬結(jié)構(gòu)材料具有優(yōu)良的機(jī)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(fēng)電裝備等領(lǐng)域應(yīng)用較為廣泛。由于上述領(lǐng)域的各類設(shè)備大部分工作環(huán)境惡劣,有些需要在寒冷或者腐蝕嚴(yán)重的條件下經(jīng)受頻繁的外力沖擊,這就對球墨鑄鐵的韌性和強(qiáng)度同時提出了更高的要求。以牌號QT400-18為代表的高強(qiáng)度高韌性球墨鑄鐵因其在強(qiáng)度和韌性平衡方面的優(yōu)越性,成為眾多船用柴油機(jī)的機(jī)體和缸蓋等關(guān)鍵鑄件的材質(zhì)選擇,在實(shí)際生產(chǎn)中,大部分企業(yè)都依靠Si或者合金元素的固溶強(qiáng)化+高溫石墨化退火實(shí)現(xiàn)球墨鑄鐵鑄件兼具強(qiáng)度和韌性。本課題是由作者所在單位中車大連機(jī)車車輛有限公司鑄鍛分公司與大連理工大學(xué)合作進(jìn)行的實(shí)踐型課題。中車大連機(jī)車車輛有限公司鑄鍛分公司生產(chǎn)的某中大型柴油機(jī)機(jī)體材質(zhì)為QT400-18A,技術(shù)要求為抗拉強(qiáng)度Rm≥390MPa,屈服強(qiáng)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(qiáng)化+高溫退火的工藝方案生產(chǎn),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(fèi)。為了縮短生產(chǎn)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(xué)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(xué)性能和金相組織的所有要求。本課題在P6型柴油機(jī)機(jī)體的生產(chǎn)過程中實(shí)施,采用兩臺5t中頻感應(yīng)電爐聯(lián)合熔化,選用本溪高純生鐵和優(yōu)質(zhì)碳素結(jié)構(gòu)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(jié)合多次孕育技術(shù),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(qiáng)度高韌性球墨鑄鐵機(jī)體。在此基礎(chǔ)上分別試驗(yàn)了三種不同位置的附鑄試塊的力學(xué)性能和金相組織,通過對比分析,發(fā)現(xiàn)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(nèi)部組織致密,無疏松和夾渣缺陷,各項(xiàng)性能指標(biāo)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(yàn)表明,當(dāng)硅含量為1.8%時其鐵素體含量最低,強(qiáng)度和硬度最低,而23。C時沖擊值最高；當(dāng)銅含量為0.25%時其珠光體含量最高,強(qiáng)度和硬度也最高,而23℃時沖擊值最低。依據(jù)該結(jié)果,將1.8%Si+0.2%Cu的方案應(yīng)用于P6型柴油機(jī)機(jī)體的批量生產(chǎn),鑄件合格,經(jīng)濟(jì)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(qiáng)度390MPa-410 MPa,屈服強(qiáng)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(shù)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