【正文】 數(shù)問題存在于熱影響區(qū)，比如淬硬，冷裂，局部脆化和再熱裂紋都和熱影響區(qū)結(jié)構(gòu)轉(zhuǎn)變和產(chǎn)生有關(guān)。關(guān)鍵字：沖擊韌性，物理模擬，CCT，耐磨鋼引言高強耐磨鋼NM360的冶金機制是增加碳和其他合金元素的組成，已經(jīng)被廣泛的應(yīng)用在挖掘機械領(lǐng)域。物理模擬是一種解決這問題的有效方法，根據(jù)熱循環(huán)曲線，它可以放大熱影響區(qū)的任意位置或者其他地方，然后可以觀察到微觀結(jié)構(gòu)而且性能也可以被方便的檢測。材料和試驗方法實驗材料是高強耐磨鋼NM360。NM360鋼的微觀結(jié)構(gòu)顯示在圖1。熱影響區(qū)粗晶粒的形成溫度從1200℃到1400℃變化。測量瞬時加熱速度WH將會產(chǎn)生很大錯誤。（4）冷去速度WC對于通常的低合金高強鋼，熱影響區(qū)的微觀結(jié)構(gòu)取決于540℃的冷卻速度或者是冷卻時間t8/5（從800℃到500℃的冷卻時間）。涉及到以下因素，t8/5被確定為5s、10s、15s、20s、25s、30s、40s、50s、60s：中間組織，鐵素體珠光體出現(xiàn)的關(guān)鍵冷卻時間；馬氏體轉(zhuǎn)變溫度Ms和Mf；CO2氣體保護焊的t8/5的最大變化范圍；NM360，15MnCrNiMo, 15MnMoVNRe, 14MnMoNbB, 14MnMoVN,BHW35和HQ系列硬化調(diào)和鋼的模擬熱影響區(qū)連續(xù)冷卻轉(zhuǎn)變曲線（SHCCT）。根據(jù)熱模擬GB265089，沖擊試樣被制作成帶夏比v型缺口的尺寸為10mm10mm55mm的形狀。當(dāng)t8/5在20s到40s變化時AKV達到最大值。當(dāng)貝氏體和馬氏體的組成達到一定比例，鋼就會具有高強度和高韌性的特點。可以從圖5（a）和圖5（b）看到當(dāng)t8/5小于20s時脊?fàn)钏毫押秃恿鳡罨哟嬖谟谒械牧鸭y中。圖5（c）（d）表明斷裂時纖維斷裂。在給定鋼的焊接條件（I，E，t8/5）下通過SHCCT圖就可以預(yù)見結(jié)構(gòu)和相轉(zhuǎn)變的過程。因為高的沖擊韌性（76J139J）和接近于基體金屬（380HV）的硬度（HV387HV360），不論在結(jié)構(gòu)和綜合性能上熱影響區(qū)粗晶區(qū)都有優(yōu)秀的變現(xiàn)。但是要指出的是預(yù)熱可能產(chǎn)生低的冷卻速度從而導(dǎo)致結(jié)構(gòu)脆性強度減小，和壞的韌性。最好的沖擊韌性在t8/5從25s到40s變化時取到，對應(yīng)的AKV在134J和139J之間。參考文獻[1] ZHONG Junjie, ZHU Hanhua, XIAO Changmo, et al. Experimental Research on the Antiwear Properties of the Steel NM360 [J]. Journal of Wuhan University of Technology. 2006, 30(3): 395397. [2] NIU Jitai. PHYSICAL SIMULATION IN MATERIALS AND HOTWORKING [M]. Beijing: National Defence Industrial Press, 1999. [3] YANG Fubao, BAI Binzhe, LIU Dongyu, et al. MICROSTRUCTURE AND PROPERTIES OF A CARBIDEFREE BAINITE/MARTENSITE ULTRAHI GH STRENGTH STEEL [J]. ACTAMETALLURGICA SINICA. 2004, 40(3): 296300.[4] Tomitay. Effect of martensite morphology on mechanical properties of low alloy steels having mixed structure of martensite and lower bainite [J]. Material Sci Technology. 1991, 7(4): 299306. [5] Youngch, Bgadeshiahkdh. Strength of mixtures of bainite and martensite [J]. Material Sci Technology. 1994, 10(3): 209214. [6] Li Deyuan ZZSD. Revision of a CCT Diagram of the Simulated ADI Weld Metal and Its Application in Actual Welding [J]. J. Mater. Sci. Technol. 1998(14): 147150. [7] Yinshike W G. Influnce of Weld Thermal Cycle on Microstructures of 10Ni5CrMoV Steel [J]. Transactions of the China Welding Institution. 1996, 17(1): 2530. 附錄Ⅱ 英文原文Study on Microstructure and Impact Ductility of Simulated Weld HAZ of HighStrength WearResistant Steel NM360Abstract: Highstrength wearresistant steel NM360 which is widely used in the field of excavating machinery always tends to welding crack during the manufacturing process due to the high carbon equivalent. The heat affected zone (HAZ) is the weakest part in a welding joint. In welding manufacture, most of the problems exist in HAZ such as harden quenching, cold crack, local brittleness as well as reheat crack are all related to the structure transformation and its products in HAZ material. In the present work, the impact ductility of NM360’s HAZ under different cooling rate has been studied by using physical simulation method. And the impact ductility evolution mechanism has been investigated according to the simulated HAZ continuous cooling transformation（CCT）diagram. The microstructure, hardness, tendency of hardenability, the possibility of generating cold crack of NM36039。 wearresistant steelIntroductionHighstrength wearresistant steel NM360, whose metallurgy mechanism is to increase the content of carbon and the other alloying elements, has been widely used in the field of excavating machinery. Th e bination property including the wear resistance, weldability and mouldability is improved by the precipitation and phase transition during the thermal refining after rolling[1]. In welding manufacture, most of the problems exist in heat affected zone (HAZ) such as harden quenching, cold crack, local brittleness as well as reheat crack are all related to the structure transformation and its products in HAZ material. It’s a difficult work to measure the HAZ phase transition in experiment because the phase transition in welding joint is very fast, as well as the temperature is high and the transition time is short. Physical simulation is an effective way to solve this kind of problem. It can amplify any position in HAZ or some other place according to the thermal cycling curve. Then the microstructure can be observed and the property can be tested conveniently. By using the least experiment, plenty of repetitive experiments which usually used before can be replaced. Thus, a great quantity of manpower and material resources can be saved. It provides a simple solution to the plex problem which can not be investigated directly[2].Materials and Experimental MethodThe experimental material is highstrength wearresistant steel NM360. To improve the hardenability, temper resistance of martensite and refined grain, alloying elements Mn, Cr, Ni, Mo, B, Si, Al and Ti have been added into NM360. Its chemical positions and mechanical properties are shown respectively in Table 1 and Table 2. It can be seen from Table 2 that the hardness and strength of NM360 steel is excellent, however, its ductility propert y is not very good. NM360 steel has been processed by thermal refining process (950℃ quenching and 500℃ tempering) after rolling and its microstructure is tempered sorbite with martensite characteristics. Microstructure of NM360 steel is shown in . Table 1 Chemical positions of NM360 steel(wt.%)CSiMnPSCuAlCrNiMoTiBNTable2 Mechanical properties of NM360 steelσbMPaσsMpaδ5%HBAKVJ(Room temperature)≥1200≥10001036042 Microstructure of highstrength wearresistant steel NM360In thermal simulation test, the specimen size which is decided by the heating system of Gleeble1500D is 11mm11mm90 mm. In order to make the coincidence between the programming curve and the actu al thermal cycling curve, the span between grips varies with t8/5. The assembly diagram of test sample is shown in [2].A: Contact Surface between Fixture Block and ColletB: Contact Surface of Electric and Heat betwee