阶段等温淬火工艺对球墨铸铁性能和组织的影响

本文研究了阶段等温淬火工艺对球墨铸铁性能和组织的影响。结果表明，只要等温时间适当，可得到一种粒状贝氏体组织，具有这种上组织的球墨铸铁有良好的综合力学性能。     

350℃-Thermal Stability of Austempered Ductile Iron

The thermal stability of an ADI has been studied by isothermal aging at 350℃ for 150 hours, measuring the amount of retained austenite and its carbon content by X-ray diffractometry. The influence of different austempering treatments, carried out at temperatures between 300 and 450℃ (300, 330, 360, 410 and 450℃) and holding times between15 and 60 minutes (15, 30, 45, 60), was considered. Thermal stability depends on whether austempering temperature is higher or lower than the ageing one. Thermal stability increases by increasing austempering temperatures, from 300° to410℃. Samples treated at 410° and 450° show a lower austenite decomposition than samples at 300-330-360℃. A drop in stability is shown by increasing the austempering temperature from 410° to 450℃. The results have been interpreted on the basis of the austenite stability out of the processing window, which in turn depends on the austempering parameters.     

奥氏体—贝氏体复相组织在模具中的应用研究

考察了等温淬火温度和时间对６０ｓｉ２ＭｎＡ钢组织和性能的影响。实验结果表明，这种钢的奥氏体—贝氏体复相组织强韧性良好。原因在于其特有的组织形貌以及贝氏体为无碳化物贝氏体。应用于模具上，使用寿命可提高４～５倍，达到基体用ＬＤ的水平。     

Mechanical Properties and Retained Austenite Transformation Mechanism of TRIP-Aided Polygonal Ferrite Matrix Seamless Steel Tube

Through the comparison of microstructure for polygonal ferrite （PF） matrix transformation induced plasticity （TRIP） seamless steel tube at different positions before and after tensile rupture, the tran...     

Effects of Austempering on the Mechanical Properties of the Hot Rolled Si-Mn TRIP Steels

The effect of austempering on the mechanical properties of the hot rolled Si- Mn TRIP steels was studied. The mechanism of transformation induced plasticity （TRIP） was discussed through the examination of the microstructure and the mechanical properties of the specimens. The results stow that the microstructures of the steels were comprised of polygonal ferrite, granular bainite and a significant amount of stable retained austenite. The specimen exhibits excellent mechanical properties for the TRIP effect. Isothermal holding time for austempering affects the stability of retained austenite. The mechanical properties such as tensile strength, total elongation and strength ductility balance reach their optimal values （ 776 MPa , 33% and 25608 MPa% , respectively） when the specimen is held at 400℃ for 25 min.     

等温淬火工艺对球铁力学性能的影响

从标准梅花形试块制取试样 ,进行系列等温淬火工艺 ,观察金相组织 ,测定试样力学性能 ,分析各编组等温淬火工艺对力学性能的影响 ,确定了较合理的球铁等温淬火工艺     

"两步法" 制备等温淬火球铁的研究

由于单一温度下的等温淬火工艺不能同时达到高硬度和高韧性，开发了两步法等温淬火热处理工艺。其原理是：工件经奥氏体化后，先在低温盐浴保温一段时间，使其基体在过冷度较大时大量形核，然后再经高温保温使基体组织转变成具有含碳量较高的残余奥氏体，细化组织，进而提高力学性能。通过在低温不同保温时间下的组织对比，确定较佳的低温盐浴保温时间；然后进行单一温度下等温淬火和两步法热处理工艺试验。将两种工艺的结果进行对比，发现两步法等温淬火工艺得到的组织和性能介于单一温度等温淬火工艺的低温和高温之间。     

The influence of cast structure on the austempering of ductile iron. Part 3. The role of nodule count on the kinetics,microstructure and mechanical properties of austempered Mn alloyed ductile iron

Austempering kinetic measurements and mechanical property measurements are reported for irons with different Mn contents and different nodule counts after austenitising at 870 °C and austempering at 375 °C. It is shown that increasing nodule count, which reduces segregation and changes the size and distribution of intercellular boundaries, increases the interphase boundary area between graphite and matrix and decreases the continuity of the unreacted austenite in the intercellular boundary. This accelerates the stage I reaction which broadens the heat treatment window and moves it to earlier austempering times. A high nodule count can be used to counter the delay of the stage I reaction caused by Mn additions used to increase the hardenability of the iron. A high nodule count produces a finer, more uniform ausferrite structure that increases the strength, ductility and impact energy of the austempered iron.     

Austempered ductile iron: a competitive alternative for forged induction-hardened steel crankshafts

The mass-production considerations in replacing forged and induction-hardened steel crankshafts with ADI are described for a four-cylinder 120 h.p. petrol engine and a single-cylinder diesel engine. Microstructure, mechanical property, solidification, casting system, heat treatment and machining problems are examined for castings made using the sandwich and inmould treatment methods. Analysis of the results shows that the steel crankshafts can be replaced without a change in design by ADI components with a 10% weight saving and 30% lower production costs. It was found also that successful production of a heavy-duty ADI component requires close control over all the manufacturing processes.