The wear resistances of austempered ductile iron （ADI） were improved through intxoduction of a new phase （carbide） into the ma- txix by addition of chromium. In the present investigation, low-caxbon-equivalent duc...The wear resistances of austempered ductile iron （ADI） were improved through intxoduction of a new phase （carbide） into the ma- txix by addition of chromium. In the present investigation, low-caxbon-equivalent ductile iron （LCEDI） （CE = 3.06%, and CE represents cax- bon-equivalent） with 2.42% chromium was selected. LCEDI was austeintized at two difl＇erent temperatures （900 and 975~C） a^ld soaked for 1 h and then quenched in a salt bath at 325~C for 0 to 10 h. Samples were analyzed using optical microscopy and X-ray diffraction. Wear tests were carded out on a pin-on-disk-type machine. The efl＇ect of austenization temperature on the wear resistance, impact strength, and the mi- crostructure was evaluated. A stxucture-property correlation based on the observations is established.展开更多
Initial firing temperatures play an important role on the combustion rate of propellant. In gun propellants, initial temperature is a key factor for both accuracy and safety. Ideally, the initial temperature of the pr...Initial firing temperatures play an important role on the combustion rate of propellant. In gun propellants, initial temperature is a key factor for both accuracy and safety. Ideally, the initial temperature of the propellant should not influence the ballistic properties of the round. Nevertheless, constant initial temperature coefficients can not be achieved easily. This work focuses on the influence of the firing temperature on the ballistic properties, the mechanical integrity and the sensitivity to impact of nitrocellulose based propellants. Combustion rates have been determined by closed vessel tests. Ballistic properties have been investigated by firing 5.56 cartridges. The propellants have been conditioned at temperatures ranging from -54 ℃ to ＋71 ℃ before firing. The largest temperature coefficient is observed at high temperatures. The temperature sensitivity of the peak pressure in the combustion chamber can not be fully explained by the results from the closed vessel test. The authors speculated that the mechanical behaviour of the propellant grains at low temperatures influences also the overall ballistic properties of the round. Impact tests with propellants conditioned at low and high temperatures permit to investigate their mechanical strength under extreme temperatures and to better understand the propellant performance during firing. Tests on aged propellants have been conducted as well.展开更多
文摘The wear resistances of austempered ductile iron （ADI） were improved through intxoduction of a new phase （carbide） into the ma- txix by addition of chromium. In the present investigation, low-caxbon-equivalent ductile iron （LCEDI） （CE = 3.06%, and CE represents cax- bon-equivalent） with 2.42% chromium was selected. LCEDI was austeintized at two difl＇erent temperatures （900 and 975~C） a^ld soaked for 1 h and then quenched in a salt bath at 325~C for 0 to 10 h. Samples were analyzed using optical microscopy and X-ray diffraction. Wear tests were carded out on a pin-on-disk-type machine. The efl＇ect of austenization temperature on the wear resistance, impact strength, and the mi- crostructure was evaluated. A stxucture-property correlation based on the observations is established.
文摘Initial firing temperatures play an important role on the combustion rate of propellant. In gun propellants, initial temperature is a key factor for both accuracy and safety. Ideally, the initial temperature of the propellant should not influence the ballistic properties of the round. Nevertheless, constant initial temperature coefficients can not be achieved easily. This work focuses on the influence of the firing temperature on the ballistic properties, the mechanical integrity and the sensitivity to impact of nitrocellulose based propellants. Combustion rates have been determined by closed vessel tests. Ballistic properties have been investigated by firing 5.56 cartridges. The propellants have been conditioned at temperatures ranging from -54 ℃ to ＋71 ℃ before firing. The largest temperature coefficient is observed at high temperatures. The temperature sensitivity of the peak pressure in the combustion chamber can not be fully explained by the results from the closed vessel test. The authors speculated that the mechanical behaviour of the propellant grains at low temperatures influences also the overall ballistic properties of the round. Impact tests with propellants conditioned at low and high temperatures permit to investigate their mechanical strength under extreme temperatures and to better understand the propellant performance during firing. Tests on aged propellants have been conducted as well.
