Research and Application of Wear Resistant Refractories for Cooling Zone of Large Scale Coke Dry Quenching Ovens

In order to prolong the service life of the cooling zone of large scale coke dry quenching ovens,six kinds possible refractories for the cooling zone of large scale coke dry quenching ovens： SiC containing brick A,SiC containing brick B,mullite-andalusite brick,spinel containing brick,zirconia containing brick,corundum-mullite brick and grade B mullite brick,were analyzed in properties. It is found that the cooling zone lining adopting SiC containing bricks or mullite-andalusite bricks has much longer service life. Based on this,a new type of wear resistant brick was developed. The brick has a compressive strength of 135 MPa,a wear loss of 2. 10cm^3（only a quarter of that of the grade B mullite brick）,and a higher bulk density than the grade B mullite brick. The application of the brick in a 140t·h^（-1）coke dry quenching oven showed that it performed better than the grade B mullite brick. The cooling zone adopting the new bricks has a lower coke discharging temperature,which is beneficial to the enhancement of heat recovery efficiency and steam power generation.

EXPERIMENTAL STUDY OF FRETTING WEAR OF TITANIUM ALLOY BEFORE AND AFTER LASER BEAM QUENCHING

The effects of amplitudes, normal loads and laser beam quenching on the fretting wear of titanium alloy (TC11) were experimentally investigated on SRV fretting wear test machine in air, at room temperature and without lubrication conditions. The purpose of this study is to learn the rules of fretting wear in a disk blades dovetail joint of an aircraft turbine so the test parameters are determined based on the relative movement and load in the joint. The wear depths are measured by a profilometer, the worn areas are observed and measured by an optical microscopy, and the microtopography of the worn scar is studied by scanning electron microscopy (SEM) .The tests and observations state clearly that fretting wear rate (FWR) is heavily influenced by sliding amplitude(SA) and load. In this experiment, if SA is greater than 60 μm at Hertz contact stress 105 MPa, the FWR is much higher, and the SEM makes it known that the wear mechanism is the combination of adhesive and contact fatigue in the above test conditions. In contrast, if SA smaller, the FWR lower too, and the SEM suggests that the major wear mechanism is contact fatigue. The experiments also reveal that the laser beam quenching greatly improve the fretting wear resistance of titanium alloy, especially at heavy load and large amplitude.

Optimization of Quenching Process for ZTAP/ High Chromium Cast Iron Composites

In order to solve the problem of cracking of ZTAP(Zirconia toughened alumina ceramic particles)reinforced HCCI(high chromium cast iron)matrix composites,the quenching process was optimized.ZTAP reinforced HCCI matrix composites were prepared by infiltration method with gravity sand casting.The thermal expansion curves of HCCI and the composites were measured at different cooling rates by Glebble-3500.The microstructure of the HCCI matrix and the composites were characterized by X-ray diffraction,light microscopy,SEM,ESD,and EPMA.The tested mechanical properties include Rockwell hardness and impact toughness.The deformation differences of HCCI and the composite at different cooling rates were obtained according to the test results of thermal expansion coefficient curve and changes in microstructure and mechanical properties,and air cooling was the most favorable for the composites to have good hardness and not easy to crack.The cooling rate during air cooling is approximately equal to 21℃/s in this work.When the quenching process was air cooling,the impact toughness and hardness of the composites are 3.7 J/cm^(2) and 61.8 HRC,respectively,and the deformation difference between the composites and HCCI was 20μm at 300℃.

Sensitivity of the Impact Toughness and Microstructure of 15CrNi3MoV Steel Under Different Quenching Rates

The sensitivities of the mechanical properties and microstructure of 15CrNi3MoV alloy steel under different quenching rates were investigated in the present study.After subjection to quenching with four different cooling rates(water cooling,forced air cooling,static air cooling and furnace cooling)followed by tempering,the microstructure was characterized by scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD),and transmission electron microscopy(TEM);and the low-temperature(−20°C)impact toughness was evaluated.The results showed that the tempered microstructure and mechanical properties had high sensitivity to the quenching rate.With a decrease in the quenching rate,the low-temperature impact energy of tempered specimens decreased with increasing fluctuation.Correspondingly,the fracture morphology changed from completely ductile to brittle.In addition,as the quenching cooling rate decreased,the as-quenched matrix changed from a lathy to a polygonal structure with the presence of carbides and martensite-austenite(M-A)constituents,and the effective grain size increased.Tempered martensite with dispersed fine carbides was found in the tempered water cooling specimen,and tempered bainite with a polygonal structure containing large carbides and rare incomplete undecomposed M-A constituents was found in the tempered forced air cooling,static air cooling and furnace cooling specimens.The small effective grain size and fine carbides contributed to the good temperature impact toughness of the tempered water cooling specimens.