Borosiliconizing of 99.9% pure nickel was performed by a powder-pack method using borosiliconizing powders at 850, 900 and 950 degrees C for 2 and 8 h. The coated samples were characterized by Optical Microscope (OM), X-ray diffraction (XRD) and hardness tests. The oxidation behavior of unborosiliconized and borosiliconized pure nickel was studied with the kinetics curves of cyclic oxidation. The results show that boride (Ni2B) and silicide phases (Ni3Si, Ni5Si2 and Ni2Si) are formed on the surface of borosiliconized pure nickel, which are confirmed by X-ray diffraction analysis. Depending on boronizing time and temperature, the thickness of coating layer ranges from 36 to 237 mu m. The hardness of the coating layer is much higher than that of pure nickel. Dry-sliding wear tests show that the wear resistance of borosiliconized pure nickel is greater than that of pure nickel. However, the oxidation test at 950 degrees C indicates that unborosiliconized sample possesses higher oxidation resistance than the borosiliconized sample.

设计了碳当量高低不同的两组铸铁,浇注凸轮轴考察其变形情况.采用大量数据统计分析碳当量对Cr-Cu-Ni合金灰铸铁冷激凸轮轴弯曲变形的影响.对统计数据初步分析的结果表明,提高铸铁的碳当量,并将其控制在4.10％～ 4.25％,可以将过度弯曲变形(跳动超过1 mm)凸轮轴的数量减少80％左右.

The hardness equation of timing position and the hardness equation of timing shaft were obtained by using multiple linear regression equation. It was considered by analysis that it is possible by properly increasing Cr content,properly decreasing C content and Si content,and as well as properly increasing chilling width of the iron melt before pouring to effectively increase hardness of the timing position and timing shaft and thereby to avoid early fracture of the Cr-Ni-Mo alloyed semi-chilled camshaft.

In this study, boronizing of 99.95% pure cobalt was performed in a solid medium by using Commercial LSB-II powders (that contain SiC) at 850, 900 and 950°C for 2, 4, 6 and 8h, respectively. The surface modified samples were examined by means of scanning electron microscopy (SEM)–energy dispersive spectroscopy (EDS), X-ray diffraction, microhardness tester and ring-on-block wear tester. Samples boronized had Co2B phase or Co2B plus Co2Si phases depending on the process temperatures. The depth of modified layer ranged from 40 to 186μm, depending on treatment temperature and time. The hardness of boride layer is much higher than that of silicide layer and substrate, and the wear resistance of the boride layer is more excellent than that of the silicide layer.

研究了机加中心孔(直径8.7mm)对DA471和DAMN两种球铁凸轮轴三点丐曲断裂性能的影响.研究表明,二者三点弯曲断裂载荷分别下降1.5％和5.9％,且都分别小于其截面积下降的百分数.同时初步分析了产生上述现象的原因.

Some properties of boride formed on gray cast iron (GCI) have been investigated. GCI was boronized by powder-pack method using Commercial LSB-II powders at 1123, 1173, and 1223 K for 2, 4, 6, and 8 h, respectively. Scanning electron microscopy showed that boride formed on the surface of boronized GCI had tooth-shaped morphology. The hardness of boride formed on surfaces of GCI ranged from 1619 to 1343 HV0.025, and quenched and tempered GCI ranged from 400 to 610 HV0.025. The boride formed in the coating layer confirmed by X-ray diffraction analysis was Fe2B single phase. Depending on boronizing time and temperature, the thickness of coating layers on boronized GCI ranged from 26 to 105 μm. The activation energy was 209 kJ/mol for boronized GCI. Moreover, the possibility of predicting the iso-thickness of boride layers variation was studied. Dry-sliding wear tests showed that the wear resistance of boronized sample was greater than that of quenched and tempered sample.

The breaking load in three points bending test of the 1AE6 semi-chilled alloyed cast iron camshaft was determined by using WE-500 model hydraulic universal tensile test machine and thereby the relationship between its breaking loads and its defections was investigated.The result showed:(a)There was some dispersivity existing in the three point bending breaking loads of camshafts of different melting heats;(b)There was a positive correlation existing between the breaking loads and deflections,and a proper amount of carbide contained in the camshaft was beneficial to both its strength and deflection.

The production data on spot have been used for statistical analysis of effect of the carbon content on bending deformation and blowhole defect of TU5JP4 chilled cast iron camshaft.It showed that increasing carbon content of the camshaft from 3.4%~3.6% to 3.6%~3.7%,has significantly reduced the bending deformation of the camshaft(radial runout more than 1mm) and porosity defect.The statistics of the user showed that as the carbon content increased,the waste rate caused due to the blowhole defect decreased by about 30%.

采用冲入法在500 kg的堤坝包中进行球化处理,用RESiFeMg合金作球化剂,球化反应时间＞40 s;用SiBa合金作孕育剂,在180 kg的浇包内进行孕育处理;用直读光谱仪分析球化处理前后铁液的激冷试样。发现:（1）球化处理后w（C）量比原铁液的w（C）量低;（2）石墨漂浮是导致球化处理后w（C）量降低的主要原因。

The CA498 semi-chilled Cr-Ni-Mo alloyed gray iron camshaft was produced with Shanxi nodular iron pig iron+ Ti-Fe alloy as melting charges.Microstructure examination was conducted by sampling from the shaft neck of the camshaft and found that the structure was eutectic consisted of large amount primary austenite+D-type graphite,and in later solid phase transformation the austenite changed into pearlite.It's considered after analysis that properly increasing C content would beneficial to avoid shrinkage porosities occurring in the base circle section of the cam.The inspection showed that hardness of camshaft neck was of 235~255,tensile strength of separately cast test bar with diameter of 30 mm was of 255~285 MPa that meeting client's requirements.

It was considered that the magnetic mark on the cam surface of C14T ductile iron was caused by the graphite floatation,and its prevention measures were proposed as follows: strict controlling the carbon equivalent,proper decreasing pouring temperature,rational using risers and setting chills.

A sort of semi-chilled Cr-Ni-Mo-alloyed gray cast iron camshaft was produced by adopting resin-coated sand vertically parted shell mold and the casting method that the iron melt enters the mold cavity from one end of the casting.The influence of the chilling width of the iron melt,w(C),pouring temperature on the shrinkage defects formation was discussed.It is possible to prevent the shrinkage defects of the camshaft by keeping the w(C) in the range of 3.65%~3.7%,keeping CE in the range of 4.25%~4.38%,reducing appropriately the chilling width of the iron melt before pouring and,as well as,keeping the pouring temperature in the range of 1 400~1 420 ℃.

The results of analysis have showed that the excessive arsenic content in the 477F-type ductile iron camshaft was the root cause of the shrinkage produced near the intake of the camshaft.The defect would be avoided with control of arsenic content less than 0.01% in ductile iron production.

The corrosion and electrochemical behavior of long-term aging on 17-4PH stainless steel in different solutions has been measured by electrochemical methods. The solutions consisted of chlorine ion sulphuric acid and neutral. Electrochemical potention dynamic reactivation test. The polarization curves results demonstrate that the pitting potential of 17-4PH stainless steel shifted negatively and the protection performance of the passive film decreased after aging treatment. The decline of corrosion resistance of aged specimens, and with the age time prolonging corrosion inhibitors is decline the sulphuric acid can control the pit corrosion of 17-4PH stainless steel because the vitriol (S) can hold back the Cl-, The anodic polarization curves illustrate that 17-4PH stainless steel can passive in 1% NaCl sulphuric acid, while in 1% NaCl neutral the passivity is deteriorated due to Cl- ion participate in electrochemical corrosion, accelerate the localized corrosion, destroy passivation and induce pit corrosion to the stainless steel. The decline of corrosion resistance of aged specimens was due to the precipitation of the second2 phase along grain boundaries and the transformation of microstructure.

A comparison study on carbon and silicon contents in Cu-Sn,Cr-Ni-C,Cr and Cr-Ni-Mo four alloy cast iron has been carried by using a thermal analyzer and a direct-reading spectrometer,resulting in that the maximum deviation rate of carbon content was 5% in four alloy cast iron;the deviation rate of the silicon content in the Cu-Sn alloy cast iron was 9.9-16.8%,the maximum deviation rate of the silicon content in other three alloy cast iron was less than 4% on which preliminary analysis has been done.

By statistical analysis,the relationship between the matrix hardness of the high pearlite-containing nodular iron and its nodularity and pearlite content was investigated.The result showed that the Rockwell hardness of the high pearlite-containing nodular iron camshaft increased with increasing of its nodularity and pearlite content.

Salt bath nitriding of 17-4 PH martensitic precipitation hardening stainless steels was conducted at 610, 630, and 650 °C for 2 h using a complex salt bath heat-treatment, and the properties of the nitrided surface were systematically evaluated. Experimental results revealed that the microstructure and phase constituents of the nitrided surface alloy are highly process condition dependent. When 17-4PH stainless steel was subjected to complex salt bathing nitriding, the main phase of the nitrided layer was expanded martensite (α′), expanded austenite (γN), CrN, Fe4N, and (Fe,Cr) x O y . In the sample nitrided above 610 °C, the expanded martensite transformed into expanded austenite. But in the sample nitrided at 650 °C, the expanded austenite decomposed into αN and CrN. The decomposed αN then disassembled into CrN and alpha again. The nitrided layer depth thickened intensively with the increasing nitriding temperature. The activation energy of nitriding in this salt bath was 125 ± 5 kJ/mol.

It was revealed by analyzing chemical compositions that when the titanium content of the camshaft was relatively low,the graphite in the ingate area was relatively coarse,and there was also shrinkage porosities found in local zones,the hardness of camshafts was of 177~198 HB;however,when the titanium content of the camshaft was relatively higher,the graphite in the ingate area was relatively fine,and there was also D type graphite and E type graphite found in local zones,the hardness of camshafts was increased to 205~210 HB.Some graphite refining methods reported in both the Chinese and overseas references was discussed including increasing cooling rate during casting solidification,lowering CE of gray irons,alloying,melt treatment,etc.Based on the practical productive conditions of the foundry and by adopting the method of adding Sichuan-produced V-Ti containing pig iron or adding ferrotitanium to increase titanium content of the melting charge,it was realized that the graphite of the camshafts was refined,and the hardness was also raised.

通过统计分析研究了高珠光体含量球铁的基体硬度HRC与球化率（n）/珠光体含量（P）的关系。结果表明,n和P都与基体硬度HRC正相关。P＞75%～80%,HRC≤23;P＞80%～85%,HRC≤25;P＞85%～90%,HRC＞25。利用上述关系,可以用HRC对球铁凸轮轴中的球化率和珠光体含量进行鉴别。该方法已经用于生产实践。

Sichuan V-Ti pig iron and Hebei ductile iron have been used to manufacture 491Q type hardened camshaft and the effect of both iron on the microstructure and hardness of the camshaft been researched.Studies have shown that the microstructure of Sichuan vanadium-titanium pig iron consists of as tiny dot graphite+A type graphite+carbide+ pearlite while the microstructure of Hebei ductile iron consists of A-type graphite+C-type graphite+pearlite.The microstructure in the camshaft manufactured from the group-Ⅰingredient(230 kg Sichuan V-Ti pig iron+100 kg scrap steel+220kg back charge+other alloys) consists of the 4-6 grade A-type graphite+small amount E-type graphite+95% pearlite+about 5% cementite,and his matrix hardness is 252-255HB.The microstructure in the camshaft manufactured from the group-Ⅱingredient(150 kg Sichuan V-Ti pig iron+80 kg Hebei ductile iron+100 kg scrap steel+220 kg back charge+other alloys)consists of the 4-6 grade A-type graphite+small amount E-type graphite+100% pearlite,and its matrix hardness 210-229HB.The above-mentioned phenomenon has been given preliminary analysis.