煤矿巷道支护技术的研究

基于煤矿巷道支护技术研究的现状,详细分析了现阶段起主导作用的锚杆支护技术,总结出巷道支护存在的问题及改进方向,对安全可靠有效巷道支护技术的研究提供借鉴经验。     

Super304H奥氏体耐热钢微观组织研究

为了深入认识新型奥氏体耐热钢Super304H(0.1C-18Cr-9Ni-3Cu-Nb,N)的微观组织,利用光学显微镜、扫描电子显微镜、电子探针和X射线衍射等手段,研究了Super304H钢合金元素的分布和析出相的组成及分布形态.试验结果表明,Super304H钢在供货状态下的显微组织由γ-基体和析出相组成.与传统的18-8不锈钢相比,这种奥氏体钢晶粒均匀细小,晶粒尺寸约46μm.析出相主要由Nb(C,N)和富铜相组成,Nb(C,N)有呈方向性分布的条块状和呈弥散分布的细小颗粒状两种形态,条块状的Nb(C,N)是软化过程中残留下来的,而弥散分布的是固溶处理及冷却过程中析出形成的.其中弥散分布的Nb(C,N)与富铜相对细化晶粒和改善钢的高温强度起重要作用,而多种复合强化机制使得Super304H钢具有优异的高温性能.     

Effects of process parameters on arc shape and penetration in twin-wire indirect arc welding

In this study, the effects of variable parameters on arc shape and depth of penetration in twin-wire indirect arc gas shielded welding were investigated. The variation of arc shape caused by changes of the parameters was recorded by a high-speed camera, and the depths of penetration of specimen were measured after bead welding by an optical microscope. Experiments indicated that proper parameters give birth to a concentrated and compressed welding arc, which would increase the depth of penetration as the incensement of the arc force. Several principal parameters including the distance of twin wires intersecting point to base metal, the included angle, and the content of shielding gas were determined. The arc turned more concentrated and the depth of penetration increased obviously as the welding current increased, the arc turned brighter while unobvious change of penetration occurred as the arc voltage increased, and the deepest penetration was obtained when the welding speed was 10.5 mm/s.     

Metal transfer modes of twin-wire indirect arc welding

Metal transfer modes of twin-wire indirect arc welding are studied and the effects of welding parameters on transfer modes are investigated in this paper. The progress of transition is captured by a high speed camera system with a xenon lamp as light source in order to remove the intense arc light. An oscilloscope is used to record the values of the parameters. Results show that anode and cathode have different transfer modes under certain conditions because of different melting rates. All the transfer modes are classified as short-circuiting transfer and free-flight transfer. The latter could be subdivided into globular transfer, projected transfer, streaming transfer, etc. The metal transfer modes of TWIAWare influenced by the welding current, arc voltage and shielding gas. With an increase in welding current and arc voltage, the transition frequency increases and droplets become smaller. Images indicate that the metal transfer modes influence arc shape periodically because of the detaching force and retainable force changing periodically.     

添加Mo对TiC金属陶瓷涂层组织和磨损性能的影响

采用Praxair 3710型等离子喷涂成套设备,在Q235钢表面制备了两种TiC金属陶瓷涂层TiC-NiCr涂层和TiC-NiCrMo涂层.通过X射线衍射、扫描电镜、电子探针等手段分析了两种涂层的相组成和涂层表面、截面组织结构及元素分布,并进行了磨损试验对比.结果显示,两种涂层均比较致密,与基体结合良好,孔隙率较低,但喷涂过程中均存在氧化现象.由于Mo的加入,在TiC-NiCrMo涂层中出现MoO2和Mo2C,在TiC颗粒周围还形成了(Ti,Mo)C固溶体包覆结构,增强了涂层内部结合强度;干摩擦条件下,TiC-NiCrMo涂层耐滑动磨损性能优于TiC-NiCr涂层.     

Amorphization of Fe38Ni30Si16B14V2 surface layers by laser cladding

Fe38Ni30Si16B14V2 amorphous composite coatings were fabricated by laser cladding on AISI 1045 steel in order to increase the wear resistance. The phase and microstructure of the coatings were analyzed by X-ray diffractometry and transmission electron microscopy. The wear properties of the coatings were also investigated by means of sliding wear test. The results show that the coating consists of amorphous phase in majority and nanocrystalline phase in minority. The amorphous coatings can be obtained while the scanning speed is 3 500 mm/min and the laser power is 4.8 kW. With increase of the laser power, the amorphous phase in the coating increases when it is lower than 4.8 kW. A gradient distribution of the microhardness ranges from Hv0.2 1 208 to Hv0.2 891 in the coating from top surface of the coating to the substrate. The amorphous coating is found to possess better property of wear than AISI 1045 steel substrate.     

时效温度对Super304H钢析出相的影响

利用扫描电子显微镜、电子探针、X射线衍射和透射电镜研究了新型奥氏体耐热钢Super304H在高温时效条件下析出相的变化.结果表明,Super304H钢经700～1250℃时效后,组织中出现4种析出相:Nb(C,N)、富Cu相、M_(23)C_6和NbCrN.随时效温度的不同,析出相发生析出或溶解的变化,同时它们的形态、分布和数量随温度变化呈现出不同的变化规律,其中M23C6在700～900℃主要沿晶界析出,这将会降低钢的高温蠕变强度及抗晶间腐蚀性能.     

激光熔覆原位自生TiC-VC复合增强铁基合金层的研究

利用钛铁、钒铁、石墨等组分,采用5kW横流CO₂激光器在低碳钢板上熔覆制备出原位自生TiC-VC复合碳化物颗粒增强Fe基合金层.利用金相显微镜、X射线衍射仪、电子探针及滑动磨损试验机,研究了合金熔覆层的显微组织及性能.研究结果表明,通过钛铁、钒铁与石墨之间的反应,可以得到TiC-VC复合碳化物增强相,细小的TiC-VC复合碳化物颗粒弥散分布在Fe基体之中,合金熔覆层的耐磨性在一定范围内随增强颗粒的增加而提高.     

Microstructure of Fe-Based Alloy Hardfacing Coating Reinforced by TiC-VC Particles

Mierostrueture of the Fe-based alloy hardfaeing coating reinforced by TiC-VC particles was investigated by means of SEM, TEM, XRD and EPMA. The thermodynamics and effect of elements on the carbides were discussed. The result shows that TiC-VC carbides can be formed during arc welding. Carbides with particle size of 2 ～4μm are uniformly dispersed in the matrix. Evidently the covering components and their amount affect the microstrueture and hardness of the coatings. An excellent microstructure and hardness of hardfacing coating were obtained, while the amount of graphite, FeTi and FeV was controlled within the range of 8%- 10%, 15%- 18% and 8%- 12%, respectively.     

Si3N4陶瓷/Nb/Cu/Ni/Inconel 600界面反应层形成机制研究

观察分析了Si3N4陶瓷/Nb/Cu/Ni/Inconel600界面处反应层的形貌、元素分布、反应层中的相结构、界面反应以及反应层的生长规律,研究了Si3N4陶瓷/Nb/Cu/Ni/Inconel600界面处反应层的形成机制.研究结果表明:在连接过程中,Cu层首先熔化,Nb、Ni向液态Cu中扩散溶解形成Cu-Nb-Ni合金,液态合金中的Nb和Ni向Si3N4表面扩散聚集并与Si3N4反应形成反应层;Si3N4侧的反应层主要物相是NbN和Nb、Ni的硅化物,Ni基合金侧反应相主要是NbNi3和Cu-Ni合金;在连接温度为1403 K的条件下,随着连接时间的增加,界面反应层厚度先快速增加,再缓慢增加.