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1.
Yilong Wang Qingliang Zhao Yuanjiang Shang Pengxiang Lv Bing Guo Lingling Zhao 《Journal of Materials Processing Technology》2011,211(12):2152-2159
With the increasing demand for the replication of structured optical elements such as Fresnel lenses and prism arrays, more attention is being paid to the development of ultra-precision diamond machining technology for the fabrication of die steel molds. However, the machining process would be a catastrophic failure because of rapid and excessive tool wear if a diamond tool is used to machine die steel. In the present paper, a micromachining method for fabricating microstructures on die steel using single crystal diamond tool is presented. The presented technology is based on a thermochemical technique that uses plasma nitriding treatment to suppress the rapid and excessive tool wear in the diamond machining of steel. Experimental findings revealed that severe chemical tool wear, which is the main wear mechanism in the diamond machining of steel, was reduced significantly after plasma nitriding treatment, and a mirror-quality surface with an average surface roughness of 20 nm root-mean-square (RMS) was achieved over a cutting distance of approximately 5.4 km. Furthermore, a Fresnel microstructure with surface roughness RMS better than 40 nm was precisely fabricated on AISI 4140 die steel using single crystal diamond tool. 相似文献
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Effect of tool nose radius and tool wear on residual stress distribution in hard turning of bearing steel 总被引:4,自引:0,他引:4
Meng Liu Jun-ichiro Takagi Akira Tsukuda 《Journal of Materials Processing Technology》2004,150(3):234-241
This study presents a experimental investigation to clarify the effects of tool nose radius and tool wear on residual stress distribution in hard turning of bearing steel JIS SUJ2. Three types of CBN tools with different nose radius (0.4, 0.8 and 1.2 mm) were used in this study. The residual stresses beneath the machined surface were measured using X-ray diffraction technique and electro-polishing technique. The results obtained in this study show that the tool nose radius affects the residual stress distribution significantly. Especially the effect on the residual stresses at the machined surface at early stage of cutting process is remarkable. For the tool wear, as the tool wear increases, the residual stress at the machined surface shifts to tensile stress range and the residual compressive stress beneath the machined surface increases greatly. 相似文献
4.
Olga Karabelchtchikova Iris V. Rivero 《Journal of Materials Engineering and Performance》2005,14(1):50-60
The distribution of residual stresses (RS) and surface integrity generated in heat treatment and subsequent multipass grinding
was investigated in this experimental study to examine the source of variability and the nature of the interactions of the
experimental factors. A nested experimental design was implemented to (a) compare the sources of the RS variability, (b) to
examine RS distribution and tensile peak location due to experimental factors, and (c) to analyze the superposition relationship
in the RS distribution due to multipass grinding technique. To characterize the material responses, several techniques were
used, including microstructural analysis, hardness-toughness and roughness examinations, and retained austenite and RS measurements
using x-ray diffraction. The causality of the RS was explained through the strong correlation of the surface integrity characteristics
and RS patterns. The main sources of variation were the depth of the RS distribution and the multipass grinding technique.
The grinding effect on the RS was statistically significant; however, it was mostly predetermined by the preexisting RS induced
in heat treatment. Regardless of the preceding treatments, the effect of the multipass grinding technique exhibited similar
RS patterns, which suggests the existence of the superposition relationship and orthogonal memory between the passes of the
grinding operation. 相似文献
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为开发高性能、长寿命的木工圆锯片、带锯条、弹簧等五金工具,在75Cr1钢中分别添加质量分数为0.2%、0.4%的Ni元素。通过力学性能检验、显微组织分析以及热处理试验,研究了不同Ni含量对75Cr1钢热轧态及热处理态力学性能与显微组织的影响。结果表明,在Ni添加量为0%~0.4%的范围内,能降低热轧75Cr1钢的强度与硬度,提高塑性,其含量越高,效果越显著,但对冲击性能影响不明显;Ni对淬火硬度影响不大,当Ni含量达到0.4%时,硬度呈降低趋势,但明显提高回火后的塑性,降低回火后的强度与硬度,并改善回火后的冲击吸收能量,Ni含量越高,改善效果越明显。显微组织方面,Ni可以细化热轧75Cr1钢珠光体球团尺寸及片层间距,促进珠光体片的球化,同时也细化淬火与回火后的显微组织。结合经济性与综合力学性能考虑,75Cr1钢中Ni的最佳添加量为0.2%。 相似文献
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文章简单介绍了ATC结构以及目前市场上ATC换刀时间的不一致局面,对现有加工中心ATC换刀时间的评定方法做了综合论述,适应ATC的模块化趋势,提出给出ATC独立换刀时间以及刀对刀时间结合切削对切削、辅助位置对位置的换刀时间评定办法. 相似文献
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CO2与O2作为MAG焊接时常用的活性气体,对1.4003不锈钢接头的金相组织与疲劳性能有不同的影响。通过金相组织分析和脉动拉伸疲劳试验,研究两种保护气氛下1.4003钢MAG焊接头的组织和疲劳性能。结果表明:两种接头焊缝组织的基体均为奥氏体,基体上分布δ铁素体;当保护气体为φ(Ar)95%+φ(CO2)5%时,中值疲劳强度为312.5 MPa;当保护气体为φ(Ar)97%+φ(O2)3%时,中值疲劳强度为302.5 MPa。两种保护气体的疲劳试件断裂位置主要集中在热影响区,均有明显的启裂源,扩展区疲劳纹清晰,终断区形态为韧窝型韧性断口。 相似文献
9.
G. Ramírez A. Mestra B. Casas I. Valls R. Martínez R. Bueno A. Góez A. Mateo L. Llanes 《Surface & coatings technology》2012
The contact fatigue behavior of three microstructurally distinct tool steels coated with a physical vapor deposited TiN film is studied. Substrate microstructural differences come from variations in either chemical composition or processing route. Experimental procedure is based on determining critical applied loads and pressures, under both monotonic and cyclic spherical indentation loading conditions, for emergence and evolution of distinct damage modes at the coating surface: circumferential cracking, cohesive spallation and interfacial decohesion. Experimental results indicate that all coating/substrate systems evaluated are susceptible to mechanical degradation associated with repetitive contact loading. This is clearly discerned from the fact that some damage mechanisms, such as cohesive spallation at the coating and adhesion failure at the interface, are exclusively observed under cyclic loading. Substrate microstructure effects are evidenced by consideration of coating detachment as the critical damage mechanism. In this regard, crack nucleation resistance of primary carbides is pointed out as the main reason for the distinct response against decohesion observed under cyclic contact loads. Hence, finer and tougher, as well as less irregular and more homogeneously distributed primary carbides are pointed out as key microstructural features for enhancing contact fatigue strength of coated cold-work tool steels. 相似文献
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采用OM、SEM、TEM、XRD、显微硬度计以及热疲劳试验机等方法研究了深冷处理对H13型热作模具钢的组织和性能的影响,并与常规淬回火工艺进行了对比分析。结果表明,在常规的淬回火工艺的基础上增加深冷处理有利于细化试验钢的晶粒组织并促进残留奥氏体向马氏体转变。此外,在深冷处理的条件下马氏体晶格由于在极低温易发生收缩而促使碳原子在位错等缺陷处偏聚,回火过程中以碳化物的形式析出。这些析出的大量细小弥散分布的碳化物可钉扎位错,对热循环引起的应力集中起到一定的缓解作用,减缓降低热疲劳裂纹扩展速率。且深冷处理后细小弥散分布的碳化物析出降低了H13钢热疲劳过程中碳化物长大速率,减少了热疲劳裂纹的数量,从而提高热疲劳性能。 相似文献
11.
《Journal of Materials Processing Technology》2014,214(2):496-506
Inability of machining steel strongly inhibits the application of diamond machining in manufacturing industry, especially in the fields of ultra-precision and micro machining. In recent years, vibration-assisted machining (VAM) has been proved to be capable of efficiently suppressing the diamond tool wear in cutting steel. Currently, the prevailing speculation claimed by most researchers for such suppression is that the tool–workpiece flash temperature was reduced in VAM, which would slow the chemical reaction between iron on steel and carbon on diamond. However, the correctness of this speculation has not been proved by any experimental or theoretical research. In this paper, in order to understand the true wear suppression mechanism of diamond tools in VAM of steel, a study is conducted by measuring the workpiece temperatures and modeling the cutting energy consumption in both VAM and conventional cutting (CC). Based on the comparison results, it is concluded that the cutting temperature and energy consumption in VAM are not smaller than in CC, and hence the reduced diamond tool wear in VAM should not be caused by the claimed reduced temperature, especially when the material removal rate is very small. Finally, based on the EDS analysis and the comparison of experimental results under different air pressure, two probable reasons are proposed for the significantly reduced diamond tool wear in VAM of steel: (i) increase of gas pressure at the tool–workpiece interface and (ii) generation of an oxide layer on the freshly machined surface. 相似文献
12.
Theoretical and experimental determination of tool life in hot machining of austenitic manganese steel 总被引:2,自引:0,他引:2
In this study, an expression for the tool life of a sintered carbide tool machining heated austenitic manganese steel was developed. The influence of surface temperature, cutting speed, feed rate, and depth of cut on the tool life were investigated. Afterwards, an expression for the effects of cutting conditions on tool life were determined using a mathematical model developed by a factorial regression method. 相似文献
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The tensile and reverse-bending fatigue behaviors of the SAE 6150 steel in the dual-phase (DP), fully martensitic, and tempered
states, respectively, have been investigated using mechanical tests, scanning electron microscopy (SEM), energy-dispersive
x-ray (EDX) microscopy, and optical microscopy. Residual stresses, inherent microcracks, and retained austenite films in the
martensitic steel, quenched from 900 °C, lead to the development of inferior tensile and fatigue strength. Tempering at 700°C
relieves the residual stresses associated with martensite, causes the precipitation of microalloy carbides (MACs), and thus
results in superior strength, increased fatigue resistance, and moderate ductility. The DP microstructure, consisting of martensite
islets in a ferrite matrix, gives rise to a combination of good strength, excellent ductility, and commendable fatigue characteristics.
MAC in the tempered steel and martensite islands in the DP variant enhance fatigue performance by causing crack tip deflection
and concomitant crack path tortuosity. Strain incompatibility between martensite and ferrite in the DP steel, and cementite
films and ferrite in the tempered variant are identified as fatigue crack initiation sites. 相似文献
15.
A numerical model incorporating the microstructure alteration for predicting residual stresses in hard machining of AISI 52100 steel 总被引:1,自引:0,他引:1
Residual stresses induced by machining processes are a consequence of thermo-mechanical and microstructural phenomena generated during the machining operation. Hard machining of AISI 52100 bearing steel is a typical case where the microstructural phenomena associated with white and dark layers formation influences the residual stress distribution. Unfortunately, very limited physical models are available for residual stress prediction including the microstructural effects. This paper presents an experimental and numerical approach to predict residual stresses by incorporating the microstructural phase transformations induced during machining of AISI 52100 steel. 相似文献
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介绍了2008年修订发布的GB/T 1298—2008《碳素工具钢》及GB/T 9943—2008《高速工具钢》2项新标准,并分别与相应旧版本做了对比分析,指出了新、旧标准之间的差异。该2项新标准与相对应的前一版本相比,在标准名称、适用范围以及技术内容方面都有不同程度的变化。两项新标准的优点是技术内容上更加完善,适用范围更广,并与现行的相关标准保持了较好的协调关系,更便于贯彻执行。 相似文献
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文章针对在采用华中HNC-1型数控系统的经济型数控车床、铣床加工零件过程中,出现的一些常见的硬件方面的加工故障及系统软件方面的不足问题进行了分析,并给出合理的解决方案. 相似文献
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L.A. Dobrzaski M Piec A. Klimpel Z. Trojanowa 《International Journal of Machine Tools and Manufacture》2007,47(5):773-778
Laser surface modification, although for a number of years, is a technology, which is still in its infancy. This paper presents the results of laser alloying influence on structure and properties of the surface of the X38CrMoV5-3 hot work steel, carried out using the high-power diode laser (HPDL). Niobium carbide powder was used for alloying. In the paper, investigation results are presented of the melting and alloying of ceramic particles on the surface layer. Results of the metallographic examinations qualitative X-ray phase analysis and the mechanical properties are presented. 相似文献
19.
为提高其热疲劳性能,对H13钢进行了贝氏体-马氏体(B/M)复相热处理,使其得到了由回火索氏体和贝氏体组成的复相组织。利用OM、SEM、TEM、洛氏硬度计、万能拉伸试验机等设备研究了热疲劳对B/M复相H13钢微观组织、碳化物及力学性能的影响。结果表明:较传统H13钢硬度随疲劳次数增加而迅速降低的现象,B/M复相H13钢的硬度随疲劳次数的增加呈先下降后上升再下降的趋势。拉伸试验表明,较传统H13钢,B/M复相H13钢的强塑性配合更加优异,且在热疲劳后,其断面收缩率反而有所增大。通过显微组织观察发现力学性能变化的主要原因是B/M复相H13钢在热疲劳过程中存在贝氏体板条合并及碳化物析出并长大粗化的行为。 相似文献
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Austenitic chromium–manganese–nitrogen stabilized stainless steels have been developed to replace chromium–nickel–nitrogen stainless steels in certain applications. In comparison, chromium–manganese–nitrogen steels have improved mechanical properties and acceptable corrosion resistance in hot, high chloride containing media. In this paper, corrosion fatigue investigations of a solution annealed and for practice more relevant 14% cold worked high alloyed chromium–manganese–nitrogen steel have been done. Inert glycerine was used as reference media and 62% calcium chloride solution as corrosive media, both aerated at a temperature of 120 °C. The stress ratio between upper and lower stress levels was 0.05 (tension–tension loading) to avoid the destruction of the fracture surfaces. As testing frequency for the dynamic experiments, 20 Hz was chosen considering possible application areas. Maximum stress versus number of cycles curves were recorded and representative specimens were investigated in a scanning electron microscope. In addition, electrochemical tests, exposure tests and constant load tests were done. This paper shows results on the corrosion fatigue of a manganese–nitrogen stabilized austenitic steel in a hot high chloride containing salt solution and helps to get a better understanding of occurring failure mechanisms. 相似文献