Advanced Materials Research Vols. 753-755

Abstract: The cutting of precision threads is an important manufacturing process. Several passes are needed to complete the cutting of a thread and the choice of appropriate cutting speed and depth of cut for each cutting pass is essential. The cutting efficiency and tool life are significantly affected by these two parameters, especially when cutting threads in difficult-to-cut materials, such as titanium alloy. This paper proposes the concept of an equal undeformed chip area for all cutting passes, in order to determine the depth of cut for each pass. The principal goal is to maintain the same cutting force throughout the cutting process. Using tool geometry, the relationship between the cumulative depth of cut and the undeformed chip area for each cutting pass are derived. The depth of cut of each corresponding cutting pass can be determined, once the dimensions of the thread and the number of cutting passes are specified. Experiments were conducted to cut an ISO metric screw thread, with a pitch of 0.5 mm, on a 40 mm in diameter bar. It was found that, for the same total number of cutting passes, the tool wear was less than that suggested by the tool makers, when a depth of cut for each pass was determined using the proposed method. The thread could be cut using a higher cutting speed, resulting in a much shorter machining time. In addition, the proposed strategy also allowed completion of cutting using less cutting passes. A 25% increase in efficiency was noted for the specific thread used in the experiment.

Abstract: Recently, abrasive-free polishing (AFP) has attracted a great deal of attention due to its gentler polishing process and lower particle residue than traditional chemical mechanical polishing (CMP). Our present work investigates the effectiveness of Cu (II) ion on AFP of hard disk substrate in peroxyacetic acid (PAA) system slurry. The polishing experimental results show that the PAA/Cu (II) system slurry has higher material removal rate (MRR) and lower roughness (Ra) than PAA system. Further, the reaction mechanism of Cu (II) ion in PAA/Cu (II) system AFP of hard disk substrate was investigated preliminarily by electrochemical analysis.

Abstract: The physical model of the flame of gunpowder composite welding rod (GCWR) is built based on the flame topography and the combustion mechanism of thermite. The chemical reactions in different flame regions are fixed with the physical model, combustion characteristics of thermite and gunpowder combustion theory. The combustion mathematic model on the relationship of combustion velocity of GCWR with thermite content is fixed with the concept of unit volume combustion heat. At last, the results of the test indicate that the rates of combustion obtained by theoretical arithmetic and test are similar.

Abstract: With the long-distance oil and gas pipelines are to development of the direction of large-diameter, high-pressure, high grade pipeline steel applications gradually become the trend of the development of the oil and gas pipeline construction. The welding process of the X100 line pipe which is about to industrial application is not yet to be determined. It is not clear that the affect to the weldability from the metallurgical composition, organization, performance, and other factors which would affect the site construction welding process and welding measures. In addition, it is not yet the discussion and analysis of the key technologies X100 line pipe-site welding process and defect types. In this paper, the X100 pipeline on-site application of welding technology research commenced work and studied the weldability and welding process of X100 which solve the field application of X100 pipeline steel pipe welding issues.

Abstract: Cu-Sn-Ti filler alloy was applied as brazing material to join UcBN grains onto the steel matrix using three different brazing temperatures (880, 900 and 920°C). The microstructure and properties of the UcBN-filler-steel joint and the compressive strength of UcBN grains were investigated respectively by means of scanning electron microscopy and energy dispersive X-ray spectroscopy and compressive test. The microstructural studies revealed an intermetallic interlayer of type TiN, TiB and TiB₂ at the joint interface, which grew with increasing brazing temperatures. The compressive force of UcBN grains with a maximum value of 79.3N was found when the brazing temperature was 900°C for 8 min. The wear process of brazed UcBN grains was a process transforming from abrasion wear to micro fracture mutually.

Abstract: Effects of welding parameters on the weld bead appearance and mechanical properties in twin-wire tandem submerged arc welding of a high-strength low-alloy steel were investigated. Steel plates were welded using different combinations of welding current, voltage, inter-wire spacing and welding speed. The weld joints were characterized in detail by metallography. Hardness and tensile properties of the specimens were measured. The experimental analysis reveals that good weld appearance can be obtained for a range of inter-wire spacing from 55mm to 80mm. Leading wire current, trailing wire voltage and welding speed are the major factors affecting weld bead profile and microstructures in weld metal and fusion zone. Greater welding speed tends to produce higher cooling rate and favors the formation of strengthening phases like acicular ferrite and bainitic structures resulting in better mechanical properties.

Abstract: In this paper, a type of high-deposition-rate, low-dilution-rate and wide-welding-bead flux-cored strip which is easy to realize automatic surfacing was designed. Considering the working condition of high temperature and abrasive wear in the iron and steel industry, a kind of high-chromium iron surfacing flux-cored strip was designed. The effect of alloy elements on the microstructure and property abrasive wear resistance of deposited metal was investigated. The abrasion and heat resistant plate deposited by the flux-cored strip was carried out on raw material transport system in steel enterprises. The service life was significantly improved and the examination and repair time is reduced.

Abstract: Hydrogen distributions of TC4 electron beam welded joints with different hydrogen contents were measured by hydrogen oxygen analyzer. Microstructures of electron beam welded joints for TC4 titanium alloy with different hydrogen contents were observed and analyzed by optical microscope and TEM. And the influence of hydrogen on microstructure of the joints was investigated. The results show that the hydrogen content of weld HAZ is higher than other zones in the electron beam welded joints, while the hydrogen content of fusion zone is lower than other zones in the electron beam welded joints. The microstructure of the weld metal is fine lamellar α + β phase after hydrogen charging. In the range of hydrogen contents discussed in this study (from 0 to 0.101 wt. %), with the increase of hydrogen content, there is little change in the appearance of the microstructure of the weld metal. There are stacking fault and dislocation in the microstructure of TC4 electron beam welded joints with different hydrogen contents after hydrogen charging. The presence of hydrogen can promote the formation of twins in electron beam welded joints. With the increase of hydrogen content, the number of twins is increased.

Abstract: Many studies have shown that during laser welding, shielding gases play a key role in many aspects. In this paper, a series of contrast experiments about CO₂ laser welding of TA15 TI-alloy were completed by using He and Ar as shielding for different pressure, respectively. The experiments results reveal that the porosities in the weld have strong relation with weld penetration, and the shielding gas have great influences on the weld penetration. So the porosities mainly form in the center of welds which are under critical penetration and lack of penetration, and have no direct relation with the type and pressure of shielding gas.From the contrast images of penetrating process, it is known that when He as shielding gas, the sizes of keyholes on the back welds are quite larger than the sizes when Ar. This means more vapor erupting from bottom keyhole and porosities not easy to form. At the same pressure, the opening times of keyholes when He as shielding gas are longer than the times when Ar. Long opening times of keyholes make the shielding gas within keyhole not easy to be involved into the molten pool and form the porosities.

Abstract: The joining materials of density ceramics and the fibre would be potential value as sealing materials for high-temperature seal field. Zirconia toughened mullite ceramics (ZTM) were chosen the density ceramics due to excellent high temperature mechanical properties. Aluminum silica ceramic fibre was attractive because of favorable elasticity properties. Combining the two materials, the high-temperature resistance elasticity seal materials would be prepared by microwave joining technique. Using the absorber-microwaves properties of Al-Si alloy, interlayer compositions of the joining materials were designed. The ZTM ceramics and fibers materials were joining by microwave hybrid heating method and the mechanism of microwave joining was discussed.