Materials Science Forum Vols. 704-705

Abstract: The relationship between textures and Young’s modulus in CVD diamond films was simulated based on the phenomenological theory, which indicates the textures induce the Young’s modulus anisotropy. The increase of methane concentration changes the density of different fiber textures in diamond films, which induces the increase of Young’s modulus in the directions that parallel to the film surface. Among the textures, {111} texture is of no influence whereas {011} texture has the maximum influence on the Young’s modulus anisotropy of diamond film.

Abstract: This study simulated Bell-type annealing technology under laboratory conditions, and researched the effect of annealing time on the mechanical properties of SPCC cold-rolled steel sheet. The results indicate that the yield strength decreased with the extending of time; the plastic strain increases with the elongation of annealing time till a given time, and then decreased with the time extending; the cold-rolled specimen brittle fractured in tension while the annealed specimen shear fractured. Key words: microstructure mechanical properties Bell-type annealing SPCC cold-rolled steel sheet

Abstract: Hydraulic support is an important part of fully mechanized equipments. The constructional steels of hydraulic support with international advanced level mainly adopt the high-strength welding structural steel with its tensile strength of more than 700~1000MPa.This paper analyzes the chemical compositions features of S890 high-strength low alloy steel for 900MPa grade.The Influence of welding parameters,peak temperature and on the microstructures and mechanical properties of welding HAZ of S890 high-strength low alloy steel were investigated by thermo-simulated tests, The influence of welding heat input on the mechanical behaviors of the welded joint was also investigated. The results show that the microstructures of S890 steel change from tempered martensite to bainite and a little ferrite , pearlitic when welding heat input changes from low to high, and accompany the austenite grains coarsening ,so the impact toughness and hardness of welding HAZ at lower peak temperatures and shorter are higher than that at higher peak temperature and long . Welding HAZ produced by the second weld bead will overlap partially with the HAZ produced by the first weld bead. In this area, primitive microstructure tempers again or partial re-phase transformations and re-cools,but the area involved in the overlap is limited,so the influence on the properties of S890 steel is not obvious. In covered arc welding,the influence on the welded join strength of S890 steel is not distinct when heat input change in a certain scope, but the plasticity of the welded join falls off steeply as heat input increases. Keywords: S890 steel; high-strength low alloy steel; weld performance; hydraulic supports

Abstract: A process for electroless copper plating on Al₂O₃ ceramic products was provided. The bath is composed of components A (containing potassium tartrate 35 ~ 45 g/L, sodium hydroxide 7 ~ 9 g/L and sodium carbonate 3 ~ 4 g/L) and B (containing copper sulfate 7 ~ 14 g/L, nickel chloride 1 ~ 2 g/L and formaldehyde 15 ~ 20 g/L) with a volume ratio of 3:1. The bath composition and technological conditions of surface pretreatment were given, including degreasing, roughening, sensitizing, activating, and reducing. The formulation and process parameters for electroplating copper followed by coloring in five different colors, which are widely demanded in the market, were introduced. The coatings obtained by the presented processes on Al₂O₃ ceramic products are smooth and bright, producing an elegant appearance and greatly extending their service lives. All these technologies have been successfully applied to practical electroplating production, showing a wide development future.

Abstract: The ethylene cracking furnace tube is one of the most important components of an ethylene cracking furnace. Carburization of furnace tube is one of the most important causes which lead the tube to fail. In this paper, the model that describes diffusion of carbon and the precipitation of carbides was established based on Fick’ law and equilibrium constant method. The finite difference method was adopted to simulate the distribution of carbon concentration. By applying the model, the distribution of carbon concentration along thickness in HP-Nb tubes was predicted for the different service times. According to the temperature distribution of furnace tube, obtained by the analysis of heat transfer, the thermal stresses of the furnace tube with various carburization extents were analyzed by using the finite element code ABAQUS for the actual heating process of an ethylene cracking furnace. The analysis results show that the maximum circumferential thermal stress exists near the inner wall of the carburized tube, which usually causes cracking of the carburized tube along the longitudinal direction.

Abstract: Q195 steel was conducted by plasma chromizing and Cr-Ni surface alloying process to research the relationship between unit diffusion and binary diffusion. After studying the thickness, composition, phase component of the layer and diffusion coefficients of alloying elements, results showed that (1) the thickness of chromizing layer was 150μm; the surface phase component was Fe-Cr solid solution; the surface chromium contents was 21.4%. The thickness of Cr-Ni co-diffusion layer was 40μm; the surface phase component was Fe-Cr-Ni solid solution; the surface contents were: Cr 16.14%, Ni 48.16%. The alloying elements distributed in downward gradient from the outside to the inside. (2) Compared with plain surface alloying technique, using plasma surface alloying technique can get higher diffusing speed and shorten production cycle time. (3) The diffusion coefficients decreased as the diffusion distance increased. (4)Compared with chromizing, Cr-Ni co-diffusion increased the utilization ratio of alloying elements but decreased the diffusion speed of alloying elements, thus the surface alloying content increased and the thickness of alloying layer decreased.

Abstract: Using plasma alloying technique, Q235 steel was firstly treated by W-Mo-Y Multi-elements co-diffusion followed by plasma nitriding process. And then the wear tests were conducted. The effects of technological parameters on alloying layer were studied. The structure, composition, phase and micro-hardness of alloying layer were analyzed by metalloscope, XRD, SEM and microhardness tester. Results show that the microstructure of W-Mo-Y Co-diffusion layer is columnar crystal; W, Mo contents decrease from the outside to the inside. The element Y is distributed mainly at the grain boundaries. The phase of alloying layer consisted of Fe, Fe₃Mo, Fe₁₇Y₂ and the solid solution of (W, Mo, Y) in α-Fe. After plasma nitriding process, the co-diffusion layer is strengthened and large amount of nitrides form and dispersedly distribute in the alloying layer. After nitriding the phase of alloying layer consist of Fe₄N, Fe₃Mo, Fe, MoN, Mo₂N, W₂N, WN. the average micro-hardness is 850HV_0.05. Compared with untreated samples, the wear resistance of alloying layer is improved by 2 times under abrasive wear conditions.

Abstract: Q195 steel was treated with titanizing followed plasma nitriding by glow plasma alloying technology using single pulse power supply. The corrosion resistances of titanizing sample and titanizing + ion nitrided sample were studied. The results show that the alloying layer is 200 μm in depth and organization is α-Fe solid solution containing Ti by plasma titanizing technology using single pulse power supply. An obvious reactive diffusion dividing line formed between alloying layer and the substrate. It shows that diffusion phenomenon happened in process of titanizing. The morphology of Ti alloy layer was columnar crystals. The content of Ti on the surface is up to 5 wt%. And the Ti content of alloying layer is in a decreasing from the surface to the inner on a gradient distribution. The phase structure of titanizing layer is composed of Fe₂Ti, Fe-Ti and TiC phases. The phase structure of titanizing + ion nitrided sample was obviously TiN phase and a few Fe-Ti phase. The surface hardness of untreated carbon steel is 110 HV and that of the alloying layer of titanizing is 310HV. The surface hardness of titanizing + ion nitrided sample is 1800HV. The corrosion resistance of titanizing sample is increased 12.15 times compared with the untreated sample and 1.42 times compared with 18-8 stainless steel in H₂SO₄ solution; The corrosion resistance of titanizing + ion nitrided sample is increased 7.444 times compared with the untreated sample and as well as 18-8 stainless steel in H₂SO₄ solution.

Abstract: Finish rolling in the two-phase region may offer new possibilities for improving the properties of the FeSi steels with phase transformation. Therefore a deeper understanding of the effects by hot rolling in the two phase region or mixed rolling: multistep hot rolling in the two phase region and in the ferrite region on the evolution of the microstructure is desirable. In this paper we will present the results of our experimental studies on the effect of hot rolling in the intercritical state on the hardening and softening in the ferrite state. It will be demonstrated that depending on the process conditions at hot rolling the austenite ferrite transformation affects the stress strain behaviour in the ferrite state at multistep hot rolling remarkable.

Abstract: The plunging process of rotational tool is simulated while the shapes of rotational tool shoulder are inner-concave-flute, concentric-circles-flute and three-spiral-flute respectively. The effect of rotational tool shoulder’s shape on transfer behavior of welding plastic metal is obtained. The results show that whatever the shape of tool shoulder is, the metal of contact surface in the workpiece undergoes relatively big plastic transfer. To the rotational tool with three-spiral-flute shoulder, the transfer velocity and displacement of plastic metal inside the workpiece slowly decrease with the increase of the distance away from the surface of workpiece. To the rotational tool with the inner-concave-flute shoulder or the concentric-circles–flute shoulder, the transfer velocity of metal inside the workpiece is very small and the value is close to zero. Using the rotational tool with no pin, the experiment of friction stir welding is processed. The results show that the size of every grain in weld nugget zone which is made by the rotational tool with three-spiral-flute shoulder is nearly the same. The degree of uniformity of grain made by three-spiral-flute shoulder is much higher than that made by inner-concave-flute shoulder or concentric-circles-flute shoulder.