丙烷浓度对45钢离子碳氮共渗的影响

首次以丙烷作为供碳剂对45钢进行离子碳氮共渗。利用金相显微镜、X射线衍射仪和显微硬度计研究了丙烷浓度对试样截面形貌、物相组成和表面硬度的影响。结果表明:随丙烷浓度的增加,化合物层厚度和表面硬度均呈现先增大后减小的趋势。当丙烷浓度为1.5%时,510℃离子碳氮共渗4h后,化合物层厚度和表面硬度分别达到最大值40μm和779HV0.05,同时得到以ε相为主,并伴有极少量渗碳体的最优物相组成。当丙烷浓度超过1.5%时,化合物层厚度和表面硬度均下降,这是由于渗碳体相含量随丙烷的增加而增加,并当丙烷浓度为2.5%时渗碳体成为主要物相,从而阻碍了C、N原子向基体内的进一步扩渗。     

AISI304钢埋弧焊工艺的研究

本文对AISI 3 0 4钢薄板的埋弧焊工艺进行了试验研究。并对焊材性能进行了工艺试验 ,在对试验结果分析的基础上确定了最佳焊接工艺参数。焊接接头的各项力学性能实验结果完全满足图纸要求。通过采取先进的焊接工艺装备 ,成功实现不锈钢薄壁筒体的焊接     

Optimized AISI 304 steel nitriding in inductive RF N2-H2 plasmas

Optimal surface nitriding is closely related to plasma chemical composition. The effects of Plasma-Immersion Ion Implantation (PIII) nitriding with 15% N₂+85% H₂ type mixtures have been studied. A simplified PIII facility was assembled around an evacuated Pyrex cylindrical 500 mm long reactor with a 190 mm inner diameter, over which a 3.2 mm wide antenna was coaxially wound with a 240 mm inner diameter. The system was supplied by a 13.56 MHz RF generator whose electric component developed the plasma discharge. After the admission of the gas mixture to the reactor vessel the breakdown took place within 5-15 Pa work pressure and 450-500W RF power. The main plasma parameters were characterized including a 1.8 × 10¹⁸ to 3.1 × 10¹⁸ m⁻³ density by means of double Langmuir probes. An additional DC power supply was selected in order to bias AISI 304 stainless steel samples with a view to improving the steel hardness properties without compromising its corrosion resistance. The samples treated at different temperatures and for several periods, were evaluated by means of X-ray diffraction (XRD), which indicated the formation of nitrides, identified as Fe₃NiN and FeNiN and can be associated with the enhanced austenitic phase of the stainless steel. Scanning electron microscopy (SEM) assessed the atomic percentages of nitrogen both on the sample surface and through their cross-section. Vickers microhardness (HV) tests exhibited up to a 6-7 times increase at a 500g load. Finally, Raman spectroscopy studies established four active modes at 215, 267, 385 and 490 cm⁻¹ with temperatures between 400 and 500 °C.     

Experimental evaluation and performance enhancement prediction of desiccant assisted separate sensible and latent cooling air-conditioning system

CO₂ and R410A desiccant wheel (DW)-assisted separate sensible and latent cooling (SSLC) air-conditioning systems were tested under the AHRI standard. At a 50 °C regeneration temperature, the coefficient of performance (COP) of the vapor compression cycles improved only 7% from the respective baseline systems for both refrigerants. This paper proposed the idea of applying divided condensers (or gas coolers) to the R410A (or CO₂) SSLC system to enhance its performance. It was found that the application of divided heat exchangers to the SSLC system provided sufficiently hot airflow for regenerating the desiccant wheel at both a reduced high side pressure (from 10.4 MPa to 9.7 MPa for CO₂, from 3.46 MPa to 3.45 MPa for R410A) and a reduced discharge temperature from the condenser (gas cooler) (4 K lower for both refrigerants). The COP improvement is 36% and 61% to R410A and CO₂ baseline systems, respectively.     

An experimental study on oil discharge ratio at inverter-driven high shell pressure scroll compressor using R410A/PVE

In this study, the oil discharge characteristics of a high shell pressure scroll compressor, which uses R410A as the refrigerant and PVE as the oil, were measured according to the conditions for oil management. The measurement of oil discharge ratio (ODR) in the system is very important to secure the operational reliability. It was made in real time through the refractive index sensor. ODR was greatly influenced by the mass flow rate and the dynamic viscosity of the refrigerant. As the rotation frequency of the compressor became higher, ODR increased rapidly. ODR at 120 Hz was 4.22 times higher than that at 60 Hz. At the same rotation frequency of the compressor, the increase of the suction pressure also played a role in increasing the ODR. In addition, in the zone where the ODR increased rapidly, the compressing efficiency of the compressor decreased significantly.     

河南省民政厅综合办公楼数码多联空调工程设计

本文着重介绍了数码涡旋技术在商用办公楼的设计及应用,该工程能在一年四季提供稳定的制冷和制热,充分体现数码涡旋技术的广泛适用性、节能可靠性、控制便利及精确性,具有安装和后期维护简单方便等突出优点。     

R22及其替代物的热物性计算及比较

本文根据R2 2、R12 5的状态方程对空调替代工质R410A热物性进行了计算 ,并对比了R410A与R2 2的热力学性质和理论制冷循环的各项指标。     

High-temperature hydrogen sulfide corrosion on the heat-affected zone of the AISI 444 stainless steel caused by Venezuelan heavy petroleum

The aim of this study was to evaluate the effect of welding on the corrosion resistance of the heat-affected zone (HAZ) of the AISI 444 ferritic stainless steel in medium containing Venezuelan heavy oil. AISI 444 steel plates were welded through the use of three levels of welding heat input (4, 6 and 8 kJ/cm). Samples were extracted from the welded plates and thermally treated in three different temperatures (200, 300 e 400 °C), while immerged in petroleum for a period of 4 h. Optical microscopy (OM), scanning electronic microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for the analysis of the surface and transversal section of the joint. Electrochemical trials of cyclic potentiokinetic reactivation of double loop (EPR-DL) were also carried out. It has been concluded that the temperature of treatment has direct influence on the level of material corrosion and that the increase in the welding heat input contributes to a higher level of corrosion.