In situ observation of recovery of lath structure in 9% chromium creep resistant steel

Abstract

The recovery process of the lath structure during tempering was investigated by in situ observations of 9% chromium creep resistant steel using TEM. A decrease of dislocation density inside the lath grains and an increase in lath width takes place during tempering. In situ observations revealed lath boundary migration and the disappearance of laths during tempering. Lath boundary migration is caused by repeat bulging and migration of local parts of the lath boundaries. Relatively small laths tend to disappear, leading to a decrease in the total energy of lath boundaries. All laths do not start to disappear at the same time; the rate of lath boundary migration differs with boundaries. The driving force of these microstructural changes is the strain accumulated by the martensitic transformation. Moreover, the recovery of the lath structure does not occur homogeneously during tempering because the strain does not distribute homogeneously in the lath structure.     

Method for welding highly crack susceptible magnesium alloy ZK60

Abstract

The highly crack susceptible magnesium alloy ZK60 plates of 2 mm thickness were successfully welded by laser beam welding (LBW) with filler strip, which has the advantages of low heat input and capability of adjusting the compositions of weld metal to a less susceptible level. The effects of the compositions of filler strips on the microstructures and mechanical properties of the joints were investigated. Compared with autogenous LBW, LBW with filler strip can produce a narrower joint and avoid the cracks and pits, which severely worsen mechanical properties of the joints. When the filler strip of ZK40 alloy is employed, the grains in fusion zone can be refined, and a high quality joint, with the ultimate tensile strength of 322 MPa up to 90·7% of the base metal, is obtained.     

Nanocrystalline zinc–nickel alloy deposition using pulse electrodeposition (ped) technique

Abstract

Zinc–nickel alloy was electrodeposited on stainless steel using pulse current deposition (PED) from a chloride–sulphate bath. Duty cycles were varied between 10 and 80% and frequency was changed from 10 to 100 Hz. The deposit characteristics were analysed using SEM, XRD and AFM and the results are presented in this paper. The corrosion resistance of zinc–nickel alloy deposited from direct current deposition (DCD) has been compared with that of the deposit obtained by pulse current using the electrochemical impedance spectroscopy method.     

KYN28A—12型高压开关柜在矿山的应用

使用KYN28A—12型高压开关柜克服了油断路器经常漏油、分合闸过程中不能相互闭锁容易烧电机和损坏设备等一系列不符合《煤矿安全规程》规定的突出问题。     

Electrodeposition of high performance multilayer coatings of Zn–Co using triangular current pulses

Abstract

Compositionally modulated alloy (CMA) coatings of Zn–Co were electrodeposited on to mild steel from an acid chloride bath containing thiamine hydrochloride, as an additive. Electroplating was carried out galvanostatically from a single bath containing Zn²⁺ and Co²⁺ ions. Gradual change in composition in each layer was effected by triangular current pulses, cycling between two cathode current densities. Compositionally modulated alloy coatings were developed under different conditions of cyclic cathode current density and number of layers, and their corrosion resistances were evaluated by potentiodynamic polarisation and electrochemical impedance spectroscopy. The formation of multilayer and corrosion mechanism was analysed using scanning electron microscopy. The corrosion resistances of CMA and monolithic alloy coatings were compared with that of the base metal. Compositionally modulated alloy coating at optimal configuration, represented as (Zn–Co)_{2·0/4·0/300}, was found to exhibit ～80 times better corrosion resistance compared with monolithic (Zn–Co)_3·0 alloy, deposited for the same length of time from the same bath. Improved corrosion resistance was attributed to the formation of n-type semiconductor film at the interface, supported by Mott–Schottky plots. Decrease in corrosion resistance at high degree of layering was found, and is due to lower relaxation time for redistribution of solutes in the diffusion double layer, during plating.     

Effect of nickel on microstructure and mechanical properties of heat affected zone of low carbon steel

Abstract

In the present study, the effect of nickel along with varying heat input on the microstructure and mechanical properties of the heat affected zone (HAZ) of a low carbon steel was investigated. Experiments were carried out in which low carbon steel specimens with five different nickel contents, 1, 2, 2.9, 4.1, and 5.2 wt-%, were welded using a submerged arc welding machine with heat inputs of 0.5, 1, and 2 kJ mm^-1. Following welding, the microstructure, hardness, and toughness of the HAZs were determined. From the results, attempts were made to establish a relationship between heat input, nickel content, microstructure, hardness, and toughness. Charpy impact testing and microstructural observation showed that, for a heat input of 0.5 kJ mm^-1, nickel contents between 2.9 and 5.2 wt-% were effective in forming lower transformation products, such as martensite, thereby producing lower toughness values. It was subsequently found that, taking into consideration the microstructure, hardness, and toughness of the HAZ, a lower heat input for a nickel content of 1 wt-% and a medium heat input for nickel contents between 2 and 5.2 wt-% gave good results.     

ZN111—4催化剂在兰州石化公司Sphripol-Ⅱ双环管聚丙烯工艺上的应用

为减少聚丙烯（PP）产品的细粉含量,确保PP装置的稳定运行,中国石油兰州石化公司试用了Basell公司ZN111—4催化剂。结果表明,与装置沿用的ZNM1催化剂（生产均聚PP产品（牌号T38F）时使用）和ZN118催化剂（生产共聚PP产品（牌号SP179）时使用）相比,使用ZN111—4催化剂生产这2种PP产品,催化活性可提高15％以上;生产T38F时外给电子体消耗量可降低5％,生产SP179时外给电子体消耗量可降低33％;PP粉料产品的平均粒径较小,但粒径小于300μm的细粉含量相当;共聚性能与ZN118催化剂相当。     

Basell ZN 111-4催化剂在聚丙烯中试装置上的应用

在中国石油兰州化工研究中心75 kg/h聚丙烯中试装置上进行了进口Basell ZN 111-4催化剂的聚合反应性能评价实验。结果表明,ZN 111-4催化剂具有较高的聚合活性和氢调敏感性,产品的等规度可在较大范围内调整,催化剂活性释放平稳,抗杂质干扰能力较强。在催化剂流量和质量浓度分别为0.18 mL/min及100 g/L,n（氢气）/n（丙烯）为0.004,m（三乙基铝）/m（给电子体）为1.08的工艺条件下,当丙烯的含水量为3.54 mg/L时,ZN 111-4催化剂的活性[m（聚丙烯）/m（催化剂）]高达31 480。     

The generalized forced oscillation method for tuning PID controllers

In this paper a generalized tuning methodology for proportional–integral–derivative (PID) controllers is proposed. The methodology is akin to the Ziegler–Nichols forced oscillation method, inheriting fully its practical appeal, but can be applied to much more general classes of plants. This generalization is achieved by employing a relay with adjustable phase (RAP) in a relay feedback experiment, and the tuning consists of formulas based on measurements obtained from this experiment. Experimental results in a liquid processing plant with of-the-shelf industrial equipments illustrate the performance of the methodology and the practical procedures involved in its application, which can be fully automated.     

Basell ZN M1催化剂在聚丙烯中试装置上的应用研究

利用中国石油石化院75 kg/h聚丙烯中试装置进行进口Basell ZN M1催化剂的聚合反应性能评价实验。聚合结果表明,ZN M1催化剂具有较高的聚合活性和氢调敏感性,产品的等规度可以在较大范围调整,催化活性的释放平稳,抗杂质干扰能力强。在催化剂流量和质量浓度分别为0.18 mL/min及100 g/L,n(氢气)/n(丙烯)为0.004,m(三乙基铝)/m(给电子体)为1.08的工艺条件下,当丙烯的含水量为3.54 mg/L时,ZN M1催化剂的活性[m(聚丙烯)/m(催化剂)]高达29654。