TESTING RESISTANCE OF ENAMELED SURFACES TO SCRATCHING GOUGING,AND ABRASION*

Seven types of cover-coat enamels were tested for resistance to scratching, gouging, and abrasion by various methods. These methods were (a) P.E.I. abrasion test, (b) P.E.I. gouge test, (c) variations of the gouge test, (d) Taber Abraser, and (e) a scratch test. Chemical durability and reflectance were found to have little or no correlation with the resistance of the enamels to abrasion. The bubble structure of the enamel layer seemed to have the greatest effect on abrasion and scratch resistance of the enamel layer.     

高活性氧化镍对搪瓷气泡结构的影响

本文研究了不同的烧成时间,添加活性氧化镍后搪瓷底釉的气泡结构所产生的变化,并对活性氧化镍作用机理作了一定的探讨,它有助于搪瓷均匀气泡结构的形成。     

喷釉管道釉层密着性的研究

用热震试验，落球试验，扫描电镜，Ｘ射线衍射等对喷釉和道釉层密着性进行了研究。结果表明，用氧气－石油天然气火焰在碳钢管里表面热喷玻璃釉料可以获得均匀，无裂纹，密着良好的釉层。釉层表面相结构 主要为玻璃态，有少量日 想Ｎａ２Ｍｏｏ４（ｍＯｏ３）ｙ析出；氮气保护可以提高釉层的抗热震性，耐冲击性及金属与瓷层界面的致密性；金属与釉层界面之间１０μｍ范围内形成了界面过渡区，对釉层密着有重要影响。     

RELATION OF THICKNESS TO IMPACT RESISTANCE OF PORCELAIN ENAMEL*

Chipping of porcelain enamel on the flanges of table tops as a result of impact was studied and compared with the results obtained from the Porcelain Enamel Institute tentative standard impact test. A correlation was found to exist between the results using the P.E.I, test on standard 1-in. tubes and those obtained on the corner of a table-top flange. The impact resistance of enamels applied over a radius also increased as the thickness of the enamel was increased.     

Improvement in mechanical properties of enamel via carbon nanotube addition

Enameled metal equipment exploits the strength of metal materials and the corrosion resistance of enamel; therefore, it is widely used in the chemical industry. However, the mechanical properties of the enamel restrict its service life. Multi-walled carbon nanotubes (MWCNTs) are one-dimensional nanomaterials with high-specific surface area, C–C bond structure, and SP₂ hybrid orbital. Herein, the effect of the dosage of MWCNTs on the mechanical properties of enamel is studied by adding MWCNTs to improve the mechanical properties of the enamel. Microscopic observation showed that the toughening mechanism of MWCNTs was mainly manifested in fracture and pull out behaviors. According to three-point bending test, when 0.4 wt% carbon nanotubes were added, the reinforcing effect of enamel layer reached the best state. These results provide reference for optimizing the formulation of enamel and extending the service life of enamel.     

Effect of bentonite content on the suspension stability of a glaze slurry and final enamel performance

The influence of bentonite as a suspending agent on the processing and performance of the final enamel product was studied with the aim of prolonging the service life of enamel. The suspension stability of the glaze slurry was also evaluated, and the influence of the layered structure of bentonite on the suspension was explored. In addition, the effect of bentonite on the flexural strength and fracture toughness of enamel coatings on metal substrates was investigated. Finally, acid corrosion resistance experiments were performed to evaluate the effect of bentonite on the corrosion performance of the enamel coating. The results showed that the stability of the glaze slurry and mechanical properties of the enamel products were significantly improved by adding 1 wt% bentonite to the glaze slurry. The addition of 0.5 wt% bentonite was optimal for enhancing the acid corrosion resistance of the enamel. This study provides a useful reference for improving the quality of enamel products and prolonging their service life.     

Evaluation of 316L stainless mill additives on microstructure and alkali corrosive behavior of enamel coatings

Excellent chemical stability, good corrosion resistance, and compositional controllability make vitrified enamel promising coating materials. The corrosion resistance of the [–Si–O–]/[–Si–O–Al–]-based enamel coatings decreases in alkaline environments, whereas can be improved by incorporating metal oxides, such as ZrO₂ and SnO₂. The introduction of these oxides results in an increase in the sintering temperature and a decrease in the toughness of the coatings. It was observed that the corrosion resistance of the coatings in an alkaline medium could be improved using metal powder-based additives without increasing the sintering temperature and affecting the mechanical properties of the coatings. We used powdered 316L stainless steel as the mill additive, and the effects of this additive on the structure and alkali corrosion resistance of the vitrified enamel coatings were studied. Results indicate that the addition of an appropriate quantity of the additive (4 wt.%) improves the extent of gas consumption during the enamel sintering, decreases the degree of porosity and the size of the pores. Furthermore, the mechanical properties of the skeleton formed between the pores could be improved, because blocklike corrosion products are not peeled off, which increases the corrosion resistance of the coatings. The corrosion products, such as Ca-based compounds, block the corrosion holes, resulting in a decrease in the corrosion rate also.     

STIFFENING EFFECT OF PORCELAIN ENAMEL ON SHEET IRON: I–II*

The stiffening effect of porcelain enamel is important in applications involving flat surfaces, such as panels, signs, tabletops, cabinets, refrigerators, and stoves. The purpose of this paper is to report on several investigations evaluating the effect. Bending tests were made on small flat specimens of 18- to 28-gauge sheet iron coated on both sides with porcelain enamel ranging in thickness from 0.004 to 0.025 in. per side. Substantial increases in stiffness reaching as high as 1500% for 28-gauge steel with 0.025 in. of enamel on each side are shown in comparisons between bare and enameled specimens. The increases in ultimate bending strength range to 500%, but the usable increase is somewhat less. Bending tests were made on porcelain-enameled corrugated sheets, which showed somewhat smaller increases in stiffness and bending strength due to enameling. The minimum thickness of base metal and maximum thickness of enamel are, of course, governed by practical considerations, such as the resistance necessary against chipping and the ability to maintain flatness during firing, which also depend on shape and proportions of the product. A method is given for computing the bending properties of flat sheets and formed sections by means of the usual formulas of mechanics with correction factors for the porcelain enamel. Conversion curves are shown by which bare and enameled sheets may be compared.     

Population balance modeling of polyurethane foam formation with pressure-dependent growth kernel

Polyurethane foams are widely used materials often chosen for their useful characteristics such as low thermal conductivity, ease of application, and high strength-to-weight ratios. Computational models are needed to predict the dynamics of the flow and expansion, and the resulting material properties, to improve manufacturing processes. In this paper, a model for PMDI, a water-blown polyurethane foam, is presented. By extending a kinetics-based approach by adding bubble-scale information via a population balance equation (PBE) using the quadrature method of moments, we can track bubble size distributions during foaming. We present results from a three-dimensional computational fluid dynamics model using arbitrary Lagrangian–Eulerian interface tracking implemented in finite element software. The model compares favorably with experimental data, including dynamics, bubble distributions measured by both camera and diffusion wave spectroscopy, and post-test bubble size from scanning electron microscopy and density measurements from x-ray computed tomography.     

THE RELATIONS BETWEEN COMPOSITION AND PROPERTIES OF ENAMELS FOR SHEET STEEL1

Very little has been reported on the relations existing between enamel composition and the properties except the resistance to acids. In this investigation a study was made of the relation between enamel composition and such properties of the enamel as expansion, strength and acid resistance, as well as the effect of the relative “fit” of the ground and cover coats on resistance of the enameled ware to impact and to thermal shock. The work was done on fourteen ground coats and white cover enamels applied to eight-inch dinner plates. The latter were tested for resistance to impact, to thermal shock, and to acetic acid. Determinations were made of the expansion and compression strength of the enamels before application to the steel. Conclusions.—1. The replacement of boric oxide by sodium oxide in the enamels increased the coefficient of expansion. Fish-scaling decreased with increase of ex- pansion, due to increases of sodium oxide. 2. The compressive strength of the ground coats appeared to decrease with re- placement of boric oxide by sodium oxide, although the reverse conditions occurred in the case of the cover enamels. 3. Impact on the parts of enameled ware not free to deflect, such as the curved corners at the bottom, gives a measure of the toughness of the enamel as applied on the steel. The resistance of the enamel on corners to impact apparently is a function of the inherent strength of the enamel rather than its “fit” on the ware. 4. For greatest resistance to thermal shock, the ware should be coated with a ground coat having a coefficient of expansion equal to or preferably greater than that for the cover enamel. 5. Acid resistance, while dependent on the enamel composition, is not affected in the same way for all enamels. For these particular cover enamels, resistance to acids decreased with replacements of boric oxide by sodium oxide.     

高原地区抗冻引气混凝土含气量设计方法研究

对高原与平原地区不同水胶比引气混凝土的含气量、气泡间距系数及抗冻耐久性指数进行测试,同时搜集整理国内外相关研究成果,研究分析了高原低气压环境对引气混凝土含气量损失、气泡间距系数变化及临界抗冻耐久性指数的影响。结果表明:相较于平原地区,高原低气压环境下引气混凝土含气量损失增大,硬化后混凝土含气量损失约1.0%~1.5%;硬化混凝土含气量与气泡间距系数的对数间存在良好的线性关系,但高原低气压环境可能劣化引气混凝土的气孔结构;硬化混凝土气泡间距系数与抗冻耐久性指数间也具有良好的线性关系,且不受环境气压影响;以引气混凝土气泡间距系数为桥梁,提出一种基于混凝土抗冻耐久性要求的高原地区引气混凝土含气量设计方法。     

Evaluation of the abrasion resistance of enamel coatings

Vitreous enamel coatings have been used for many centuries to protect metallic substrates from corrosion phenomena and improve the aesthetics of the coated objects. They are manufactured by smelting frits, thus forming an inorganic, adherent and protective layer on the metal.The durability of aesthetic properties is related to the resistance of the surface to mechanical damage. One kind of possible damages is the abrasion which can impair the characteristics of the enamel layer.In this work the abrasion resistance of different enamel samples has been investigated. Low-carbon steel panels were coated with three distinct enamels applied by two different methods: wet dip coating and electrostatic powder coating. The composition of the enamel samples is characterized by refractory mill additions that improve the high temperature resistance for applications as ovens or burners. The abrasion resistance has been studied by the standard abrasion test ISO 10545-7 and the Taber test comparing the level of damage and the morphologies.     

泡沫玻璃气泡缺陷与解决方案

泡沫玻璃是一种具有均匀气泡结构的玻璃制品,具有隔热、吸声、防潮、防火等特点的轻质高强建筑材料和装饰材料。泡沫玻璃的生产过程中,经常会遇到气泡结构不均或大气泡等气泡缺陷。本文从气泡的产生机理分析入手,针对具体的气泡缺陷种类,分析产生原因,提出解决方案,更好地实现泡沫玻璃的内在和外观质量。     

Improving the mechanical impact and bending resistances of enamel via B2O3 addition

Enameled metal equipment possesses the advantages of the material strength of metal and the corrosion resistance of glass; therefore, such equipment is used extensively in industries involving chemical processes. However, the mechanical properties of enamel affect its service life. Therefore, the enhancement of the mechanical properties of enamel to extend its service life is important. To improve the mechanical impact and bending resistances of enamel, we used enameled samples with Q345R steel as a metal matrix for controlled-temperature sintering. The enameled samples were prepared using varying amounts of B₂O₃ in the formulation of the enamel glaze, and the mechanical impact and bending resistances of the enamel were studied via the ball impact and three-point bending methods. The results show that B₂O₃ addition improves the mechanical impact and bending resistances of enamel significantly, although these resistances decrease when the B₂O₃ content is too high. The enamel exhibits an optimal mechanical impact resistance with a B₂O₃ content of 2%, and an optimal bending resistance with a B₂O₃ content of 3%. These results provide important reference values that can be used to optimize the formulation of enamel and extend the service life of enamel equipment.     

CHEMICAL DURABILITY OF PORCELAIN ENAMELS *

The resistance of representative porcelain enamel surfaces to the chemical attack of different concentrations of various solutions was investigated in considerable detail. Cylindrical cup-shaped samples were coated with (1) a ground coat, (2) a white fluoride cover enamel, (3) a white antimony cover enamel, (4) a white zirconium cover enamel, (5) an acid-resistant white cover enamel, (6) a sign blue cover enamel, (7) a blue zirconium enamel, and (8) a chemical acidproof blue cover enamel. The loss in weight of these enamel surfaces, after exposure to chemical attack, was determined at definite time intervals. The solutions studied consisted of different concentrations of the inorganic acids, alkalis, several organic acids, as well as selected salt solutions at both room and boiling temperatures. Numerous curves are presented showing the comparative chemical durability of the various porcelain enamel surfaces in which the cumulative loss in weight is plotted against time. Several photomicrographs show the nature and type of chemical attack on the different surfaces. The porcelain enamel surfaces showed considerable variation in their resistance to the chemical attack of the various solutions. All of the porcelain enamels were, in general, resistant to attack at room temperature by the alkali and salt solutions. The acid-resistant and acidproof enamels were resistant to the action of both inorganic and organic acids at room and at boiling temperatures; a wide variance, however, was shown in the comparative acid resistance of the non-acid-resisting enamel to the attack of either organic acids or inorganic acids at room temperature. AU porcelain enamels showed equally low resistance to boiling alkali solutions, but some of the enamel surfaces were attacked markedly by the boiling salt solutions.     

Transient elongational viscosity of LLDPE/LDPE blends and its relevance to bubble stability in the film blowing process

Transient elongational viscosity of linear low density polyethylene (LLDPE) and its blends with 10% and 20% of low density polyethylene (LDPE) was measured at two temperatures by a constant strain rate elongational rheometer. In addition, the performance of the blends in the film blowing process was assessed in terms of bubble stability at two processing temperatures. An operating window for stable bubble production was determined. The elongational viscosity measurements on blends revealed stronger strain hardening characteristics at a higher temperature of testing. These results correlate favorably with findings from a bubble stability investigation where it was found that the size of the operating window for stable bubble production increased with increasing extrusion temperature. This work seems to indicate that increasing processing temperature during the film blowing of LLDPE-rich blends could lead to a processability improvement of these blends as far as bubble stability is concerned.     

MARANGONI BUBBLE MOTION PHENOMENON IN ZERO GRAVITY

The Marangoni phenomenon is shown to be the primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low-gravity environment. In such a two-phase system, local variations in surface tension at the bubble surface are caused by a temperature gradient in the liquid. Shearing stresses thus generated at the bubble surface lead to convection in both media, as a result of which the bubble moves. A mathematical model consisting of the Navier-Stokes and thermal energy equations, together with the appropriate boundary conditions for both media, is presented. Parameter perturbation theory is used to solve this boundary value problem, with the expansion parameter being the Marangoni number. The zeroth, first- and second-order approximations for the velocity, temperature and pressure distributions in the liquid and in the bubble, and the deformation and terminal velocity of the bubble are determined. Experimental zero-gravity data for a nitrogen bubble in ethylene glycol, ethanol, and silicone oil subjected to a linear temperature gradient were obtained using the NASA Lewis zero-gravity drop tower. Comparison of the zeroth order analytical results for the bubble terminal velocity showed good agreement with the experimental measurements. The first- and second-order solutions for the bubble deformation and bubble terminal velocity are valid for liquids having Prandtl numbers on the order of one, but there is a lack of appropriate data to fully test the theory.     

MARANGONI BUBBLE MOTION PHENOMENON IN ZERO GRAVITY

The Marangoni phenomenon is shown to be the primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low-gravity environment. In such a two-phase system, local variations in surface tension at the bubble surface are caused by a temperature gradient in the liquid. Shearing stresses thus generated at the bubble surface lead to convection in both media, as a result of which the bubble moves. A mathematical model consisting of the Navier-Stokes and thermal energy equations, together with the appropriate boundary conditions for both media, is presented. Parameter perturbation theory is used to solve this boundary value problem, with the expansion parameter being the Marangoni number. The zeroth, first- and second-order approximations for the velocity, temperature and pressure distributions in the liquid and in the bubble, and the deformation and terminal velocity of the bubble are determined. Experimental zero-gravity data for a nitrogen bubble in ethylene glycol, ethanol, and silicone oil subjected to a linear temperature gradient were obtained using the NASA Lewis zero-gravity drop tower. Comparison of the zeroth order analytical results for the bubble terminal velocity showed good agreement with the experimental measurements. The first- and second-order solutions for the bubble deformation and bubble terminal velocity are valid for liquids having Prandtl numbers on the order of one, but there is a lack of appropriate data to fully test the theory.     

冰乙酸储运设备联合涂层结构及材料的研究

采用联合涂层结构,在碳钢基体上,用耐冰乙酸的铝、不锈钢等金属涂层作为底层涂层,用AT-1涂层作为面层,经一年的浸泡试验,筛选出以铝涂层作为底层涂层、以AT-1涂层作为面层涂层的联合涂层,联合涂层无鼓泡、变色现象,浸泡液冰乙酸颜色无变化。     

新型无磷前处理剂在阴极电泳涂装中的应用及性能研究

开发了一种新型的无磷转化液,通过浸渍或喷淋的方式在样板表面镀上一层氧化锆／硅烷复合膜层,利用SEM、EDS和XRD等测试手段对膜层的表面形貌和物相结构进行分析,结果发现膜层为非晶结构;通过对电泳后的样板进行附着力、耐冲击、耐腐蚀性等试验,得出复合膜层的主要性能指标为：附着力试验合格、冲击无裂纹、500h中性盐雾试验后漆膜单边腐蚀宽度约为1him,表面无起泡现象。通过与磷化液的对比试验发现,该复合膜具有与磷化膜相当甚至超过磷化膜的耐腐蚀性能。