Possibilities of grading pipes of high-strength and grey cast iron

The main process leading to the destruction of the cast elements of gas-collection bell of electrolyzer, made of grey cast iron, is the oxidation of iron by oxygen, SO2 gas and sulfur vapors to form magnetite, hematite and pyrrhotin. The simultaneous formation of iron oxides and sulfides does not prevent further corrosion, since scale is formed with a loose structure that does not have protective properties. Reducing the length of the interfacial boundaries inside the material of the cast enables to reduce the rate of corrosion destruction, which can be achieved by modifying the cast iron to change the shape of graphite inclusions, i.e. obtaining high-strength cast iron with a spherical shape of graphite inclusions. However, the obtaining spherical graphite in cast iron using magnesium modification does not exclude the access of aggressive gases to the surface of the products and the possibility of their diffusion along the grain boundaries. It was shown that alloying can be an alternative, which leads not only to the exclusion of lamellar secretions of graphite in the structure of cast iron, but also to the formation of surface oxide layers based on the alloying element preventing the corrosion. Alloying with chromium gives cast iron high abrasive resistance due to the presence of a carbide component in the structure, as well as corrosion resistance due to the alloying of the metal base, heat resistance due to increasing the electrochemical potential of the metal base and creating a strong neutral oxide film on the surface of the castings, heat resistance, etc. An experimental comparative analysis of the corrosion resistance of cast iron used for manufacturing of gas collecting bell of electrolyzers showed that chromic cast iron ЧХ3 has a higher corrosion resistance than high-strength cast iron with spherical graphite ВЧ50 and much higher than grey cast iron with lamellar graphite. However, chromic cast iron ЧХ3 has low casting properties, is very sensitive to the cooling rate and has a large heterogeneity in structure, which makes it difficult to use it for the manufacture of gas collecting bell of electrolyzers.

Download Full-text

Development of High-Performance Enamel Coating on Grey Iron by Low-Temperature Sintering

Materials ◽

10.3390/ma11112183 ◽

2018 ◽

Vol 11 (11) ◽

pp. 2183 ◽

Cited By ~ 4

Author(s):

Dan Song ◽

Ren Tang ◽

Falin Yang ◽

Yanxin Qiao ◽

Jiapeng Sun ◽

...

Keyword(s):

Wear Resistance ◽

Cast Iron ◽

Low Temperature ◽

High Performance ◽

Alkali Metals ◽

Enamel Coating ◽

High Strength ◽

Grey Cast Iron ◽

Wear Volume ◽

Grey Cast

In this study, we report on a low-temperature sintered enamel coating with a high-strength bonding and wear-resistance that protected a grey cast iron substrate. The SiO2–Al2O3–B2O3 composited prescription for the enamel coating was modified by the partial substitutions of SiO2 for B2O3 and alkali metals for Li2O. The optimized enamel coating was prepared by sintering at a relatively low temperature (730 °C) for seven minutes. Due to the composition of both the amorphous and crystalline phases, the enamel coating presented sufficient hardness and excellent wear resistance. The wear volume loss and the specific wear rate of the enamel coating were obviously lower than that of the metal substrate. The enamel coating can effectively improve the service life of the grey cast iron substrate in a complex frictional environment.

Download Full-text

RESTORATION OF THE CONSTRUCTION AND ROAD MACHINES’ DETAILS FROM GREY CAST IRON: IMPROVEMENT OF THE REPAIR DIMENSIONS’ METHOD EFFICIENCY

The Russian Automobile and Highway Industry Journal ◽

10.26518/2071-7296-2019-6-658-668 ◽

2019 ◽

Vol 16 (6) ◽

pp. 658-668

Author(s):

V. E. Ovsyannikov ◽

V. I. Vasilyev

Keyword(s):

Cast Iron ◽

High Strength ◽

Grey Cast Iron ◽

Special Device ◽

Technical And Economic Analysis ◽

Grey Cast ◽

Final Manuscript ◽

Friction Assemblies ◽

Operational Failures ◽

Technical Solutions

Introduction. The total mass of some grey cast iron details in construction and road machines reaches 60%. Cylinder blocks, parts of braking systems, flywheels, etc. are made of cast-iron. One of the main causes of operational failures (up to 70%) of construction and road machines is failure of friction units. Considering that the contacting parts in these units take the load mainly by surface layers. The operability looses at relatively small values of dimensional wear. Although mass wear of the part usually does not exceed 1%.Materials and methods. The authors carried out a comprehensive technical and economic analysis of repair methods of friction assemblies. As a result, the best combination of criteria was the repair size method. However, the strengthened layer was removed to the repair dimension by conventional reconditioning technology. At the same time grey cast iron was strengthened only by very expensive and labor-intensive methods, which in conditions of real repair production were not applicable. The authors considered the possibility of using a new method of strengthening iron parts in repair works.Results. The developed method strengthened grey cast iron with layer thickness up to 3 mm. The distinctive feature was that hardness of the strengthened layer in thickness increased. At the same time the microhardness increased in comparison with the initial grey iron more than 2 times and wear resistance became comparable to high-strength hardened stun.Discussion and conclusions. The authors obtain the best results with the usage of reducing atmosphere furnaces. In order to expand the scope of the method, the researches proposed to use a special device creating the necessary conditions in any furnace. The application of the proposed technical solutions increases the efficiency of the construction and road machines’ repair.The authors have read and approved the final manuscript. Financial transparency: the authors have no financial interest in the presented materials or methods. There is no conflict of interest.

Download Full-text