Metallurgy and Technology of Steel Castings
This book brings technical aspects of steel castings production explained on everyday engineers' tasks accompanied with global steel market trends. Although only 4-10% of the total amount of produced steel is used by steel foundries, there is a significant number of industries which rely heavily on its usage in their machineries and infrastructures. More than 50% of US railroad industry tonnage is steel casting and in construction machinery, it is over 15%. Global castings production in 2015 was 105.18 million metric tons, of which 11.3 million tons were steel castings. The largest steel castings producing countries in 2016 were: China (5 m tons), USA (1.55 m), India (1.1 m), and Russia (0.97 m). As a machine component, steel castings represent the most direct method of producing parts for their final forms. Casting production is also an economical process in cost and time. However, it is only true if the quality of the casting is at a very good level: without porosity, segregations effects and after proper heat treatment. The quality refers to the molten steel before a tapping and to the optimal pouring conditions from the ladle to the mould. Metallurgy and Technology of Steel Castings will certainly equip students and industry practitioners with necessary tools to assess what good quality is and how to achieve it in a production process.
It starts with topics related to melting methods (Chapter 2) – Including oxidation of elements according to Ellingham-Richardson diagram and desulphurisation of the melt. It explains the concepts of melt quality in various chapters related to the type of the melt (Chapter 3), the content of gases (oxygen, nitrogen and hydrogen – Chapter 4), and methods of deoxidation (Ch.5). These problems are especially relevant because, in contrast to rolling or forging processes, in steel castings the nonmetallic inclusions are invariable and content of gases must be lower (Ch.4 and Ch.5). The modern melting processes bring into relief several new methods (mainly in vacuum). Steel foundries adopted these manners of steel smelting but there are some important differences: the cooling rate of molten steel in large ladles (in metallurgy above 150 tons) is 1-2 C/hr and in foundries conditions (ladles 10-30 tons) 6-8 c/min. So, criteria for selection of secondary metallurgy for small ladles are quite different (Chapter 6).
The next chapters describe the properties of steel castings in service conditions:
– High strength cast steels used in construction machinery for thin and thick wall sections, carbon cast steels, low alloyed castings, castings with yield stress above 90 MPa; (Chapter 7);
– Steel castings for low temperature applications (Chapter 8 contains brittle-ductile transition, influence of alloying elements, effects of deoxidation and heat treatment);
– Corrosion resistant steel castings selection process on the basis of the type of corrosion (pitting, intergranular or general) and its usage in chemical, marine or petrochemical industry (Chapter 9);
– Working in elevated temperatures (600-1200 C) at oxidising or carburising conditions (Chapter 10). These castings are intended for petrochemical, chemical processing or mill equipment industries;
– Wear resistant castings are used in mining, crashing machineries, railroads and conveying conditions.
– Wear resistance is considered on the structural parameters and service conditions (for examples, in impact loaded Hadfield castings), (Chapter 11). The effects of microstructures, austenite-martensitic transformation or retained austenite are the basis for selecting the grades of these cast steels;
The last two chapters (12- pouring systems, 13- heat treatment) deal with typical problems in steel castings forming. Foundry engineers employed in industry will find good examples for their practice.
The book is addressed to two groups of readers:
– Students of foundry engineering, metallurgy or material science,
– Engineers operating in these branches which apply steel castings.
This work is also useful for readers studying in similar fields, such as manufacturing, material engineering or mechanical engineering.
Faizan ul Haq