QUALITY OF STEEL FOR STEEL BUILDINGS
Steel is an immensely useful alloy, made by combining two metals, iron and carbon. The amount of carbon used in steel determines its hardness, ductility, and malleability. In terms of durability, endurance, and versatility, steel has become the new choice for metal fabrications for many builders, initiating a revolution in the building industry through the introduction of steel construction.
The physical properties of steel include high metallic strength, low weight, durability, flexibility and resistant against corrosion. Steel offers great strength even though it is light in weight. In fact, when compared to any other building material, steel has the lowest strength to weight ratio. In terms of being flexible, steel can be easily molded to form any desired shape. Steel does not corrode easily even when exposed to moisture and water. Its dimensional stability makes it resistant against rust, scraping and other general forms of deterioration and remains unchanged even after many years of being subjected to extreme environmental conditions.
METHODS USED TO IMPROVE THE QUALITY OF STEEL
The percentage of carbon in steel may range from 0.2% to 2.14% of the total weight. Aside from carbon, the alloying materials used in steel may include aluminium, manganese, phosphorous, sulfur, silicon, copper, boron, chromium, nickel, molybdenum, tungsten and many more. These alloying materials perform the function of hardening the metal during the cooling process.
Carbon is the primary hardening element in steel and is the most cost-effective. The hardness and tensile strength of steel increases as the carbon content increases. However, ductility and weldability decreases as the amount of carbon increases.
Boron is a very potent alloying element of steel. In fact, a very small amount o of boron (about 0.001%) has a strong effect on the material’s hardness.
Chromium is commonly added to steel to increase its resistance against corrosion and oxidation, and to increase its hardenability. When used as a hardening element, chromium is frequently combined with nickel to produce steel’s superior mechanical properties.
Compared to earlier forms of the steel, which had a greater carbon content, today’s steel has less carbon and the metal is cooled down immediately during the process. This way, the desirable properties of steel, is retained.
JUDGING THE QUALITY OF STEEL
The quality of an alloy, such as steel, can be judged by its appearance and the lustrous surface. The more lustrous the surface, the more refined the steel. The alloy is also subjected to a series of tests involving stress and shock to be able to judge its properties like tenacity and endurance. The way the metal reacts to these processes determines whether its quality is fit for the purpose it was made.
Another measure of quality of steel is the so called, R-Factor, or the resistant factor. It measures the amount of resistance present in a particular kind of steel. The R-Factor of steel used in the construction of steel buildings must be about 28 gauge to ensure the building’s perpetual strength.
Classification of steel gauges based on the composition and the physical properties of the metal, is done by many standard organizations. Steel grading is determined by the hardness of the metal or basically, its carbon content. The higher the carbon content, the harder is the steel but it is more prone to fractures due to its brittleness. High quality steel contains lesser amount of carbon, but is strong and hard, not brittle.
To summarize, the quality of steel is measured by its hardness, brightness and smoothness of surface, and the absence of depressions or troughs.
Steel is the backbone of a metal building. It is the building’s basic building material hence its quality is of utmost importance. Aside from its strength, another major advantage of steel is that it can be recycled without losing any of its physical properties in the process. These advantages, cost-effectiveness and strength, make it the most widely used building material for roads, railways, bridges, buildings, and stadiums. The importance of steel is such, that the economic progress of the country is marked by the growth and development of the steel industry.