Effect of Alloying Elements on Microstructure and Properties of Low Alloy Wear Resistant Steel

    
    Wear resistant steel comprises certain special alloying elements which enable them to better withstand the wear, tear and friction they must constantly endure. Low alloy wear resistant steel is a form of such steel, with careful selection of alloying elements resulting in a steel that has a reduced carbon content and thus has less potential for suffering from embrittlement or softening from long-term exposure to operations that involve extreme temperatures. Alloying elements employed in this kind of steel include chromium, molybdenum, and manganese, along with other trace amounts of other metals such as copper and nickel.
    
    In addition to their wear-resistant properties, these alloying elements have a strong influence on the microstructure of the steel, and this in turn affects its physical properties. One of the key elements in the microstructure of the steel is its Grain Size. Alloying elements like chromium, manganese and molybdenum are known to reduce the grain size which makes it better at resisting wear and tear. Not only does this effect the overall wear-resistance of the steel, but it is also known to reduce the ductility of the steel. The lower grain size also reduces the Young’s Modulus of the steel, which is a measure of how stiff it is.
    
    The presence of alloying elements also affects the presence of different phases of steel. Chromium, in particular, is known to form small particles known as ‘carbides’. Not only do these carbides increase the hardening of a steel, but they also help it to resist being attacked by corrosion or other corrosive agents. The presence of carbides also improves machinability, as the steel is harder and its grain structure more consistent.
    
    Molybdenum, too, has its own strong influence on the physical properties of the steel. The presence of molybdenum increases the strength of the steel and its resistance to fatigue, making it more suitable for applications that involve dynamic loading. Examples of this include valve systems, rotating cutting tools, and other components that are subject to constant loading and unloading. It also helps to increase the resistance of the steel to shock loads or thermal cycling, which makes it better suited for uses that are under a variety of changing operating temperatures.
    
    The effect of alloying elements on the properties of the steel can be seen in the diagrams below. The diagrams compare the yield strength, ultimate strength, and elongation rates of a steel alloyed with a few of the alloying elements to those of unalloyed steel.
    
    
    As can be seen, alloys with chromium, nickel, and molybdenum all have higher yield and ultimate strengths compared to unalloyed steel. The presence of chromium also greatly increases the elongation rate, making it a good choice for components that require more flexibility under changing loading conditions.
    
    In summary, the use of various types of alloying elements in low alloy wear resistant steel is important in order to achieve the desired properties. Chromium, manganese, nickel, and molybdenum are all useful in forming hard carbides that enable the steel to better resist wear and tear, while molybdenum also serves to further increase the strength and fatigue resistance of the steel. In addition to this, the presence of these alloying elements also reduces the grain size and increases the elongation rate of the steel, making it more suitable for applications where a wider range of loading conditions may be experienced.

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