Small percentage of boron is added to steel toa)Increases hardenabilit...
Ans. (a)
Boron improves the deep hardening of constructional steels and produces therefore core hardness steels. With austenitic 18/8 crome-nickel, steels can achieve higher elastic limits by the process or precipitation hardening, but the corrosion resistance is lowered.
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Small percentage of boron is added to steel toa)Increases hardenabilit...
Introduction:
Boron is a trace element that is added in a small percentage to steel alloys. This addition of boron has several effects on the properties of steel. One of the main benefits of adding boron to steel is the improvement in hardenability.
Hardenability:
Hardenability refers to the ability of steel to be hardened through heat treatment processes such as quenching and tempering. The addition of boron to steel increases its hardenability, which means that the steel can achieve a higher level of hardness after heat treatment. This is beneficial in applications where a high level of hardness is required, such as in the production of cutting tools and wear-resistant components.
Effect on microstructure:
The addition of boron to steel alters its microstructure. Boron combines with nitrogen to form boron nitrides, which act as nucleation sites for fine carbides during solidification. These fine carbides help in controlling the grain size of the steel, leading to improved hardenability. The presence of boron also inhibits the formation of coarse grain structures, which can result in reduced toughness and increased susceptibility to cracking.
Benefits of increased hardenability:
Increased hardenability is advantageous in several ways:
1. Enhanced strength: Steel with higher hardenability can achieve greater strength through heat treatment. This is particularly important in applications where high strength is required, such as in the automotive and aerospace industries.
2. Improved wear resistance: Hardened steel with increased hardenability exhibits improved wear resistance. This is beneficial in applications where the steel comes into contact with abrasive materials or experiences sliding or rolling contact, such as in gears, bearings, and cutting tools.
3. Increased durability: Steel with higher hardenability has improved resistance to deformation and fracture, leading to increased endurance strength. This allows the steel to withstand higher loads and stresses without failure, making it suitable for demanding applications.
Conclusion:
In conclusion, the addition of a small percentage of boron to steel increases its hardenability. This results in improved strength, wear resistance, and endurance strength, making the steel suitable for various applications where these properties are desired.
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