Which of the following does not affect the tensile strength of steel?

The tensile strength of steel is influenced by various alloying elements, which can enhance or detract from its properties. Boron, while a significant alloying element in some steel grades, is generally used in very small amounts and primarily affects the hardenability of the steel rather than its tensile strength directly. It plays an important role in improving the steel’s ability to harden during heat treatment processes, which can indirectly contribute to strength, but it does not have a significant effect on the tensile strength compared to elements like sulphur, cobalt, and phosphorous.

On the other hand, sulphur can have a detrimental effect on tensile strength, especially when present in higher concentrations, as it can cause brittleness. Cobalt, while less common than other alloying elements, can enhance the hardness and strength of steel. Phosphorous also impacts tensile strength negatively by causing brittleness at higher concentrations. Therefore, these elements have a more direct and significant impact on tensile strength compared to boron, which is used primarily for enhancing hardenability under specific circumstances.