where the iron heat for carbon is increased

where this iron heat function to heat the iron high temperature until the color of its iron reddish,

iron after the input into the place of heating and then we enter into the oil because of its increased carbon iron is not quickly broken and not easily bent,

the wheel of the car at the end of the wheel was a thread where the binding of the nut so as not to loose its wheels,
wheels that we have made thread we put into a hot place because the thread was not quickly destroyed and can not bind the nut again.