a picture of the atomic structure of carbon steel
This is actually a quite complex question... The atomic arrangement in steels can be controlled over a pretty wide range of different structures. This is really the fundamental reason why steel is such a commonly used material. The different atomic structures produce different physical properties so metallurgists have developed many different processes to control the atomic structure to get the properties they want. One simple answer is that Fe is BCC, body centered cubic at room temperature at equilibrium conditions. When you heat Fe up, it transforms to FCC, face centered cubic. If you continue heating Fe, it goes back to BCC, then it melts. The addition of C makes these structures (and the transformation temperatures) different. Deviating from equilibrium conditions by, for example, cooling very quickly (quenching) creates different atomic structures (one of the most important is known as martensite). Depending on how much C is in the steel, you can also have two different atomic structures (two different phases) present in equilibirum, for example, pearlite which is a mix of alpha Fe (BCC) and iron carbide Fe3C (orthorombic crystal structure). So... you need to think a little more about exactly what you want a picture of. I hope this helps
