General Contractor Practice Exam 2025 - Free Contractor License Practice Questions and Study Guide

Steel begins to deform at approximately 500 degrees Celsius. This temperature represents a critical threshold where the mechanical properties of steel start to change significantly due to thermal effects. At temperatures approaching this value, the yield strength of steel decreases, meaning that it requires less force or stress to produce permanent deformation. This phenomenon is crucial for understanding how steel structures behave under extreme conditions, such as in a fire, where temperatures can rise rapidly.

When considering the process of thermal expansion and dislocation movements in the metal's crystal structure, the 500 degrees Celsius mark highlights a point where these processes occur more readily, leading to deformation. Understanding this characteristic is essential for engineers and contractors in order to ensure structural integrity and safety in construction practices.

Higher temperatures, such as 800 or 1000 degrees Celsius, can lead to even greater deformation and ultimately failure, but they are not the initial deformation threshold. Therefore, recognizing that deformation starts at around 500 degrees Celsius is critical for applications involving steel in various environmental conditions.