Sulgumisel

Sulgumisel is the Estonian term for the melting or fusion of a solid into a liquid, a fundamental process in physics, chemistry, and materials science. The word describes the phase change that occurs when a substance absorbs enough thermal energy to overcome the forces maintaining its solid structure. In most materials, melting occurs at a characteristic melting point at standard pressure; the energy required is called the latent heat of fusion.

In crystalline materials, melting involves disruption of the orderly lattice and the emergence of a disordered liquid with short-range order. Some materials, particularly alloys, melt over a range of temperatures rather than at a single point, due to varying compositions of phases.

Ice and metals serve as common examples: ice melts at 0°C at 1 atmosphere, while pure iron melts at about 1538°C. In practice, sulgumisel is a central concept in metalworking, glassmaking and polymer processing, governing processes such as casting, forging, welding, and annealing. Control of temperature and pressure during sulgumisel determines microstructure, mechanical properties and product quality.

In Estonian technical literature, sulgumisel is discussed alongside related concepts such as solidification, crystallization, and phase diagrams. The term also appears in educational contexts to explain energy changes during heating and the conditions under which materials switch from solid to liquid.