2. Tutorial: Engineering technology Topic: Hot forming Prepared by: Ing. Elena Nová Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

3. Hot forming

4. Recrystallization temperature Is a temperature at which starts regeneration of deformed grains originated at cold forming without lattice change. Division of forging technologies according to temperature is: 1.Cold forging (under recrystallization temperature when temperature is under 30% under melting point of forged material)

5. 2. Forming is above recrystallization temperature2. Forming is above recrystallization temperature, recrystallization speed is so high that hardening disappear already during forming or immediately after.

6. Hot forming temperature is above 70% of the formed material melting point. Material is not strengthened, the actual forming require force 10x smaller than needed for cold forming. At higher temperatures is deformation accompanied by recovery and recrystallization.

7.  At hot forming a texture might or might not be initiated but surface is not of good quality due to scales, furthermore grain become coarser, which can influence next technological operations.  Whole process is time consuming and expensive, on the other side bubbles, tears, etc. are eliminated.

8.  Undesired effect of Hot Forming is formation of a ‘fibrous structure’.  Fibrous structure is impossible to change by heat treatment or subsequent forming.  Fibrous structure influence mechanical properties and anisotropy.  Is initiated by impurities on grain surface.

9.  Influence of grain size on cut quality:  Small grain Large grain

10.  At recovery starts drop of internal stress. Recovery speed is dependent on temperature and time.  Grain size dependence on time

11.  strojirenstvi.studentske.cz/2008/10/kontrola -vady-odlitk.html  /www.ksp.tul.cz/cz/kpt/obsah/vyuka/skripta _tkp/sekce/01.htm