GGD 2738 HH steel is a steel specially developed for making plastic injection molds that require greater mechanical and wear resistance. Its chemical composition, combining the contents of chromium, nickel and molybdenum, confers greater hardenability and, consequently, good homogeneity, even at high hardness along the cross section. It brings together important features such as good polishability and response to texturing. Unlike conventional GGD P20 steels (DIN W.Nr. 1.2311 and AISI P20 standards) the new GGD 2738 HH steel is supplied in the processed state (Tempered and Tempered) with hardness in the range of 38 to 42 HRc.
It is used in thermoplastic injection molds in the most varied types, of medium and high abrasiveness. Especially used in molds that require greater mechanical strength. Never use in chlorinated plastic molds.
Stress Relief: On tools with complex shapes, with heterogeneous material removals in the rough machining process, section changes, etc., stress relief heat treatment must be performed to minimize dimensional variations. The treatment must be carried out at a temperature close to 500 °C for at least 1 hour for every 25 mm of thickness. Then cool slowly in still air.
Quenching:During heating for austenitization, preheating must be carried out to ensure temperature homogeneity between the surface and the core to minimize distortions. Preheat at a temperature close to 550 °C, Austenitize at a temperature between 815 – 870 °C. Heat for 1 hour for every 25mm of thickness and add 1 hour for every additional 25mm. Cool preferably in oil, preheated to around 70 °C, with stirring.
Tempering: Must be carried out immediately after tempering when the temperature reaches about 70 °C. The Tempering temperature must be selected according to the hardness targeted. For this steel, tempering preferably at temperatures close to 500 / 550 °C, to reach the desired differentiated hardness level, generally in the range 38 – 42 HRc. For this, use the tempering curve as a reference. Keep at tempering temperature for at least 1 hour for every 25 mm of thickness and at least double temper.