Sand- and chilled cast pieces in AlSi7Mg are increasingly being used because of the higher strength and hardness, the better resistance against fatigue and the acceptable elongation. (Mg additions to AlSi alloys can raise the hardness with 50 % after precipitation hardening, and the elongation is better than the one of 11 % Silicon castings.)
Lastek 712 contains 0.5 – 0.8 % Mg and 6.5 – 7.5 % Si with max 0.05 % Cu and max 0.20 % Fe, in order not to influence the good corrosion resistance.
Castings in AlSi7Mg, like LM25 (BS1490), G-AlSi7Mg0.3, G-AlSi7Mg0.6, A356.0, 357.0, A-S7G03 and A-S7G06, 3.2371, 3.2384, ASTMB26 and B108 - SG70A, UNI3599 aso.
Pumpcomponents, pressure tight castings, rims for the car-industry, moulds for plastic swimming baths and so on.
Hardness: 55 HB
Use Argon or Helium as protection gas (For oxy-acetylenic welding use flux Lastek 71A).
After welding you can submit the deposit to a precipitation hardening process. (8 to 12 h at 530 - 550 °C (986 - 1020 °F): quenching in water; 3 to 6 h. at 150 - 160 °C (300 - 320 °F); this treatment will increase the hardness up to 110 HB and a tensile strength up to about 300 N/mm² (44ksi))