Magnesium-treated, decarburizingly-annealed cast iron material

A two-phase process for producing a magnesium-treated, decarburized and annealed cast iron material with good workability properties, comprising

• annealing a cast iron material comprising less than or equal to 4% carbon by weight;
• less than or equal to 2% silicon by weight;
• at least 0.010% to about 0.03% magnesium by weight;
• and at least 0.001% to about 0.004% sulphur, the remainder being iron, in a first phase to produce a surface zone having spheroidal graphitic carbon portions therein;
• burning out said spheroidal graphitic carbon portions that had been formed in said first phase in a second annealing phase, thereby generating a surface zone having less than 0.3% by weight of spheroidal graphitic carbon x and cavities in a ferritic matrix.

A magnesium-treated, decarburized and annealed cast iron material, comprising

• less than or equal to 4% carbon by weight;
• less than or equal to 2% silicon by weight;
• at least 0.001% 0.010% to about 0.03% magnesium by weight;
• at least 0.001% to about 0.004% sulphur by weight;
• the remainder being iron, said cast iron material including a surface zone having less than 0.3% spheroidal graphitic carbon by weight and cavities in a substantially ferritic matrix, said cavities comprising about 6 to 13 percent by volume of said surface zone, the remainder of said cast iron material being substantially cavity free.