Question

What is the purpose of strainer in the gating system?

(a) To make uniform flow

(b) To make smooth surface finish of the casting

(c) To remove dross from the molten metal

(d) To create positive pressure throughout to avoid aspiration effect

I got this question during a job interview.

My enquiry is from Aspiration Effect topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I

Answer 1

Right answer is (c) To remove dross from the molten metal

The explanation: Ceramic strainer in the sprue removes dross and prevent slag from entering to the castings. Strainer additionally useful to laminize the flow.  A typical strainer might be a cylinder of 30-50 mm diameter, 10-20 mm long, containing ten or more holes, of diameter approximately 3-5 mm.