Question

A cast steel slab of dimension 30 × 20 × 5 cm is poured horizontally using a side riser. The riser is cylindrical in shape with diameter and height, both equal to D. The freezing ratio of the mould is

• A. 8D/75
• B. 75/8D
• C. 4D/75
• D. 75/4D

Answer 1

The correct option is A 8D/75

$\text{Given data:}$

$\text{Case steel slab = 30 × 20 × 5}c{m}^3$

$\text{Modulus of Casting}$

$M_c=\frac{V}{A}=\frac{30\times 20\times 5}{(2\times 30\times 20)+(2\times 30\times 5)+(2\times 20\times 5)}=\frac{30}{17}$

$M_c=1.76$

$\text{Modulus of Riser}$

$M_r=\frac{V}{A}=\frac{\frac{\pi }{4}{D}^3}{2\times \frac{\pi }{4}{D}^2+\pi D^2}=\frac{D/4}{6/4}=\frac{D}{6}$

$\text{Freezing ratio}=\frac{M_r}{M_c}$

$\text{F.R}=\frac{D}{6}\times \frac{17}{30}=\frac{17D}{180}=0.094D\approx \frac{8D}{75}$