# Design of gating system for fixture casting (part 2)

#### Calculation of resistance cross section

The total sectional area a can be calculated according to the following formula

=Q/KTL in A

Q – total mass of molten steel poured into the mold (kg), K – pouring specific speed, L – fluidity correction coefficient, carbon steel 1.0, T – pouring time (s)

A internal = q / KTL = 13.33kg/0.7 * 4.75 * 1.0 = 4cm2

#### Calculation of section area of internal sprue

The internal sprue is to control the filling speed and direction, distribute the liquid metal, adjust the temperature and solidification sequence of each part of the casting. The liquid metal in the pouring system has a certain feeding effect on the casting through the internal sprue.

Four internal gates are designed, so s internal = 4cm2 / 4 = 1.0cm? 2. According to table 6-100 of foundry engineer’s manual, the size of internal gate is a = 23mm, B = 21mm, H = 4.5mm

The shape of internal sprue is trapezoid section, as shown in the figure

#### Calculation of cross-sectional area of runner

The function of the runner is to distribute the clean liquid metal to the inner runner, to store the low temperature liquid metal containing gas and slag and to prevent the dross, so as to make the liquid metal flow stable and reduce the generation of oxide inclusions.

Since there are two design crossgates, s = 4 * (0.8-0.9) = 3.2-3.6 cm? Takes 3.4cm 2

According to table 6-100 of foundry engineer manual, a = 28mm, B = 23mm, H = 14mm

The cross sprue shape is trapezoid section shape, as shown in the figure

#### Calculation of sectional area of sprue

The function of the sprue is to guide the liquid metal down from the sprue cup into the transverse sprue, the internal sprue or directly into the mold cavity. Sufficient pressure head is provided to enable the liquid metal to overcome various flow resistances under the action of gravity.

Because there is one designed gate, s-straight = 4 * (1.1-1.2) = 4.4-4.8cm ~ 2, take 4.6cm2

According to table 6-100 of foundry engineer’s manual, the diameter of sprue section is 24mm

In order to make it convenient to take the sprue of the mold and make it into a small inverted cone (usually the taper is 1 / 50).

Therefore, the diameter of the upper end of the sprue is about:

D1 = 24 – (1 / 50) * 150 = 21mm. The shape of the sprue is round, as shown in the figure

#### Design of gate nest

The sprue nest can buffer the metal from the sprue, shorten the turbulent area at the turning of the sprue, improve the pressure distribution in the sprue, and float the bubbles in the liquid metal.

The sprue socket diameter is twice the diameter of the lower end of the sprue, so d = 2 * 24 = 48mm

The height of the sprue socket is twice that of the transverse sprue, so h = 2 * 14 = 28mm

Refractory bricks are placed at the bottom of the gate socket to prevent filling.

#### Design of sprue cup

The sprue cup is used to receive the liquid metal from the ladle, prevent the splashing and overflow of the liquid metal, facilitate pouring, reduce the impact of the liquid metal on the cavity, separate the dregs and bubbles, and prevent them from entering the cavity.

The section size of sprue cup can be obtained from table 1-51 of basic knowledge of casting process

D1 = 62mm, D2 = 58mm, H = 46mm, liquid iron capacity 0.8kg

The sprue cup is a common funnel-shaped sprue cup 