Ceramic Strainer Cores
Strainer cores were originally meant to retain sand detachments
due to erosion in the casting system. In modern casting techniques,
the almost exclusively used ceramic strainer cores fulfill
other task. They basically serve:
- as a regulation for the current flow, i.e. predominantly
for calming down the flow and, with that, the assurance
of a laminar entry of the casting metal into the runner
and the sections that branch of from it. The jam caused
by the straining core also allows the necessary "full
stop“ of the sprue while casting-up, even for inexperienced
foundrymen
Picture 1
- In many cases, also as a support for inoculants or other
metallurgical additives, which are to be inserted into
the mould, whereby a reaction and/or collecting space is
to be supplied above and below the strainer core (Picture
2).
Picture 2
In accordance with these tasks, picture 1 shows the only
reasonable possibility of installing a strainer core, being
at the division between the head box and lower box with its
support in the lower box. The formerly used configuration
of the strainer core in the upper part of the sprue cup should
no Ionger be used, because the pouring flow will be divided
into many thin jets through the holes in the strainer core
and will be split up over a large area, consequently not
filling up the sprue gate and thus infiltrated air will be
sucked up according to the injector principle. Due to this,
bubbles are often formed in the casting.
The choice of the strainer core dimensions depends on the
pouring performance Q in cm3/sec. and/or kg/sec. and the
actual casting height “h“. Picture 3 shows data
concerning the pouring performance “Q“ for various
diameters “d‘ at the sprue gate base depending
on the effective casting height “h“. Factor "k" takes
the loss of flow due to the friction of the openings into
consideration. Strictly speaking, the form of a parabola
results from the Ö-Law for the outer contours oft he
sprue cup. This is not favourable with respect to pattern
and mould technology so that, in practice, it was generally
agreed to subdivide the height "h" into two sections,
whereby the upper section "h1" is about h/3 (Picture
2). Guide values for the pouring height "h" and
the pouring performance can be seen in table 1.
Picture 3
Table 1
|
|
Q
= 200 cm³/s |
1000
cm³/s |
3000
cm³/s |
4000
cm³/s |
5000
cm³/s |
h |
h1 |
D1 |
D2 |
d |
D1 |
D2 |
d |
D1 |
D2 |
d |
D1 |
D2 |
d |
D1 |
D2 |
d |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
cm |
10 |
3 |
2,00 |
1,70 |
1,56 |
4,5 |
3,70 |
3,50 |
7,7 |
6,5 |
6,0 |
9,0 |
7,50 |
7,0 |
10,0 |
8,4 |
7,8 |
15 |
5 |
1,80 |
1,50 |
1,39 |
4,0 |
3,40 |
3,10 |
7,0 |
5,9 |
5,4 |
8,1 |
6,80 |
6,3 |
9,0 |
7,6 |
7,0 |
20 |
7 |
1,70 |
1,40 |
1,29 |
3,8 |
3,20 |
2,90 |
6,5 |
5,5 |
5,0 |
7,5 |
6,30 |
5,8 |
8,4 |
7,1 |
6,5 |
25 |
8 |
1,60 |
1,33 |
1,20 |
3,6 |
3,00 |
2,70 |
6,2 |
5,2 |
4,7 |
7,1 |
6,00 |
5,4 |
8,0 |
6,7 |
6,0 |
30 |
10 |
1,50 |
1,28 |
1,15 |
3,4 |
2,90 |
2,60 |
5,9 |
5,0 |
4,5 |
6,8 |
5,70 |
5,2 |
7,6 |
6,4 |
5,8 |
35 |
12 |
1,46 |
1,23 |
1,10 |
3,3 |
2,80 |
2,50 |
5,7 |
4,8 |
4,3 |
6,5 |
5,50 |
5,0 |
7,3 |
6,1 |
5,6 |
40 |
13 |
1,40 |
1,19 |
1,07 |
3,2 |
2,70 |
2,40 |
5,5 |
4,6 |
4,2 |
6,3 |
5,30 |
4,8 |
7,0 |
6,0 |
5,4 |
45 |
15 |
1,36 |
1,15 |
1,04 |
3,1 |
2,60 |
2,30 |
5,3 |
4,5 |
4,0 |
6,1 |
5,15 |
4,7 |
6,8 |
5,8 |
5,2 |
50 |
17 |
1,33 |
1,13 |
1,02 |
3,0 |
2,50 |
2,25 |
5,2 |
4,4 |
3,9 |
6,0 |
5,00 |
4,5 |
6,7 |
5,6 |
5,1 |
55 |
18 |
1,30 |
1,10 |
1,00 |
2,9 |
2,45 |
2,20 |
5,1 |
4,3 |
3,8 |
5,9 |
4,90 |
4,4 |
6,6 |
5,5 |
5,0 |
60 |
20 |
1,28 |
1,07 |
0,94 |
2,8 |
2,40 |
2,17 |
5,0 |
4,2 |
3,7 |
5,8 |
4,80 |
4,3 |
6,4 |
5,4 |
4,9 |
Concerning the calculation of an optimum ceramic strainer
core we are pleased to send a sample-calculation.
You will find more detailed informations (including a
safety-data-sheet) in our delivery program.
A complete delivery program can be downloaded under the point Download-Productinfo. We also have the possibility to send you all catalogues by standard mail. Please be kind and give us a short info for this.
|
