 General
FAQs
To get answers to the following general questions,
please select one of the links below:
|
| 1. |
How is gray iron
graded? |
| 2. |
How do I select the moulding
process for my foundry? |
| 3. |
Which type of nobake moulding
system is preferable – furan based or phenol based? |
| |
|
| 1. |
How is gray iron graded? |
| |
|
| |
Gray Iron is classified into different grades, depending
upon the desired tensile strength. The IS standards for
gray iron are tabulated below:
|
| |
IS : 210 – 1970
(CGS UNIT) |
IS : 210 – 1978
(SI UNIT) |
| Grade |
Tensile
Strength
Kgf/mm²(min.) |
Grade |
Tensile
Strength
N/mm²(min.) |
B H N |
15
20
25
30
35
40 |
15
20
25
30
35
40 |
FG 150
FG 200
FG 220
FG 260
FG 300
FG 350
FG 400 |
150
200
220
260
300
350
400 |
130 – 180
160 – 220
180 – 220
180 – 230
180 – 230
207 – 241
207 – 270
|
|
| |
|
| |
|
| |
|
| 2. |
How do I select the moulding process for my
foundry? |
| |
|
| |
Various factors such as castings quality, complexity
of the shape, tooling costs, quantity required and capital
costs need to be considered during selection of moulding
process. A comparative chart of various molding processes
is given in the following table. |
| |
| |
Green Sand |
Precision Molding |
Chemically Bond Mold |
| Sand Casting |
Perm Mold |
Die casting |
Ceramic & Invest. |
Shell, CO2 Nobake |
| Typ. dimen. tol. |
±.010" ±.030" |
±.010" ±.050" |
±.001" ±.015" |
±.010" ±.020" |
±.005" ±.015" |
| Rel. cost in qty. |
Low |
Low |
Lowest |
Highest |
Med. High |
Rel. cost for small
qty. |
Lowest |
High |
Highest |
Medium |
Med. High |
| Permiss. cast wt. |
Unlimit. |
100 lb |
75 lb |
oz-100 lb |
Shell (oz.-250 lb.)CO2 & Nobake(.5 lb-tons)
|
| Thinnest cast sect. |
1/10" |
1/8" |
1/32" |
1/16" |
1/10" |
| Rel. surface fin. |
Fair-Good |
Good |
Best |
V-good |
Shell-goodCO2-fair |
Ease of casting
complex design |
Fair-good |
Fair |
Good |
Best |
Good |
Ease of designchange
in production |
Best |
Poor |
Poorest |
Fair |
Fair |
Range of alloys
thatcan be cast |
Unlimit. |
Al-base & Cu-base preferr. |
Al-base preferr. |
Unlimit. |
Unlimit. |
| (Characteristics are approximate and
depend upon the metal.) |
| *This article has been excerpted from
the publication, "Casting Buyers' Guide,"
American Foundrymen's Society, Des Plaines, Illinois.
|
|
| |
|
| |
|
| |
|
| 3. |
Which type of nobake moulding system is better
– furan or phenol based? |
| |
|
| |
Phenol based nobake moulding system is commonly used
in Indian foundries. However moulds made using phenolic
binders tend to crack easily. Furan resins are easier
to use especially for preparing larger moulds. Due to
its advantages, furan based nobake moulding system is
preferred internationally by foundry units over phenol
system. |
| |
|
Grad IIF Exam
Yellow
pages
