04 metal casting

����� 4���� ���

�������� ���������������������� ���!��� ����� ��� ��"�#�$��%��

• Sand Casting

High Temperature Alloy,

Complex Geometry,

Rough Surface Finish

• Investment Casting

High Temperature Alloy,

Complex Geometry,

Moderately Smooth Surface

Finish

• Die Casting

High Temperature Alloy,

Moderate Geometry,

Smooth Surface

Casting Methods

�&�������� ��'(����

�����)* (Viscosity)

����������� ��������������� (Inertia)

/�#$�%&�'

��������()#(���������*+��,-����.�����+���� �/+ ��&�'���� 0��(�-#�

�����4�!�� (Surface Tension)

��=� (Flow)

����A����� ����

��� ���*,���(�����12��3(4�5� (Grains)

����-����+���3(4�5� (Grain Boundaries)

�,.����� .��4�5� 0�3.,�)��<'���5�

��� ����3)��+��= �#-.,�

(>�-)��#-.,��������+��<<? (Pipe)

(����(.,�B0�C&�?��� Centerline Shrinkage)

����A����� �������&���B

����A����� ����!��

�����>�0J (Latent Heat)

Three Cast Structures of Solidified Metals

•FIGURE 5.8 Schematic illustration of three cast structures of metals solidified in a square mold:

•(a) pure metals;

•(b) solid-solution alloys; and

•(c) the structure obtained by heterogeneous nucleation of grains, using nucleating agents.

����C�����A���� Chvorinoy’s Rule

��������D=����'�=*D�* ���'�%�D� (Riser)

�����������*F���

�G ��HA�����*���

�������������

I �������(��*� � (Single Type Pattern)I ������ �=*D (Split Pattern)I ������4��� �F�� (Half Pattern) ��(��������������������������) ����

Features of a Sand Mold

•Schematic illustration of a sand mold, showing various features.

�����

����������

���

�����

Electric Furnaces

�� �� ( Green Sand)

.>��.'�.,�1��M� (Binders)

�- *�*? ����01N �����(�O?*�� (Dextrine).,�1��M�<'�CR ���0�>� (Water Glass) ��O' (Resins) ����O���.? (Cement)

B/>4V+��' 4����.�� 4V+� �>� ����4����W*? 1����$ 1% 4M��,-*�����+� �<���*��B�>4'����+�������������( M����VV�(0--����(>+��

�&�������� ��� ��

�5��&1�(>+��

�Z�O���4+�����(>M�(��

��3(*���.>�����(<������

*�����>�)����� ��� �/+ ���3��������+�1����$ 1,500°-1,550°C

��,-��B/>�(>���

����V&�

��+��'(1`'�'�'��*����� ��������*-����M,�4,M�,-��� ���

���*� ��� �� (Sand Testing)

����� �� (Sand Molding)

Steps in Sand Casting

Steps in Sand Casting

��������� *D� ������ )��Q (Other Expendable Mold Casting Processes)

����� �G�) � (Shell Molds)

Sٍhell CastingDump-Box Technique

Figure 11.13 A common method of making shell molds. Called dump-box technique, the limitations are the formation of voids in the shell and peelback (when sections of the shell fall off as the pattern is raised). Source: ASM International.

Sٍhell CastingDump-Box Technique

�������� �����D � (Hot Box Method)

����� �%YY���Z (Vacuum Molding) V-Process

����� �$��� ���� (Expanded Polystyrene Process)

���� ��� ������������ (InvestmentCasting)

����� ���� �=* �=H*� (CO2 Mold Process)

����� �� !��H������ (Sand Mold with Cement Binder)

����� �H���� (Ceramic_Mold Casting)

Operation Sequence of Making a Ceramic Mold

•Sequence of operations in making a ceramic mold.

Figure 11.17 A typical ceramic mold (Shaw process) for casting steel dies used in hot forging.

���� �����%YY���Z (Vacuum Casting)

���� ���� � (Centrifugal Casting)

FIGURE 5.30 Schematic illustration of the centrifugal casting process.

Pipes, cylinder liners, and similarly shaped parts can be cast by this

process.

Semicentrifugal Casting Process

•FIGURE 5.31 (a) Schematic illustration of the semicentrifugal casting process. (b) Schematic illustration of casting by centrifuging. The molds are placed at the periphery of the machine, and the molten metal is forced into the molds by centrifugal forces.

Squeeze-Casting Process�������������

���� ����$� (Slush Casting)