(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Biodiversity Heritage Library | Children's Library | Advanced Microdevices Manuals | Linear Circuits Manuals | Supertex Manuals | Sundry Manuals | Echelon Manuals | RCA Manuals | National Semiconductor Manuals | Hewlett Packard Manuals | Signetics Manuals | Fluke Manuals | Datel Manuals | Intersil Manuals | Zilog Manuals | Maxim Manuals | Dallas Semiconductor Manuals | Temperature Manuals | SGS Manuals | Quantum Electronics Manuals | STDBus Manuals | Texas Instruments Manuals | IBM Microsoft Manuals | Grammar Analysis | Harris Manuals | Arrow Manuals | Monolithic Memories Manuals | Intel Manuals | Fault Tolerance Manuals | Johns Hopkins University Commencement | PHOIBLE Online | International Rectifier Manuals | Rectifiers scrs Triacs Manuals | Standard Microsystems Manuals | Additional Collections | Control PID Fuzzy Logic Manuals | Densitron Manuals | Philips Manuals | The Andhra Pradesh Legislative Assembly Debates | Linear Technologies Manuals | Cermetek Manuals | Miscellaneous Manuals | Hitachi Manuals | The Video Box | Communication Manuals | Scenix Manuals | Motorola Manuals | Agilent Manuals
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Modern Mechanical Engineering Vol-I"

140

FOUNDRY  WORK

It is desirable to take test bars when making mixtures from new brands of
pig or selected scrap. Thorough melting is essential, and more coke will
have to be used than for the more fluid grey irons. The precautions to be
observed in venting, gating, and pouring for sand moulds are required here.
The Design of Moulds to Chill.—Only that portion of the mould which
corresponds with the area to be chilled is of cast iron, the remainder being

Z3£s&±yKtfr—i h\ i""r ' k'vt '   "i\ V«" V v'411

Fig. 48.—Chill Mould for Roller

Fig. 49.—Chill Mould for Roll

rammed in green or in dry sand. Success mainly depends on the mass of
metal in the chill. It must be large, in order to enable it to carry off the
heat from the casting poured, with sufficient rapidity to produce the necessary-
depth of chill. If this action were delayed too long, what would happen is,
that the cementite would have time to break up into iron and graphite, thus:
Fe8C = jFe + C. Cementite or iron carbide, Fe3C, is unstable when
cooled slowly. The walls of a chill therefore range from 4 in. to 8 in. in
thickness, depending on its diameter. The risk attendant on thick walls is
that of fracture, since the inner zones, expanding most, are tied by the outer.