Blow hole and pin hole porosity, Other Engineering

Blow Holes

                  (i) Excessive moisture in the moulding sand.

                  (ii) Low permeability and excessive fine grain sands.

                  (iii) Cores, neither properly baked not adequately vented.

                  (iv) Extra hard rammed sand.

                  (v) Rusted and damp chills, chaplets and inserts.

                  (vi) Excessive use of organic binders.

        Remedies

                   (i) Control moisture content.

                   (ii) Use clean and rust free chills, chaplets and metal insert.

                   (iii) Bake cores properly.

                   (iv) Proper use of organic binders.

                   (v) Cores and moulds should be properly vented.                                               

   (vi) Moulds should not be rammed excessively hard.  

Porosity or Pin Holes : Surface reactions sometimes cause subsurface porosity or pinholes. In aluminium alloys containing more than about 1% magnesium, magnesium reacts with water vapor of the mould to form H2 gas resulting in hydrogen filled pinholes at the surface, as shown in figure.

          In steel castings subsurface pinholes may result from incomplete de oxidation of the molten metal.

          Causes

                    (i) High pouring temperature.

                  (ii) Less flux used.

                  (iii) Gas dissolved in metal charge.

                  (iv) High moisture and low permeability in mould.

          Remedies

                   (i) Ensure effective degassing.

                   (ii) Reduce moisture and increase permeability.

                   (iii) Increase flux proportions.

Posted Date: 8/3/2012 2:43:12 AM | Location : United States







Related Discussions:- Blow hole and pin hole porosity, Assignment Help, Ask Question on Blow hole and pin hole porosity, Get Answer, Expert's Help, Blow hole and pin hole porosity Discussions

Write discussion on Blow hole and pin hole porosity
Your posts are moderated
Related Questions
Assignment on Risk and Return# Stock has beta of 1.5 & an expected return 11%. A risk free asset earns 2%. Determine the expected return on a portfolio that is equally invested in

Principles of Sprinkler Systems-Fire safety Engineering Sprinkler systems may be installed in a building to achieve a number of different objectives.  Very often the primary r

Hello this is Lee, I have an Econometrics coursework to be helped by some experts from your company. Please send me your reply asap Lee

Synchro resolvers for high load The receiver rotor is driven by an electric motor to a null position, i.e. the receiver coil will be aligned at 90 o  to the transmitter coil. A

how to become robotics engneer


can i get prportional and integral controller matlab coding to solve my load flow analysis

Students are to undertake a tunnel blast design for the following conditions: • Tunnel is 5.5m wide by 5.5.m high • Rock is a granite with a UCS of 300 MPa • Drill hole diameter is

hi there i wonder if you could help me with this quistion? where would i find information specifying the minimum conductor size for electrial circuits can be obtained from A. BS76

Expertsmind.com brings you unique solution in physicsWhat processes shape Earth's surface? What processes shape Earth’s surface? -Impact craters: bowl-shaped cr