What is the difference between Olivine and Silica Sand?

These are both natural deposits. With Olivine, a finer sand may be used due to increased permeability, and thermal expansion is much lower than silica, therefore reducing expansion defects resulting in a smoother casting. There are also significant heath advantages with Olivine in that it does not cause silicosis.

Why is it called green sand when it is black?

The sand takes the black color due to the burning of the sand by hot metal. The term "green sand" refers to the green strength property that the sand "stands up" by itself and does not fall over or get hard.

How do I mix green sand molding sand?

The optimum mixing procedures require a muller. The motion of the plows and wheels activate the clay and additives in the molding sand along with the addition of water. If a muller is not available the recommendation is to buy premulled sand or oil activated J-82MX and discard the burnt sand.

How much water should be added to the sand?

Unfortunately there is not a definite answer to this question. This varies with each foundry environment. Generally a starting point is 3% moisture. This additive is a "necessary evil"; it is required to hold the molds together but also creates a number of other problems. This is the most important additive in a green sand system and must be controlled consistently.

What is permeability?

Measurement of the amount of gas permitted to pass through a sand mass.

What is collapsibility?

To permit the normal contraction of metal during solidification and cooling the bonding material in cored and molds must be destroyed by hear from the metal, allowing the cored and molds to collapse somewhat.

What is baume pertaining to mold and core wash?

The baume gauge is nothing more than a hydrometer that is designed to measure the specific gravity of pure liquids in degrees of baume, which is graduated from 0 to 100. The specific gravity of water which is 1.00, is set at 0 degrees baume. These numbers are used to determine the adequate viscosity for suggested applications of core and mold wash.

J-82 MX - What is it?

This sand consists of a mulled mixture of fine sand, oil, AIRDRY binder, and a small amount of catalyst. J-82 MX sand contains oil instead of water, and needs much less venting. The amount and type of oil used creates considerable less gas than is created in ordinary water sands. This permits the use of much finer sands with lower permeability than allowable with water sand molds. This means precise castings using only ordinary foundry equipment. In practice the standard mixture using sand with a GFN of 140 has a permeability of only 15. Nevertheless, this is adequate for non-ferrous alloys because of much lower gas evolution.

OLIVINE MOLDING SAND

As a foundry aggregate, olivine is noted for its high fusion point, low uniform thermal expansion, and its remarkable ability to resist fracture from thermal shock. Olivine has been famous for years in producing excellent non-ferrous castings. Today, more foundrymen are realizing that olivine works equally well in iron, manganese and stainless steel.

The angular olivine grain acts to control the rammed or squeezed density of the mold. This feature combined with the favorable coefficient of thermal expansion, usually permits the elimination of organic filler from molding sand formulations. This angular grain also allows use of finer sands while retaining good permeability.

Another advantage of using olivine sand is its industrial hygiene characteristics. Medical research indicates that olivine will not cause silicosis.

Olivine sand is available in several grades and packaged in 3000# sacks or 100# bags.