1. Application

This applies to test method of measuring green sand mulling efficiency.

2. Definition

Mulling efficiency is an indication of degree of mulling obtained by comparing the actual sand on the production floor with a sand after full mulling. Mulling efficiency is defined as the ratio of the product of green sand compression strength (Green sand compression test method) and compactability (Green sand compactability test method) divided by moisture content (Green sand moisture content test method) expressed in %. This test does not apply to experimental sand prepared from a new sand.

3. Muller

A small-size sand mill such as that for laboratory use can be conveniently used, though any type that gives sufficient mulling may be used. An agitator-type mixer giving excessive temperature rise is not suitable.

4. Testing procedure

4.1 Measurement of production sand

Sand as sampled from a production line is tested for compression strength, compactability, and moisture content, respectively, according to; TJFS-102: Green sand compression test method, TJFS-107: Green sand compactability test method, TJFS-201: Preparation of standard green sand specimen

4.2 Preparation of reference sand by full mulling

Sand is sampled in volume appropriate to the muller in use and mulled for more than 10minutes. Compactability variation before and after the mulling should be less than 5%. For this purpose, water volatilization during mulling should be minimized, and if necessary water is added during mulling. If water is added, mulling should be continued at least 5 more minutes.

4.3 Measurement of the reference sand

The reference sand thus prepared is tested for compression strength, compactability, and moisture content, according to the methods as in 4.1. If the compactability before and after mulling differ more than 5%, mulling must be repeated by adjusting moisture content until the difference is confirmed to be less than 5%. Here also mulling should be continued at least 5 more minutes after water addition.

4.4 Calculation of bond index

Bond index is calculated by the following equation.

\[B.I. = {G.C.S \times C.B \over M} \]

where

\[ \left\{ \begin{array}{l} B.I. &= bond \ index \\ G.C.S. &= green \ sand \ compression \ strength \ (N/cm^2) \\ C.B. &= green \ sand \ compactability \ (％) \\ M &= green \ sand \ moisture \ content \ (％) \end{array} \right. \]

4.5 Calculation of mulling efficiency

Mulling efficiency of the tested sand is calculated by the following equation.

\[M.E. = {B.I.(A) \over B.I.(B)} \times 100 \]

where

\[ \left\{ \begin{array}{l} M.E. &= mulling \ efficiency \ (％) \\ B.I.(A) &= bond \ index \ of \ the \ production \ sand \\ B.I.(B) &= bond \ index \ of \ the \ reference \ sand \ with \ full \ mulling \end{array} \right. \]

5. Expression

Mulling index is expressed in %

6. Record

The result is calculated to the first decimal place.

Note:

This test method has been substantially modified from the former standard TIKS-108 (Green sand mulling efficiency test method) as explained below.

1. In the former standard, the muller for the test was specified to the laboratory type muller of the capacity of 5kg. This limitation was deleted, because this type has almost disappeared in the current foundry.
2. In the former standard, it was required that the moisture content of the sand before and after mulling should be equal. This requirement was replaced with the requirement of 5% difference in compactability.
3. In the former standard, only the compression strength was used in evaluating
   mulling efficiency, with the assumption of constant moisture content. The present method, on the contrary, adopted the concept of bond index, where mulling efficiency is evaluated by comparing bond index before and after full mulling.

Standard compliant product