How to determine AFS grading Or Grain fineness number of the ssand PDF

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Summary

Contents 1 Objective 2 Introduction 2 Casting 2 Types of castings 2 Sand casting 3 Theory 3 Pattern 3 Types of patterns 3 Match plate pattern 4 Experimental work 4 Apparatus 4 Procedure.................................................................................................................. ...

Description

Contents 1.0 Objective

2.0 Introduction

.................................................................................................................................. 2

.............................................................................................................................. 2

2.1

Casting ...................................................................................................................... 2

2.2

Types of castings ...................................................................................................... 2

2.3

Sand casting ............................................................................................................. 3

3.0 Theory

.................................................................................................................................. 3

3.1

Pattern....................................................................................................................... 3

3.2

Types of patterns ...................................................................................................... 4

3.3

Match plate pattern ................................................................................................... 4

4.0 Experimental work ........................................................................................................................ 5 4.1

Apparatus .................................................................................................................. 5

4.2

Procedure.................................................................................................................. 5

4.3

Result

.................................................................................................................... 5

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Determine AFS Grading Or Grain Fineness Number Of The Sand 1.0 Objective To determine the AFS grading or grain fineness number of the sand.

2.0 Introduction Sieve shakers are used for separation and size determination of particles. A typical sieve shaker separates particles by passing them through a series of chambers with mesh filters and agitating the sample in order to obtain complete separation. Depending on the equipment, there are options for sieving both solid and liquid samples. Equipment can differ in the type of sieving, the maximum and minimum particle size that can be processed, and level of automation. Choice of equipment will depend on the type of lab and the samples being processed.

Figure 1: Sieve Shaker

Theory The AFS Grain Fineness Number (AFS-GFN) is one means of measuring the grain fineness of a sand system. GFN is a measure of the average size of the particles (or grains) in a sand sample. The optimal grain fineness number (GFN) in a sand system is determined by the type of metal poured, pouring temperatures, casting product mix (heavy vs. light castings) and required surface finish. Once that optimal fineness level is determined, maintaining a consistent grain structure becomes a critical factor in the quality of the final castings. Sand that is too fine (higher GFN) can create low permeability and result in gas defects. Sand that is too coarse (lower GFN) can create high permeability and lead to problems with metal penetration, rough surface finish, burn-in and burn-on. By itself, GFN does not identify if the sand will be a good molding material or produce the qualities needed in a particular metalcasting sand system. Because GFN represents an average fineness, sands with very different grain size distribution may have similar GFN numbers

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3.0 Experimental work 3.1 Apparatus US Standard Sieves Sieve Shaker Weight Balance Trays Brushes

    

3.0 Chemicals / Materials: Dry sand



3.1 Procedure i. ii. iii. iv. v. vi. vii. viii.

Clean the meshes of each sieve with the brush provided. Place the required set of standard sieves with coarsest mesh on the top and finest at the bottom. Place the required weight quantity of washed/dried sand, usually 300 grams at the top sieve. After that, put the lid on the top sieve. Transfer the nest of sieves on the shaker and clamp them in the position. Turn on the motor to shake the sieves. Stop the motor after required time and remove the sieves. Carefully remove the lid from the top sieve and separate each sieve. Weight each sieve and then find the weigh retained on each sieve. Check sieve number and mesh size and record them in the table.

4.0 Calculations Weight of sand initially taken Sieve Number

Mesh Size

= 400 g

weight retained on each sieve

% retained on each sieve (A)

previous sieve number (B)

Product (A*B)

20

0.05

0

0

0

0

25

0.04

0

0

20

0

80

0.0125

330

82.5

25

2062.5

100

0.01

28

7

80

560

120

0.008

10

2.5

100

250

150

0.006

14

3.5

120

420

170

0.005

0

0

150

0

200

0.005

0

0

170

0

18

4.5

200

900

400

100

Pan Total

4192.5

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AFS Grain Fineness Number =

𝑝𝑟𝑜𝑑𝑢𝑐𝑡 %𝑎𝑔𝑒 𝑤𝑡. 𝑟𝑒𝑡𝑎𝑖𝑛𝑒𝑑

= 4192.5/100 = 41.92

Graph between % retained & US Sieve number 90 80

% WT. RETAINED ON EACH SIEVE

70 60 50 40 30 20 10 0 20

25

80

100

120

150

170

200

SIEVE NUMBER

Table 1: AFS-GFN

Result The average GFN of given sand is 41.92 .

Refference: 

https://www.thefreelibrary.com/Calculating+your+grain+fineness+number.a0215115858

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