1. Parul Institute of Engineering & Technology
Subject Code :
Name Of Subject : Material Science And Metallurgy
Name of Unit : Metallic Materials
Topic : Various Test of Metals/Alloy
Name of Studnets :DESAI HARDIKKUMAR RAMESHBHAI

2. Introduction Different test metals: Macro – examination Spark test
Sulphur print
Macro - etching

3. Macro Examination DEFINATION:
“Study of the structure of metals and their alloys with naked eye or using a low power magnification( upto x15 ) is known as MACRO EXAMINATION. Structure so observed is called MACROSTRUCTURE.”
Macro examination is the procedure in which a specimen is etched and evaluated macro structurally at low magnifications (upto 15X). Macro examination is a frequently used technique for evaluating steel products such as billets, bars, blooms, and forgings.
During macro examination, there are several procedures for rating a steel specimen by use of a graded series of photographs showing the incidence of certain conditions and is applicable to carbon and low alloy steels.

4. Macro Examination (cont.)
A number of different etching reagents may be used depending upon the type of macro examination to be made. Steels react differently to etching reagents because of variations in chemical composition, method of manufacturing, heat treatment and many other variables. Examples of a few testing methods we can perform for macro examination: ASTM E381 (Standard Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings), A561 (Standard Practice for Macrotech Testing of Tool Steel Bars), A604 (Standard Test Method for Macro etch Testing of Consumable Electrode Remelted Steel Bars and Billets), E340 (Standard Test Method for Macro etching Metals and Alloys).
Macro examination can also be performed on welding materials. Macro examination can also be performed on a polished and etched cross-section of a welded material. During the macro examination, a number of features can be determined including weld run sequence, important for weld procedure qualifications tests.

5. Macro Examination (cont.)
In addition, any defects on in the sample can be assessed for compliance with relevant specifications. Slag, porosity, lack of weld penetration, lack of sidewall fusion and poor weld profile are among the features that are searched for in such examinations. It is normal to look for such defects either by standard visual examination or at magnifications of up to 50X. It is also routine to photograph the section to provide a permanent record. This is known as a photo macrograph.

6. Macro Examination (cont.)
Macro-Examination is carried out for the following purposes:
To reveal size, from and arrangement of crystallites (dendrites) in cast metals.
To reveal size , form & fibers in deformed metals.
To check manufacturing method (forging , welding , casting, etc..)
To check cavities due to gas and porosity during solidification shrinkage.
To find chemical non-homogeneity during solidification.
To find inclusion
To find cause of failure
To find non metallic inclusions.

7. Spark Test
The Spark Test involves identification of metals by applying them to a grinding wheel and observing the spark that is generated. The color, shape, average length, and activity of the sparks are characteristics of the material being tested.
The shape and characteristic of sparks created when metal is ground will help determine its properties
When a piece of metal is held against a revolving grinding wheel, abrasive grain tear off small particle from metal piece which are heated to melting temp. accelerating glowing particle produce a visible beam of spark.
It consists of holding piece of metal against rotating ,grinding wheel & observing characteristic of spark produced.

8. Spark Test (cont.)
It relies on perception of metal worker to distinguish colors, shape, average length & activity of spark to determine material being tested.
Colors of spark test: Red, Orange, White & Yellow
Major types of spark:
Stream
Shaft
Fork
Sprigs
Dashes
Appendages
Bud break arrow

9. Spark Test (cont.)
Various grades of steel give sparks with typical patterns which serves as means of identification.
Even small quantities of some elements added for special purpose, such as aluminium and titanium, can be detected.
With care and practice , spark testing developed into a particularly reliable and inexpensive method of rapid identification and it is one of the most used method for identifying metals.
By visually inspecting the spark stream, an experienced metalworker can identify the metals with considerable accuracy. This test is fast, economical, convenient, and easily accomplished, and there is no requirement for special equipment. We can use this test for identifying metal salvaged from scrap. Identification of scrap is particularly important when selecting material for cast iron or cast steel heat treatment.

10. Spark Test (cont.)
Identification of different metals by spark test:

11. Spark Test (cont.)
Referring now to figure 1-4, notice that in low-carbon steel (view A), the spark stream is about 70 inches long and the volume is moderately large. In high-carbon steel (view B), the stream is shorter (about 55 inches) and the volume larger.
The few sparklers that may occur at any place in low-carbon steel are forked, and in high-carbon steel, they are small and repeating. these metals must be distinguished from each other by Both metals produce a spark stream white in color.Gray cast iron (view C) produces a stream of sparks about 25 inches in length.

12. Spark Test (cont.)
The sparklers are small and repeating, and their volume is rather small. Part of the stream near the wheel is red, and the outer portion is straw-colored.
Monel and nickel (view D) form almost identical spark streams. The sparks are small in volume and orange in color. The sparks form wavy streaks with no sparklers. Because of the similarity of the spark picture, some other method.
Stainless steel (view E) produces a spark stream about 50 inches in length, moderate volume, and with few sparklers. The sparklers are forked. The stream next to the wheel is straw-colored, and at the end, it is white.
The wrought-iron spark test (view F) produces a spark stream about 65 inches in length. The stream has a large volume with few sparklers. The sparks appear near the end of the stream and are forked. The stream next to the wheel is straw-colored, and the outer end of the stream is a brighter red.

13. Sulphur Print Test It is a method to detect sulphur in steel. Method:
Process include grinding flat surfaces , smoothened emery paper, cleaning surface from dirt & grease.
Next step is to to soak pieces of bromide paper into 3% solution of HCL in water for 2 minutes & to remove excess solution with blotting paper.
Next is to place sensitized surfaces in contact with 1 edge of prepared surfaces & time of contact 1-2 minute & corner of paper is lifted to examine intensity of brown stain.
The paper is removed, swilled in water for 3 minutes & then immerse in 20% hypo solution for 5 minutes.
It is then swilled in water for 20 minutes & then dried.

14. Macro Etching
Macro examination can also be carried out on an etched surfaces which is known as macro etching.
Different type:
HNO3 – 25CC, H2O – 75 CC
It is used for steel to find flaw line , crack, porosity , structure of fusion weld.
HF – 20 CC, H2O – 80 CC
It finds application for Al, & alloy. It involves degreasing specimen in C – tetrachride , weloshing in hot water & then swabbing with etchant.
FeCl3- 25 gm, HCl -25 CC, H2O – 100 CC
It is used for microscopic examination of dendritic structure of alpha solid solution in copper alloy. 

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