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M aterials required: Grinding Wheel

Scrap Metal

Ident i f icat ion Chart (pages 2-3)

Background:Spark t est ing is an o ld method of ident i fy ing the chemistry of ferrous (i ron- based) mat eria ls. At some steel mi l ls , there is st i l l a spark tester or two around . They are ca l led on when the exactcomposit ion of a sample is unknown. They may be asked, for instance, to f ind the bad batch of stee l tub ing in a group of genera l ly good steel tub ing. Today, h igh-tech instrum ents more precise lymeasure the const i tu t ion of meta ls.

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Spark Testingfor M ystery M etals

} Both easy to get . We l l show you how!The student will

make and accuratelyrecord ob servations,

inferences,hypotheses and

explanations.

O H I O sSTATE CURRICULUM

Stee l Elem ents

Steps to follow:1 . Secure mystery meta ls. You wi l l need three or four p ieces of ferrous meta l that you , as the teacher, can posit ive ly ident i fy. Here are a few suggest ions:

( 1 ) wro u g h t i ro n (h o rse sh o e s, o rn a me n ta l i ro n wo rk ) ; ( 2 ) sta in less steel (kn ives, tab le utensi ls); ( 3 ) high-speed steel (dri l l b i ts); ( 4 ) carbon too l stee l (hammers, ch isels); ( 5 ) cast i ron (o ld cast i ron ski l le t ).For addit ional materia ls, v is i t a local scrap yard, junk yard or manufactur ing faci l i ty . For a scrap yard near you, ca l l the Inst i tu te of Scrap Recycl ing Industries at 740-3 97-7 680.

2 . Rent a hand-held or stat ionary d ie grinder (n ot a Dremel) f rom a too l renta l store at a cost o f about $10. You wi l l probably need to buy a grind ing wheel (an at tachment) a t a cost o f about $5. Buy a wheellarge enough to produ ce at least 5 ,000 surface feet per minu te. Calcu late surface feet per minu te in th is way:

(Cau t io n : Do n o t exceed m ax im u m r eco m m en d ed RPM r a t in g for g r in d in g w h ee l se lected . )

3 . Divide the students in to smal l groups of three to f ive students.

4 . Print out t he spark ident i f icat ion t ab les on the fo l lowing pages. Distribute the documents to students. The documents conta in spark propert i es for 11 steel materi a ls. Expla in to students how the sparks are c lassi f ied.Make sure they understand each of the s ix propert ies to be observed and recorded.

5 . Ensure that a l l s tudents have adequate eye, face and hand pr otect ion. Have them stand back for safety and so a l l present can see the sparks.

6 . Secure each of the mystery m eta ls in a v ise and gent ly apply the grin der. Pause between each appl icat ion t o a l low each student gr oup t im e to record the spark pr opert ies. (You might consider conceal ing the samples

in such a way that students wi l l not be able to ident i fy them by s ight . )7 . Once the groups have recorded the propert i es of each p iece of meta l , they should at tem pt to ident i fy the four mystery m eta ls, using the chart .8 . After a l l groups have completed the ir id ent i f icat ion of the mystery m eta ls, d iscuss the spark pr opert ies of each meta l one by one. Have a spokesperson f rom each group expla in the groups observat ions, decision

process and conclusion.9 . When each group has comm it ted to an ident i f icat ion, reveal the actual ident i ty o f the steel sample.1 0 . Proceed with d iscussion on the next stee l sample.

Analysis:The benef i t o f th is exercise l ies in the pr ocess of observat ion. Students learn to com pare subt le d i f ferences in spark streams, to record pr opert ies of spark streams and to use the ir records to dr aw conclusions. Each t ime astudent evaluates a spark stream, he or she is looking at s ix d i f ferent propert ies. Great at tent ion to d eta i l is necessary for accurate results.

= Su r fa ce Fe e t Pe r Min u te(RPMs) x (Circumference of Wheel in Inches)

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Spark Identification Illustrations

Material Spark Illustration

Wrought Iron

Carbon Tool Steel

Gray Cast Iron

White Cast Iron

Annealed Malleable

Iron

High-Speed Steel

Austentic Manganese

Steel

Material Spark Illustration

Stainless Steel

Tungsten-Chromium

Die Steel

Stellite

Cemented Tungsten

Carbide

Nickel

Copper, Brass,

Aluminum

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Spark Testing Identification Table

Material Volume of Relative Length Color of Stream Color of Streaks Quantity of Nature of Spurts Used For Type Stream of Stream Close to Wheel Near End of Spurts

in Inches Stream

Wrought Iron Large 65 Straw White Very few Forked Shipbuilding, farmequipment andornamental work

Carbon Tool Steel Moderately large 55 White White Very many Fine, repeating Hammers, chisels, dies,drills, cutters, taps andwood-cutting tools

Gray Cast Iron Small 25 Red Straw Many Fine, repeating Auto cylinder blocks andheads, crankcases,crankshafts, brake drums,camshafts, pipes, auto andlocomotive castings

White Cast Iron Very small 20 Red Straw Few Fine, repeating Rolls used forrolling steel

Annealed Malleable Moderate 30 Red Straw Many Fine, repeating Gears, universal joints,

Iron connecting rods,differential cases, steeringgear housings, flanges,pipe fittings and valveparts

High-Speed Steel Small 60 Red Straw Extremely few Forked Drill bits

Austenitic Manganese Moderately large 45 White White Many Fine, repeating Railroad switches, rock Steel crushers, grinding mills

Stainless Steel Moderate 50 Straw White Moderate Forked Cooking utensils andflatware, fasteners,chemical, health,sanitation andpetrochemical equipment

Tungsten-Chromium Small 35 Red Straw Many Fine, repeating Engine valves,Die Steel gun barrel liners and

rifling, dies and punchesfor steel materials

Stellite Very small 10 Orange Orange None Cast pipe valves andpumps for chlorineresistance in chemicalplants

Cemented Tungsten Extremely small 2 Light orange Light orange None Mining, rock drillingCarbide and metal cutting

Nickel Very small 10 Orange Orange None None Plating

Copper, Brass, None None None None None None Piping, plumbing,Aluminum ornamentation, cans