STEEL.— Bessemer Process, Chemistry of.
867
cient to the practised ear to determine this point.The proper amount of carbon and manganese arethen added by pouring into the vessel a certainquantity of molten spiegeleisen, or dropping intothe vessel a known weight of ferro-manganese, ifvery soft steel is desired. When iron containingover 2 per cent, manganese is being blown, thepoint of decarburization is very difficult to ascertainby the flame test, and recourse has to be had to theslag and metal test. The carbon is known to be allblown out when the slag just begins to pass from abrown colour to a smoky black, and the globules ofmetal taken out with the testing pad flatten underthe hammer without breaking. When very siliceousiron is being blown, the same test may be applied;or if manganese is absent, the colour of the smokeis a guide. While any quantity of silicon remains,the smoke will, as it issues from the convertor, havea grey colour; but when all the carbon and siliconhave been burnt, it comes out of the convertor a deep,
ruddy, brown colour, showing that combustion ofiron is taking place. In making soft steel by theBessemer process great care is needed to insure thethorough admixture of the ferro-manganese withthe molten metal, so as to remove the excess ofoxygen before the metal begins to set in the moulds,as otherwise very dangerous explosions in themoulds may take place. After the steel has beenteemed from the ladle into the moulds, it must beinstantly covered up, so as to solidify the topsurface, and fastened down, unless an excess ofmanganese be employed or the steel be hard, inwhich case it will lie dead in the moulds, and not“ rise ” or “ boil over,” as the men term it. Theiron moulds may be lifted from the ingots five orten minutes after they are cast.
The Bessemer Process considered Chemically .—Thefollowing analyses exhibit the nature of the pig ironusually treated by the Bessemer process, and thechanges which occur during the “ blow ” :—
TABLE II.—ANALYSIS BY SNELUS, AT DOWLAIS, SOUTH WALES.
Melted
Charge of Pig.*
No. 1 Sample,taken at the end oflirst Btage, 6 minutesfrom start.
No. 2.
taken 9 minutesfrom start.
No. 3,
taken at tinish,before addingSpiegel, 13 min.from start.
Steel Boringsfrom Rail Cropends.
Iron,.
94-682
97-245
_
_
_
_
Carbon,.
( Graphite,...\ Combined,..
i-w} 3 ' 218 t
2* 17+
1*55
•097
•566
•519
Silicon,.
1SS} —
•792\
•798 J ' yD
*6351 CQf .•635/ 635
•020
•030
•033
Sulphur,.
•014
trace.
trace.
trace.
trace.
trace.
Phosphorus,.
<£?} '° 48
•055") ns,•058/ 051
•064
•067
•055
•053
Manganese,.
•086
trace.
trace.
trace.
•309
•309
Copper,.
—
—
—
—
•039
•039
TABLE III.—ANALYSIS BY BARKER, AT ATLAS WORKS,SHEFFIELD.
1 .
2 .
3 .
4.
5 .
Per cent.
Per cent.
Per cent.
Per cent.
Per cent.
Graphite,.
2*570
—
—
—
—
Combined carbon,.
1-000
3-040
1*640
0*190
0*370
Silicon,.
2*260
0*955
0*470
trace.
trace.
Manganese,.
0*410
trace.
trace.
trace.
0*540
Sulphur,.
0*107
0*091
0*098
0*093
0*090
Phosphorus,.
0*073
0*070
0*070
0*070
0*059
1 .
2 .
3.
4.
5.
Per cent.
Per cent.
Per cent
Per cent.
Per cent.
Graphite,.
3*180
—
—
—
—
Combined carbon,.
0*750
2*465
0-949
0-087
0-234
Silicon.
1-960
0-443
0*112
0*028
0*033
Manganese,.
3-460
1-645
0-429
0*113
0-139
Sulphur,.
Phosphorus,.
0*018
trace.
trace.
trace.
trace.
0*010
0*040
0-045
0-045
0*044
Copper,.
0*085
0-091
0-095
0-120
0-105
No. 1, original pig iron.
No. 2, metal and slag taken at the end of the first period(six minutes).
No. 3, metal and slag taken at the end of the boil (twelveminutes).
No. 4, metal and slag taken at the end of the blow.
No. 5, metal and slag after addition of spiegel.
2 .
3.
4.
5.
Per cent.
Per cent.
Per cent.
Per cent.
Silica,.
46-78
51*75
46-75
47*27
Alumina,.
Iron protoxide,.
4*65
2*98
2*80
3*45
6*78
5*58
16*86
15*43
Manganese protoxide, ..
37*00
37*90
32*23
31*89
Lime,.
Magnesia.
2*98
1*76
1*19
1 *23
1-53
0*45
0-52
0*61
Alkalies,.
traces.
—
traces.
traces.
Sulphur,. > .
0-04
trace.
_
_
Phosphorus,.
0-03
0-02
o-oi
0*01
TABLE V.
Iron used atSoraing for run-
Rail Steel made
ning direct intothe Convertor.
without Spiegel.
Iron,.
89*40
99*07
Carbon,.
4-50
*32
2*25
*15
Sulphur,..
*04
*04
Phosphorus,.
•06
*07
Manganese,.
3*75
*35
100-00
100-00
* This was the composition of the metal run into the con-vertor. It had been melted in a reverberatory furnace.
t The total carbon is estimated by direct combustion ; thegraphitic and combined by separate experiments,f All combined.