Ferroalloys
Ferroalloys are used for deoxidation and alloying of steel, high content grades are also used for reduction of metals from oxides.Ferrosilicon is a ferroalloy main components of which are iron and silicon. It is used for dioxidation and alloying of steel.
Ferrochromium is an alloy of iron and chromium, used for alloying of steel and alloys.
Ferromanganese is used for steel deoxidation.
Ferrosilicon
Ferrosilicon is an alloy of iron and silicon.
Ferrosilicon is used for dioxidation and alloying of steel as well as reducer in ferroalloy production.
Ferrosilicon is produced in electric furnaces with silicon content 18-50 and 60-95%. The most usual market formulations are ferrosilicon FS45 and FS65.
Among all produced ferroalloys ferrosilicon occupies the first place. If the content of silicon in alloy is within 50-60% and the alloy is admixed with phosphorus and aluminium the alloy is crumbled into powder educing poisonous volatile compounds. That is why manufacturers do not produce such alloys.
Ferrosilicon is smelt from the ore burden the main component of which is quartzite containing more than 95% of SiO2, less than 0.02 of P2O5 and as less as possible of slag-forming admixtures (alumina). The quartzite is crushed to the pieces of 25-80 mm and washed from the clay. While smelting the ferrosilicon of 45 and 75% content the metallurgical coke of pieces 10-25 mm is used as a reducer.
The main requirements for the reducer are low ash content, high electrical resistance, low content of volatile matters, toughness of pieces at heating.
Charcoal, petroleum and pitch coke contain small amount of ash but they are rather expensive. The dimensions of coke nut influence the process of smelting, if the coke contains a lot of fines it impedes the gas outlet.
The boulders increase the electrical conductivity of the burden and decrease of electrodes’ planting depth and furnace productivity.
If the ferrosilicon is produced in pigs the quantity of fines passing through the sieve with mesh 20õ20 ìì should not exceed: 10% of lot mass – for ferrosilicon FS90, FS75, FS70, FS65; 12% of lot mass – for ferrosilicon FS50 and FS45; 5% of lot mass – for ferrosilicon FS25, FS20.
GOST 1415 - 93 (ISO 5445 - 80)
1. Chemical composition.| Grades (GOST) | Fraction of total mass, % | ||||||
| Si | C | S | P | Al | Mn | Cr | |
| max | |||||||
| FS90 | 87,0 - 95,0 | 0,1 | 0,02 | 0,03 | 3,5 | 0,3 | 0,2 |
| FS 75 | 74,0 - 80,0 | 0,1 | 0,02 | 0,04 | 3,0 | 0,4 | 0,3 |
| FS 70 | 68,0 - 74,0 | 0,1 | 0,02 | 0,04 | 2,0 | 0,4 | 0,4 |
| FS 70Al1 | 68,0 - 74,0 | 0,1 | 0,02 | 0,04 | 1,0 | 0,3 | 0,3 |
| FS 65 | 63,0 - 68,0 | 0,1 | 0,02 | 0,05 | 2,5 | 0,4 | 0,4 |
| FS 50 | 47,0 - 52,0 | 0,1 | 0,02 | 0,05 | 1,8 | 0,6 | 0,5 |
| FS 45 | 41,0 - 47,0 | 0,2 | 0,02 | 0,05 | 2,0 | 1,0 | 0,5 |
| FS 25 | 23,0 - 29,0 | 0,8 | 0,02 | 0,06 | 1,0 | 1,0 | 0,8 |
| FS 20 | 19,0 - 23,0 | 1,0 | 0,02 | 0,10 | 1,0 | 1,0 | 0,8 |
| Grades (ISO) | Fraction of total mass, % | |||||||
| Si | Al | P | S | C | Mn* | Cr* | Ti* | |
| max | ||||||||
| FeSi10 | 8,0 - 13,0 | max 0,2 | 0,15 | 0,06 | 2,00 | 3,0 | 0,8 | 0,30 |
| FeSi15 | 14,0 - 20,0 | max 1,0 | 0,15 | 0,06 | 1,50 | 1,5 | 0,8 | 0,30 |
| FeSi25 | 20,0 - 30,0 | max 1,5 | 0,15 | 0,06 | 1,00 | 1,0 | 0,8 | 0,30 |
| FeSi45 | 41,0 - 47,0 | max 2,0 | 0,05 | 0,05 | 0,20 | 1,0 | 0,5 | 0,30 |
| FeSi50 | 47,0 - 51,0 | max 1,5 | 0,05 | 0,05 | 0,20 | 0,8 | 0,5 | 0,30 |
| FeSi65 | 63,0 - 68,0 | max 2,0 | 0,05 | 0,04 | 0,20 | 0,4 | 0,4 | 0,30 |
| FeSi75Al1 | 72,0 - 80,0 | max 1,0 | 0,05 | 0,04 | 0,15 | 0,5 | 0,3 | 0,20 |
| FeSi75Al1,5 | 72,0 - 80,0 | 1,0 - 1,5 | 0,05 | 0,04 | 0,15 | 0,5 | 0,3 | 0,20 |
| FeSi75Al2 | 72,0 - 80,0 | 1,5 - 2,0 | 0,05 | 0,04 | 0,20 | 0,5 | 0,3 | 0,30 |
| FeSi75Al3 | 72,0 - 80,0 | 2,0 - 3,0 | 0,05 | 0,04 | 0,20 | 0,5 | 0,5 | 0,30 |
| FeSi90Al1 | 87,0 - 95,0 | max 1,5 | 0,04 | 0,04 | 0,15 | 0,5 | 0,2 | 0,30 |
| FeSi90Al2 | 87,0 - 95,0 | 1,5 - 3,0 | 0,04 | 0,04 | 0,15 | 0,5 | 0,2 | 0,30 |
* - max. values are applicable.
2.Size.Ferrosilicon is supplied in pieces 25 kg max, pigs 45 kg max. and in form of crushed sifted pieces.
| Main requirements | |||
| Size grade | Piece dimensions, mm | Max fraction of product’s total mass, % | |
| oversize | undersize | ||
| 1 | 100 - 315 | 10 | 10 |
| 2 | 50 - 200 | 10 | 10 |
| 3 | 20 - 100 | 10 | 10 |
| 4 | 10 - 50 | 10 | 10 |
| 5 | 3,2 - 20 | 10 | 10 |
| 6 | 3,2 - 10 | 10 | 10 |
| 7 | up to 3,2 | 10 | - |
| Recommended requirements | ||||
| Size grade | Piece dimensions, mm | Max fraction of product’s total mass, % | ||
| oversize | undersize | |||
| total | less than 3,15 ìì | |||
| 1 | 100 - 315 | 10 Any piece should not exceed more than1.15 times the maximum limit of the given size range in two or three directions. | 20 | 6* |
| 2 | 75 - 200 | 20 | 6* | |
| 3 | 35 - 100 | 18 | 6* | |
| 4 | 10 - 75 | 18 | 7* | |
| 5 | 3,15 - 35 | 8 | ||
| 6 | 3,15 - 10 | 10 | ||
| 7 | 3,15 - 6,3 | 10 | ||
| 8 | max 3,15 | - | ||
If the ferrosilicon is produced in pieces 25kg max. the quantity of fines passing through the sieve with mesh 20õ20 ìì should not exceed: 10% of lot mass for all ferrosilicon grades.
For long-term storage ferrosilicon is produced in ingots with thickness not more than 100 mm if cast in one layer and not more than 150 mm if cast in two layers.
Ferrosilicon shouldn’t be contaminated with foreign substances. Some impurities of stick sand, traces of antiburning-on matters and graphite, as well as dross are allowed.