Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR MANUFACTURING FERROCHROMIUM ALLOY WITH DE¨
SIRED CONTENT OF MANGANESE, NICKEL AND MOLYBDENUM
The invention relates to a process for manu-
facturing ferrochromium alloy with desired content of
manganese, nickel and molybdenum.
Desired means in this context the composition
of the ferrochrome alloy that results from the process.
The main components of stainless steels are
iron and chromium and depending on the type of stainless
steel additionally at least one of nickel, manganese and
molybdenum. Stainless steels are typically categorized
to ferritic (e.g. AISI 400), austenitic (e.g. AISI 200,
300) and to duplex series. Duplex stainless steels are
having properties from ferritic and austenitic steels.
Chromium content in stainless steel is over 10.5 wt-%.
Certain stainless steel grades also comprise manganese,
such as the 200 series, where nickel is at least partly
substituted by manganese. The manganese source is typ-
ically ferromanganese, silicomanganese or electrolytic
manganese. The nickel content in austenitic 300 series
stainless steel is most between 8 and 12 wt-% but there
is variation between different grades. For example in
the 200 series the nickel content is lower, typically
at 0 to 7 wt-% and in certain special stainless steel
up to 30 wt-%. Nickel is an expensive raw material and
its availability and price varies with time. Nickel
sources used in stainless steel making are typically
acid-proof scrap, ferronickel and pure nickel cathodes.
Steels are well recyclable and significant part
of the stainless steel making is based on stainless and
carbon steel scrap. Yet, in this method, virgin feed of
key elements is also required for achieving desired
grades and for diluting possible impurities enriching
in the recycling of steel. As an example of melting
batch of a lean 300 series stainless steel from scrap
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metals can be following: 50 wt-% of 300 series scrap (18
wt-%Cr, 8 wt-% Ni, 1 wt-% Mn); 30 wt-% of carbon steel
scrap (mostly Fe); 14 wt-% of high carbon FeCr (7 wt-
%C, 65 wt-% Cr); 4 wt-% of nickel briquettes (mostly Ni)
and 1 wt-% high carbon FeMn (7 wt-%, 65 wt-% Mn). This
mixture will end up in composition of about 18 wt-% Cr,
8 wt-% Ni, 1 wt-% Mn and 1 wt-% C.
Chromium form a surface film of chromium oxide
to make the stainless steel corrosion resistant. Chro-
mium also increases the scaling resistance at elevated
temperatures.
Nickel stabilizes the austenitic structure and
increases ductility, making stainless steel easier to
form. Nickel also increases high temperature strength
and corrosion resistance, particularly in industrial and
marine atmospheres, chemical, food and textile pro-
cessing industries.
Manganese promotes the stability of austenite,
at or near room temperature and improves hot rolling
properties. Addition of up to 2 wt-% manganese has no
effect on strength, ductility and toughness. Manganese
is important as a partial or complete replacement of
nickel in 200 series austenitic stainless grades.
Molybdenum increases corrosion resistance,
strength at elevated temperatures, and creep resistance.
It expands the range of passivity and counteracts ten-
dency to pit especially in chloride environments.
An object of the invention is to provide an
improved process for the manufacture of ferrochromium
alloy with desired content of manganese, nickel and mo-
lybdenum, which is characterised by high recovery of
desired elements such as chromium, iron, manganese,
nickel and molybdenum.
It has been realized that production of ferro-
chromium alloy with desired content of manganese, nickel
and molybdenum is a most reasonable way to reduce the
production costs of any stainless steels. Minimization
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of the consumption of electrical energy and obtainment
of maximum capacity from the process equipment improve
the profitability and competitiveness of stainless steel
production. The invention enables the use of cheaper
manganese, nickel and molybdenum sources compared to the
typical sources used in the stainless steel alloying
step.
It has been found out that the addition of
manganese, nickel and molybdenum bearing raw materials
to iron and chromium bearing material when producing
agglomerates is advantageous for the manufacture of the
corresponding heat-treated agglomerates and the manu-
facture of the corresponding ferrochromium manganese
nickel molybdenum alloys. For the purpose of this de-
scription, the terms relating in "ferrochromium alloy
with desired content of manganese, nickel and molyb-
denum" are abbreviated as "FeCrMn", "FeCrNi", "FeCrMo",
"FeCrNiMo", "FeCrMnMo", "FeCrMnNi" and "FeCrMnNiMo".
The ferrochromium alloy contains typically also carbon,
silicon and also other elements that are less stable as
oxide form in a reducing and high temperature conditions
and do not evaporate in smelting conditions.
The invention relates to a process for manu-
facturing ferrochromium alloy with desired content of
manganese, nickel, and molybdenum, wherein the process
comprising the steps of:
- providing a feed mix comprising iron bearing mate-
rial and chromium bearing material and optionally
manganese bearing raw material, optionally nickel
bearing raw material and optionally molybdenum
bearing raw material;
- the feed mix containing iron bearing material and
chromium bearing material in an amount sufficient
to provide iron content between 5 and 75 wt-% in
the feed mix and sufficient to provide chromium
content between 5 and 70 wt-% in the feed mix;
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- the feed mix containing manganese bearing raw ma-
terial in an amount sufficient to provide a manga-
nese content between 0 and 70 wt-% in the feed mix;
- the feed mix containing nickel bearing raw material
in an amount sufficient to provide a nickel content
between 0 and 50 wt-% in the feed mix;
- the feed mix containing molybdenum bearing raw ma-
terial in an amount sufficient to provide a nickel
content between 0 and 40 wt-% in the feed mix;
- mixing the feed mix with a reducing agent and flux-
ing agent to obtain smelting feed; and
- smelting the smelting feed in an smelting vessel
to obtain ferrochromium alloy with desired content
of manganese, nickel and molybdenum.
The feed mix can contain iron bearing material
in an amount sufficient to provide an iron content be-
tween 5 and 75 wt-% in the feed mix, preferably between
10 and 50 wt-% in the feed mix, more preferably between
10 and 45 wt-% in the feed mix, even more preferable
between 10 and 30 wt-% in the feed mix.
The feed mix can contain chromium bearing ma-
terial in an amount sufficient to provide a chromium
content between 5 and 70 wt-% in the feed mix, preferably
between 12 and 50 wt-% in the feed mix, more preferably
between 12 and 35 wt-% in the feed mix.
The feed mix can contain manganese bearing raw
material in an amount sufficient to provide a manganese
content between 0.01 and 70 wt-% in the feed mix; pref-
erably between 0.01 and 40 wt-% in the feed mix, more
preferably between 0.01 and 30 wt-% in the feed mix,
even more preferably between 0.01 and 25 wt-% in the
feed mix.
The feed mix can contain nickel bearing raw
material in an amount sufficient to provide a nickel
content between 0.01 and 50 wt-% in the feed mix; pref-
erably between 0.01 and 30 wt-% in the feed mix, more
preferably between 0.01 and 25 wt-% in the feed mix,
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even more preferably between 0.01 and 20 wt-% in the
feed mix.
The feed mix can contain molybdenum bearing raw
material in an amount sufficient to provide a molybdenum
5 content between 0.01 and 40 wt-% in the feed mix, pref-
erably between 0.01 and 30 wt-%, in the feed mix more
preferably between 0.01 and 10 wt-% in the feed mix.
The smelting feed can be in an agglomerated
form or an unagglomerated form or mixture of them.
In some stainless steel grades also copper and
and/or niobium (referred also as Columbium) is alloyed
in small quantities (in major stainless steel grades
copper is an impurity). In order to increase the alloys
copper and niobium content, copper-bearing raw materials
may also be added as an agglomerated feed or as a fine
feed to the smelting. The feed mix may contain copper
bearing raw material in an amount sufficient to provide
a copper content between 0.01 and 30 wt-%, preferably
0.5 and 30 wt-%, more preferably 0.5 and 10 wt-%, most
preferably between 0.5 and 5 wt-% in the feed mix. The
feed mix may contain niobium (also referred as colum-
bium) bearing raw material in an amount sufficient to
provide a niobium content between 0.01 and 30 wt-%,
preferably between 0.5 and 30 wt-%, more preferably be-
tween 0.5 and 10 wt-%, most preferable between 0.5 and
5 wt-% in the feed mix.
Copper is added to stainless steels to increase
their resistance to certain corrosive environments. Cop-
per also decreases susceptibility to stress corrosion
cracking and provides age-hardening effect.
Niobium combines with carbon to reduce suscep-
tibility to intergranular corrosion. Niobium acts as a
grain refiner and promotes the formation of ferrite.
The manganese, nickel and molybdenum content
in the smelting feed may be selected based on the end
product (stainless steel) requirements so that the con-
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sumption of the traditional (typically expensive) al-
loying elements is minimized in the following refining
stages of the stainless steel (converting, alloying).
Also the produced ferrochromium alloy with desired con-
tent of manganese, nickel and molybdenum can be later
refined and/or diluted with scrap addition and/or al-
loyed with traditional alloying substances in the down-
stream process steps. Examples of compositions of stain-
less steel grades are presented in Tables 1-4.
7
0
tµ.)
o
1-,
oe
TABLE 1: CHEMICAL COMPOSITION OF SOME REGISTERED 200-SERIES GRADES (in wt-%)
O-
1-,
1-,
.6.
c,
--1
AI
201 2011N 202 203 204 205 214
216
SI
UN S2010 S2010 S2015 S2016 S2020 S2040 S2043 S2050 S2140
S2160 S2160 S2400
S20300
S 0 3 3 1 0 0 0 0
0 0 3 0
16.0 16.0 16.0 15.0 17.0 15.0 15.5 15.5 17.0
17.5 17.5 17.0
16.0 -
Cr
18.0 P
18.0 18.0 17.5 18.0 19.0 17.0 17.5 17.5 18.5
22.0 22.0 19.0 .
14.0
14.0 11.5 .
5.5 - 5.5 - 6.4 - 4.0 - 7.5 - 5.0 - 7.0 - 6.5 -
7.5 - 7.5 -
Mn
.
7.5 7.5 7.5 6.0 10.0 6.5 9.0 9.0
9.0 9.0 .
15.5
16.0 14.5
.
2.25 ,
3.5 - 3.5 - 4.0 - 4.0 - 4.0 - 4.0 - 1.5 - 1.5 -
1.5 - 1.0 5.0 - 5.0 - I
Ni
,
5.5 5.5 5.0 6.0 6.0 6.0 3.0 3.5 3.5 max.
7.0 7.0 ,
.
3.75 .
0.10 0.08 0.15 0.05 0.32 0.25 0.25
0.20
N
0.25 0.25 0.25 0.35
max. max. max. min.
0.25 0.20 0.30 0.25 0.40 0.50 0.50
0.40
0.12
C
0.15 0.03 0.03 0.15 0.15 0.08 0.03 0.15 0.12
0.08 0.03 0.08
max. max. max. max. max. max. max. max. max. max. max. max.
0.25
0.030 0.030 0.030 0.040 0.030 0.18 - 0.030 0.030
0.030 0.030 0.030 0.030 0.030 Iv
n
s 1-i
max. max. max. max. max. 0.35 max. max. max. max. max. max. max.
F-Ii3
Ot Cu Cu Cu
Mo Mo w
=
he 1.0 1.75 - 2.0 -
2.0 - 2.0 - 1..
--1
rs max. 2.25 4.0
3.0 3.0 =
un
=
un
w
m
8
0
t..)
o
1-
cio
Table 2: CHEMICAL COMPOSITION OF SOME REGISTERED 300-SERIES GRADES (in wt-%)
.6.
-4
AISI C N Cr Ni Mo Mn Si
Other Other Other
301 tensile 0.08 0.4 16.6 6.8 0.2 1.0
0.45 0.001 S 0.03 P 0.3 Cu
301 drawing 0.08 0.04 17.4 7.4 0.02 1.7 0.4
0.007 S 0.03 P 0.6 Cu
304 0.05 0.05 18.3 8.1 0.3 1.8
0.45 0.001 S 0.03 P 0.3 Cu
304 drawing 0.05 0.04 19.4 8.6 0.3 1.8
0.45 0.001 S 0.03 P 0.3 Cu
304 extra drawing 0.06 0.04 19.3 9.1 0.3 1.8
0.45 0.001 S 0.030 P 0.4 Cu p
304L tubing 0.02 0.09 18.3 8.1 0.3 1.8
0.45 0.013 S 0.030 P 0.4 Cu
r.,
305 0.05 0.02 18,8 12.1 0.2 0.8
0.60 0.001 S 0.02 P 0.2 Cu
r.,
321 0.05 0.10 17.7 9.1 0.03 1.0
0.45 0.001 S 0.03 P 0.4 Ti ,
,
316L 0.02 0.0 16.4 10.5 2.1 1.8
0.50 0.001 S 0.03 P 0.4 Cu
,-o
n
,-i
F-t
t..,
=
-4
=
vi
Table 3: CHEMICAL COMPOSITION OF SOME REGISTERED 400-SERIES GRADES (in wt-%)
=
vi
w
cio
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0 1111111
c) c) c) c) c) c) c)
X-1 ¨1 ¨1 ¨1 ¨1 ¨1 ¨1
c) c) Lo
or) or) or)
c) c) c)
Z c) I I I I c) c)
Lo Lo c)
CV CV Lo
CV
CS)
I I 1
Lo Lo Lo
[---- r--- r---
0
X I I I 0 0 I H
O 0 Lo c) c)
Lo k.o r--- Lo c)
-H
Z 0 0 0 I I 0 H
r--- Lo c) c) c) Lo c)
cs) o-, co
¨1 ¨1 CV
1111111
Lo Lo c) c) cs) Lo c)
c)rH o k.o r---- r--- Lo
u ¨1 ¨1 CV
O 0 Lo
or) CO CV CV CV Or) CV
O 0 H H H 0 0
U 0 0 0 0 0 0 0
----.
>i H
0 Cf)
H H CS) Lo
H F4 0 0 Or) Or) Cr) Cr)
Lo c)
10
0
w
o
1-
cio
Table 4: CHEMICAL COMPOSITION OF SOME REGISTERED DUPLEX STAINLESS STEEL GRADES
(in wt-%)
.6.
-4
Common UNS No, C Cr Ni Mo N
Mn Cu Other
name
S31200 0.030 24.0-26.0 5.5-6.5 1.20-2.00 0.14-0.20 2.00
S31260 0.030 24.0-26.0 5.5-7.5 2.5-3.5
0.10-0.30 1.00 0.2- W 0.10-
0.8
0.50 P
S32001 0.030 19.5-21.5 1.00-3.00 0.60 0.05-0.17
2.0-6.0 1.00 - .
S32003 0.030 19.5-22.5 3.0-4.0
1.50-2.00 0.14-0.20 2.00 .3
S32101 0.040 21.0-22.0 1.35-1.7 0.10-0.80 0.20-0.25 4.0-6.0 0.10- -
.
,
,
0.80
,
,
S32202 0.030 21.5-24.0 1.00-2.80 0.45
0.18-0.26 2.00-
2.50
2304 S32304 0.030 21.5-24.5 1.0-5.5 0.05-0.60 0.05-0.20 2.00
0.05- -
0.60
2205 S31803 0.030 21.0-23.0 4.5-6.5 2.5-3.5 0.08-0.20 2.00
Iv
2205 S32205 0.030 22.0-23.0 4.5-6.5 3.0-3.5 0.14-0.20 1.00 n
,-i
F-t
S32506 0.030 24.0-26.0 5.5-7.2 3.0-3.5
0.08-0.20 1.50 W 0.05- w
o
,..,
0.30
--.1
o
v,
o
v,
w
m
11
0
O4
S32520 0.030 24.0-26.0 5.5-8.0 3.0-4.0 0.20-0.35 1.50
0.50- -
It
2.00
t
-1
255 S32550 0.04 24.0-27.0 4.5-6.5 2.9-3.9 0.10-0.25 1.50
1.50- -
2.50
2507 S325750 0.030 24.0-26.0 6.0-8.0 3.0-5.0 0.24-0.32 1.20 0.50 -
S325760 0.030 24.0-26.0 6.0-8.0 3.0-4.0
0.20-0.30 1.00 0.50- W 0.50-
1.00
1.00
S325808 0.030 27.0-27.9 7.0-8.2 0.8-1.2
0.30-0.40 1.10 W 2.10- P
2.50
2
2
.f3
S325906 0.030 28.0-20.0 5.8-7-5 1.50-2.60 0.30-0.40 0.80-
1.5 0.80 - 2g
r.,
S32950 0.030 26.0-29.9 3.50-5.20 1.00-2.50 0.15-0.35 2.00
,E!
I
S39274 0.030 24.0-26.0 6.8-8.0 2.5-3.5
0.24-0.32 1.0 0.20- W 1.50-
0.80
2.50
S82011 0.030 20.5-23.5 1.0-2.0 0.10-1.00 0.15-0.27 2.0-
3.0 0.50 .
Iv
n
1-i
;:t7".1
o
t7;
a
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All raw materials used in the process according
to the invention may contain certain impurities (typical
slag formers), such as A1203, MgO, CaO, SiO2 and similar
oxides to these. Similar compounds are also contained
in the chromite concentrate and fluxing agents used in
the conventional FeCr smelting. Therefore, those impu-
rities need not be removed from the raw materials when
directed to smelting stage. This enables the use of low
cost manganese, nickel and molybdenum sources compared
to the use of highly refined alloying elements used in
traditional stainless steel production, such as FeMn,
SiMn, FeNi or FeMo. The consumption of traditional al-
loying elements is decreased according to the invention.
The manganese bearing raw material is a solid
compound, typically manganese ore or manganese ore con-
centrate. Manganese may exist as manganese oxide, man-
ganese hydroxide, metallic manganese, manganese car-
bonate, manganese sulphide, manganese sulphates manga-
nese salts or similar compounds and any mixtures of
them. The manganese-bearing raw material can contain,
for instance, calcinated molybdenum bearing material.
The nickel-bearing raw material is a solid com-
pound and typically contains at least part of the fol-
lowing: nickel hydroxides, nickel carbonates, nickel
oxides, nickel sulphides, metallic nickel, nickel sul-
phates or other compounds, and any mixtures of thereof
and/or known nickel salts. The nickel-bearing raw mate-
rial can contain, for instance, calcinated nickel con-
centrate from sulfidic ore beneficiation, or an inter-
mediate product from hydrometallurgical process steps
of lateritic nickel ore processing.
The molybdenum bearing raw material is a solid
compound, typically molybdenum ore or molybdenum ore
concentrate. Molybdenum may exist as molybdenum oxide,
molybdenum hydroxide, molybdenum salt, metallic molyb-
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denum, molybdenum carbonate, molybdenum sulphide, mo-
lybdenum sulphates or similar compounds and any mixtures
of them. Molybdenum source can be also originating as
an intermediate product from chemical industry or from
beneficiation process. The molybdenum-bearing raw mate-
rial can contain, for instance, calcinated molybdenum
bearing material.
The copper-bearing raw material is a solid com-
pound, typically copper ore or copper ore concentrate.
Copper may exist as copperoxide, coppersulphide, cop-
persulphate, metallic copper, copperhydroxide, copper-
salts or similar compounds or any mixtures of them.
The smelting vessel for the smelting feed can
be any kind of, where smelting and reducing energy orig-
mating from chemical and/or electrical energy. The
smelting vessel can for example be a furnace vessel of
an AC, DC, or induction electric furnace or gas heated
furnaces or oxidizable substance heated furnaces.
Preferably the smelting feed for production of
ferrochromium alloy with desired content of manganese,
nickel and molybdenum is as a form of agglomerates, more
preferably as sintered pellets and are preferably di-
rected to preheating prior to submerged arc furnace
smelting and reduced with carbon based reductant.
The smelting feed can be also reduced with re-
ducing gases but more preferably by carbon to gain de-
sired reduction degree of the smelting feed.
Energy for smelting can be provided by chemical
energy or/and by electrical energy; preferably in a sub-
merged electric arc furnace if smelting feed is as a
form of mechanically durable agglomerates. Preferably
the smelting can be conducted in an open/semiopen bath
method if the smelting feed is too fine to ensure proper
gas flow from the reaction zone.
The smelting feed in preceding process can be
pretreated prior to smelting such methods as grinding,
agglomeration, drying, calcinating, heat-treatment,
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prereduction, preheating, and similar to these processes
and any combination of these processes.
In another embodiment, smelting feed according
to the invention further comprises at least one fluxing
agent as defined herein. Preferable fluxing agents com-
prise silicon, aluminium, calcium and magnesium bearing
materials or any mixture thereof. Such flux materials
include e.g. quartz, bauxite, olivine, wollastonite,
lime, and dolomite. Mixture of the flux materials men-
tioned above may be used depending on the ratio of slag
forming components in the smelting feed without the
fluxes.
In the preferred embodiment, where major part of
the smelting feed is agglomerates or lumpy ore which
are reduced with carbon reductant. Submerged arc AC
furnace is utilized with preheating kiln. Typically
quartz is used as a primary fluxing agent. Also other
fluxes such as limestone, olivine, bauxite, or dolomite
may be added for adjusting the slag chemistry.
The smelting feed as an agglomerated feed or a
lumpy feed or a fine feed mix may also contain the
mixture of them. For example, the fine mix feed as a
smelting feed may also contain lumpy feed materials as
an additional feed material as desired fluxes, reduct-
ant, possible residuals or pyrometallurgical slags.
For the purpose of this description, the term
"carbonaceous material" stands for any compound serving
as a source of elemental carbon which can undergo oxi-
dation to carbon dioxide in metallurgical processes such
as smelting. Typical examples for carbonaceous material
are carbides, coke, char, coal, and anthracite and the
combination of thereof.
The novel ferrochromium alloy (with desired
content of manganese, nickel and molybdenum) production
technology described herein is based on using the iron,
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chromium, bearing feed mix as the smelting feed with
variable content of at least one of the following ele-
ments: manganese, nickel and molybdenum. The composition
of the feed mix is advantageous for smelting because due
5 to its manganese, nickel and molybdenum content. The use
of these feed materials reduces the smelting process
energy per tapped ferrochromium alloy, enhances energy
efficiency and enables high productivity. It has been
observed that the smelting feed containing manganese,
10 nickel or molybdenum reduces more easily in solid state
reduction, as the reducing gases, such as CO, reduce the
feed material more aggressively than in the case of
normal ferrochrome smelting. Another benefit is that
especially the combination of manganese and nickel in
15 the ferrochromium alloy lowers the alloy liquidus tem-
perature compared to traditional FeCr smelting. These
factors stated above together reduce the electrical en-
ergy consumption and enhance significantly the reaction
kinetics (better metal recovery) compared to the tradi-
tional FeCr smelting. Furthermore, if ferrochromium al-
loy smelting is integrated with stainless steel plant,
more key elements can be directed as a molten ferro-
chromium alloy to the stainless steel plant and the
energy as molten ferrochromium alloy is saved compared
to the conventional way, where mostly all of the key
elements are smelted from solid substances.
In an embodiment of the process, the feed mix
containing in percentages of mass:
= Mn 1.5 to 35 wt-%, preferably 2 to 25 wt-%,
more preferably 2 to 20 wt-%,
= Ni below 30 wt-%,
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%.
In an embodiment of the process, the feed mix con-
taining in percentages of mass:
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= Ni 1.0 to 30 wt-%, preferably 2 to 26 wt-%,
more preferably 2 to 24 wt-%, most pref-
erably 2 to 20 wt-%,
= Mn below 35 wt-%,
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%.
In an embodiment of the process, the feed mix
containing in percentages of mass:
= Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%,
more preferably 1 to 5 wt-%,
= Mn below 35 wt-%,
= Ni below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%.
In an embodiment of the process, the feed mix
containing in percentages of mass:
= Cu 0.5 to 30 wt-%, preferably 1 to 10 wt-%,
more preferably 1 to 5 wt-%,
= Mn below 35 wt-%,
= Ni below 30 wt-%,
= Mo below 30 wt-%, and
= Nb below 30 wt-%.
In an embodiment of the process, the feed mix
containing in percentages of mass:
= Nb 0.5 to 30 wt-%, preferably 1 to 10 wt-%,
more preferably 1 to 5 wt-%,
= Mn below 35 wt-%,
= Ni below 30 wt-%,
= Mo below 30 wt-%, and
= Cu below 30 wt-%.
In an embodiment of the process, the feed mix
containing in percentages of mass:
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= Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%,
more preferably 2 to 20 wt-%,
= Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%,
more preferably 1 to 24 wt-%, most pref-
erably 1 to 20 wt-%,
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%.
In an embodiment of the process, the feed mix
containing in percentages of mass:
= Mn 1.0 to 35 wt-%, preferably 2 to 25
wt-%, more preferably 2 to 20wt-%,
= Ni 1.0 to 30 wt-%, preferably 1 to 26
wt-%, more preferably 1 to 24 wt-%, most
preferably 1 to 20 wt-%,
= Mo 0.5 to 30 wt-%, preferably 1 to 10
wt-%, more preferably 1 to 5 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%.
In an embodiment of the process, the feed mix con-
taining in percentages of mass:
= Mn 1.5 to 35 wt-%, preferably 2 to 25 wt-%,
more preferably 2 to 20 wt-%,
= Ni below 30 wt-%,
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%,
= the balance being Fe, Cr and inevitable
impurities such as Ti, V. S, Mg, Ca, Si,
and Al.
In an embodiment of the process, the feed mix con-
taming in percentages of mass:
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= Ni 1.0 to 30 wt-%, preferably 2 to 26 wt-%,
more preferably 2 to 24 wt-%, most pref-
erably 2 to 20 wt-%,
= Mn below 35 wt-%,
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%,
= the balance being Fe, Cr and inevitable
impurities such as Ti, V. S, Mg, Ca, Si,
and Al.
In an embodiment of the process, the feed mix con-
taining in percentages of mass:
= Mo 0.5 to 30 wt-%, preferably 1 to 10 wt-%,
more preferably 1 to 5 wt-%,
= Mn below 35 wt-%,
= Ni below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%,
= the balance being Fe, Cr and inevitable
impurities such as Ti, V, S, Mg, Ca, Si,
and Al.
In an embodiment of the process, the feed mix con-
taming in percentages of mass:
= Cu 0.5 to 30 wt-%, preferably 1 to 10 wt-%,
more preferably 1 to 5 wt-%,
= Mn below 35 wt-%,
= Ni below 30 wt-%,
= Mo below 30 wt-%, and
= Nb below 30 wt-%,
= the balance being Fe, Cr and inevitable
impurities such as Ti, V, S, Mg, Ca, Si,
and Al.
In an embodiment of the process, the feed mix con-
taining in percentages of mass:
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= Nb 0.5 to 30 wt-%, preferably 1 to 10 wt-%,
more preferably 1 to 5 wt-%,
= Mn below 35 wt-%,
= Ni below 30 wt-%,
= Mo below 30 wt-%, and
= Cu below 30 wt-%,
= the balance being Fe, Cr and inevitable
impurities such as Ti, V. S, Mg, Ca, Si,
and Al.
In an embodiment of the process, the feed mix con-
taining in percentages of mass:
= Mn 1.0 to 35 wt-%, preferably 2 to 25 wt-%,
more preferably 2 to 20 wt-%,
= Ni 1.0 to 30 wt-%, preferably 1 to 26 wt-%,
more preferably 1 to 24 wt-%, most pref-
erably 1 to 20 wt-%,
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%,
= the balance being Fe, Cr and inevitable
impurities such as Ti, V, S, Mg, Ca, Si,
and Al.
In an embodiment of the process, the feed mix con-
taining in percentages of mass:
= Mn 1.0 to 35 wt-%, preferably 2 to 25
wt-%, more preferably 2 to 20 wt-%,
= Ni 1.0 to 30 wt-%, preferably 1 to 26
wt-%, more preferably 1 to 24 wt-%, most
preferably 1 to 20 wt-%,
= Mo 0.5 to 30 wt-%, preferably 1 to 10
wt-%, more preferably 1 to 5 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%,
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= the balance being Fe, Cr and inevitable
impurities such as Ti, V. S, Mg, Ca, Si,
and Al.
5 In an embodiment of the process, the feed mix containing
in percentages of mass:
= Mn 2 to 30 wt-%, preferably 5 to 30 wt-%,
more preferably 10 to 30 wt-%
= Ni 0.1 to 20 wt-%, preferably 0.1 to 15
10 wt-%, more preferably 0.1 to 11 wt-%,
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%.
One reason for using the selected manganese
15 content is that a high compressive strength is achieved
at a low heat-treatment temperature, which means that
the energy needed in the heat-treatment is low. Addi-
tionally, cheap manganese sources can be utilized in the
production of certain stainless steels. Manganese also
20 replaces expensive nickel in (austenic) stainless steel.
Both magnanese and nick-el in FeCr lowers the liquidus
point of the ferroal-loy. A high Manganese amount en-
hances reducibility of the heat treated agglomerates
One reasons for using the selected nickel content is
that every added nickel enhances the pro-cess chain. A
Higher amount of nickel is not needed, because manganese
bearing stainless steels are to replace nickel. However,
higher nickel amounts are suitable. Additionally low
cost nickel bearing material can be used to produce
metallic Ni into ferroalloy.
In an embodiment of the process, the feed mix con-
taining in percentages of mass:
= Mn 0.1 to 20 wt-%, preferably 0.1 to 15
wt-%, more preferably 0.1 to 10 wt-%,
= Ni 2 to 30 wt-%, preferably 1 to 20 wt-%,
more preferably 2 to 12 wt-%,
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= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%.
One reason for using the selected manganese
content is that in basic austenitic steels, the man-
ganese content has limits. Therefore, it is prefera-ble
to limit active addition of Manganase in FeCrNi(Mn) to
certain amount. However, every added manganese has ben-
efit in the process chain of pro-ducing ferroalloy. Add-
ing manganese minimizes the need of additional fluxes.
Together with nickel into ferrochromium alloy, manganese
decreases the liqui-dus of the metal.
One reasons for using the selected nickel content is
that nickel mixed and bound together with iron and chro-
mium bearing material is advantageous and enhances the
process, especially in the reducing stage. Additionally,
a vast amount of stainless steel contains nickel as a
base metal and every add-ed nickel amount is preferable
for the whole process chain.
In an embodiment of the process, the feed mix con-
taining in percentages of mass:
= Mn 2 to 30 wt-%, preferably 5 to 30 wt-%,
more preferably 10 to 30 wt-%,
= Ni 0.1 to 20 wt-%, preferably 0.1 to 15
wt-%, preferably 0.1 to 11 wt-%
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%,
= the balance being Fe, Cr and inevitable
impurities such as Ti, V. S, Mg, Ca, Si,
and Al.
One reason for using the selected manganese
content is that a high compressive strength is achieved
at a low heat-treatment temperature, which means that
the energy needed in the heat-treatment is low. Addi-
tionally, cheap manganese sources can be utilized in the
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production of certain stainless steels. Manganese also
replaces expensive nickel in (austenic) stainless steel.
Both magnanese and nick-el in FeCr lowers the liquidus
point of the ferroal-loy. A high Manganese amount en-
hances reducibility of the heat treated agglomerates
One reasons for using the selected nickel content is
that every added nickel enhances the pro-cess chain. A
Higher amount of nickel is not needed, because manganese
bearing stainless steels are to replace nickel. However,
higher nickel amounts are suitable. Additionally low
cost nickel bearing mate-rial can be used to produce
metallic Ni into ferroalloy.
In an embodiment of the process, the feed mix con-
taming in percentages of mass:
= Mn 0.1 to 20 wt-%, preferably 0.1 to 15
wt-%, more preferably 0.1 to 10 wt-%,
= Ni 1 to 30 wt-%, preferably 1 to 20 wt-%,
more preferably 2 to 12 wt-%
= Mo below 30 wt-%,
= Cu below 30 wt-%, and
= Nb below 30 wt-%,
= the balance being Fe, Cr and inevitable
impurities such as Ti, V. S, Mg, Ca, Si,
and Al.
One reason for using the selected manganese
content is that in basic austenitic steels, the man-
ganese content has limits. Therefore, it is prefera-ble
to limit active addition of Manganase in FeCrNi(Mn) to
certain amount. However, every added manganese has ben-
efit in the process chain of producing ferroalloy. Add-
ing manganese minimizes the need of additional fluxes.
Together with nickel into ferrochromium alloy, manganese
decreases the liquidus of the metal.
One reasons for using the selected nickel con-
tent is that nickel mixed and bound together with iron
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and chromium bearing material is advantageous and en-
hances the process, especially in the reducing stage.
Additionally, a vast amount of stainless steel contains
nickel as a base metal and every add-ed nickel amount
is preferable for the whole process chain.
In the process, it is possible that the chro-
mium bearing raw material is not 100 % chromium, that
the iron bearing raw material is not 100 % iron, that
the optional manganese bearing raw material is not 100
% manganese, that the optional nickel bearing raw mate-
rial is not 100 % nickel, that the optional molybdenum
bearing raw material is not 100 % molybdenum, the op-
tional copper bearing raw material is not 100 % copper,
and that the optional niobium bearing raw material is
not 100 % niobium, which means that any one of said raw
materials can contain other elements and in some cases
these elements can be stated to be impurities leading
to that the agglomeration feed will consequently contain
additionally other elements as impurities, i.e. compo-
nents which are not actively added to the agglomeration
feed. These other elements as impurities in some cases
can varied in the composition from couple of part of
million to several percentages of the added material.
For example chromium bearing material can also contain
some manganese within concluding that the materials can
contain simultaneously several elements both as desired
and as impurities.
REFERENCE 1
As a reference, a process balance model was
constructed, simulating the typical ferrochrome smelt-
ing process with a 100 000 tpa FeCr alloy production.
In the balance pellets are used as the main feed mate-
rial. The sintered pellets comprises of chromite con-
centrate (no manganese or nickel addition).
23.0 t/h sintered pellets are fed together with
6.6 t/h of metallurgical coke and 3.8 t/h quartz to a
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preheating kiln. From the preheater a furnace feed mix
at 600 C is fed to the closed and sealed submerged arc
AC furnace equipped with three electrodes. Furnace ac-
tive power is 35.8 MW (heat loss assumed at 8 %).
As a product 11.4 t/h of FeCr at 1580 C is
obtained together with 11.2. t/h of slag at 1700 C. The
resulted specific energy consumption is 3135 kWh/t of
tapped alloy. Alloy composition is 38.7 wt-% Fe, 49.6
wt-% Cr, 7.2 wt-% C, 4.5 wt-% Si.
EXAMPLE 1
A process balance model was constructed, sim-
ulating the novel process with a 100 000 tpa FeCrMn
alloy production. In the balance pellets are used as the
main feed material. The sintered pellets comprises 70
wt-% of chromite concentrate and 30 wt-% of manganese
ore (carbonate based ore). This addition results in a
sintered pellet with 16.0 wt-% of manganese content.
20.4 t/h sintered pellets are fed together with
5.8 t/h of metallurgical coke and 1.9 t/h quartz to a
preheating kiln. From the preheater a furnace feed mix
at 600 C is fed to the closed and sealed submerged arc
AC furnace equipped with three electrodes. Furnace ac-
tive power is 30.0 MW (heat loss assumed at 8 %).
As a product 11.4 t/h of FeCrMn at 1568 C is
obtained together with 7.1 t/h of slag at 1688 C. The
resulted specific energy consumption is 2628 kWh/t of
tapped alloy. Alloy composition is 31.4 wt-% Fe, 33.2
wt-% Cr, 26.3 wt-% Mn, 6 to 9wt-% C, because the amount
of carbon can fluctuate in the process, and 3.0 wt-% Si.
EXAMPLE 2
A process balance model was constructed, sim-
ulating the novel process with a 100 000 tpa FeCrMnNi
alloy production. In the balance pellets are used as the
main feed material. The sintered pellets comprises 40
wt-% of chromite concentrate, 31 wt-% of manganese ore
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(carbonate based ore) and 29 wt-% of nickel hydroxide.
This addition results in a sintered pellet with 17.5 wt-
% manganese content and 16.1 wt-% nickel content.
18.1 t/h sintered pellets are fed together with
5 5.3 t/h of metallurgical coke and 1.7 t/h quartz to a
preheating kiln. From the preheater a furnace feed mix
at 600 C is fed to the closed and sealed submerged arc
AC furnace equipped with three electrodes. Furnace ac-
tive power is 24.6 MW (heat loss assumed at 8 %).
10 As a product 11.4 t/h of FeCrMnNi at 1447 C is
obtained together with 5.1 t/h of slag at 1567 C. The
resulted specific energy consumption is 2155 kWh/t of
tapped alloy. Alloy composition is 20.9 wt-% Fe, 19.5
wt-% Cr, 25.5 wt-% Mn, 25.1 wt-% Ni, 5 to 8 wt-% C,
15 because the amount of carbon can fluctuate in the pro-
cess, and 3.0 wt-% Si.
Conclusions
20 In table 2 the furnace sizes and energy consumptions for
the examples are presented. In all of the cases the same
100 000 tpa alloy production (100 % availability) is
assumed, making them comparable to one another.
25 Table 5. Furnace power and energy consumption.
Example Alloy type Furnace size
Specific energy
consumption
No. - MW kWh/t alloy
1 (reference) FeCr 35.8 3135
2 FeCrMn25 30.0 2628
3 FeCrMn25Ni25 24.6 2155
As it can be seen the best scenario is clearly the
production of the FeCrMnNi alloy as the energy consump-
tion / t of alloy is reduced by about 30 % to the
traditional FeCr alloy production. Energy is typically
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the one of the major OPEX component in smelting furnace
operation.
Another significant difference of the novel methods com-
pared to the traditional methods is the lower slag/metal
ratio in the novel processes. However, if needed it can
be increased based on the process requirements and it
is depended on gangue minerals of the smelting feed
materials.
Another major benefit of the novel process is that the
manganese, nickel and molybdenum sources are signifi-
cantly cheaper to the sources used in the stainless
steel alloying step. In the novel process manganese,
nickel and molybdenum are already included cost effec-
tively in the alloy going into the stainless steel man-
ufacturing process. Furthermore, if ferrochromium alloy
smelting is integrated with stainless steel plant, at
least part of the ferrochromium alloy production can be
directed to the stainless steel plant as a molten phase,
which is even more cost-effective.
