Yin R. Metallurgical Process Engineering
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8 Metallurgical Process Engineering
In sum, from a global point
of
view, the steel industry is not a "setting-sun in-
dustry," and expanding the steel industry constitutes a most important fundamen-
tal and economic growth point for China, India and other developing nations.
Steel consumption will continue to increase in the world (and especially China) in
order to bolster the rising national economies and social civilizations. To put it in
a nutshelI, steel is stilI the "material
of
choice," and we wilI stilI be faced with the
serious issue
of
developing the steel industry in a scientific and sound manner.
1.3 The Rise of the Chinese Steel Industry
A review
of
the development
of
the Chinese steel industry shows that the indus-
try has traversed a winding path marked by advances, fluctuations, and a rapid
rise. Its course
of
development has been arduous but rich and rewarding (Fig.
1.9).
1986
~
1996:1Oyears
1949
~
1986:37years
o
1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Year
Fig. 1.9 Crude steel output over the years in China
450
.--
- - - - - - - - - - - - - - - - - - -----'----..
400
350
~
300
S
0.
250
'5
o
] 200
~
]50
-g
U 100
50~~~;2:::c:
~
~
The rapid development
of
the Chinese steel industry has been
of
global impor-
tance, especialIy since the 1990s. China's crude steel output was 65 milIion tons
in 1990. By 2006, it had risen to 423 million tons and accounted for about 34%
of
the world's steel output. Per capita output in that year stood at 322 kg/person in
China. China has been the world's top steel producer in the
11
years since 1996
(Fig.1.10). Its steel output increased by 540% from 1990 to 2006.
Due to a series
of
technological advances and effective investments in China's
steel plants since the 1990s, the structure
of
China's steel plants has been adjusted
and optimized and the distribution
of
Chinese steel enterprises has been further
expanded and regulated.
In the process
of
revamping and development, a large number
of
steel plants
have undergone economic optimization in terms
of
scale. In 1990, only 14 steel
plants had an annual output
of
over 1 million tons. In 2002, the number had in-
Chapter I Steel- the "Material
of
Choice" 9
423
352
283
222
182
152
150
109 115 123 128
'::
nnnnnn'0'
OLL-LL-'----'--'--'----'--'--'--JL.L.J--'-.LLLL.-L...L-'--'----'--'--'----'--'--'----'--'---'--JL.L.L--'--LL-.L.L.JL..L-'--'----LL.L.....L-L.L--'-J
1990 199119921993 1994 199519961997 1998199
92
0002001200
22
003200420052006
"il
200
to
"
-g
u
creased to 53, and by 2006, to 67 (Fig. 1.11).
450
,-----
- - - - - - - - - - - - - - - - - - - - - - - -
----,-,
'"
400
350
~
300
B- 250
"
o
Year
Fig. 1.10 Increases inChina'ssteeloutputsince 1990
67
63 64
59
53
47
33 33 36
nnnnnn
24 27
10
o
1990 1991 1992 1993199419951996199719981999 2000 20012002 200320042005 2006
Year
Fig
.l.lI
Increases inthenumberof Chinesesteelplants with
annual
outputs of
over I milliontonssincethe
1990s
80
70
'"
§ 60
~
50
"
*40
'-
o
i; 30
.D
§ 20
Z
Meanwh ile, the distribution
of
Chi
na's
stee l plants has been correspon
ding
ly
ex
pan
ded and optimized.
The
reg ional distribu
tion
of
stee
l p
roduc
tion
in China is
shown in Table 1.2 and Fig. 1.12. On the whole, the majority of Chi
na's
steel
plants are concentrated along the eastern seaboard and the middle and lower
reac
hes
of
the Yangtze River.
Table 1.2 Changes in regional steel production from 1950 to 2006 in mainland China
~
1950 1970 1980 1990 2000 2002 2004 2006
Region
North China
12.7 20.0 2\.5 22.7 25.8 28.9 33.1 33.4
Northeast China 82.8 37.3 26.4 20.9 14.2 12.7 I\.8
I\.
I
East China 2.0 23.7 24.8 27.6 3\.9 3\.4 30.3 28.7
Central- south China 0.9 13.6 15.1 16.6 15.8 16.3 15.3 17.4
Southwest China \.6 4.5 10.3 9.4 8.9 7.8 6.6 6.0
Northwest China 0.0 0.9 \.9 2.8 3.4 2.9 2.9 3.4
10 Metallurgical
Proce
ss
Engineering
116
38
50
21
13
EastSouthwest Central -southNortheastNorthern
140
120
100
~
80
%
0
v
60
"to
"
."
:::l
40
U
20
11
0
Northwest
China
Fig. 1.12 Regional distribution
of
crude steel output
of
mainland China in 2005
The technical and economic indexes
of
the Chinese steel industry have risen
dramatically. China's overall yield
of
finished steel products averaged 95.65% in
2006, 12% higher than in 1990. Comparable energy consumption per ton steel in
the same period dropped from 1.611 tee (tons
of
coal equivalents) to 0.741 tee".
In 2006, the average utilization coefficient
of
blast furnaces at key large and me-
dium steel enterprises reached 2.675 t/(m". d), the average coke ratio fell to 390
kg/t, the average PCI rate rose to 135 kg/t, and the average campaign
of
convert-
ers stood at 6052 heats and even exceeded 10,000 heats on many converters. Also
in 2006, the continuous casting ratio in the Chinese steel industry reached 98.57%,
a significant increase over the 25.07% attained in 1990, and a large number
of
fully continuous casting steel plants had emerged. Outdated technologies and
equipment were also discarded in large numbers. Due to these remarkable struc-
tural improvements, many steel plants have become economically effective in
scale, reduced their production costs, and increased their profits.
The product structure has changed as well, and the output
of
flat products, in
particular, has risen rapidly.
The main reasons for the rapid rise
of
the Chinese steel industry since 1990
(Yin, 2004) are as follows:
• Increased market traction on the demand for steel products in the course
of
national economic development;
• Correct judgments and choices and the orderly implementation
of
techno-
logical progress strategies (i.e. the development, popularization and integration
of
6 key/common technologies and the optimization
of
production processes);
o ce: coal equivalent; 1kgce=29308 kJ.
Chapter 1 Steel
-t
he "Material
of
Choice" 11
• The promotional effect
of
extensive utilization
of
world mineral resources
and scrap iron;
• The domestication
of
substantial amounts
of
advanced technology and
equipment and reductions in unit production capacity investment; and
• Coordinated techno-economic efficacy brought about by the orderly integra-
tion
of
effective investments and technological progress strategies.
1.3.1 The traction
of
market demand
The background to the rapid development
of
the Chinese steel industry since the
1990s is the continuous and rapid development
of
the national economy. China's
GOP, which was 1854.79 billion yuan(RMB) in 1990, rose to 20940.7 billion
yuan(RMB) in 2006. Meanwhile, changes have taken place in China's industrial
structure. The proportion
of
secondary industries in the national economy has
increased sharply and that
of
the primary industries has registered a significant
decrease. That such factors as the growth
of
China's GOP and constant increases
of
total investment since the 1990s have strongly promoted the demand for steel
products is shown in Fig. 1.13. China's GOP in the years 1990 to 2006 and the
contributions
of
the primary, secondary and tertiary industries to the total GOP are
shown in Table 1.3.
Table 1.3 China's GDP in recent years and contributions to the GDP by
the primary, secondary and tertiary industries
Contribution Contribution of
Contribution of
Total GOP by primary
Percent
secondary
Percent tertiary industries Percent
Year Ibillion industries industries
yuan(RMB )
Ibillion
1%
Ibillion
1% Ibillion yuan 1%
yuan(RMB ) yuan(RMB)
(RMB )
1990 1854.79 501.70 27. 1 77 1.74 41.6 581.35 31.3
1999 8205.40 1421.20 17.3 4080.60 49.7 2703.60 33.0
2000 8940.40 1455.30 16.4 4472.30 50.6 2914 .50 33.0
2001 9593.30 1461.00 15.2 4906 .90 51.2 3225.40 33.6
2002 10239.80 1488.30 14.5 5298.20 51.8 3453.3 0 33.7
2003 11669.40 1724.70 14.8 6177.80 52.9 3766.90 32.3
2004 13651 .50 2074.40 15.2 7238.70 53.0 4338.40 31.8
2005 18232.10 227 1.80 12.4 8620.80 47.3 7339.50 40.3
2006 20940.70 2470.00 11.8 10200.40 48.7 8270.30 39.5
2007 24661.90 2891.00 11.7 12138.10 49.2 9632.80 39.1
Year
--GDP
---
Investment
~
Apparent consumption of steel products
12 Metallurgical Process Engineering
_ 25
,---
- - - - - - - - - - - - - - - - - - - - - - - - - -
---,
00:2
oo~~
::§
~
"'
20
~('ju
§
~.g
=>
t:
2
~~:=
15
~EM
:Eo~
s
~
~
10
0-0
~
5 'a
is
~
§
o
~
~
5
c 0
- u
"
~
olj:~~~~~~~~~~~~~~~:;;~::~
=
'_;;_;;c
='::
~
c'=
~=
j
5:
1990 1991 1992 1993 19941995 1996 1997 1998 1999 2000 2001 2002 20032004 2005 2006
<t:
Fig. 1.13 Impact
of
investment increase on China's apparent consumption
of
steel products
China's apparent consumption
of
steel products rose from 53.12 million tons in
1990 to 386 million tons in 2006.
1.3.2 Correct judgments and choices and the orderly implemen-
tation
of
technologicalprogress strategies
To clarify the line
of
thinking for the steel industry's technical advances, it was
imperative to start by analyzing the "technical bottlenecks" that structurally af-
fected the entire production process in order to define these bottlenecks and their
order
of
importance. Since the I990s, the Chinese steel industry has made break-
throughs in 6 key/common technologies (this will be discussed in 1.4). These
were, in chronological order: the continuous casting technology, the PCI technol-
ogy, the technology for the elongation
of
BF campaigns, the technology
of
con-
tinuous rolling
of
long products, the comprehensive energy saving technology
with production process adjustments, and the slag splashing technology for BOFs.
When discussing the technological progress strategy for the Chinese steel in-
dustry in the 1990s, mention must also be made
of
the significant progress in the
UHP EAF techniques and production processes at modern EAF steelmaking
plants. Beginning in the mid-1990s, China has set up 36 UHP EAFs and phased
out about 1,400 small electric furnaces . China's UHP EAFs are currently used to
make both flat and long products and have registered substantial technological
progress.
While China is rapidly increasing its manufacturing
of
steel products, the rela-
tive shortage
of
steel scrap and the high price
of
electricity have had a restricting
effect on the rapid development
of
electric steel. However, total EAF steel output
is still increasing although the ratio
of
electric steel is decreasing (Table 1.4).
Chapter 1 Steel- the "Material of Choice" 13
Table 1.4 Total output and ratio
of
EAF steel in China since 1990
Year 1990 1991 1992 1993 1994 1995 1996 1997 1998
Total steel
output/Mt 65.4 71.0 80.9 89.5 92.6 95.4
10l.2
108.9 114.6
Electric steel outputiMt 14.0 15.0 17.6 20.3 19.7 18.1 18.9 19.1 18.1
Proportion of electric
21.5 21.1 21.9 23.2 21.2 19.0 18.7 17.6 15.8
steell%
Year 1999 2000 200 1 2002 2003 2004 2005 2006 2007
Total steel output/Mt 124.0 128.5 151.6 182.3 222.3 282.8 352.4 422.7 494.9
Electric steel outputiMt 19.5 20.2 24.0 30.5 39.1 42.9 41.8 44.2 58.4
Proportion of electric
15.7 15.7 15.9 16.7 17.6 15.2 11.9 10.5 11.8
steell%
1.3.3 The promotional effect
of
using international mineral re-
sources and scrap
Since China began to implement its policy
of
opening up to the outside world, the
Chinese steel industry has been making active use
of
mineral and steel scrap re-
sources from other countries. Table 1.5 lists China's output and imports of iron,
manganese and chromium ores in the years 1990 to 2006, and Table 1.6 lists
China's import volume of steel scrap from 1991 to 2006.
Table 1.5 China's outputs and imports
of
iron, manganese and chromium
ores from 1990 to 2006
Output (Raw ores) Import volume (Rich ores)
Year
Iron ores Manganese ores Chromium ores Iron ores Manganese ores Chromium ores
IMt IMt IMt IMt IMt IMt
1990 179.3 4.1 0.10 14.2
-
0.5
1991 190.6 4.2 0.02 19.0
-
1.1
1992 209.8 5.3 0.10 25.2
-
7.4
1993 226.4 5.9 0.05 33.0
-
0.0
1994 250.7 5.8 0.06 37.3 1.0 0.7
1995 261.9 6.9 0.20 41.2
1.3
1.4
1996 252.3 7.7 0.13 43.9 1.6 0.8
1997 268.6 6.0 0.20 55.1
1.3
0.9
1998 246.9 5.3 0.02 51.8 1.2 0.7
1999 237.2 3.2
-
55.3 1.1 0.8
2000 222.6 2.6
-
70.0 1.2 1.1
2001 217.0 2.3
-
92.3 1.7 1.1
2002 231.4 2.5
-
111.5 2.1 1.1
14 Metallurgical Process Engineering
Continued Table 1.5
Output (Raw orcs) Import volume (Rich orcs)
Year
Iron ores Manganese ores Chromium ores Iron ores Manganese ores Chromium ores
IMt IMt IMt IMt IMt IMt
2003 26 1.5 2.9 0.02 148.2 2.9 1.8
2004 310.1 8.5
-
208.1 4.6 2.2
2005 426.2 10.0
-
275.3 4.6 3.0
2006 588.2 12.0
-
326.3 6.2 4.3
Table 1.6 China's scrap imports from 1991 to 2006 (Unit: Mt)
Year 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 200 1 2002 2003 2004 2005 2006 2007
Im-
0.1 1.5 3.2 2.1 1.4
1.3
1.2 2.0 3.3 5.1 9.8 7.8 9.2 10.2 10.1 5.4 3.4
port
1.3.4 Domestication
of
advanced technology and equipment
From the perspective
of
China's total investment in, and its effect on, the Chinese
steel industry in the 1990s, the domestication of advanced technologies and
equipment from abroad has done much to promote reductions in investment for
unit production capacity. In the 1990s, total investment in China on steel plants
was 400.6 billion RMB, overall steel production capacity increased by 82 million
tons per year, and investment on unit steel production capacity amounted to ap-
proximately 4,800 RMB, or about 55% of the average world level (Yin, 2004).
There are, of course, different ratios of flat and long products in China and abroad,
but an important factor that cannot be ignored is that domestication has decreased
unit investment and improved investment returns.
1.3.5 The coordinating effect
of
effective investments and a tech-
nological progress strategy
In the 1990s, investment in the 6 key/common technologies mentioned earlier
amounted to 140 billion RMB, or 35% of the total investment in the steel industry
in that period (Yin, 2004). Timely and well-ordered investments gave impetus to
measures for technological progress that promoted the rapid maturing, populariza-
tion, and application of key/common technologies and produced excellent techno-
logical and economic results. A large number of steel plants optimized their pro-
duction and product structures and improved the quality of their products. China's
practice in adjusting its steel industrial structure has proved that the orderly com-
bination of timely and effective investments with a strategy for technological pro-
gress is able to produce a coordinating technological/economic effect. This is an-
other key factor for developing comprehensive competitive strengths in the steel
Chapter 1 Steel
-the
"Material of Choice" 15
market.
1.4 Technological Progress
of
the Chinese Steel Industry
There have been six important key/common technologies for the development
of
the Chinese steel industry since the 1990s.
1.4.1 Continuous casting technology
Starting in 1988, China has adopted the policy
of
"centering on continuous
casting" and used this to guide the technical reform of, and investment in, the
steel industry. Since the 1990s, the development
of
continuous casting has
received much more attention and has been constantly promoted and im-
proved by means
of
technological optimizations, equipment improvements,
and domestication.
Continuous casting technology in the Chinese steel industry has gone through 3
stages:
• The stage
of
"taking continuous casting as the center, steelmaking as the
foundation, and equipment as a guarantee," during which the design parameters
of
continuous casters was optimized, problems in production organization were re-
solved, the design capacity of the casters was attained, and full play was given to
the production functions
of
the casters.
• The stage
of
"optimization
of
the three-in-one integration
of
steelmaking,
secondary refining, and continuous casting", during which steel plant produc-
tion operations by means
of
complete continuous casting was realized and in-
got-casting was discarded, which in turn triggered the elimination
of
open
hearth.
• The stage
of
"making further leaps forward in terms
of
coordination and op-
timization by means
of
developing high-efficiency, high-speed continuous casting
technology, and near-net shaped continuous casting technology", during which
optimal matches were effected between steelmaking furnaces and continuous
casters and between casters and rolling mills, and the manufacturing process and
product structures
of
China's steel plants were optimized.
As a result
of
more than 10 years' efforts, the continuous casting ratio
of
the
Chinese steel industry rose from 25.07% in 1990 to 98.57% in 2006.
Advances in the continuous casting technology have given impetus to the de-
velopment
of
secondary refining technology (Fig. 1.14). This was required not
only for quality and variety, but also for the logistic management and "buffer"
function
of
multi-furnace continuous casting.
Today, the argon bubbling and wire-feeding technology are advancing basically
in synch with continuous casting.
16 Metallurgical Process Engineering
100
,---
- - - - - - - - - - - - - -
-----,
80
;oR
60
~
"
~
~
40
' Single argon bubbling excluded
Secondary refining
*
o
';-;
1
9
!'
90
'?':
1
c::'99""'
1":-
1
9
"'
9:::;-
2';-;
1
9
:::;-
9
3~
1
""99
;:-;
4~
1
9
"'
9c:'
5
';-;
1
9"'"
9
6o':
l""
99
;O:
7
f:-
1
9"'
9"'"
8':-:
1
999~
2
"'
OOO~
2
O-;:
O:c!
0
I
Year
Fig. 1.14 Increases in the ratios
of
continuous casting, argon bubbling & wire feeding, and
secondary refining in the Chinese steel industry
Domestic high-efficiency and high-speed continuous casting technology and
equipment have been developing rapidly in China since 1996. The independent
development
of
such technology has brought about a general increase
of
50% to
80% both in casting speed and annual single-strand output, advanced the develo-
pment
of
hot charge technology, and promoted productivity and energy savings at
rolling mills.
China's thin slab casting/rolling technology has been developing swiftly since
1998. By the end
of
year 2006, 12 production lines were already in operation, i.e.
at Zhujiang Steel, Handan Steel, Baotou Steel, Anshan Steel, Tangshan Steel,
Ma'anshan Steel and Lianyuan Steel respectively (Yin, 2008). China's output
from thin slab casting and rolling lines will, in the near future, constitute a large
proportion
of
the world's output from such lines.
The rapid development
of
the continuous casting technology has generated the
following technological and economic benefits:
• The overall yield
of
steel products has risen by about 12%
(of
course, the
contribution by continuous rolling technology is included).
• The productivity
of
converters has been significantly raised with increased
utilization coefficient. Particularly, the utilization coefficient
of
small and medium
converters increased from 22.60 t/(t'd) in 1990 to 34.20 t/(t'd) in 2006.
• Blooming mills and breaking down mills were quickly eliminated. At the
same time, a large number
of
open-train bar and wire mills lost their competitive-
ness and were replaced by continuous rolling mills.
• The process has been adjusted with hot charging with energy saving.
• Since 1996, when China's continuous casting ratio exceeded 50% and a large
number
of
complete continuous casting steel plants appeared, the open
hearth-
ingot-casting technology has been quickly eliminated and by the end
of
2002,
open hearths were abandoned completely (Table 1.7).
Chapter I Steel- the "Material
of
Choice" 17
Table 1.7 Effects
of
increasing continuous casting ratios
on the use
of
China's open hearths
OH steel BOF steel EAF steel
Total
Continuous
output
of
Proportion Proportion Proportion
Year
crude
casting
Output in crude Output in crude Output in crude
steel
ratio/%
IMt
steel out-
IMt steel out- IMt
steel out-
put/% put/%
putl%
1990 6535.0 25.1 13.2 20. 1 39.1 59.8 14.0 21.4
1991 7100.0 27.7 13.1 18.4 42.8 60.3 15.0 21.1
1992 8093.0 31.8 14.0 17.3 49.2 60.7 17.6 21.8
1993 8954.0 36.1 14.4 16.1 54.2 60.6 20.8 23.2
1994 9261.0 41.8 13.8 15.0 58.9 63.4 19.7 21.2
1995 9536.0 49.4 13.1 13.7 63.6 66.7 18.1 19.0
1996 10124.0 55.9 12.6 12.6 69.8 68.6 18.9 18.7
1997 10891.0 63.8 9.7 8.9 79.8 73.3 19.1 17.6
1998 11459.0 71.1 5.4 4.7 90.8 79.2 18.1 15.8
1999 12395.0 78.6 1.8 1.5 102.5 82.7 19.5 15.7
2000 12850.0 84.8 1.1 0.8 105.8 82.4 21.6 16.8
2001 15163.0 89.7 0.8 0.3 126.0 83.1 24.0 15.8
2002 18225.0 93.0 0.0 0.0 153.6 85.0 28.0 15.0
1.4.2
pel
technology
Since the 1990s, China has taken further steps to independently develop PCI by
devising numerous new technologies and investing in corresponding technologi-
cal renovations, with the result that PCI technology has made rapid advances and
found extensive application. The average PCI for hot metal at major steel plants
rose significantly from 50 kg/t in 1990 to 125 kg/t in 2002.
It
was 135 kg/t in
2006. At the same time, the average coke ratio for blast furnaces
(SF) in China
dropped from 557 kg/t in 1990 to 396 kg/t in 2006.
1.4.3 Technology
for
the elongation
of
BF
campaigns
Multiple technological measures were implemented at the beginning
of
the 1990s
to resolve the bottleneck caused by short
SF campaigns, and in consequence the
SF campaign at most Chinese steel plants now exceeds 8 years (it is 8 to 10 years
at 24 blast furnaces, and the record campaign is 15 years). Significant results have
been achieved in China by the systematic development and integrated application
of the
SF campaign elongation technology, which has promoted the efficiency of