Note: Descriptions are shown in the official language in which they were submitted.
CA 02748641 2012-10-26
STEEL AND COUPLER MADE FROM THE SAME
FIELD OF THE TECHNOLOGY
[0001] The present invention relates to metallurgical technology, in
particular to a type of
steel with higher property and to a coupler made from the same.
BACKGROUND
[0002] Along with the development of industry, the requirement to the
mechanical
property of steel material becomes higher and higher. For example, during the
development
of "speed-rising and heavy-haul" of railway wagon, total traction weight of
railway wagon
has been increased greatly and therefore the requirement to the quality of
components on
wagon also becomes higher and higher; as a connection part between wagons, the
coupler
bears large tensile stress and impact force in a running railway wagon; the
coupler knuckle of
the coupler is a weak link of a railway wagon and easy to be fractured in a
running railway
wagon. The fracture of the coupler knuckle in a running railway wagon is
generally fatigue
fracture, for which the reasons include poor toughness, insufficient strength
etc. of the
materials for coupler knuckle.
[0003] Therefore, the strength and toughness of steel should be improved to
meet the
constantly increasing industry equipment, such as prolonging the fatigue life
of a wagon
coupler.
SUMMARY
[0004] The present invention aims at providing a type of steel and a coupler
made from the
same, so as to improve mechanical property of steel, in particular the
strength and toughness
thereof, and to therefore provide a coupler with excellent mechanical
property.
[0005] In order to achieve the above purposes, the present invention provides
a steel,
comprising the following elements in percentages by weight: carbon: 0.24-
0.32%, silicon:
0.20-0.50%, manganese: 1.30-1.70%, phosphorus: less than or equal to 0.02%,
sulphur: less
than or equal to 0.02%, copper: 0.01-0.30%, chromium: 0.50-0.80%, nickel: 0.40-
0.70%,
1
CA 02748641 2014-01-28
molybdenum: 0.25-0.45%, aluminium: 0.02-0.08%, and the remainders are iron and
other
inevitable elements.
[0006] Wherein, the percentage of carbon by weight is preferably 0.25-0.29%,
and more
preferably 0.25-0.28%.
[0007] The percentage of manganese by weight is preferably 1.35-1.60%, and
more
preferably 1.35-1.55%.
[0008] The percentage of phosphorus by weight is preferably: less than or
equal to 0.015%.
[0009] The percentage of sulphur by weight is preferably: less than or equal
to 0.015%.
[0010] The percentage of aluminium by weight is preferably 0.02-0.06%, and
more
preferably 0.02-0.05%.
[0011] In order to achieve the above purpose, the present invention further
provides a
coupler made of the steel provided by the present invention.
[0011a] According to another aspect of the present invention, there is
provided a steel,
comprising the following elements in percentages by weight: carbon: 0.26-
0.32%, silicon:
0.35-0.50%, manganese: 1.46-1.70%, phosphorus: less than or equal to 0.02%,
sulphur: less
than or equal to 0.02%, copper: less than or equal to 0.30%, chromium: 0.50-
0.63%, nickel:
0.48-0.70%, molybdenum: 0.25-0.34%, aluminium: 0.02-0.06%, and the remainders
are iron
and other inevitable elements.
[0011b] According to another aspect of the present invention, there is
provided a steel,
comprising the following elements in percentages by weight: carbon: 0.26-
0.29%, silicon:
0.35-0.41%, manganese: 1.46-1.55%, phosphorus: less than or equal to 0.014%,
sulphur: less
than or equal to 0.013%, copper: 0.01-0.10%, chromium: 0.57-0.63%, nickel:
0.40-0.55%,
molybdenum: 0.28-0.34%, aluminium: 0.03-0.06%, and the remainders are iron and
other
inevitable elements, wherein the yield strength of the steel is at least equal
to 760 Mpa, and
wherein the tensile strength of the steel is at least equal to 910 Mpa.
2
CA 02748641 2014-01-28
[0012] The steel and the coupler made from the same are advantaged in high
strength and
excellent toughness and therefore the mechanical property thereof is better
than the standard or
conventional grade E steel.
DETAILED DESCRIPTION
[0013] The technical solution of the present invention is further described in
detail in
connection with embodiments.
[0014] The present invention provides a steel, comprising the following
compositions in
percentages by weight: carbon: 0.24-0.32%, silicon: 0.20-0.50%, manganese:
1.30-1.70%,
phosphorus: less than or equal to 0.02%, sulphur: less than or equal to 0.02%,
copper: less than
or equal to 0.30%, chromium: 0.50-0.80%, nickel: 0.40-0.70%, molybdenum: 0.25-
0.45%,
aluminium: 0.02-0.08%, and the remainders are iron and other inevitable
elements.
[0015] Wherein, the percentage of carbon by weight is preferably 0.25-0.29%,
and more
preferably 0.25-0.28%; the percentage of manganese by weight is preferably
1.35-1.60% and
2a
CA 02748641 2011-06-23
more preferably 1.35-1.55%; the percentage of phosphorus by weight is
preferably: less than
or equal to0.015%; the percentage of sulphur by weight is preferably: less
than or equal
to0.015%; and the percentage of aluminium by weight is preferably 0.02-0.06%,
and more
preferably 0.02-0.05%.
[0016] The percentage of silicon by weight is preferably 0.20-0.40%, and more
preferably
0.21-0.39%; the percentage of chromium by weight is preferably 0.50-0.65%, and
more preferably
0.50-0.60%; the percentage of nickel by weight is preferably 0.40-0.60%, and
more preferably
0.40-0.55%; and the percentage of molybdenum by weight is preferably 0.25-
0.35%, and more
preferably 0.25-0.30%.
[0017] The chemical compositions of steel substantially decide the mechanical
property thereof; by
improving the purity of molten steel and reducing the content of gas and
harmful elements therein,
the metallurgical process can create a good condition for the subsequent
processing of the steel
material; the heat treatment process after smelting process can achieve best
potential of the
mechanical property of the steel material. Therefore, chemical compositions
play an important role
in improving the mechanical property of steel. Among all compositions, carbon
and manganese are
major elements to improve the strength of material; the toughness of material
can be improved by
reducing the content of harmful elements P and S and properly increasing the
content of nickel; the
hardenability of material can be improved by properly increasing the content
of manganese,
chromium and molybdenum; meanwhile, the increasing of the content of
molybdenum can
effectively restrict the temper brittleness of material; the content of
aluminium can be controlled to
refine grains in subsequent heat treatment.
[0018] The present invention further provides a coupler made of the steel
provided by the present
invention. The couple has excellent mechanical property such as high strength
and good toughness
and can bear larger tensile stress and impact force. The wagon coupler can be
applied to multiple
applications, for example, to the railway wagon or railway carriage.
EMBODIMENTS
[0020] The chemical compositions of the steel of the embodiments 1-Ito 1-10
provided by the
3
CA 02748641 2011-06-23
present invention are shown in Table 1; the mechanical properties of the steel
of embodiments 1-1 to
1-10 are shown in Table 2. Wherein the heat treatment process of embodiments 1-
1 to 1-10 is the
conventional heat treatment process, namely thermal refining (including
quenching and tempering
processes), in which the quenching temperature is 910 DEG C, the temperature
holding time is 2
hours, and the cooling method is water quenching; and the tempering
temperature is 560 DEG C, the
temperature holding time is 3.5 hours, and the cooling method is wind cooling.
Table 1
Embodiments C% Si% Mn% P% S% Cr% Ni% Mo% Cu% Al%
1-1 027 0.39 1.48 0.014 0.012 0.59 0.48 029 0.08 0.04
1-2 028 0.38 150 0.011 0.013 0.60 0.52 0.30 0.09 0.05
1-3 026 0.40 1.52 0.010 0.011 0.62 0.53 0.33 0.10 0.04
1-4 029 0.35 1.49 0.012 0.013 0.58 0.51 0.31 0.07 0.05
1-5 028 0.41 1.54 0.013 0.011 0.61 0.54 0.32 0.08 0.03
1-6 027 0.38 1.53 0.010 0.011 0.63 0.49 0.34 0.09 0.04
1-7 026 0.36 1.55 0.012 0.010 0.60 0.50 0.32 0.010 0.06
1-8 028 0.37 1.46 0.011 0.012 0.57 0.55 028 0.08 0.05
1-9 027 0.39 1.47 0.010 0.012 058 0.53 0.30 0.09 0.04
1-10 029 0.40 1.50 0.014 0.012 0.61 0.49 0.32 0.08 0.05
Table 2
Yield strength Tensile strength Elongation
Reduction of cross Impact energy
Embodiment
MPa MPa section %
J(-40 DEG C)
1-1 835 930 17.0 53.5
55.3
1-2 855 945 16.5 46.0
47.0
1-3 845 930 18.0 53.5
57.0
1-4 840 930 17.5 53.5
51.0
1-5 850 940 17.5 55.0
52.3
4
CA 02748641 2011-06-23
1-6 855 965 17.0 50.5
39.7
1-7 860 960 17.0 49.5
47.7
1-8 840 940 17.5 51.5
53.0
1-9 850 955 18.0 53.5
48.7
1-10 845 945 17.5 50.5
49.3
Grade E More than or equal More than or equal More than or equal More than
or equal to More than or
steel to 690 to 830 to 14 30 equal to
27
,
[0021] Table 1 and Table 2 show that the mechanical property of the steel
provided by the present
invention is significantly better than that of grade E steel; for example, the
yield strength is 20%
higher than that of grade E steel; the tensile strength is 13% higher than
that of grade E steel; the
impact energy is 90% higher than that of grade E steel; in addition, the
elongation and reduction of
cross section are also much higher than those of grade E steel; hereinto,
higher impact energy means
higher toughness of steel.
[0022] According to standard M201 of American AAR (Association of American
Railroads), steel
is classified into the following grades on the basis of strength thereof:
grade A steel, grade B steel,
grade B+ steel, grade C steel, and grade E steel, in which the grade E is the
highest grade.
[0023] Due to the above chemical compositions, the steel provided by the
present invention has
excellent mechanical property, including high strength and good toughness, and
the mechanical
property is better than that of grade E steel.
[0024] In order to further improve the mechanical property of material, the
steel material of the
present invention can be obtained through the following heat treatment
process, which includes
pre-heat treatment and thermal refining; the pre-heat treatment comprises
normalizing treatment; the
thermal refining comprises quenching and tempering procedures. Specifically,
the process
comprises the following steps:
[0025] Step 1: performing pre-heat treatment to steel, wherein the normalizing
temperature is
900-960 DEG C, the temperature holding time is 3-5 hours, and the cooling
method is air cooling or
wind cooling; the normalizing temperature is preferably 920-950 DEG C, and
more preferably
930-950 DEG C; the temperature holding time is preferably 3.5-4.5 hours, and
more preferably 4
CA 02748641 2011-06-23
hours.
[0026] Step 2: quenching the steel after the pre-heat treatment of step 1,
wherein the quenching
temperature is 900-920 DEG C, the temperature holding time is 2-3 hours, and
the cooling method
is water quenching.
[0027] Step 3: tempering the steel after quenching of step 2, wherein the
tempering temperature is
520-580 DEG C, the temperature holding time is 3-5 hours, and the cooling
method is water cooling;
the tempering temperature may also be 550-570 DEG C or 530-550 DEG C.
[0028] After the pre-heat treatment procedure to the steel provided by the
present invention, the
as-cast structure of steel can be eliminated and the crystalline grain can be
refined, so as to prepare
for the thermal refining; furthermore, water cooling is adopted in the
tempering procedure to
eliminate the temper brittleness, and therefore the mechanical property of
steel can be greatly
improved.
[0029] Before the heat treatment to steel, metallurgy procedure should also be
executed. The
metallurgy procedure can be ex ecuted using the conventional metallurgy
process, for example,
including the following steps:
[0030] Step al: preparing raw material: according to the requirements of
compositions of steel to
be melted, weighing the iron alloy necessary in smelting process, conveying it
beside arc furnace,
and also conveying various slagging materials, carburetant, oxidizing material
and reduction
materials beside the furnace.
[0031] Step a2: feeding material: feeding the cut and selected waste steel, of
which the size and
weight meet the requirements of furnace, into the hopper of furnace, according
to the arrangement of
"large, medium, small and light"; adding carburetant and a part of iron alloy
to the steel; conveying
all materials to charging bay via battery truck; weighing these materials; and
feeding the materials in
batches into the arc furnace.
[0032] Step a3: electrifying the furnace to melt the materials: electrifying
the arc furnace after the
waste steel is fed thereinto, where different currents and voltages can be
adopted to covert electric
energy into heat energy and therefore to melt the waste steel into molten
steel. In order to speed up
the smelting, oxygen can be blown to accelerate the melting when the arc
furnace is electrified.
[0033] Step a4: oxidizing: adding the slagging materials to make a layer of
slag cover on the
6
CA 02748641 2011-06-23
surface of molten steel after the waste steel is melted into molten steel; and
adding oxidizing
material when the molten steel is at a proper temperature, to boil the molten
steel under the reaction
of carbon and oxygen, so as to eliminate gas from the molten steel. Since the
molten steel is boiled,
the molten steel can contact with slag fully, and therefore the harmful
element phosphorus can be
transferred from the molten steel to the slag. The compositions of the molten
steel can be checked
for 2-3 times during the oxidizing process. At the end of the oxidizing
process, steel ladle can be
dried.
[0034] Step a5: removing slag: at the end of oxidizing, under the condition
that all compositions
and temperature comply with the technical requirements, shutting off the power
and removing all
slag generated in the oxidizing process, so as to prevent the harmful element,
phosphorus, from
entering molten steel again.
[0035] Step a6: reduction: after all slag generated in oxidizing process is
removed, electrifying the
arc furnace and adding slagging materials rapidly; removing oxygen element
from the molten steel
by diffusible desoxydation method and precipitation desoxydation method; and
adding iron alloy
into the molten steel in sequence according to oxidability of iron alloy. In
reduction process, inert
gas can be adopted for mixing so as to make the molten steel flow and contact
with the slag fully
and therefore transfer the harmful element sulphur from the molten steel into
the slag. The
temperature of molten steel is continuously improved to prepare for tapping
during deoxygenation,
desulfuration and adjustment of molten steel compositions.
[0036] Step a7: tapping: on the basis that compositions of molten steel are
qualified, the
temperature of molten steel and drying of steel ladle are in accordance with
requirements and
desoxydation experiment of molten steel is under good condition, the power can
be shut off and the
tapping can be executed.
[0037] And step a8: refining molten steel: during the tapping process, blowing
inert gas into the
steel ladle and keeping it for a certain time; and after the end of tapping,
feeding deoxidant into steel
ladle.
[0038] In order to ensure the reliability and safety of vehicles running at a
high load, more
requirement to the mechanical property of material for making coupler has been
proposed by mine
manufacturer; the requirement is even higher than grade E; the steel hereafter
meets the requirement
7
CA 02748641 2011-06-23
is classified as grade E+ steel; the requirement to the mechanical property of
grade E+ steel is shown
in Table 3.
Table 3
Reduction of cross
Mechanical Yield strength Tensile strength
Elongation Impact energy
section
property MPa MPa
4-40 DEG C)
More than or More than or More than or
More than or More than or
Grade E steel
equal to 690 equal to 830 equal to 14 equal to 30
equal to 27
More than or More than or More than or
More than or More than or
Grade E+ steel
equal to 760 equal to 910 equal to 14 equal to 30
equal to 33
[0039] As shown in Table 3, the mechanical property of grade E+ steel is
higher than that of grade
E steel; the yield strength and tensile strength of grade E+ steel are 10%
higher than those of grade E
steel; and the impact energy is 20% higher than that of grade E steel.
[0040] The mechanical property of grade E steel part can be obtained as shown
in Table 4 from the
grade E steel (embodiments 2-1 to2-10) through the conventional heat treatment
process. Wherein,
the raw material of embodiments 2-1to 2-10 can be either commercial grade E
steel or the grade E
steel made by manufacturer according to the requirements thereof.
Table 4
Yield strength Tensile strength Elongation Reduction of cross Impact energy
Embodiments
MPa MPa section %
J(-40 DEG C)
2-1 855 945 16.5 46.0 25.6
2-2 855 945 18.0 52.5 31.3
2-3 865 945 17.0 52.5 39.7
2-4 845 935 19.0 52.5 32.7
2-5 865 955 16.5 51.5 30.7
2-6 865 945 18.0 50.5 36.5
8
CA 02748641 2011-06-23
2-7 845 935 17.0 51.5 40.5
2-8 870 955 17.5 55.0 41.3
2-9 870 960 17.5 52.5 24.0
2-10 855 955 18.0 53.5 38.7
Grade E+
steel standard 760 910 14 30 33
values
[0041] Wherein, the heat treatment process of the conventional grade E steel
part comprises:
quenching temperature is 910 DEG C, the temperature holding time is 2 hours
and the quenching
method is water quenching; the tempering temperature is 560 DEG C, the
temperature holding time
is 3.5 hours and the cooling method is wind cooling.
[0042] As shown in Table 4, with the increasing of strength (yield strength
and tensile strength),
the parameter of impact energy (toughness) of grade E steel part reduces and
cannot be stabilized.
Compared with the requirement of grade E+ steel, the mechanical property can
only meet 50% of
the requirement thereof.
[0043] The mechanical property of the steel (embodiments 3-1to 3-10) with new
compositions
provided by the present invention, after smelting process and through the heat
treatment process
provided by the present invention is shown in Table 5:
Table 5
Impact
Yield Tensile Reduction of
Elongation
energy
Embodiments strength strength cross section
J(-40 DEG
MPa MPa
C)
3-1 840 945 19.0 55.0 81.3
3-2 880 955 18.5 48.5 65.7
3-3 850 940 18.5 51.5 78.3
9
CA 02748641 2011-06-23
3-4 875 960 20.0 52.0 66.3
3-5 875 955 19.0 58.0 65.0
3-6 865 945 18.5 52.0 71.7
3-7 855 945 19.5 52.5 70.0
3-8 880 970 18.5 54.0 71.3
3-9 865 955 19.0 57.0 72.3
3-10 875 975 16.0 42.5 60.3
Grade E+ steel
standard 760 910 14 30 33
values
[0044] Wherein, the specific compositions of the steel in embodiments 3-1 to 3-
10 are shown in
Table 6.
Table 6
C Si Mn P S Cr Ni Mo Cu Al
Embodiments
% % % % % % % % % %
3-1 0.27
0.39 1.48 0.014 0.012 0.59 0.48 0.29 0.08 0.04
3-2 0.28
0.38 1.50 0.011 0.013 0.60 0.52 0.30 0.09 0.05
3-3 0.26
0.40 1.52 0.010 0.011 0.62 0.53 0.33 0.10 0.04
3-4 0.29
0.35 1.49 0.012 0.013 0.58 0.51 0.31 0.07 0.05
3-5 0.28
0.41 1.54 0.013 0.011 0.61 0.54 0.32 0.08 0.03
3-6 0.27
0.38 1.53 0.010 0.011 0.63 0.49 0.34 0.09 0.04
3-7 0.26
0.36 1.55 0.012 0.010 0.60 0.50 0.32 0.010 0.06
3-8 0.28
0.37 1.46 0.011 0.012 0.57 0.55 0.28 0.08 0.05
3-9 0.27
0.39 1.47 0.010 0.012 0.58 0.53 0.30 0.09 0.04
3-10 0.29
0.40 1.50 0.014 0.012 0.61 0.49 0.32 0.08 0.05
CA 02748641 2012-10-26
[0045] As shown in Table 5, the mechanical property of the steel, with new
compositions, provided
by the present invention after the heat treatment process provided by the
present invention is
noticeably higher than that of grade E+ steel (in particular the impact
energy) and completely meets
the requirement thereof. Compared with the conventional grade E steel shown in
Table 4, the
mechanical property provided by the present invention is greatly higher than
that of grade E steel.
[0046] As shown in Table 5 and Table 2, the mechanical property of the steel
with new
compositions provided by the present invention after special heat treatment
process (Table 5) is
noticeably higher than that of the steel only executed with the conventional
heat treatment process;
especially, based on keeping the strength, the impact energy is greatly
improved; namely, the
toughness of the steel with new compositions provided by the present invention
is also improved on
the basis of keeping or even improving the strength thereof.
[0047] The present invention provides a steel material with high strength and
excellent toughness,
the steel can be applied to multiple fields, such as coupler of railway wagon,
in order to meet the
requirement of "speed-rising and heavy-haul" of railway wagon.
11
