EP1031631A2 - A method of spheroidizing annealing of hypo-eutectoid low alloy steel - Google Patents
A method of spheroidizing annealing of hypo-eutectoid low alloy steel Download PDFInfo
- Publication number
- EP1031631A2 EP1031631A2 EP00850027A EP00850027A EP1031631A2 EP 1031631 A2 EP1031631 A2 EP 1031631A2 EP 00850027 A EP00850027 A EP 00850027A EP 00850027 A EP00850027 A EP 00850027A EP 1031631 A2 EP1031631 A2 EP 1031631A2
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- EP
- European Patent Office
- Prior art keywords
- temperature
- hypo
- eutectoid
- until
- ferrite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/78—Combined heat-treatments not provided for above
- C21D1/785—Thermocycling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
Definitions
- the present invention relates to a method of spheroidizing annealing of hypo-eutectoid low alloy steel, and more specifically to a method of heat treatment of hypo-eutectoid low alloy steel for obtaining a desired amount of spherical carbides in a ferritic matrix in order to enhance the cold forming characteristics of the steel.
- low and medium carbon steels are normally delivered having a mixed structure comprising perlite and ferrite, sometimes bainite and/or martensite, tempered or not. This may lead to problems in machining and/or cold deformation. In turning processes this is experienced as heavy wear of the tools and in cold deforming processes unwanted cracks in the treated objects occur.
- the two conventional heat treatment methods currently used for softening steels do not result in spheroidisation of low or medium carbon steel.
- Spherodizing annealing of high carbon steel is one of the conventional heat treatment methods giving a perlite structure, and the other is tempering at about 700°C of low carbon steel, which gives perlite and non-spherical carbides.
- the object of the invention is to provide a method for spheroidizing annealing of hypo-eutectoid low alloy steel resulting in improved cold forming characteristics and machinability.
- a) and b) are repeated at least twice. This will decrease the material grain size and thus increase the diffusion rate and reduce the diffusion distances of alloying elements. This could be necessary in order to successfully anneal a hypo-eutectoide steel with a low amount of carbide forming elements.
- Fig. 1 illustrates one embodiment of the spheroidizing annealing method according to the invention for low and medium carbon steels (Ovako 234, 0.2 wt.% C).
- Fig. 2 illustrates second embodiment of the method according to the invention, for low and medium carbon steel (Ovako 593, 0.5 wt.% C, 157, 245, och 255, 0.2 wt.% C.
- Fig. 3 illustrates a third embodiment of the method according to the invention for low and medium carbon steels (Ovako 593, 0.5 wt.% C) 157, 245 and 255, 0.2 wt.% C.
- Products produced and delivered to a customer can be divided into three different categories related to the final treatment before delivery:
- FIG. 1 A graph illustrating the method is shown in Fig. 1.
- the steel grade Ovako 234 with about 0.2 wt.% C was treated with the method according to the invention, by raising the temperature to between A1 and A3, in this case about 740°C, and maintaining the temperature for a prolonged time, lowering the temperature to underneath A1 and then holding the temperature until the desired degree of spheroidization has been obtained.
- FIG. 2 A graph illustrating this embodiment of the method is shown in Fig. 2.
- the following steel grades were tested: Ovako 593 with about 0.5 wt.% C, and Ovako 157, 245, and 255 with about 0.2 wt.% C.
- the temperature was increased to between A1 and A3, in this case about 740°C, this temperature was maintained for about one hour, then lowered to well below A1, i.e. about 600°C, and then increased again to about 670°C and maintained there until the desired degree of spheroidization was obtained.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
Method of spheroidizing annealing of hypo-eutectoid low alloy
steel, wherein a hot rolled steel typical comprising ferrite and
a high carbon phase such as pearlite or martensitic/bainitic
microstructural constituents
- a) is heated to a temperature between A1 and A3 until austenitic domains with higher carbon content than the base composition has been created,
- b) the temperature is lowered and held under A1 to enable the austenite to transform into ferrite and carbides,
- c) the temperature is held under A1 until a desired degree of spheroidizing of the carbide is obtained.
Description
The present invention relates to a method of spheroidizing
annealing of hypo-eutectoid low alloy steel, and more specifically
to a method of heat treatment of hypo-eutectoid low alloy
steel for obtaining a desired amount of spherical carbides in a
ferritic matrix in order to enhance the cold forming characteristics
of the steel.
Today, low and medium carbon steels are normally delivered
having a mixed structure comprising perlite and ferrite, sometimes
bainite and/or martensite, tempered or not. This may lead to
problems in machining and/or cold deformation. In turning processes
this is experienced as heavy wear of the tools and in
cold deforming processes unwanted cracks in the treated objects
occur. The two conventional heat treatment methods currently
used for softening steels do not result in spheroidisation of
low or medium carbon steel.
Spherodizing annealing of high carbon steel is one of the conventional
heat treatment methods giving a perlite structure, and
the other is tempering at about 700°C of low carbon steel, which
gives perlite and non-spherical carbides.
Further, the sulphur addition used today to enhance workability,
results in manganese sulphides, which increase the risk of
fatigue failure at high loads. In continuous casting the
problems are even worse, and the sulphur may result in segregations
and sulphide stringers.
Thus, it is desirable to obtain good workability without sulphur
addition, since the loads on many components produced today tend
to increase rather than decrease.
The object of the invention is to provide a method for spheroidizing
annealing of hypo-eutectoid low alloy steel resulting in
improved cold forming characteristics and machinability.
This is achieved with the method according to the present invention,
wherein a hot rolled steel typical comprising ferrite and
a high carbon phase such as pearlite or martensitic/bainitic
microstructural constituents
According to one embodiment of the invention, a) and b) are
repeated at least twice. This will decrease the material grain
size and thus increase the diffusion rate and reduce the diffusion
distances of alloying elements. This could be necessary in
order to successfully anneal a hypo-eutectoide steel with a low
amount of carbide forming elements.
Fig. 1 illustrates one embodiment of the spheroidizing annealing
method according to the invention for low and medium carbon
steels (Ovako 234, 0.2 wt.% C).
Fig. 2 illustrates second embodiment of the method according to
the invention, for low and medium carbon steel (Ovako 593, 0.5
wt.% C, 157, 245, och 255, 0.2 wt.% C.
Fig. 3 illustrates a third embodiment of the method according to
the invention for low and medium carbon steels (Ovako 593, 0.5
wt.% C) 157, 245 and 255, 0.2 wt.% C.
Today hot rolling of products is common. These products are then
delivered non-treated, tempered, toughened or treated in an
isothermal heat treatment furnace.
Products produced and delivered to a customer can be divided
into three different categories related to the final treatment
before delivery:
- Hot rolling at about 1150°C - cooling down to 20°C - to customer.
- Hot rolling at about 1150°C - cooling down to 20°C - tempering at about 650°C - to customer (tempered);
- Hot rolling at about 1150°C - cooling down to 20°C - austenitization at about 900°C - quenching (water/oil) + tempering at about 650°C - to customer (toughened)
- Hot rolling at about 1150°C - cooling dowm to approximately
650°C -holding
time 1 hour at about 650°C - to customer.
To the best of our knowledge no supplier today offer shperoidized
structures when it comes to low and/or medium carbon steels.
For these types of steels three embodiments of the method according
to the invention have been illustrated, i.e. heating to or
holding isothermally at a temperature between A1 and A3 until
austenitic domains with higher carbon content than the base
composition has been created, thereafter lowering the
temperature to and holding it underneath A1 to enable the
austenite to transform into ferrite and carbides, and holding
the temperature underneath A1 until a desired degree of
spheroidizing of the carbides is obtained.
Two different steel grades were treated, Ovako 157 with about
0.2 wt.% C, and Ovako 057 with about 0.5 wt.% C.
The respective steels were normalized 4 times by raising the temperature to between A1 and A3, for these steels about 790°C, and then lowering the temperature to below A1, in this case about 600°C, then holding the temperature at about 690°C until the desired degree of spheroidization was obtained, resulting in a structure not containing any perlite. Four or more normalisations results in a grain refining giving a large amount of grain boundaries which will increase the amount of high energetic nucleation sites for the austenite. An increased number and thus reduced size of austenitic domains will decrease the diffusion distances for alloying element making the desired spheroidization possible.
high-energy grain formation sites, making posible 100 % spheroidization with very small, spherioidal grains thanks to a successive grain refining with only small amounts of carbon having to diffuse each time.
The respective steels were normalized 4 times by raising the temperature to between A1 and A3, for these steels about 790°C, and then lowering the temperature to below A1, in this case about 600°C, then holding the temperature at about 690°C until the desired degree of spheroidization was obtained, resulting in a structure not containing any perlite. Four or more normalisations results in a grain refining giving a large amount of grain boundaries which will increase the amount of high energetic nucleation sites for the austenite. An increased number and thus reduced size of austenitic domains will decrease the diffusion distances for alloying element making the desired spheroidization possible.
high-energy grain formation sites, making posible 100 % spheroidization with very small, spherioidal grains thanks to a successive grain refining with only small amounts of carbon having to diffuse each time.
A graph illustrating the method is shown in Fig. 1.
The steel grade Ovako 234 with about 0.2 wt.% C was treated with
the method according to the invention, by raising the temperature
to between A1 and A3, in this case about 740°C, and maintaining
the temperature for a prolonged time, lowering the temperature
to underneath A1 and then holding the temperature until the
desired degree of spheroidization has been obtained.
A graph illustrating this embodiment of the method is shown in
Fig. 2.
The following steel grades were tested: Ovako 593 with about 0.5
wt.% C, and Ovako 157, 245, and 255 with about 0.2 wt.% C. The
temperature was increased to between A1 and A3, in this case
about 740°C, this temperature was maintained for about one hour,
then lowered to well below A1, i.e. about 600°C, and then increased
again to about 670°C and maintained there until the desired
degree of spheroidization was obtained.
In all three embodiments of the method according to the invention
100 % spheroidization was obtained. The effect of lowering
the temperature to a minimum value as in example 3, did not give
any significant improvment of the characteristics of the resulting
material to be delivered to the customer.
Claims (2)
- Method of spheroidizing annealing of hypo-eutectoid low alloy steel, wherein a hot rolled steel typical comprising ferrite and a high carbon phase such as pearlite or martensitic/bainitic microstructural constituentsa) is heated to a temperature between A1 and A3 until austenitic domains with higher carbon content than the base composition has been created,b) the temperature is lowered and held under A1 to enable the austenite to transform into ferrite and carbides,c) the temperature is held under A1 until a desired degree of spheroidizing of the carbide is obtained.
- Method according to claim 1, wherein steps a) and b) are repeated at least twice.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9900598 | 1999-02-22 | ||
| SE9900598A SE521770C2 (en) | 1999-02-22 | 1999-02-22 | Spheroidal annealing of undereutectic low alloy steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP1031631A2 true EP1031631A2 (en) | 2000-08-30 |
| EP1031631A3 EP1031631A3 (en) | 2003-10-08 |
Family
ID=20414556
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP00850027A Withdrawn EP1031631A3 (en) | 1999-02-22 | 2000-02-14 | A method of spheroidizing annealing of hypo-eutectoid low alloy steel |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP1031631A3 (en) |
| JP (1) | JP2000239737A (en) |
| CN (1) | CN1265427A (en) |
| SE (1) | SE521770C2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2543744A1 (en) * | 2011-07-08 | 2013-01-09 | Aicher, Max | Method and device for treating a steel product and steel product |
| CZ305540B6 (en) * | 2014-05-21 | 2015-11-25 | Západočeská Univerzita V Plzni | Heat treatment process of high-alloy steel |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100348742C (en) * | 2006-03-14 | 2007-11-14 | 钢铁研究总院 | Spheroidal annealing process of deep-punched steel plate for preventing bullet |
| KR100653134B1 (en) * | 2006-04-25 | 2006-12-04 | 광진실업 주식회사 | Spheroidal Annealing Method of Medium Carbon Steel Bar Using Electric Induction Heating Equipment |
| CN102226228B (en) * | 2011-06-08 | 2013-06-19 | 马鞍山钢铁股份有限公司 | Technology for testing pearlite in low carbon steel structure in mesophase spheroidizing annealing |
| CN106755852A (en) * | 2016-11-30 | 2017-05-31 | 中国船舶重工集团公司第十二研究所 | A kind of steel alloy soft softening method |
| CN107723435B (en) * | 2017-11-30 | 2023-06-06 | 贵州大学 | Method and device for obtaining refined full pearlite structure in hypoeutectoid steel wire rod |
| CN109628713B (en) * | 2018-12-12 | 2020-11-06 | 河钢股份有限公司承德分公司 | Spheroidizing annealing method of low-carbon steel |
| CN109517949B (en) * | 2018-12-12 | 2020-10-30 | 河钢股份有限公司承德分公司 | Spheroidizing annealing method of steel for shafts |
| CN109593929B (en) * | 2018-12-12 | 2020-10-30 | 河钢股份有限公司承德分公司 | Spheroidizing annealing method of cold forging steel |
| CN109487052B (en) * | 2018-12-12 | 2020-10-30 | 河钢股份有限公司承德分公司 | Spheroidizing annealing method of B-containing cold forging steel |
| CN115013601B (en) * | 2022-07-01 | 2023-11-07 | 江苏徐工工程机械研究院有限公司 | Concrete conveying pipe, manufacturing method thereof and concrete pump truck |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4322256A (en) * | 1979-01-31 | 1982-03-30 | Snap-On Tools Corporation | Tool made from alloy steel for severe cold forming |
| RU2023026C1 (en) * | 1991-07-02 | 1994-11-15 | Украинский государственный научно-исследовательский институт металлов | Method for heat treatment of rails |
-
1999
- 1999-02-22 SE SE9900598A patent/SE521770C2/en not_active IP Right Cessation
-
2000
- 2000-02-14 EP EP00850027A patent/EP1031631A3/en not_active Withdrawn
- 2000-02-17 JP JP2000039585A patent/JP2000239737A/en active Pending
- 2000-02-22 CN CN 00102387 patent/CN1265427A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2543744A1 (en) * | 2011-07-08 | 2013-01-09 | Aicher, Max | Method and device for treating a steel product and steel product |
| CZ305540B6 (en) * | 2014-05-21 | 2015-11-25 | Západočeská Univerzita V Plzni | Heat treatment process of high-alloy steel |
Also Published As
| Publication number | Publication date |
|---|---|
| EP1031631A3 (en) | 2003-10-08 |
| SE521770C2 (en) | 2003-12-02 |
| SE9900598D0 (en) | 1999-02-22 |
| SE9900598L (en) | 2000-08-23 |
| CN1265427A (en) | 2000-09-06 |
| JP2000239737A (en) | 2000-09-05 |
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