EP0586179B1 - Forging and a method for its manufacture - Google Patents
Forging and a method for its manufacture Download PDFInfo
- Publication number
- EP0586179B1 EP0586179B1 EP93306710A EP93306710A EP0586179B1 EP 0586179 B1 EP0586179 B1 EP 0586179B1 EP 93306710 A EP93306710 A EP 93306710A EP 93306710 A EP93306710 A EP 93306710A EP 0586179 B1 EP0586179 B1 EP 0586179B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- percent
- weight
- forging
- quenching
- temperature
- 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.)
- Expired - Lifetime
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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
- C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
-
- 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
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- 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
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
- C21D1/60—Aqueous agents
Definitions
- the invention relates to an improved forging with favourable strength features and toughness and a method of manufacturing the forging.
- Raising the carbon content increases the strength effectively, but high contents, especially contents substantially over 0.1%, impair toughness and machinability.
- Raising the manganese content to more than 1% is in many cases useful, but manganese has a strong tendency to segregation. This easily causes quite large strength variations over the cross-section of a component and between components in continuous production. In addition, the segregation of manganese impairs the machinability of the steel.
- chromium has a low tendency to segregation, so that not even contents above 1% impair machinability.
- an improvement of the known technique is achieved by adding small amounts of molybdenum, so that the molybdenum content is 0.04 to 0.25 percent by weight, preferably 0.04 to 0.15 percent by weight.
- the present invention therefore provides a forging with favourable strength features and toughness, characterised in that it is produced of a material, which in addition to iron and incidental impurities has the following material contents in percent by weight C from 0.04 to 0.14, preferably from 0.07 to 0.14 Si from 0.05 to 0.50 Mn from 0.6 to 1.0 Cr from 1.0 to 2.0 Mo from 0.04 to 0.25, preferably from 0.04 to 0.15 S from 0 to 0.15, preferably from 0.02 to 0.15 Al from 0 to 0.1 B from 0 to 0.015 Ti from 0 to 0.05 and that the component has been hot forged within a temperature range of 800°C to 1300°C and immediately thereafter quenched, but has not been tempered.
- the invention also provides a method for producing an improved forging with favourable strength features and toughness, characterised in that the billet for the desired improved forging is produced of a material which in addition to iron and incidental impurities consists of the following elements: C from 0.04 to 0.14 percent by weight Si from 0.05 to 0.50 percent by weight Mn from 0.6 to 1.0 percent by weight Cr from 1.0 to 2.0 percent by weight Mo from 0.04 to 0.25 percent by weight S from 0 to 0.15 percent by weight Al from 0 to 0.1 percent by weight B from 0 to 0.015 percent by weight Ti from 0 to 0.05 percent by weight that the billet is forged within a temperature range of 800°C to 1300°C and that the billet, which has then become a forging, immediately after the forging procedure is quenched in water or in a water-based emulsion or solution, but is not tempered.
- a new alloying element By alloying a steel according to the invention with molybdenum the strength can be raised effectively at low contents. This is caused by the high hardenability factor of molybdenum, especially when the carbon content is low, as in the invention. Further, the introduction of a new alloying element has a synergistic effect on hardenability, in other words, a new alloying element improves hardenability more effectively when employed together with other alloying elements (in this case manganese and chromium) than when employed alone.
- Molybdenum also favours the formation of bainite, which can be seen, for example, in a so-called CCT-diagram as a wide area of bainite.
- the wide bainite area minimises the strength difference between the surface and the core, because the formation of martensite on the surface can be prevented, which results in that the component becomes practically fully bainitic.
- a wide bainite area means in practice that the quenching rate used is not very critical, so that quite a wide range of quenching rates may be used. In quenching large cross-section components the quenching rate is by necessity relatively low, but this does not cause any essential disadvantages when applying the invention.
- molybdenum does not impair toughness but improves it.
- the relatively high price of molybdenum restricts its economical use to low contents.
- molybdenum is a considerably cheaper alloying element than for instance nickel.
- the molybdenum content is at the most 0.25 percent by weight and a preferred content is at the most 0.15 percent by weight, whereby the synergistic effect of molybdenum on hardenability is at its peak. At increasing contents of molybdenum its effect on hardenability per content unit decreases.
- a quenching technique can be used for minimising non-uniformity in strength.
- a forging in water or in a water-based (polymer) emulsion or solution sufficiently uniform strength properties over the cross-section of the component are normally obtained when using a steel according to the invention.
- Water is usually the most desirable quenching fluid.
- Other substances may be added to the water so that a water-based emulsion or solution is formed. This has an influence on the quenching effect of the water.
- the quenching effect of water may also be influenced by controlling its temperature. By raising the water temperature over room temperature, preferably to a temperature of over 30°C or 40°C, the best results are usually obtained.
- Another recommendable quenching technique, when applying the invention, is spray quenching, because its adjustability is outstanding. The effect of spray quenching can easily be adjusted and the quenching can be directed to only a part of a component. Thereby only the desired portion of the component becomes hardened, while the other portions remain soft and tough.
- a particularly preferred steel according to the invention consists in addition to iron (and incidental impurities) the following contents of other elements, in percent by weight: C 0.06%, Si 0.28%, Mn 0.91%, S 0.080%, Cr 1.11%, Al 0.038%, Mo 0.10%, Ti 0.019%, B 0.005%.
- a steel according to the invention is also well suited for nitriding or nitrocarburising.
- Molybdenum improves the resistance to softening during nitriding.
- molybdenum improves the toughness if the component is nitrided.
- Forging billets according to the invention may be cold cropped from continuous cast or hot-rolled steel bars and the finished forging may be directly quenched from the forging temperature. Forgings according to the invention may be machined and are used without tempering.
- Forgings may be assembled also by fusion welding of several component parts.
- a steel according to the invention is very well suited also for carburising hardening.
- the advantage is then that core elongation and toughness exceed normal values, which is caused by the lower than usual carbon content of the steel. This allows the use of the steel in particular in such carburising hardened elements in which large deformations occur and which for that reason must be straightened, for example by cold-straightening.
- the strength and toughness of a component according to the invention can be improved by controlling relatively carefully the end temperature of the hot forging.
- the most preferred end temperature of the forging is 950°C to 1050°C.
- Another way of increasing the strength is to avoid very low carbon contents. It is recommended that the carbon content is at least 0.07 percent by weight/ In general terms the carbon content should preferably, within the limits of the invention, be sufficiently high that the tensile strength of the finished forging is, without tempering, at least 900 N/mm 2 .
- the machinability of the steel can be improved quite significantly.
- the sulphur content should not be more than 0.15 percent by weight, above which value the mechanical properties are impaired.
- the invention is also illustrated in the accompanying drawing which is a CCT-diagram showing the structure of a forging according to the invention (preferred composition) at different quenching rates.
- the horizontal axis of the diagram shows the time in seconds and the vertical axis the temperature in degrees centigrade.
- the martensite area is indicated by the letter M, the bainite area by the letter B, the ferrite area by the letter F and the perlite area by the letter P.
- the areas have been determined by using different heating temperatures of test samples.
- the set of curves shown in full lines reflects the situation when the heating has been to 1200°C, the broken line curves show heating to 900°C and dotted line curves show heating to 1200°C as well as forming of the test sample by upsetting to 50 percent area reduction.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Forging (AREA)
- Heat Treatment Of Steel (AREA)
Description
The invention relates to an improved forging with
favourable strength features and toughness and a method of
manufacturing the forging.
From EP-B-191873 a method for producing a directly
quenched hot forging with favourable strength properties is
known. The present invention seeks to improve this known
technique so that the strength of the component, in
particular the uniformity of the strength over the cross-section
of the component, and the toughness of the component
in direct quenching are improved.
The strength features of a forging can in principle be
improved by the following means:
- raising the carbon content
- raising the manganese content
- raising the chromium content
- alloying with nickel
- alloying with molybdenum.
Raising the carbon content increases the strength
effectively, but high contents, especially contents
substantially over 0.1%, impair toughness and machinability.
Raising the manganese content to more than 1% is in
many cases useful, but manganese has a strong tendency to
segregation. This easily causes quite large strength
variations over the cross-section of a component and between
components in continuous production. In addition, the
segregation of manganese impairs the machinability of the
steel.
Raising the chromium content to more than 2% impairs
the toughness, especially when the carbon content is more
than 0.06%. On the other hand, chromium has a low tendency
to segregation, so that not even contents above 1% impair
machinability.
Alloying with nickel is quite an expensive measure and
its influence on the strength is relatively low, especially
at low contents.
Alloying with molybdenum is not a very popular measure,
because molybdenum is an expensive alloying element and its
effect on improving the strength decreases the more the
content increases. In addition, the bainite formation
caused by molybdenum usually impairs toughness, especially
if the carbon content is 0.15% or higher.
According to the present invention an improvement of
the known technique is achieved by adding small amounts of
molybdenum, so that the molybdenum content is 0.04 to 0.25
percent by weight, preferably 0.04 to 0.15 percent by
weight.
The present invention therefore provides a forging with
favourable strength features and toughness, characterised in
that it is produced of a material, which in addition to iron
and incidental impurities has the following material
contents in percent by weight
and that the component has been hot forged within a
temperature range of 800°C to 1300°C and immediately
thereafter quenched, but has not been tempered.
| C | from 0.04 to 0.14, preferably from 0.07 to 0.14 |
| Si | from 0.05 to 0.50 |
| Mn | from 0.6 to 1.0 |
| Cr | from 1.0 to 2.0 |
| Mo | from 0.04 to 0.25, preferably from 0.04 to 0.15 |
| S | from 0 to 0.15, preferably from 0.02 to 0.15 |
| Al | from 0 to 0.1 |
| B | from 0 to 0.015 |
| Ti | from 0 to 0.05 |
The invention also provides a method for producing an
improved forging with favourable strength features and
toughness, characterised in that the billet for the desired
improved forging is produced of a material which in addition
to iron and incidental impurities consists of the following
elements:
that the billet is forged within a temperature range of
800°C to 1300°C and that the billet, which has then become
a forging, immediately after the forging procedure is
quenched in water or in a water-based emulsion or solution,
but is not tempered.
| C | from 0.04 to 0.14 percent by weight |
| Si | from 0.05 to 0.50 percent by weight |
| Mn | from 0.6 to 1.0 percent by weight |
| Cr | from 1.0 to 2.0 percent by weight |
| Mo | from 0.04 to 0.25 percent by weight |
| S | from 0 to 0.15 percent by weight |
| Al | from 0 to 0.1 percent by weight |
| B | from 0 to 0.015 percent by weight |
| Ti | from 0 to 0.05 percent by weight |
By alloying a steel according to the invention with
molybdenum the strength can be raised effectively at low
contents. This is caused by the high hardenability factor
of molybdenum, especially when the carbon content is low, as
in the invention. Further, the introduction of a new
alloying element has a synergistic effect on hardenability,
in other words, a new alloying element improves
hardenability more effectively when employed together with
other alloying elements (in this case manganese and
chromium) than when employed alone.
Molybdenum also favours the formation of bainite, which
can be seen, for example, in a so-called CCT-diagram as a
wide area of bainite. The wide bainite area minimises the
strength difference between the surface and the core,
because the formation of martensite on the surface can be
prevented, which results in that the component becomes
practically fully bainitic. In addition, a wide bainite
area means in practice that the quenching rate used is not
very critical, so that quite a wide range of quenching rates
may be used. In quenching large cross-section components
the quenching rate is by necessity relatively low, but this
does not cause any essential disadvantages when applying the
invention.
Experiments have shown that, in a steel according to
the invention, molybdenum does not impair toughness but
improves it. The relatively high price of molybdenum
restricts its economical use to low contents. However, with
regard to its effect on improving hardenability, molybdenum
is a considerably cheaper alloying element than for instance
nickel. In a steel according to the invention the
molybdenum content is at the most 0.25 percent by weight and
a preferred content is at the most 0.15 percent by weight,
whereby the synergistic effect of molybdenum on
hardenability is at its peak. At increasing contents of
molybdenum its effect on hardenability per content unit
decreases.
A quenching technique can be used for minimising non-uniformity
in strength. By quenching a forging in water or
in a water-based (polymer) emulsion or solution sufficiently
uniform strength properties over the cross-section of the
component are normally obtained when using a steel according
to the invention. Water is usually the most desirable
quenching fluid. Other substances may be added to the water
so that a water-based emulsion or solution is formed. This
has an influence on the quenching effect of the water.
The quenching effect of water may also be influenced by
controlling its temperature. By raising the water
temperature over room temperature, preferably to a
temperature of over 30°C or 40°C, the best results are
usually obtained. Another recommendable quenching
technique, when applying the invention, is spray quenching,
because its adjustability is outstanding. The effect of
spray quenching can easily be adjusted and the quenching can
be directed to only a part of a component. Thereby only the
desired portion of the component becomes hardened, while the
other portions remain soft and tough.
A particularly preferred steel according to the
invention consists in addition to iron (and incidental
impurities) the following contents of other elements, in
percent by weight: C 0.06%, Si 0.28%, Mn 0.91%, S 0.080%, Cr
1.11%, Al 0.038%, Mo 0.10%, Ti 0.019%, B 0.005%.
A steel according to the invention is also well suited
for nitriding or nitrocarburising. Molybdenum improves the
resistance to softening
during nitriding. In addition, molybdenum
improves
the toughness if the component is nitrided.
Forging billets according to the invention may be cold
cropped from continuous cast or hot-rolled steel bars and
the finished forging may be directly quenched from the
forging temperature. Forgings according to the invention
may be machined and are used without tempering.
Forgings may be assembled also by fusion welding of
several component parts.
A steel according to the invention is very well suited
also for carburising hardening. The advantage is then that
core elongation and toughness exceed normal values, which is
caused by the lower than usual carbon content of the steel.
This allows the use of the steel in particular in such
carburising hardened elements in which large deformations
occur and which for that reason must be straightened, for
example by cold-straightening.
It has been experimentally established that the
machinability of a steel according to the invention is
clearly better than that of normal steels (containing more
carbon and often also more manganese). The better
machinability has been observed as a lower wear in high
speed steel cutting edges.
The strength and toughness of a component according to
the invention can be improved by controlling relatively
carefully the end temperature of the hot forging. The most
preferred end temperature of the forging is 950°C to 1050°C.
Another way of increasing the strength is to avoid very low
carbon contents. It is recommended that the carbon content
is at least 0.07 percent by weight/ In general terms the
carbon content should preferably, within the limits of the
invention, be sufficiently high that the tensile strength of
the finished forging is, without tempering, at least 900
N/mm2.
By adding a small quantity of sulphur to a steel
according to the invention, at least 0.02 percent by weight,
the machinability of the steel can be improved quite
significantly. The sulphur content should not be more than
0.15 percent by weight, above which value the mechanical
properties are impaired.
The invention is also illustrated in the accompanying
drawing which is a CCT-diagram showing the structure of a
forging according to the invention (preferred composition)
at different quenching rates. The horizontal axis of the
diagram shows the time in seconds and the vertical axis the
temperature in degrees centigrade. The martensite area is
indicated by the letter M, the bainite area by the letter B,
the ferrite area by the letter F and the perlite area by the
letter P. The areas have been determined by using different
heating temperatures of test samples. The set of curves
shown in full lines reflects the situation when the heating
has been to 1200°C, the broken line curves show heating to
900°C and dotted line curves show heating to 1200°C as well
as forming of the test sample by upsetting to 50 percent
area reduction. As is evident from the diagram, a large
quenching rate area, from about 0.2 to about 30°C/s, is
available for achieving the desired fully bainitic
structure. Quenching rates above 30°C/s may also be used,
because a slight martensite formation does not usually cause
problems. Additionally it can be seen that the CCT-curves
are almost independent of the heating temperature and of the
degree of deformation. This means that the structure and
hence the mechanical properties of a forging made of a
preferred composition according to the invention are almost
independent of how the hot forging is started.
The invention is not limited to the disclosed examples
since several modifications are feasible within the scope of
the following claims.
Claims (13)
- A forging with favourable strength features and toughness, characterised in that it is produced of a material, which in addition to iron and incidental impurities has the following material contents in percent by weight
C from 0.04 to 0.14 Si from 0.05 to 0.50 Mn from 0.6 to 1.0 Cr from 1.0 to 2.0 Mo from 0.04 to 0.25 S from 0 to 0.15 Al from 0 to 0.1 B from 0 to 0.015 Ti from 0 to 0.05 - A forging according to claim 1, characterised by a carbon content of 0.07 to 0.14 percent by weight.
- A forging according to claim 1 or 2, characterised by a molybdenum content of 0.04 to 0.15 percent by weight.
- A forging according to claim 1, 2, or 3, characterised by a sulphur content of 0.02. to 0.15 percent by weight.
- A forging according to any preceding claim, characterised in that its quenching has been performed in water or in a water-based emulsion or solution, the temperature of which preferably is above room temperature.
- A method for producing an improved forging with favourable strength features and toughness, characterised in that the billet for the desired improved forging is produced of a material which in addition to iron and incidental impurities consists of the following elements:
C from 0.04 to 0.14 percent by weight Si from 0.05 to 0.50 percent by weight Mn from 0.6 to 1.0 percent by weight Cr from 1.0 to 2.0 percent by weight Mo from 0.04 to 0.25 percent by weight S from 0 to 0.15 percent by weight Al from 0 to 0.1 percent by weight B from 0 to 0.015 percent by weight Ti from 0 to 0.05 percent by weight - A method according to claim 6, characterised in that the molybdenum content of the material is 0.04 to 0.15 percent by weight.
- A method according to claim 6 or 7, characterised in that the temperature of the quenching liquid is kept above room temperature, preferably at a temperature above 30°C.
- A method according to any of claims 6 to 8, characterised in that the end temperature of the hot forging of the billet is 950°C to 1050°C.
- A method according to any of claims 6 to 9, characterised in that the carbon content of the material is at least 0.07 percent by weight.
- A method according to any of claims 6 to 10, characterised in that the carbon content of the billet is kept at such a high level that the tensile strength of the forging is, without tempering, at least 900 N/mm2.
- A method according to any of claims 6 to 11, characterised in that the sulphur content of the material is at least 0.02 percent by weight.
- A method according to any of claims 6 to 12, characterised in that the quenching is performed by spray quenching either the whole forging or just a desired portion thereof.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI923929 | 1992-09-02 | ||
| FI923929A FI95049C (en) | 1992-09-02 | 1992-09-02 | Improved forging piece and its manufacturing process |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0586179A1 EP0586179A1 (en) | 1994-03-09 |
| EP0586179B1 true EP0586179B1 (en) | 1998-11-11 |
Family
ID=8535802
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP93306710A Expired - Lifetime EP0586179B1 (en) | 1992-09-02 | 1993-08-24 | Forging and a method for its manufacture |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0586179B1 (en) |
| DE (1) | DE69322028T2 (en) |
| FI (1) | FI95049C (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102006045871B4 (en) * | 2006-09-28 | 2010-01-28 | Rothe Erde Gmbh | Process for thermomechanical treatment of rings produced seamlessly on radial-axial ring rolling machines |
| CN111057933B (en) * | 2019-12-17 | 2021-01-15 | 宁波海琰伟业金属制品有限公司 | Manufacturing process of hot-work die steel for high-performance die-casting die |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE749477C (en) * | 1941-12-23 | 1953-03-23 | Edelstahlwerke A G Krefeld Deu | Steel with high resistance to sudden loads |
| DE927213C (en) * | 1942-08-12 | 1955-05-02 | Oberhuetten Vereinigte Obersch | Items made from construction steel |
| US3348981A (en) * | 1964-02-21 | 1967-10-24 | Yawata Iron & Steel Co | High tension low temperature tough steel |
| JPS61264170A (en) * | 1985-05-17 | 1986-11-22 | Tsubakimoto Chain Co | Pin for chain |
-
1992
- 1992-09-02 FI FI923929A patent/FI95049C/en not_active IP Right Cessation
-
1993
- 1993-08-24 DE DE1993622028 patent/DE69322028T2/en not_active Expired - Lifetime
- 1993-08-24 EP EP93306710A patent/EP0586179B1/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| WEGST: "STAHLSCHLÜSSEL", VERLAG STAHLSCHLÜSSEL, PP. 58-61 * |
Also Published As
| Publication number | Publication date |
|---|---|
| FI923929A0 (en) | 1992-09-02 |
| FI95049C (en) | 1995-12-11 |
| EP0586179A1 (en) | 1994-03-09 |
| FI95049B (en) | 1995-08-31 |
| FI923929A (en) | 1994-03-03 |
| DE69322028D1 (en) | 1998-12-17 |
| DE69322028T2 (en) | 1999-04-01 |
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