CA2519509C - Method for the thermomechanical treatment of steel - Google Patents
Method for the thermomechanical treatment of steel Download PDFInfo
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- CA2519509C CA2519509C CA2519509A CA2519509A CA2519509C CA 2519509 C CA2519509 C CA 2519509C CA 2519509 A CA2519509 A CA 2519509A CA 2519509 A CA2519509 A CA 2519509A CA 2519509 C CA2519509 C CA 2519509C
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- rod
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- steel
- skew rolling
- heating
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- 238000000034 method Methods 0.000 title claims abstract description 87
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 68
- 239000010959 steel Substances 0.000 title claims abstract description 68
- 230000000930 thermomechanical effect Effects 0.000 title claims abstract description 14
- 238000005096 rolling process Methods 0.000 claims abstract description 50
- 238000010438 heat treatment Methods 0.000 claims abstract description 48
- 238000001953 recrystallisation Methods 0.000 claims abstract description 32
- 230000008569 process Effects 0.000 claims abstract description 19
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 8
- 238000003303 reheating Methods 0.000 claims description 16
- 239000007858 starting material Substances 0.000 claims description 13
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 238000005496 tempering Methods 0.000 claims description 9
- 230000015572 biosynthetic process Effects 0.000 claims description 7
- 239000003381 stabilizer Substances 0.000 claims description 6
- 238000004804 winding Methods 0.000 claims description 5
- 238000009826 distribution Methods 0.000 claims description 4
- 229910000639 Spring steel Inorganic materials 0.000 claims description 3
- DYRBFMPPJATHRF-UHFFFAOYSA-N chromium silicon Chemical compound [Si].[Cr] DYRBFMPPJATHRF-UHFFFAOYSA-N 0.000 claims description 2
- 229910001220 stainless steel Inorganic materials 0.000 claims description 2
- 229910000742 Microalloyed steel Inorganic materials 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 16
- 230000003068 static effect Effects 0.000 abstract description 4
- 230000009466 transformation Effects 0.000 description 31
- 229910001566 austenite Inorganic materials 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910000669 Chrome steel Inorganic materials 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- QKJXFFMKZPQALO-UHFFFAOYSA-N chromium;iron;methane;silicon Chemical compound C.[Si].[Cr].[Fe] QKJXFFMKZPQALO-UHFFFAOYSA-N 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
-
- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
-
- 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/02—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for springs
-
- 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
- C21D1/34—Methods of heating
- C21D1/42—Induction heating
-
- 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
- C21D2221/00—Treating localised areas of an article
- C21D2221/01—End parts (e.g. leading, trailing end)
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
- Metal Rolling (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
The invention relates to a method for the thermomechanical treatment of steel.
According to said method, the parent material is heated to a temperature in excess of the re-crystallisation temperature, the structure is austenitised, held at an equalised temperature and then formed and subsequently quenched to form martensite and tempered. Round steel bars, whose re-crystallisation temperature is adjusted over the bar length in a compensation furnace, constitute the parent material. The round steel bars are subsequently re-modelled by cross-rolling, remaining substantially straight and after the critical deformation degree has been exceeded are subjected to dynamic re-crystallisation processes. The round steel bars are then subjected to a post-heating process above the Ac3 temperature, in order to undergo a complete static re-crystallisation and finally are quenched from the austenitic state to form martensite and tempered.
According to said method, the parent material is heated to a temperature in excess of the re-crystallisation temperature, the structure is austenitised, held at an equalised temperature and then formed and subsequently quenched to form martensite and tempered. Round steel bars, whose re-crystallisation temperature is adjusted over the bar length in a compensation furnace, constitute the parent material. The round steel bars are subsequently re-modelled by cross-rolling, remaining substantially straight and after the critical deformation degree has been exceeded are subjected to dynamic re-crystallisation processes. The round steel bars are then subjected to a post-heating process above the Ac3 temperature, in order to undergo a complete static re-crystallisation and finally are quenched from the austenitic state to form martensite and tempered.
Description
METHOD FOR THE THERMOMECHANICAL TREATMENT OF STEEL
Field of the Invention The invention relates to a method for the thermomechanical treatment of steel.
Background of the Invention DE 43 40 568 C2 describes a method for the continuous heat treatment of steel wire, which comprises the following steps:
- Rapidly heating the wire to a temperature in the austenitic range at a rate between 85 and 100 C/s;
- Holding the steel wire in the austenitic range for a period of 10 to 60 s;
- Quenching the steel wire to room temperature at a rate > 80 C/s;
- Rapidly heating to the drawing temperature at a rate of 85 to 95 C/s;
- Holding at the drawing temperature for a period of 60 to 100 s;
- Cooling the wire at a rate of > 50 C/s common for water cooling.
Between steps 2 and 3, the wire can be rolled at a temperature just above the Ac3 temperature, the wire being ovalized in a first pass, rolled round in the second pass, and thereafter drawn through a gauging die.
In DE 195 45 204 Cl, a method is described for the manufacture of high-strength objects from a quenched and tempered steel and for using this process for the production of springs. The steel with (in weight %) 0.4 to 0.6%C, up to 1% Si, up to 1.8%
Mn, 0.8 to 1.5% Cr, 0.03 to 0.10% Nb, 0 to 0.2% V, the remainder being iron, is to be treated as follows:
- The raw material is solution annealed in the austenitic region at temperatures of 1050 to 1200 C;
- Immediately thereafter the raw material is shaped hot at a temperature above the recrystallization temperature in a first step;
- Immediately thereafter the raw material is hot-formed at a temperature below the recrystallization temperature, but above the Ac3 temperature in a second step;
- The rolling product is then held at a temperature above the Ac3 temperature for the performance of additional transformation and working processes, and thereafter - cooled to below the martensite temperature, whereupon - it is then tempered.
In DE 196 37 968 C2, a method is to be found for the high-temperature thermomechanical manufacture of spring leaves for leaf springs and/or leaf spring control arms, is the method being based on a two-step thermomechanical method of manufacturing parabolic springs, which is based on the following steps:
The starting material is heated at a heating rate between 4 C/s and 30 C/s to the austenitizing temperature;
The austenitizing temperature is 1100 + 100 C, The material is cooled from the austenitizing temperature to the temperature of the first rolling stage at a cooling rate between 10 Gs and 30 C/s.
- Then, in the first rolling step, at a temperature of 1050 + 100 C, with a non-constant changing of shape between 15% and 80%, it is roughed down in one or more passes.
- In the second rolling step, it is finish-rolled with rolls adjustable under load, at a temperature of 880 + 30 C with a change of shape between 15% and 45% over the length of the leaf spring.
Finally, the DE 198 39 383 C2 discloses a method for the thermomechanical treatment of steel for torsionally stressed spring elements, wherein the starting material is worked at a temperature above the recrystallization temperature and then reshaped at such a temperature above the recrystallization temperature in at least two transformation steps that a dynamic and/or static recrystallization of the austenite results.
The recrystallized austenite of the converted product is quenched and annealed. A
silicon-chromium steel is to be used, having a carbon content of 0.35 to 0.75%, which is microalloyed with vanadium or other alloying element.
The methods to be taken from the state of the art for the thermomechanical treatment of steel are based essentially on multiple converting steps, repeated cooling and heating of the starting material being necessary in order to produce the parameters obtained later on in the end product.
Summary of the Invention It is an object of the invention to make a method available for the thermomechanical treatment of steel, the method permitting a targeted improvement in the property parameters directed to the loading profile of the end product.
In accordance with one aspect of the present invention there is provided a method for thermomechanical treatment of a round steel rod, said method comprising:
deforming said steel rod in a single deforming step, coordinated with heat treatment of said steel rod, wherein said single deforming step, coordinated with heat treatment, includes:
heating said steel rod to a heating temperature that is above a recrystallization temperature;
equalizing the heating temperature of the steel rod over its length; causing said steel rod to be deformed by a single step of skew rolling while it remains substantially straight, such that a predetermined twisting of the steel rod occurs in a marginal area of said rod and a desired deformation gradient is achieved over a cross section of the rod, whereby, after a critical degree of deformation is exceeded, dynamic recrystallization process takes place with greatest intensity in the marginal area; reheating the rod to a temperature above Ac3 and hardening and tempering the rod.
Field of the Invention The invention relates to a method for the thermomechanical treatment of steel.
Background of the Invention DE 43 40 568 C2 describes a method for the continuous heat treatment of steel wire, which comprises the following steps:
- Rapidly heating the wire to a temperature in the austenitic range at a rate between 85 and 100 C/s;
- Holding the steel wire in the austenitic range for a period of 10 to 60 s;
- Quenching the steel wire to room temperature at a rate > 80 C/s;
- Rapidly heating to the drawing temperature at a rate of 85 to 95 C/s;
- Holding at the drawing temperature for a period of 60 to 100 s;
- Cooling the wire at a rate of > 50 C/s common for water cooling.
Between steps 2 and 3, the wire can be rolled at a temperature just above the Ac3 temperature, the wire being ovalized in a first pass, rolled round in the second pass, and thereafter drawn through a gauging die.
In DE 195 45 204 Cl, a method is described for the manufacture of high-strength objects from a quenched and tempered steel and for using this process for the production of springs. The steel with (in weight %) 0.4 to 0.6%C, up to 1% Si, up to 1.8%
Mn, 0.8 to 1.5% Cr, 0.03 to 0.10% Nb, 0 to 0.2% V, the remainder being iron, is to be treated as follows:
- The raw material is solution annealed in the austenitic region at temperatures of 1050 to 1200 C;
- Immediately thereafter the raw material is shaped hot at a temperature above the recrystallization temperature in a first step;
- Immediately thereafter the raw material is hot-formed at a temperature below the recrystallization temperature, but above the Ac3 temperature in a second step;
- The rolling product is then held at a temperature above the Ac3 temperature for the performance of additional transformation and working processes, and thereafter - cooled to below the martensite temperature, whereupon - it is then tempered.
In DE 196 37 968 C2, a method is to be found for the high-temperature thermomechanical manufacture of spring leaves for leaf springs and/or leaf spring control arms, is the method being based on a two-step thermomechanical method of manufacturing parabolic springs, which is based on the following steps:
The starting material is heated at a heating rate between 4 C/s and 30 C/s to the austenitizing temperature;
The austenitizing temperature is 1100 + 100 C, The material is cooled from the austenitizing temperature to the temperature of the first rolling stage at a cooling rate between 10 Gs and 30 C/s.
- Then, in the first rolling step, at a temperature of 1050 + 100 C, with a non-constant changing of shape between 15% and 80%, it is roughed down in one or more passes.
- In the second rolling step, it is finish-rolled with rolls adjustable under load, at a temperature of 880 + 30 C with a change of shape between 15% and 45% over the length of the leaf spring.
Finally, the DE 198 39 383 C2 discloses a method for the thermomechanical treatment of steel for torsionally stressed spring elements, wherein the starting material is worked at a temperature above the recrystallization temperature and then reshaped at such a temperature above the recrystallization temperature in at least two transformation steps that a dynamic and/or static recrystallization of the austenite results.
The recrystallized austenite of the converted product is quenched and annealed. A
silicon-chromium steel is to be used, having a carbon content of 0.35 to 0.75%, which is microalloyed with vanadium or other alloying element.
The methods to be taken from the state of the art for the thermomechanical treatment of steel are based essentially on multiple converting steps, repeated cooling and heating of the starting material being necessary in order to produce the parameters obtained later on in the end product.
Summary of the Invention It is an object of the invention to make a method available for the thermomechanical treatment of steel, the method permitting a targeted improvement in the property parameters directed to the loading profile of the end product.
In accordance with one aspect of the present invention there is provided a method for thermomechanical treatment of a round steel rod, said method comprising:
deforming said steel rod in a single deforming step, coordinated with heat treatment of said steel rod, wherein said single deforming step, coordinated with heat treatment, includes:
heating said steel rod to a heating temperature that is above a recrystallization temperature;
equalizing the heating temperature of the steel rod over its length; causing said steel rod to be deformed by a single step of skew rolling while it remains substantially straight, such that a predetermined twisting of the steel rod occurs in a marginal area of said rod and a desired deformation gradient is achieved over a cross section of the rod, whereby, after a critical degree of deformation is exceeded, dynamic recrystallization process takes place with greatest intensity in the marginal area; reheating the rod to a temperature above Ac3 and hardening and tempering the rod.
In accordance with another aspect of the present invention there is provided a method for thermomechanical treatment of steel rods, said method comprising:
starting with a round steel rod; heating said steel rod to a temperature that exceeds a recrystallization temperature of steel of said rod; and causing formation of a desired gradient in a degree of recrystallization of said steel of said rod over a cross section of said rod, with a marginal area having a fine-grained martensite structure, whereby said rod has a cross sectional strength profile that reaches a maximum value in said marginal area of said rod; wherein said step of causing formation of said desired gradient comprises: equalizing the temperature of said steel rod over its entire length;
maintaining said steel rod at said equalized temperature; skew rolling said rod while it remains straight, said steel rod entering said skew rolling at said equalized temperature, whereby a predetermined twisting of said steel in said rod is achieved in said marginal area; reheating the rod to a temperature above Ac3; and hardening and tempering the rod.
In accordance with yet another aspect of the present invention there is provided a method for producing a steel coil spring or stabilizer, said method, comprising: heating said steel rod to a heating temperature that is above a recrystallization temperature;
equalizing the heating temperature of the steel rod over its length; using a round steel rod as a starting material; deforming said steel rod in a single deforming step, coordinated with heat treatment of said steel rod, wherein the single step of deforming coordinated with heat treatment includes: causing said steel rod to be deformed by a single skew rolling step while it remains substantially straight, such that a predetermined twisting occurs in a marginal area of said steel rod and a desired deformation gradient is achieved over a cross section of the rod, dynamic recrystallization processes take place with greatest intensity in the marginal area; reheating the rod to a temperature above Ac3;
forming the rod into one of the coil spring and the stabilizer; and hardening and tempering the formed rod.
3a Brief Description of the Drawing Fig. 1 shows a production line for producing coil springs.
Detailed Description For the inventive method, the starting material is first heated to a temperature above the recrystallization temperature and subsequently the temperature is equalized over the entire length of the rod. Furthermore, the temperature, to which the rod is heated, is kept constant virtually up to the entry of the rod into the roll gap. With these working steps a highly uniform structure of the rod is sought, both over its length and through its cross section, before it enters the roll gap, which is of advantage for the transformation process that 3b follows. On account of the process-specific peculiarities of the skew rolling and due to a targeted establishment of the rolling parameters, a predetermined twisting of the material in the marginal area of the rods and a transformation gradient over the cross section of the rod set in. Since the direction of transformation during the skew rolling is at an angle to the axis of the material and the maximum of the transformation is in the marginal region of the rods, the structural stretching in this marginal zone, caused by the transformation, is especially greatly pronounced and the structural alignment corresponds to the transformation direction and also extends at an angle to the axis of the rolled material. After the critical degree of transformation is exceeded, the dynamic recrystallization process takes place with special intensity in this marginal zone, so that a gradient of the degree of recrystallization from the outside to the inside may be noted over the cross section of the rod. In the reheating following the transformation process to a temperature above Ac3, the static recrystallization is completed and leads to the formation of fine-grained austenite, especially in the marginal zone. After hardening followed by tempering, the marginal zone is characterized by a martensite structure of great strength.
The invention has considerable advantages over the solutions known from the state of the art. As a result of the combination of a targeted, one-step transformation by means of skew rolling and a heat treatment coordinated therewith, the treated rods have a strength profile on their cross section, which reaches its maximum values in the marginal area. The direction of the twist of the structure produced by the skew rolling in the marginal region of the round rods corresponds to the main direction of stress of a component subjected to torsion, and the properties developed by the rods as a result thus provide optimum prerequisites for their use especially in the spring industry. The distribution of structures over the cross section of the rod produced by the inventive method results in a property profile, which is adequate for the stress profile over the cross section of the rod during bending and torsional stresses.
Since only a transformation step is necessary for the development of these advantageous strength effects, and the working steps that follow are performed essentially at an elevated temperature, only a heating process for the starting material is therefore necessary. This leads to considerable savings of energy and time resulting from the procedure itself. The inventive method is distinguished therefore from known methods not only by an improvement in the stress-oriented strength and toughness properties of the finished product, but also by economic advantages offered by the minimal number of process steps.
Advantageously, the starting material, in the form of round rods, is heated inductively at a rate of 100 to 400 K/s to a temperature between 7000 and 1100 C.
Subsequently, the heating temperature of the rod is equalized over its length during a period of at least 10 seconds. With that, it is assured that the temperature difference does not exceed 5 K over the length of the rod. By means of reheating equipment, the heating temperature of the rod is kept constant until it enters the roll gap. The transformation itself is performed by skew rolling in a single step, in which the rods run uniformly straight through the roll gap. Depending on the quality of the starting material, the transformation is carried out in a temperature range of 700 - 1150 C. The ratio of the starting diameter to the finished diameter is selected so that the skew rolling of the rods is performed with a mean degree of stretching A. of more than 1.3, and that the maximum transformation amounts to W
= 0.3. By the targeted setting of the rolling parameters, such as rotational speed and rate of feed, and by the special choice of roll contours with specific angular relationships, it is brought about that the maximum transformation in the marginal region is between 0.65 and 1.0 of the diameter of the rods, and that a desired transformation gradient is established over the cross section. Preferably, the skew rolling process is controlled so that a maximum local temperature increase of 50 K is not exceeded in the rolled material.
Due to the transformation action, after a critical transformation degree is exceeded, dynamic recrystallization processes take place, which, on account of the maximum transformation, are more strongly pronounced in the marginal zone than in the core region of the rods. The targeted influencing of the formation of a transformation gradient over the cross section of the rod has the result that the first indications of a differentiated structure distribution appear across the cross section of the rod already during the course of the dynamic recrystallization. Thus, metallographic studies on rods in the recrystallized state, which have been rolled pursuant to the invention, show that the proportion of fine austenite crystals decreases clearly from the marginal zone toward the core region.
The differentiated structural formation across the cross section of the rolled material is furthermore additionally intensified by a typical peculiarity of skew rolling. Since the direction of transformation runs at an angle to the direction of the rolled material in skew rolling, a striking stretching of structure occurs especially in the marginal areas of the material due to the greater degree of transformation. The structure is also stretched at an angle to the axis of the rolled material and leads to a twisting of the material in the marginal zones. In the course of the inventive process, the direction of the twisting of the structure in the marginal region of the rods is 35 to 65 degrees of angle with respect to the longitudinal axis of the rod and thus corresponds to the main direction of stress of a component subjected to torsion.
In the process of single-step skew rolling shown, the rod being rolled runs on its entire length through a roll gap with a diameter remaining uniform over the entire length of the rod. This procedure is selected whenever rods with uniform diameter over their entire length are to be produced. The inventive method furthermore makes an alternative variation of the process possible, in which the roll gap geometry is varied in the operating state while the rod is passing though the roll gap. This flexible manner of operation is achieved with a skew roll stand, the rolls of which can be adjusted in the axial and/or radial direction as needed during the transformation. The inventive method thus permits round rods to be produced, the diameter of which varies over the length of the rods.
Immediately after they exit from the roll stand, the skew-rolled rods are subjected to reheating at a temperature above Ac3 in such a manner, that the temperature difference over the length of a rod is limited to 5 K.
Depending on their later intended use, the rods, skew-rolled and reheated to the recrystallization temperature, are coiled hot either to form coil springs or bent to form a stabilizer.
The coiled or bent components are then hardened and afterward tempered.
Rods, which are intended for manufacturing torsion bar springs, are mechanically worked at their ends in the cold state after reheating, then heated to above Ac3, quenched and tempered.
Macro-examinations of the finished rods show a typical distribution of structures over the cross sections of the rods as a consequence of the inventive combination of skew rolling and heat treatment. The immediate marginal zone has fine-grained martensite structure of high strength. The marginal area has a continuous structure extending at an angle to the axis of the rod, the direction of twist corresponding to the main direction of tension of a torsionally stressed component. The mixed pearlite-niartensite structure of the characteristic zone is coarser than the structure in the marginal area and exhibits no twisting phenomena.
To provide optimum toughness and strength parameters in the finished product, round rods of spring steel, preferably silicon-chrome steels with carbon contents <
0.8%, are used as starting material in the inventive method. Alternatively, these steels can be micro-alloyed with vanadium or niobium.
The inventive object is represented by an embodiment in the drawing and is described as follows.
The sole Figure shows the diagrammatic arrangement of a continuous working line for the inventive thermomechanical treatment of round steel rods of a silicon-chrome steel.
The rods to be treated are heated in an induction apparatus I to a temperature above the recrystallization temperature, while its structure is austenitized.
In the present example, the round steel rods are heated at a rate of 130 K/s to a temperature of 980 C. In an equalization furnace 2 following the induction apparatus 1, the heating temperature of the rods is equalized for a period of 15 s, so that the temperature curve over the length of the rods has a gradient of 4 K.
In this state the round steel rods, now at uniform temperature, are brought into a holding oven 3 to keep their temperature constant until they enter the roll gap. The heated rods are transported by means of gang rolls 6 and 7, both in the equalizing oven 2 and in the holding oven 3.
In a skew rolling stand 4, the round steel rods, heated to 980 C, are shaped in a rolling step. At the same time the ratio of starting diameter to finish diameter is chosen so that the average degree of stretching IL is 1.5 and that the maximum transformation w is at least 0.3. By the targeted setting of rolling parameters, such as the roller speed or the rate of feed and by the special selection of rolling shapes with specific angular relationships, the maximum transformation in the marginal region between 0.65 and 1.0 of the diameter of the rods is achieved and thus a desired transformation gradient is established over the rod's cross section. The rolling parameters are coordinated with one another so that a maximum local temperature elevation of 50 K is not exceeded in the material due to the transformation process. The direction of transformation at an angle to the rolling axis during the skew rolling produces in the marginal regions of the material rolled a pronounced stretching of its structure because of the greater transformation. Corresponding to the direction of transformation, this stretching of structure likewise runs at an angle to the axis of the rolled material and, in the marginal regions of the rods, results in a twisting of the material. In the course of the inventive process, the direction of the twisting of the structure, with respect to the longitudinal axis of the rods, amounts to 35 to 65 degrees of angle and thus corresponds to the main direction of stress of a component subjected to torsion.
After they exit from the skew rolling stand 4, the rolled rods pass into a downstream reheating furnace 5, in which they are reheated above the Ac3 temperature to assure complete static recrystallization. The rods are transported through the reheating furnace 5 by means of a roller conveyor 8. After leaving the reheating furnace 5 the skew-rolled rods are carried away on transfer roller conveyors 9. From this transfer roller conveyor 9 the rods are delivered to the rest of the intended processing steps.
Figure 1 diagrammatically shows a production line for producing wound coil springs. Accordingly, the rods are passed over the transfer roller conveyor 9 to a lift table 10 and pass from there into a CNC winding bench 11 where the hot winding to coil springs takes place after the recrystallization. After the winding process, the rods, now wound into coil springs, are transferred to a hardening vat 12, in which they are quenched and their structure is converted to martensite. The hardened coil springs are then subjected to a tempering treatment, which is not shown.
List of Reference Numbers 1. Induction apparatus 2. Equalization furnace 3. Holding Oven 4. Skew rolling stand 5. Reheating furnace 6. Gang rolls 7. Gang rolls 8. Gang rolls 9. Transfer roller conveyors 10. Lift table 11. CNC winding bench 12. Hardening vat
starting with a round steel rod; heating said steel rod to a temperature that exceeds a recrystallization temperature of steel of said rod; and causing formation of a desired gradient in a degree of recrystallization of said steel of said rod over a cross section of said rod, with a marginal area having a fine-grained martensite structure, whereby said rod has a cross sectional strength profile that reaches a maximum value in said marginal area of said rod; wherein said step of causing formation of said desired gradient comprises: equalizing the temperature of said steel rod over its entire length;
maintaining said steel rod at said equalized temperature; skew rolling said rod while it remains straight, said steel rod entering said skew rolling at said equalized temperature, whereby a predetermined twisting of said steel in said rod is achieved in said marginal area; reheating the rod to a temperature above Ac3; and hardening and tempering the rod.
In accordance with yet another aspect of the present invention there is provided a method for producing a steel coil spring or stabilizer, said method, comprising: heating said steel rod to a heating temperature that is above a recrystallization temperature;
equalizing the heating temperature of the steel rod over its length; using a round steel rod as a starting material; deforming said steel rod in a single deforming step, coordinated with heat treatment of said steel rod, wherein the single step of deforming coordinated with heat treatment includes: causing said steel rod to be deformed by a single skew rolling step while it remains substantially straight, such that a predetermined twisting occurs in a marginal area of said steel rod and a desired deformation gradient is achieved over a cross section of the rod, dynamic recrystallization processes take place with greatest intensity in the marginal area; reheating the rod to a temperature above Ac3;
forming the rod into one of the coil spring and the stabilizer; and hardening and tempering the formed rod.
3a Brief Description of the Drawing Fig. 1 shows a production line for producing coil springs.
Detailed Description For the inventive method, the starting material is first heated to a temperature above the recrystallization temperature and subsequently the temperature is equalized over the entire length of the rod. Furthermore, the temperature, to which the rod is heated, is kept constant virtually up to the entry of the rod into the roll gap. With these working steps a highly uniform structure of the rod is sought, both over its length and through its cross section, before it enters the roll gap, which is of advantage for the transformation process that 3b follows. On account of the process-specific peculiarities of the skew rolling and due to a targeted establishment of the rolling parameters, a predetermined twisting of the material in the marginal area of the rods and a transformation gradient over the cross section of the rod set in. Since the direction of transformation during the skew rolling is at an angle to the axis of the material and the maximum of the transformation is in the marginal region of the rods, the structural stretching in this marginal zone, caused by the transformation, is especially greatly pronounced and the structural alignment corresponds to the transformation direction and also extends at an angle to the axis of the rolled material. After the critical degree of transformation is exceeded, the dynamic recrystallization process takes place with special intensity in this marginal zone, so that a gradient of the degree of recrystallization from the outside to the inside may be noted over the cross section of the rod. In the reheating following the transformation process to a temperature above Ac3, the static recrystallization is completed and leads to the formation of fine-grained austenite, especially in the marginal zone. After hardening followed by tempering, the marginal zone is characterized by a martensite structure of great strength.
The invention has considerable advantages over the solutions known from the state of the art. As a result of the combination of a targeted, one-step transformation by means of skew rolling and a heat treatment coordinated therewith, the treated rods have a strength profile on their cross section, which reaches its maximum values in the marginal area. The direction of the twist of the structure produced by the skew rolling in the marginal region of the round rods corresponds to the main direction of stress of a component subjected to torsion, and the properties developed by the rods as a result thus provide optimum prerequisites for their use especially in the spring industry. The distribution of structures over the cross section of the rod produced by the inventive method results in a property profile, which is adequate for the stress profile over the cross section of the rod during bending and torsional stresses.
Since only a transformation step is necessary for the development of these advantageous strength effects, and the working steps that follow are performed essentially at an elevated temperature, only a heating process for the starting material is therefore necessary. This leads to considerable savings of energy and time resulting from the procedure itself. The inventive method is distinguished therefore from known methods not only by an improvement in the stress-oriented strength and toughness properties of the finished product, but also by economic advantages offered by the minimal number of process steps.
Advantageously, the starting material, in the form of round rods, is heated inductively at a rate of 100 to 400 K/s to a temperature between 7000 and 1100 C.
Subsequently, the heating temperature of the rod is equalized over its length during a period of at least 10 seconds. With that, it is assured that the temperature difference does not exceed 5 K over the length of the rod. By means of reheating equipment, the heating temperature of the rod is kept constant until it enters the roll gap. The transformation itself is performed by skew rolling in a single step, in which the rods run uniformly straight through the roll gap. Depending on the quality of the starting material, the transformation is carried out in a temperature range of 700 - 1150 C. The ratio of the starting diameter to the finished diameter is selected so that the skew rolling of the rods is performed with a mean degree of stretching A. of more than 1.3, and that the maximum transformation amounts to W
= 0.3. By the targeted setting of the rolling parameters, such as rotational speed and rate of feed, and by the special choice of roll contours with specific angular relationships, it is brought about that the maximum transformation in the marginal region is between 0.65 and 1.0 of the diameter of the rods, and that a desired transformation gradient is established over the cross section. Preferably, the skew rolling process is controlled so that a maximum local temperature increase of 50 K is not exceeded in the rolled material.
Due to the transformation action, after a critical transformation degree is exceeded, dynamic recrystallization processes take place, which, on account of the maximum transformation, are more strongly pronounced in the marginal zone than in the core region of the rods. The targeted influencing of the formation of a transformation gradient over the cross section of the rod has the result that the first indications of a differentiated structure distribution appear across the cross section of the rod already during the course of the dynamic recrystallization. Thus, metallographic studies on rods in the recrystallized state, which have been rolled pursuant to the invention, show that the proportion of fine austenite crystals decreases clearly from the marginal zone toward the core region.
The differentiated structural formation across the cross section of the rolled material is furthermore additionally intensified by a typical peculiarity of skew rolling. Since the direction of transformation runs at an angle to the direction of the rolled material in skew rolling, a striking stretching of structure occurs especially in the marginal areas of the material due to the greater degree of transformation. The structure is also stretched at an angle to the axis of the rolled material and leads to a twisting of the material in the marginal zones. In the course of the inventive process, the direction of the twisting of the structure in the marginal region of the rods is 35 to 65 degrees of angle with respect to the longitudinal axis of the rod and thus corresponds to the main direction of stress of a component subjected to torsion.
In the process of single-step skew rolling shown, the rod being rolled runs on its entire length through a roll gap with a diameter remaining uniform over the entire length of the rod. This procedure is selected whenever rods with uniform diameter over their entire length are to be produced. The inventive method furthermore makes an alternative variation of the process possible, in which the roll gap geometry is varied in the operating state while the rod is passing though the roll gap. This flexible manner of operation is achieved with a skew roll stand, the rolls of which can be adjusted in the axial and/or radial direction as needed during the transformation. The inventive method thus permits round rods to be produced, the diameter of which varies over the length of the rods.
Immediately after they exit from the roll stand, the skew-rolled rods are subjected to reheating at a temperature above Ac3 in such a manner, that the temperature difference over the length of a rod is limited to 5 K.
Depending on their later intended use, the rods, skew-rolled and reheated to the recrystallization temperature, are coiled hot either to form coil springs or bent to form a stabilizer.
The coiled or bent components are then hardened and afterward tempered.
Rods, which are intended for manufacturing torsion bar springs, are mechanically worked at their ends in the cold state after reheating, then heated to above Ac3, quenched and tempered.
Macro-examinations of the finished rods show a typical distribution of structures over the cross sections of the rods as a consequence of the inventive combination of skew rolling and heat treatment. The immediate marginal zone has fine-grained martensite structure of high strength. The marginal area has a continuous structure extending at an angle to the axis of the rod, the direction of twist corresponding to the main direction of tension of a torsionally stressed component. The mixed pearlite-niartensite structure of the characteristic zone is coarser than the structure in the marginal area and exhibits no twisting phenomena.
To provide optimum toughness and strength parameters in the finished product, round rods of spring steel, preferably silicon-chrome steels with carbon contents <
0.8%, are used as starting material in the inventive method. Alternatively, these steels can be micro-alloyed with vanadium or niobium.
The inventive object is represented by an embodiment in the drawing and is described as follows.
The sole Figure shows the diagrammatic arrangement of a continuous working line for the inventive thermomechanical treatment of round steel rods of a silicon-chrome steel.
The rods to be treated are heated in an induction apparatus I to a temperature above the recrystallization temperature, while its structure is austenitized.
In the present example, the round steel rods are heated at a rate of 130 K/s to a temperature of 980 C. In an equalization furnace 2 following the induction apparatus 1, the heating temperature of the rods is equalized for a period of 15 s, so that the temperature curve over the length of the rods has a gradient of 4 K.
In this state the round steel rods, now at uniform temperature, are brought into a holding oven 3 to keep their temperature constant until they enter the roll gap. The heated rods are transported by means of gang rolls 6 and 7, both in the equalizing oven 2 and in the holding oven 3.
In a skew rolling stand 4, the round steel rods, heated to 980 C, are shaped in a rolling step. At the same time the ratio of starting diameter to finish diameter is chosen so that the average degree of stretching IL is 1.5 and that the maximum transformation w is at least 0.3. By the targeted setting of rolling parameters, such as the roller speed or the rate of feed and by the special selection of rolling shapes with specific angular relationships, the maximum transformation in the marginal region between 0.65 and 1.0 of the diameter of the rods is achieved and thus a desired transformation gradient is established over the rod's cross section. The rolling parameters are coordinated with one another so that a maximum local temperature elevation of 50 K is not exceeded in the material due to the transformation process. The direction of transformation at an angle to the rolling axis during the skew rolling produces in the marginal regions of the material rolled a pronounced stretching of its structure because of the greater transformation. Corresponding to the direction of transformation, this stretching of structure likewise runs at an angle to the axis of the rolled material and, in the marginal regions of the rods, results in a twisting of the material. In the course of the inventive process, the direction of the twisting of the structure, with respect to the longitudinal axis of the rods, amounts to 35 to 65 degrees of angle and thus corresponds to the main direction of stress of a component subjected to torsion.
After they exit from the skew rolling stand 4, the rolled rods pass into a downstream reheating furnace 5, in which they are reheated above the Ac3 temperature to assure complete static recrystallization. The rods are transported through the reheating furnace 5 by means of a roller conveyor 8. After leaving the reheating furnace 5 the skew-rolled rods are carried away on transfer roller conveyors 9. From this transfer roller conveyor 9 the rods are delivered to the rest of the intended processing steps.
Figure 1 diagrammatically shows a production line for producing wound coil springs. Accordingly, the rods are passed over the transfer roller conveyor 9 to a lift table 10 and pass from there into a CNC winding bench 11 where the hot winding to coil springs takes place after the recrystallization. After the winding process, the rods, now wound into coil springs, are transferred to a hardening vat 12, in which they are quenched and their structure is converted to martensite. The hardened coil springs are then subjected to a tempering treatment, which is not shown.
List of Reference Numbers 1. Induction apparatus 2. Equalization furnace 3. Holding Oven 4. Skew rolling stand 5. Reheating furnace 6. Gang rolls 7. Gang rolls 8. Gang rolls 9. Transfer roller conveyors 10. Lift table 11. CNC winding bench 12. Hardening vat
Claims (38)
1. A method for thermomechanical treatment of a round steel rod, said method comprising:
deforming said steel rod in a single deforming step, coordinated with heat treatment of said steel rod, wherein said single deforming step, coordinated with heat treatment, includes:
heating said steel rod to a heating temperature that is above a recrystallization temperature;
equalizing the heating temperature of the steel rod over its length;
causing said steel rod to be deformed by a single step of skew rolling while it remains substantially straight, such that a predetermined twisting of the steel rod occurs in a marginal area of said rod and a desired deformation gradient is achieved over a cross section of the rod, whereby, after a critical degree of deformation is exceeded, dynamic recrystallization process takes place with greatest intensity in the marginal area;
reheating the rod to a temperature above Ac3 and hardening and tempering the rod.
deforming said steel rod in a single deforming step, coordinated with heat treatment of said steel rod, wherein said single deforming step, coordinated with heat treatment, includes:
heating said steel rod to a heating temperature that is above a recrystallization temperature;
equalizing the heating temperature of the steel rod over its length;
causing said steel rod to be deformed by a single step of skew rolling while it remains substantially straight, such that a predetermined twisting of the steel rod occurs in a marginal area of said rod and a desired deformation gradient is achieved over a cross section of the rod, whereby, after a critical degree of deformation is exceeded, dynamic recrystallization process takes place with greatest intensity in the marginal area;
reheating the rod to a temperature above Ac3 and hardening and tempering the rod.
2. The method of claim 1, wherein, in said heating step the rod is heated at a rate between 100 - 400 K/s.
3. The method of claim 1, wherein, in said heating step the rod is heated to the heating temperature between 700° and 1100°C.
4. The method of claim 1, wherein, in said heating step the heating is performed inductively.
5. The method of claim 1, wherein the equalizing of the heating temperature of the rod takes place for at least 10 seconds.
6. The method of claim 1, wherein a temperature difference over the length of the rod is equal to or lower than 5 K.
7. The method of claim 1, wherein the skew rolling of the rod is performed with an average degree of stretching .lambda. of at least 1.3.
8. The method of claim 1, wherein a maximum deformation occurs in the marginal area of the rod between 0.65 and 1.0 times a diameter of the rod and a maximum degree of deformation is at least 0.3.
9. The method of claim 1, wherein, in the skew rolling, a maximum local temperature elevation is equal to or lower than 50 K.
10. The method of claim 1, wherein a direction of the twisting of a structure in the marginal region of the rod corresponds to a main direction of tension of a component stressed by torsion.
11. The method of claim 10, wherein the direction of twisting of the structure in the marginal region, with respect to the axis of the rod, amounts to 35 - 65 degrees of angle.
12. The method of claim 1, wherein structural distribution over a cross section of a finish-worked rod leads to a property profile which is adequate for a tension profile over the cross section in the case of at least one of flexural and torsional stress.
13. The method of claim 1, wherein the skew rolling is performed in a temperature range of 700° to 1150°C.
14. The method of claim 1, wherein said skew rolling is performed in a skew rolling stand;
rolls of a skew rolling stand are adjusted in one of an axial and a radial direction during the deformation process; and round rod is produced with a diameter which varies over its length.
rolls of a skew rolling stand are adjusted in one of an axial and a radial direction during the deformation process; and round rod is produced with a diameter which varies over its length.
15. The method of claim 14, wherein the heating temperature of the rod is kept constant virtually up to its entry into a roll gap of said rolls of the skew rolling stand.
16. The method of claim 1, wherein during the reheating of the rod above Ac3 following the skew rolling, a temperature difference over a length of the rod is limited to a maximum of 5 K.
17. The method of claim 1, wherein said steel rod comprises spring steel.
18. The method of claim 1, wherein the skew-rolled substantially straight rod is wound into a coil spring.
19. The method of claim 18, wherein the winding is performed in the same heat after recrystallization and before the hardening and tempering.
20. A method for thermomechanical treatment of steel rods, said method comprising:
starting with a round steel rod;
heating said steel rod to a temperature that exceeds a recrystallization temperature of steel of said rod; and causing formation of a desired gradient in a degree of recrystallization of said steel of said rod over a cross section of said rod, with a marginal area having a fine-grained martensite structure, whereby said rod has a cross sectional strength profile that reaches a maximum value in said marginal area of said rod;
wherein said step of causing formation of said desired gradient comprises:
equalizing the temperature of said steel rod over its entire length;
maintaining said steel rod at said equalized temperature;
skew rolling said rod while it remains straight, said steel rod entering said skew rolling at said equalized temperature, whereby a predetermined twisting of said steel in said rod is achieved in said marginal area;
reheating the rod to a temperature above Ac3; and hardening and tempering the rod.
starting with a round steel rod;
heating said steel rod to a temperature that exceeds a recrystallization temperature of steel of said rod; and causing formation of a desired gradient in a degree of recrystallization of said steel of said rod over a cross section of said rod, with a marginal area having a fine-grained martensite structure, whereby said rod has a cross sectional strength profile that reaches a maximum value in said marginal area of said rod;
wherein said step of causing formation of said desired gradient comprises:
equalizing the temperature of said steel rod over its entire length;
maintaining said steel rod at said equalized temperature;
skew rolling said rod while it remains straight, said steel rod entering said skew rolling at said equalized temperature, whereby a predetermined twisting of said steel in said rod is achieved in said marginal area;
reheating the rod to a temperature above Ac3; and hardening and tempering the rod.
21. A method for producing a steel coil spring or stabilizer, said method, comprising:
using a round steel rod as a starting material;
deforming said steel rod in a single deforming step, coordinated with heat treatment of said steel rod, wherein the single step of deforming coordinated with heat treatment includes:
heating said steel rod to a heating temperature that is above a recrystallization temperature;
equalizing the heating temperature of the steel rod over its length;
causing said steel rod to be deformed by a single skew rolling step while it remains substantially straight, such that a predetermined twisting occurs in a marginal area of said steel rod and a desired deformation gradient is achieved over a cross section of the rod, dynamic recrystallization processes take place with greatest intensity in the marginal area;
reheating the rod to a temperature above Ac3;
forming the rod into one of the coil spring and the stabilizer; and hardening and tempering the formed rod.
using a round steel rod as a starting material;
deforming said steel rod in a single deforming step, coordinated with heat treatment of said steel rod, wherein the single step of deforming coordinated with heat treatment includes:
heating said steel rod to a heating temperature that is above a recrystallization temperature;
equalizing the heating temperature of the steel rod over its length;
causing said steel rod to be deformed by a single skew rolling step while it remains substantially straight, such that a predetermined twisting occurs in a marginal area of said steel rod and a desired deformation gradient is achieved over a cross section of the rod, dynamic recrystallization processes take place with greatest intensity in the marginal area;
reheating the rod to a temperature above Ac3;
forming the rod into one of the coil spring and the stabilizer; and hardening and tempering the formed rod.
22. The method of claim 21, wherein a direction of the twisting of a structure in said marginal area of said rod corresponds to a main direction of tension of the coil springs or the stabilizer stressed by torsion.
23. The method of claim 21, wherein a direction of twisting of a structure in said marginal area of the rod is oriented with respect to the axis of the round rod within a range of 35 - 65 degrees.
24. The method of claim 21, wherein said skew rolling of the rod is performed with an average degree of stretching .lambda. of at least 1.3.
25. The method of claim 21, wherein a maximum deformation in said marginal area of the rod is between 0.65 and 1.0 times the diameter of the rod and is at least 0.3.
26. The method of claim 21, wherein, in said heating step, the rod is heated at a rate between 100 - 400 K/s.
27. The method of claim 21, wherein, in said heating step, the heating temperature is between 700 and 1100 degrees C.
28. The method of claim 21, wherein, in said heating step, the heating is performed inductively.
29. The method of claim 21, wherein the equalizing of the heating temperature of the rod takes place for at least 10 seconds.
30. The method of claim 21, wherein a temperature difference over a length of the rod is equal to or lower than 5 K.
31. The method of claim 21, wherein, during the skew rolling, a maximum local temperature increase is equal to or lower than 50 K.
32. The method of claim 21, wherein the skew rolling is performed in a temperature range of 700 to 1100 degrees C.
33. The method of claim 21, wherein the skew rolling is performed in a skew rolling stand;
rolls of the skew rolling stand are adjusted in one of an axial and a radial direction during deformation operation; and the round rod is produced with a diameter which varies over its length.
rolls of the skew rolling stand are adjusted in one of an axial and a radial direction during deformation operation; and the round rod is produced with a diameter which varies over its length.
34. A method as defined in claim 33, wherein the heating temperature of the rod is kept constant virtually up to its entry between said rolls of said skew rolling stand.
35. The method of claim 21, wherein, during the reheating step, a temperature difference over a length of the rod is limited to a maximum of 5 K.
36. The method of claim 21, wherein the starting material of the rod is spring steel.
37. The method of claim 21, wherein the starting material of the rod is silicon-chromium steel.
38. The method of claim 21, wherein the starting material of the rod is microalloyed steel.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10315418A DE10315418B3 (en) | 2003-04-04 | 2003-04-04 | Thermomechanical treatment of round steel bars heated above the recrystallization temperature useful in the thermomechanical and heat treatment of steel |
| DE10315418.3 | 2003-04-04 | ||
| PCT/EP2004/002281 WO2004087968A2 (en) | 2003-04-04 | 2004-03-05 | Method for the thermomechanical treatment of steel |
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| CA2519509A1 CA2519509A1 (en) | 2004-10-14 |
| CA2519509C true CA2519509C (en) | 2011-09-20 |
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| CA2519509A Expired - Fee Related CA2519509C (en) | 2003-04-04 | 2004-03-05 | Method for the thermomechanical treatment of steel |
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| EP (1) | EP1613783B1 (en) |
| JP (1) | JP4415009B2 (en) |
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| CN116219129A (en) * | 2021-12-02 | 2023-06-06 | 中国科学院金属研究所 | A method for constructing gradient grain structure in metal direct axis |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2261878A (en) * | 1939-09-11 | 1941-11-04 | L A Young Spring & Wire Corp | Method of manufacturing coil springs |
| US3988915A (en) * | 1974-11-22 | 1976-11-02 | Jannes Jonge Poerink | Method and apparatus for the production of prestressed coil springs |
| US4798071A (en) * | 1986-06-25 | 1989-01-17 | Kocks Technik Gmbh & Co. | Seamless tube production |
| DE3633058C1 (en) * | 1986-09-29 | 1987-07-30 | Brueninghaus Krupp Gmbh | Method and device for producing a coil spring |
| KR950007182B1 (en) * | 1987-08-17 | 1995-07-03 | 에이 .이 .비숍 앤드 어소시에이츠 피티와이 리미티드 | Contorl of straightness in scanning induction hardening of steel |
| DE4340568C2 (en) * | 1993-11-29 | 1996-04-18 | Sendner Thermo Tec Anlagen Gmb | Process for the continuous tempering of steel wire |
| TW281710B (en) * | 1994-05-02 | 1996-07-21 | Koshuha Netsuren Kk | |
| MX9702792A (en) * | 1994-10-20 | 1998-02-28 | Sumitomo Metal Ind | Method of manufacturing seamless steel pipes and manufacturing equipment therefor. |
| DK0828007T3 (en) * | 1995-05-15 | 2002-02-25 | Sumitomo Metal Ind | Process for Manufacturing High Strength Seamless Steel Pipe and Excellent Sulfide Stress Crack Resistance |
| DE19546204C1 (en) * | 1995-12-11 | 1997-03-20 | Max Planck Inst Eisenforschung | High strength steel object prodn.,esp. leaf spring |
| DE19637968C2 (en) * | 1996-09-18 | 2002-05-16 | Univ Freiberg Bergakademie | Process for the high-temperature thermomechanical production of spring leaves for leaf springs and / or leaf spring links |
| EP0974676A3 (en) * | 1998-07-20 | 2003-06-04 | Firma Muhr und Bender | Process for thermo-mechanically treating steel for torsion spring elements |
| DE19839383C2 (en) * | 1998-07-20 | 2001-04-19 | Muhr & Bender | Process for the thermomechanical treatment of steel for spring elements subject to torsion |
| KR100368530B1 (en) * | 1998-12-21 | 2003-01-24 | 가부시키가이샤 고베 세이코쇼 | Spring Steel Superior in Workability |
| US6341767B1 (en) * | 1999-06-29 | 2002-01-29 | Joseph B. Seale | Spring for valve control in engines |
| DE10030823C2 (en) * | 2000-06-23 | 2003-08-07 | Gmt Ges Fuer Metallurg Technol | 3-roll cross-rolling mill |
| JP2002254103A (en) | 2001-03-01 | 2002-09-10 | Sanyo Special Steel Co Ltd | Method for producing ferritic stainless steel wire rod, bar steel and steel pipe excellent in cold workability, and wire rod, bar steel and steel pipe produced by the method |
-
2003
- 2003-04-04 DE DE10315418A patent/DE10315418B3/en not_active Expired - Lifetime
-
2004
- 2004-03-05 JP JP2006504560A patent/JP4415009B2/en not_active Expired - Fee Related
- 2004-03-05 MX MXPA05009897A patent/MXPA05009897A/en active IP Right Grant
- 2004-03-05 CN CNB2004800092811A patent/CN100564549C/en not_active Expired - Fee Related
- 2004-03-05 ES ES04717575.7T patent/ES2640467T3/en not_active Expired - Lifetime
- 2004-03-05 CA CA2519509A patent/CA2519509C/en not_active Expired - Fee Related
- 2004-03-05 US US10/551,537 patent/US7828918B2/en not_active Expired - Lifetime
- 2004-03-05 PT PT47175757T patent/PT1613783T/en unknown
- 2004-03-05 KR KR1020057017200A patent/KR100776955B1/en not_active Expired - Fee Related
- 2004-03-05 BR BRPI0408922-7A patent/BRPI0408922B1/en not_active IP Right Cessation
- 2004-03-05 EP EP04717575.7A patent/EP1613783B1/en not_active Expired - Lifetime
- 2004-03-05 WO PCT/EP2004/002281 patent/WO2004087968A2/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| PT1613783T (en) | 2017-09-22 |
| US20060231175A1 (en) | 2006-10-19 |
| MXPA05009897A (en) | 2006-05-31 |
| CN100564549C (en) | 2009-12-02 |
| WO2004087968A3 (en) | 2005-04-28 |
| US7828918B2 (en) | 2010-11-09 |
| WO2004087968A2 (en) | 2004-10-14 |
| EP1613783B1 (en) | 2017-06-14 |
| KR20050115283A (en) | 2005-12-07 |
| JP4415009B2 (en) | 2010-02-17 |
| CN1771341A (en) | 2006-05-10 |
| CA2519509A1 (en) | 2004-10-14 |
| DE10315418B3 (en) | 2004-07-22 |
| BRPI0408922A (en) | 2006-03-28 |
| KR100776955B1 (en) | 2007-11-21 |
| BRPI0408922B1 (en) | 2011-11-29 |
| JP2006524573A (en) | 2006-11-02 |
| ES2640467T3 (en) | 2017-11-03 |
| EP1613783A2 (en) | 2006-01-11 |
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