CA2284124A1 - Method for producing a highly resistant, very ductile steel strip - Google Patents
Method for producing a highly resistant, very ductile steel strip Download PDFInfo
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- CA2284124A1 CA2284124A1 CA002284124A CA2284124A CA2284124A1 CA 2284124 A1 CA2284124 A1 CA 2284124A1 CA 002284124 A CA002284124 A CA 002284124A CA 2284124 A CA2284124 A CA 2284124A CA 2284124 A1 CA2284124 A1 CA 2284124A1
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- steel
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- temperature
- hot strip
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Classifications
-
- 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
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
-
- 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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention relates to a method for producing a highly resistant (at least 900MPa), very ductile steel strip. The steel, containing (in mass per cent); 0.10 to 0.20 % C; 0.30 to 0.60 % Si; 1.50 to 2.00 % Mn; max. 0.08 % P; 0.30 to 0.80 % Cr; up to 0.40 % Mo; up to 0.20 % Ti and/or Zr; up to 0.08 % Nb; the remainder being Fe and unavoidable impurities, is melted, cast in slabs and then rolled out into a hot rolled strip. The roll end temperature is above 800oC, the cooling speed on the delivery roller table is at least 30oC/s and the reel temperature is 300 to 600oC.
Description
s WE/wa 97752 05. March 1998 A METHOD FOR PRODUCING A STRIP STEEL WITH HIGH STRENGTH
AND GOOD FORMING ABILITIES
The invention relates to a method for producing a strip steel with high strength of at least 900 MPa and good forming abilities.
The demand for the reduction of fuel consumption of vehicles requires the application of lightweight concepts. Lightweight constructions can be achieved by a reduction of the thicknesses of sheet steel. For compensating any thus caused losses in strength of the component it is necessary to increase the strength of the material. Any increase in the strength usually causes a reduction in the deformability. Sheet steels used in the construction of vehicles must be brought into the final shape required for design or functional purposes by forming. If the increase in the strength and the thus resulting decrease in forming abilities become too high, failures will occur during the forming by local constrictions and tearing. For this reason an increase in the strength is limited.
The development of steels is always aimed at improving the ratio between deformability and strength.
Considerable success has already been achieved in the range of strength under 500 MPa concerning a reduction of the sheet thickness by using phosphorus-alloyed or micro-alloyed steels. Even better results were achieved with bake-hardening steels. In the strength range between 500 and 800 MPa the developments of the dual-phase and TRIP
(transformation-induced plasticity) steels yielded relatively good forming ability values.
The characteristic values relevant for the forming can be gained with high representativity for practical operation from the tension test. In particular, breaking elongation and the n-value (amount for strengthening capacity) represent important dimensional figures. The n-value is characteristic for the deformability under stretch-forming stress. This is the predominant deformation mechanism in most steel sheet parts of a vehicle. The n-value corresponds relatively well to the ratio of yield stress to tensile strength, which is also a value representative in practical operation for the strengthening capacity of a material.
In order to exploit the advantage of increasing the strength for reducing the sheet thickness to the highest possible extent, the highest possible values concerning breaking elongation (A) and the strengthening value (n-value) are pursued.
Steels with very high strengths over 800 MPa can be used very efficiently for the reduction of weight of crash-relevant components such as door impact beams, bumper beams. For this purpose, however, it is necessary to reduce the sheet thickness from over 2.0 mm to thicknesses under 2.0 mm such as 1.5 mm for example. Such super high strength steel products could only be provided in the past as cold-rolled sheet.
Particularly in the area of the highest strengths of over 800 MPa the deformation properties are insufficient for forming sheets into useful parts when employing conventional material concepts for producing cold rolled strip or hot rolled strip. The high strength is achieved by setting martensitic structures. The apparent yielding stresses are also very high in such steels, however. The thus resulting values for the ratio between yield stress to tensile strength and the strengthening are respectively low. In addition to low workability, this leads to high backspringing values, so that pressed parts can be produced only with difficulty or not true to form.
It is the object of the present invention to develop strip steels which are provided with a high strengthening property in conjunction with good forming abilities and high component strength.
For achieving this object a method is proposed in accordance with the invention in which a steel consisting of (in percent by mass) 0.10 0.20 $ C
to 0.30 0.60 ~ Si to 1.50 2.00 ~ Mn to max. 0.08 ~ P
0.30 0.80 ~ Cr to up to 0.40 $ Mo up to 0.20 ~ Ti and/or Zr up to 0.08 ~ Nb remainder and Fe unavoidable impurities, is molten, cast into slabs and thereafter rolled into hot strip, with the finish rolling temperature being above 800 °C, the cooling speed on the run-out roller table being at least 30 °C/s and the coiling temperature being 300 to 600 °C.
The purposeful setting of very fine microstructures consisting of soft and hard phases next to one another in combination with a distribution of ultrafine precipitations opened up the possibility of attractive, previously unknown properties for processing and use. A
hardening of the structure by multiphaseness in conjunction with hardening by fine grain and fine particles lead to a multiple strengthening process.
The particular economical relevance of the method in accordance with the invention is the production ability as hot strip in thicknesses below 2.0 mm, e.g. 1.5 mm.
The production process thus does not mandatorily require the complex production process of a cold rolled strip production with the additional steps of cold rolling and subsequent annealing.
The present material concept also includes the possibility of factory-applied surface refinement. Thus, an electrolytically deposited zinc layer can be applied for example. The considerable improvement of the corrosion protection by a zinc layer can be assumed as a known fact. It is further known that super high strength steels tend towards an embrittlement by absorption of hydrogen during the electrolytic galvanizing process. It could be proved that the strip steel in accordance with the invention is free from these feared galvanizing problems.
The relevance of the alloying elements and the production parameters are described below.
Carbon is required for structure hardening and the formation of ultra-fine precipitations. For reasons of , weldability the content should be restricted to 0.1 to 0.2 ~.
Silicon increases the hardness of the solid solution, for which at least 0.3 ~ are required. For reasons of weldability and to avoid unfavourable formation of forging scales the content should be restricted to 0.6 ~.
Manganese at a content of at least 1.5 ~ delays the transformation and leads to the formation of hard transformation products. In order to avoid impermissbly strong microsegregation the content should be restricted to 2.0 Phosphorus can be used for the further increase of the solid solution hardening, but should not exceed a content of 0.08 $ for reasons of weldability.
Chromium promotes the formation of a high-bainite end structure at at least 0.3 $. In order to avoid delaying the transformation too strongly, the content should be restricted to a maximum of 0.80 Titanium or zirconium can be used for the formation of ultra-fine precipitations with a hardening effect. The effect, however, decreases considerably at contents of over 0.2 %. That is why the maximum value has been set to 0.2 ~.
Niobium can also be used for precipitation hardening. It should preferably be added by alloying with at least 0.04 ~. The content is restricted to a maximum of 0.08 ~
for reasons of effectiveness.
Boron improves the hardenability at contents in the range of 0.0005 to 0.005 ~. According to current knowledge it is used for martensitic transforming steels. It has surprisingly been seen that boron also causes in the present case a significant increase of the strength in the bainitic basic structure with an only low reduction of the forming abilities.
The finish rolling temperature should be in the range of the homogeneous austenite and should thus not be below 800 °C in order to ensure a sufficiently low dimensional change resistance and to keep other deformation-induced precipitations low.
The cooling conditions should be selected such that a transformation into perlite is avoided and the transformation occurs to the highest possible extent in the bainite stage. Shares of martensite can contribute to the further strengthening. Moreover, a strengthening is to be achieved by the precipitation of ultra-fine particles. For this purpose a cooling of the finish rolling temperature with a cooling speed of at least 30 °C/s is required. This cooling process must be ended at a temperature of under 600 °C by winding up the strip on a coiler and thereafter allowing it to cool on the coil.
The invention is now described by reference to the following examples.
Table 1 shows the chemical compositions of the strip steels 1 and 2 produced in accordance with the invention and steel 3, a martensitic reference steel.
Table 2 shows the characterizing mechanical properties of the strip steels 1 and 2 produced in accordance with the invention and of the reference steel 3 which was aged artificially by a subsequent heat treatment to the values as given in table 2.
A comparison of the properties clearly shows the big advantages of the strip steel produced in accordance with the invention. It shows a higher breaking elongation and a better ratio yield stress to tensile strength as a rate for the strengthening.
Table 3 shows the influence of a low coiling temperature and a subsequent heat treatment on the properties of a strip steel produced in accordance with the invention having the composition of the steel 1 in table 1. As a result of the low coiling temperature of preferably 330 °C it is possible to achieve considerable increases in the strength properties (cf. example 4 in table 3).
A further object of the invention is the achievement of an advantageous effect of a subsequent heat treatment. It has surprisingly been seen that by thermally treating the strip steel produced in accordance with the invention in a temperature range of between 500 °C and 850 °C the forming ability properties can be improved even further.
The examples 4, 5 and 6 in table 3 show the effect of such a heat treatment on steel 1 with the composition in accordance with table 1. A state of material is achieved which offers advantages to components which overall require high strengths and in particular high apparent yield stresses at good forming abilities. This picture of properties can be used for the production of cold-rolled sections with a high energy absorption capacity (example 5a). By choosing higher annealing temperatures it is possible to achieve high strengths with exceptionally low ratios between yield stress to tensile strength and similar high strengthening at favourable extensibility values (examples 5b, 6a to 6c).
Many hot-rolled products have the disadvantage that they lose their advantageous properties once they are subsequently cold-rolled and are recrystallization-annealed. It was found for the strip steel in accordance with the invention, however, that it has advantageous properties also after subsequent cold rolling and annealing. Thus, example 7 in table 3 shows that the strip steel 1 produced in accordance with the invention also achieves high strengths at even further improved ratios between yield stress to tensile strength after a cold rolling with 50 $ degree of deformation as compared with strip steels 1 and 2 that were only hot rolled.
Table 1 (in percent,by mass [mass-$]) SteelC Si Mn P S A1 N Cr Mo Ti 1 0.14 0.47 1.83 0.007 0.0020.025 0.0090.34 0.12 0.15 2a 0.19 0.43 1.67 0.013 0.0070.032 0.0070.49 0.30 0.18 2b 0.17 0.53 1.82 0.013 0.0120.049 0.0120.77 0.02 0.18 3* 0.15 0.01 1.75 0.011 0.0030.020 0.0040.55 0.01 0.003 *) martensitic reference steel _ g _ Table 2 pos. Re Rm Re/Rm Ag A5 A80 WET HT
Steelof N/mm2 N/mm2 % % % C C
sample 1 long. 653 1065 0.61 8 18 11 trans.652 1098 0.59 8 17 12 2a long. 670 1115 0.60 7 16 10 880 550 2b long. 680 1140 0.60 7 15 9 880 550 3* long. 1050 1096 0.96 2 10 5 880 280 *) reference steel Re yield point Rm ultimate tensile strength Ag uniform elongation A5 breaking elongation Ag0 breaking elongation WET finish rolling temperature HT coiling temperature Table 3 ExampleAnnealing Re Rm Re/Rm A80 WET HT
C min N/mm2 N/mm2 % C C
4 ./. ./. 1203 1395 O.B6 3 910 330 5a 600 120 1040 1070 0.97 9 910 330 5b 750 1 690 1190 0.58 7 910 330 6a 750 1 620 1095 0.58 6 910 530 6b 800 1 600 1086 0.55 10 910 530 6c 850 1 492 913 0.54 14 910 530 7*a 800 1 627 1149 0.55 8 910 530 7*b 850 1 446 959 0.47 12 910 530 *) cold rolled with 50 $
AND GOOD FORMING ABILITIES
The invention relates to a method for producing a strip steel with high strength of at least 900 MPa and good forming abilities.
The demand for the reduction of fuel consumption of vehicles requires the application of lightweight concepts. Lightweight constructions can be achieved by a reduction of the thicknesses of sheet steel. For compensating any thus caused losses in strength of the component it is necessary to increase the strength of the material. Any increase in the strength usually causes a reduction in the deformability. Sheet steels used in the construction of vehicles must be brought into the final shape required for design or functional purposes by forming. If the increase in the strength and the thus resulting decrease in forming abilities become too high, failures will occur during the forming by local constrictions and tearing. For this reason an increase in the strength is limited.
The development of steels is always aimed at improving the ratio between deformability and strength.
Considerable success has already been achieved in the range of strength under 500 MPa concerning a reduction of the sheet thickness by using phosphorus-alloyed or micro-alloyed steels. Even better results were achieved with bake-hardening steels. In the strength range between 500 and 800 MPa the developments of the dual-phase and TRIP
(transformation-induced plasticity) steels yielded relatively good forming ability values.
The characteristic values relevant for the forming can be gained with high representativity for practical operation from the tension test. In particular, breaking elongation and the n-value (amount for strengthening capacity) represent important dimensional figures. The n-value is characteristic for the deformability under stretch-forming stress. This is the predominant deformation mechanism in most steel sheet parts of a vehicle. The n-value corresponds relatively well to the ratio of yield stress to tensile strength, which is also a value representative in practical operation for the strengthening capacity of a material.
In order to exploit the advantage of increasing the strength for reducing the sheet thickness to the highest possible extent, the highest possible values concerning breaking elongation (A) and the strengthening value (n-value) are pursued.
Steels with very high strengths over 800 MPa can be used very efficiently for the reduction of weight of crash-relevant components such as door impact beams, bumper beams. For this purpose, however, it is necessary to reduce the sheet thickness from over 2.0 mm to thicknesses under 2.0 mm such as 1.5 mm for example. Such super high strength steel products could only be provided in the past as cold-rolled sheet.
Particularly in the area of the highest strengths of over 800 MPa the deformation properties are insufficient for forming sheets into useful parts when employing conventional material concepts for producing cold rolled strip or hot rolled strip. The high strength is achieved by setting martensitic structures. The apparent yielding stresses are also very high in such steels, however. The thus resulting values for the ratio between yield stress to tensile strength and the strengthening are respectively low. In addition to low workability, this leads to high backspringing values, so that pressed parts can be produced only with difficulty or not true to form.
It is the object of the present invention to develop strip steels which are provided with a high strengthening property in conjunction with good forming abilities and high component strength.
For achieving this object a method is proposed in accordance with the invention in which a steel consisting of (in percent by mass) 0.10 0.20 $ C
to 0.30 0.60 ~ Si to 1.50 2.00 ~ Mn to max. 0.08 ~ P
0.30 0.80 ~ Cr to up to 0.40 $ Mo up to 0.20 ~ Ti and/or Zr up to 0.08 ~ Nb remainder and Fe unavoidable impurities, is molten, cast into slabs and thereafter rolled into hot strip, with the finish rolling temperature being above 800 °C, the cooling speed on the run-out roller table being at least 30 °C/s and the coiling temperature being 300 to 600 °C.
The purposeful setting of very fine microstructures consisting of soft and hard phases next to one another in combination with a distribution of ultrafine precipitations opened up the possibility of attractive, previously unknown properties for processing and use. A
hardening of the structure by multiphaseness in conjunction with hardening by fine grain and fine particles lead to a multiple strengthening process.
The particular economical relevance of the method in accordance with the invention is the production ability as hot strip in thicknesses below 2.0 mm, e.g. 1.5 mm.
The production process thus does not mandatorily require the complex production process of a cold rolled strip production with the additional steps of cold rolling and subsequent annealing.
The present material concept also includes the possibility of factory-applied surface refinement. Thus, an electrolytically deposited zinc layer can be applied for example. The considerable improvement of the corrosion protection by a zinc layer can be assumed as a known fact. It is further known that super high strength steels tend towards an embrittlement by absorption of hydrogen during the electrolytic galvanizing process. It could be proved that the strip steel in accordance with the invention is free from these feared galvanizing problems.
The relevance of the alloying elements and the production parameters are described below.
Carbon is required for structure hardening and the formation of ultra-fine precipitations. For reasons of , weldability the content should be restricted to 0.1 to 0.2 ~.
Silicon increases the hardness of the solid solution, for which at least 0.3 ~ are required. For reasons of weldability and to avoid unfavourable formation of forging scales the content should be restricted to 0.6 ~.
Manganese at a content of at least 1.5 ~ delays the transformation and leads to the formation of hard transformation products. In order to avoid impermissbly strong microsegregation the content should be restricted to 2.0 Phosphorus can be used for the further increase of the solid solution hardening, but should not exceed a content of 0.08 $ for reasons of weldability.
Chromium promotes the formation of a high-bainite end structure at at least 0.3 $. In order to avoid delaying the transformation too strongly, the content should be restricted to a maximum of 0.80 Titanium or zirconium can be used for the formation of ultra-fine precipitations with a hardening effect. The effect, however, decreases considerably at contents of over 0.2 %. That is why the maximum value has been set to 0.2 ~.
Niobium can also be used for precipitation hardening. It should preferably be added by alloying with at least 0.04 ~. The content is restricted to a maximum of 0.08 ~
for reasons of effectiveness.
Boron improves the hardenability at contents in the range of 0.0005 to 0.005 ~. According to current knowledge it is used for martensitic transforming steels. It has surprisingly been seen that boron also causes in the present case a significant increase of the strength in the bainitic basic structure with an only low reduction of the forming abilities.
The finish rolling temperature should be in the range of the homogeneous austenite and should thus not be below 800 °C in order to ensure a sufficiently low dimensional change resistance and to keep other deformation-induced precipitations low.
The cooling conditions should be selected such that a transformation into perlite is avoided and the transformation occurs to the highest possible extent in the bainite stage. Shares of martensite can contribute to the further strengthening. Moreover, a strengthening is to be achieved by the precipitation of ultra-fine particles. For this purpose a cooling of the finish rolling temperature with a cooling speed of at least 30 °C/s is required. This cooling process must be ended at a temperature of under 600 °C by winding up the strip on a coiler and thereafter allowing it to cool on the coil.
The invention is now described by reference to the following examples.
Table 1 shows the chemical compositions of the strip steels 1 and 2 produced in accordance with the invention and steel 3, a martensitic reference steel.
Table 2 shows the characterizing mechanical properties of the strip steels 1 and 2 produced in accordance with the invention and of the reference steel 3 which was aged artificially by a subsequent heat treatment to the values as given in table 2.
A comparison of the properties clearly shows the big advantages of the strip steel produced in accordance with the invention. It shows a higher breaking elongation and a better ratio yield stress to tensile strength as a rate for the strengthening.
Table 3 shows the influence of a low coiling temperature and a subsequent heat treatment on the properties of a strip steel produced in accordance with the invention having the composition of the steel 1 in table 1. As a result of the low coiling temperature of preferably 330 °C it is possible to achieve considerable increases in the strength properties (cf. example 4 in table 3).
A further object of the invention is the achievement of an advantageous effect of a subsequent heat treatment. It has surprisingly been seen that by thermally treating the strip steel produced in accordance with the invention in a temperature range of between 500 °C and 850 °C the forming ability properties can be improved even further.
The examples 4, 5 and 6 in table 3 show the effect of such a heat treatment on steel 1 with the composition in accordance with table 1. A state of material is achieved which offers advantages to components which overall require high strengths and in particular high apparent yield stresses at good forming abilities. This picture of properties can be used for the production of cold-rolled sections with a high energy absorption capacity (example 5a). By choosing higher annealing temperatures it is possible to achieve high strengths with exceptionally low ratios between yield stress to tensile strength and similar high strengthening at favourable extensibility values (examples 5b, 6a to 6c).
Many hot-rolled products have the disadvantage that they lose their advantageous properties once they are subsequently cold-rolled and are recrystallization-annealed. It was found for the strip steel in accordance with the invention, however, that it has advantageous properties also after subsequent cold rolling and annealing. Thus, example 7 in table 3 shows that the strip steel 1 produced in accordance with the invention also achieves high strengths at even further improved ratios between yield stress to tensile strength after a cold rolling with 50 $ degree of deformation as compared with strip steels 1 and 2 that were only hot rolled.
Table 1 (in percent,by mass [mass-$]) SteelC Si Mn P S A1 N Cr Mo Ti 1 0.14 0.47 1.83 0.007 0.0020.025 0.0090.34 0.12 0.15 2a 0.19 0.43 1.67 0.013 0.0070.032 0.0070.49 0.30 0.18 2b 0.17 0.53 1.82 0.013 0.0120.049 0.0120.77 0.02 0.18 3* 0.15 0.01 1.75 0.011 0.0030.020 0.0040.55 0.01 0.003 *) martensitic reference steel _ g _ Table 2 pos. Re Rm Re/Rm Ag A5 A80 WET HT
Steelof N/mm2 N/mm2 % % % C C
sample 1 long. 653 1065 0.61 8 18 11 trans.652 1098 0.59 8 17 12 2a long. 670 1115 0.60 7 16 10 880 550 2b long. 680 1140 0.60 7 15 9 880 550 3* long. 1050 1096 0.96 2 10 5 880 280 *) reference steel Re yield point Rm ultimate tensile strength Ag uniform elongation A5 breaking elongation Ag0 breaking elongation WET finish rolling temperature HT coiling temperature Table 3 ExampleAnnealing Re Rm Re/Rm A80 WET HT
C min N/mm2 N/mm2 % C C
4 ./. ./. 1203 1395 O.B6 3 910 330 5a 600 120 1040 1070 0.97 9 910 330 5b 750 1 690 1190 0.58 7 910 330 6a 750 1 620 1095 0.58 6 910 530 6b 800 1 600 1086 0.55 10 910 530 6c 850 1 492 913 0.54 14 910 530 7*a 800 1 627 1149 0.55 8 910 530 7*b 850 1 446 959 0.47 12 910 530 *) cold rolled with 50 $
Claims (15)
1. A method for producing strip steel with high strength of at least 900 MPa and good forming abilities, comprising (in percent by mass) 0.10 to 0.20 % C
0.30 to 0.60 % Si 1.50 2.00 % Mn max. 0.08 % P
0.30 0.80 % Cr up to 0.40 % Mo up to 0.20 % Ti and/or Zr up to 0.08 % Nb remainder Fe and unavoidable impurities, which is molten, cast into slabs and thereafter rolled into hot strip, with the finish rolling temperature being above 880 °C, the cooling speed on the run-out roller table being at least 30 °C/s and the coiling temperature being 300 to 600 °C.
0.30 to 0.60 % Si 1.50 2.00 % Mn max. 0.08 % P
0.30 0.80 % Cr up to 0.40 % Mo up to 0.20 % Ti and/or Zr up to 0.08 % Nb remainder Fe and unavoidable impurities, which is molten, cast into slabs and thereafter rolled into hot strip, with the finish rolling temperature being above 880 °C, the cooling speed on the run-out roller table being at least 30 °C/s and the coiling temperature being 300 to 600 °C.
2. A method as claimed in claim 1, characterized in that the hot strip is coiled at a temperature of not more than 550 °C.
3. A method as claimed in claim 1, characterized in that the hot strip is coiled at a temperature of not more than 350 °C.
4. A method as claimed in one of the claims 1 to 3, characterized in that the hot strip is not coiled under a temperature of 330 °C.
automatically calculates the average
automatically calculates the average
5. A method as claimed in one or several of the claims 1 to 4, characterized in that the hot strip is rolled into an end thickness of not more than 2.0 mm.
6. A method as claimed in one or several of the claims 1 to 5, characterized in that the hot strip is temper rolled.
7. A method as claimed in one or several of the claims 1 to 6, characterized in that the strip is pickled and metallically coated.
8. A method as claimed in claim 7, characterized in that the metal coating is applied electrolytically.
9. A method as claimed in claim 7, characterized in that the metal coating is applied by hot dip galvanizing.
10. A method as claimed in one or several of the claims 1 to 6, characterized in that the hot strip is annealed in the range of 500 to 850 °C.
11. A method as claimed in one or several of the claims 1 to 6, characterized in that after the hot rolling a cold rolling of at least 30 $ and a continuous annealing at temperatures of between 700 and 900 °C
are performed.
are performed.
12. A method as claimed in one of the claims 1 to 11, characterized in that the steel is added by alloying not more than 0.15 % Mo.
13. A method as claimed in one or several of the claims 1 to 12, characterized in that the steel is added by alloying at least 0.04 % Ti and/or Zr.
14. A method as claimed in one or several of the claims 1 to 13, characterized in that the steel is added by alloying 0.0005 to 0.005 % B.
15. A method as claimed in one or several of the claims 1 to 14, characterized in that the steel is added by alloying at least 0.04 % Nb.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19710125A DE19710125A1 (en) | 1997-03-13 | 1997-03-13 | Process for the production of a steel strip with high strength and good formability |
| DE19710125.9 | 1997-03-13 | ||
| PCT/EP1998/001376 WO1998040522A1 (en) | 1997-03-13 | 1998-03-10 | Method for producing a highly resistant, very ductile steel strip |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2284124A1 true CA2284124A1 (en) | 1998-09-17 |
Family
ID=7823066
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002284124A Abandoned CA2284124A1 (en) | 1997-03-13 | 1998-03-10 | Method for producing a highly resistant, very ductile steel strip |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0966547B1 (en) |
| CN (1) | CN1082549C (en) |
| AR (1) | AR010130A1 (en) |
| AT (1) | ATE206472T1 (en) |
| CA (1) | CA2284124A1 (en) |
| CZ (1) | CZ290944B6 (en) |
| DE (2) | DE19710125A1 (en) |
| ES (1) | ES2165157T3 (en) |
| PL (1) | PL186831B1 (en) |
| WO (1) | WO1998040522A1 (en) |
| ZA (1) | ZA982115B (en) |
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| US10071416B2 (en) | 2005-10-20 | 2018-09-11 | Nucor Corporation | High strength thin cast strip product and method for making the same |
| US11193188B2 (en) | 2009-02-20 | 2021-12-07 | Nucor Corporation | Nitriding of niobium steel and product made thereby |
| US11970753B2 (en) | 2018-09-18 | 2024-04-30 | Voestalpine Stahl Gmbh | Method of producing ultrahigh-strength steel sheets and steel sheets therefor |
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| DE10161465C1 (en) * | 2001-12-13 | 2003-02-13 | Thyssenkrupp Stahl Ag | Production of hot strip used in vehicle chassis comprises casting steel into pre-material, hot rolling to form hot strip, cooling in first cooling step, and cooling in second cooling step after pause to coiling temperature |
| FR2847270B1 (en) * | 2002-11-19 | 2004-12-24 | Usinor | METHOD FOR MANUFACTURING AN ABRASION RESISTANT STEEL SHEET AND OBTAINED SHEET |
| FR2847271B1 (en) * | 2002-11-19 | 2004-12-24 | Usinor | METHOD FOR MANUFACTURING AN ABRASION RESISTANT STEEL SHEET AND OBTAINED SHEET |
| AU2003284496A1 (en) † | 2002-12-24 | 2004-07-22 | Nippon Steel Corporation | High strength steel sheet exhibiting good burring workability and excellent resistance to softening in heat-affected zone and method for production thereof |
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| EP2031081B1 (en) * | 2007-08-15 | 2011-07-13 | ThyssenKrupp Steel Europe AG | Dual-phase steel, flat product made of such dual-phase steel and method for manufacturing a flat product |
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| DE102010056264C5 (en) * | 2010-12-24 | 2020-04-09 | Voestalpine Stahl Gmbh | Process for producing hardened components |
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| CN102864377B (en) * | 2012-09-10 | 2015-05-20 | 山西太钢不锈钢股份有限公司 | Hot rolled strip steel and manufacturing method thereof |
| MX2017008027A (en) | 2014-12-19 | 2017-10-20 | Nucor Corp | Hot rolled light-gauge martensitic steel sheet and method for making the same. |
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| DE2201855C2 (en) * | 1972-01-15 | 1982-03-04 | Estel Hoesch Werke Ag, 4600 Dortmund | Process for the production of high-strength, easily weldable and cold-deformable heavy and medium plates and their use |
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| DE3007560A1 (en) * | 1980-02-28 | 1981-09-03 | Kawasaki Steel Corp., Kobe, Hyogo | METHOD FOR PRODUCING HOT-ROLLED SHEET WITH LOW STRETCH STRESS, HIGH TENSILE STRENGTH AND EXCELLENT SHAPING CAPACITY |
| JPS5877528A (en) * | 1981-10-31 | 1983-05-10 | Nippon Steel Corp | Manufacture of high tensile steel with superior toughness at low temperature |
| JPS58185719A (en) * | 1982-04-20 | 1983-10-29 | Kobe Steel Ltd | Manufacture of high yield ratio type unnormalized hot-rolled high-tension steel plate |
| US4472208A (en) * | 1982-06-28 | 1984-09-18 | Sumitomo Metal Industries, Ltd. | Hot-rolled high tensile titanium steel plates and production thereof |
| JPS60190518A (en) * | 1984-03-12 | 1985-09-28 | Kobe Steel Ltd | Manufacture of high tension steel having superior cold workability and requiring no heat treatment |
| TW363082B (en) * | 1994-04-26 | 1999-07-01 | Nippon Steel Corp | Steel sheet having high strength and being suited to deep drawing and process for producing the same |
-
1997
- 1997-03-13 DE DE19710125A patent/DE19710125A1/en not_active Ceased
-
1998
- 1998-03-10 EP EP98916911A patent/EP0966547B1/en not_active Expired - Lifetime
- 1998-03-10 CA CA002284124A patent/CA2284124A1/en not_active Abandoned
- 1998-03-10 ES ES98916911T patent/ES2165157T3/en not_active Expired - Lifetime
- 1998-03-10 AT AT98916911T patent/ATE206472T1/en active
- 1998-03-10 CZ CZ19993219A patent/CZ290944B6/en not_active IP Right Cessation
- 1998-03-10 PL PL98335639A patent/PL186831B1/en not_active IP Right Cessation
- 1998-03-10 WO PCT/EP1998/001376 patent/WO1998040522A1/en active IP Right Grant
- 1998-03-10 CN CN988040182A patent/CN1082549C/en not_active Expired - Fee Related
- 1998-03-10 DE DE59801637T patent/DE59801637D1/en not_active Expired - Lifetime
- 1998-03-12 AR ARP980101113A patent/AR010130A1/en unknown
- 1998-03-12 ZA ZA982115A patent/ZA982115B/en unknown
Cited By (5)
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|---|---|---|---|---|
| US9149868B2 (en) | 2005-10-20 | 2015-10-06 | Nucor Corporation | Thin cast strip product with microalloy additions, and method for making the same |
| US9999918B2 (en) | 2005-10-20 | 2018-06-19 | Nucor Corporation | Thin cast strip product with microalloy additions, and method for making the same |
| US10071416B2 (en) | 2005-10-20 | 2018-09-11 | Nucor Corporation | High strength thin cast strip product and method for making the same |
| US11193188B2 (en) | 2009-02-20 | 2021-12-07 | Nucor Corporation | Nitriding of niobium steel and product made thereby |
| US11970753B2 (en) | 2018-09-18 | 2024-04-30 | Voestalpine Stahl Gmbh | Method of producing ultrahigh-strength steel sheets and steel sheets therefor |
Also Published As
| Publication number | Publication date |
|---|---|
| PL335639A1 (en) | 2000-05-08 |
| ATE206472T1 (en) | 2001-10-15 |
| CN1252105A (en) | 2000-05-03 |
| PL186831B1 (en) | 2004-03-31 |
| DE19710125A1 (en) | 1998-09-17 |
| ES2165157T3 (en) | 2002-03-01 |
| CN1082549C (en) | 2002-04-10 |
| EP0966547A1 (en) | 1999-12-29 |
| WO1998040522A1 (en) | 1998-09-17 |
| EP0966547B1 (en) | 2001-10-04 |
| CZ290944B6 (en) | 2002-11-13 |
| ZA982115B (en) | 1998-09-14 |
| DE59801637D1 (en) | 2001-11-08 |
| AR010130A1 (en) | 2000-05-17 |
| CZ321999A3 (en) | 2000-07-12 |
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