EP2430199A1 - Method for manufacturing hot rolled steel strip product, and hot rolled steel strip product - Google Patents

Method for manufacturing hot rolled steel strip product, and hot rolled steel strip product

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Publication number
EP2430199A1
EP2430199A1 EP10727754A EP10727754A EP2430199A1 EP 2430199 A1 EP2430199 A1 EP 2430199A1 EP 10727754 A EP10727754 A EP 10727754A EP 10727754 A EP10727754 A EP 10727754A EP 2430199 A1 EP2430199 A1 EP 2430199A1
Authority
EP
European Patent Office
Prior art keywords
steel
steel strip
strip product
temperature
product according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP10727754A
Other languages
German (de)
French (fr)
Other versions
EP2430199B1 (en
Inventor
Tommi Liimatainen
Mikko HEMMILÄ
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rautaruukki Oyj
Original Assignee
Rautaruukki Oyj
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Filing date
Publication date
Application filed by Rautaruukki Oyj filed Critical Rautaruukki Oyj
Priority to PL10727754T priority Critical patent/PL2430199T3/en
Publication of EP2430199A1 publication Critical patent/EP2430199A1/en
Application granted granted Critical
Publication of EP2430199B1 publication Critical patent/EP2430199B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • 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
    • C21D2211/005—Ferrite

Definitions

  • the invention relates to a method for manufacturing a hot rolled steel strip product having a wall thickness of 2 to 12 mm using steel whose composition in percentage by weight is
  • Ni ⁇ 0.5 and the rest iron and unavoidable impurities.
  • Low carbon content is excellent for providing steel with good welding characteristics. Also the low carbon equivalent of steel has a positive effect to good weldability.
  • the invention further relates to a steel product with a wall thickness of 2 to 12 mm and a composition as described above.
  • EP 1319725 discloses a method for manufacturing a steel strip having the above composition.
  • the strength of the steel strip thus manufactured is relatively high, its yield strength exceeding 690 MPa, combined with a relatively high percentage of elongation after fracture (12 to 21%).
  • these mechanical properties are arrived at by subjecting the steel to a two-step cooling.
  • an extremely fast cooling is carried out, the cooling rate being over 150°C/s after hot rolling, followed by a pause of 3 to 10 seconds without active cooling, after which a second cooling step is carried out to the coiling temperature of the steel strip to be manufactured, the temperature being chosen according to the desired strength.
  • the recommended coiling temperature for yield strengths exceeding 690 MPa is 580 0 C.
  • the high cooling rate of over 150°C/s at the first quenching step may be obtained only at low strip thicknesses, and the publication only discusses strip thicknesses lower than 4 mm.
  • the cooling pause is meant to provide time for a phase change, during which the yield strength of the material in particular decreases and the yield strength/tensile strength value decreases compared with continued cooling.
  • the publication does not disclose how a yield strength of over 690 MPa is obtained in the steel when the coiling temperature is below 580 0 C.
  • the publication shows that the yield strength obtained in a coiling temperature of less than 580 0 C remains below 690 MPa.
  • Said two-step cooling is in practice more complicated to carry out than a one-step cooling and requires more complex production equipment.
  • the bendability of the steel strip obtained by two-step cooling is not particularly good, although the steel strip has relatively good values for percentage of elongation after fracture. Bendability means the ability of steel strip to bend to a small bending radius without surface damage emerging at the bending point.
  • Two-step cooling has not succeeded in providing steel with particularly good impact strength values at low temperatures in combination with high strength.
  • An object of the invention is to overcome said drawbacks of the prior art and to provide a method that is easy to implement for manufacturing strip steel product, typically a steel strip, of high strength and a particularly good bendability, the strip steel product having a chemical composition as mentioned above.
  • the method of the invention is characterized by
  • the invention has surprisingly shown that said steel composition is capable of producing high-strength steel which also has good bend- ability. Also surprisingly, it was discovered that the strength of the steel is isotropic, i.e. its yield strength does not vary considerably irrespective of whether it is measured lengthwise or crosswise in relation to the rolling direction.
  • the direct quenching rate is preferably 120 °C/s at the most, because this enables to obtain a steel microstructure that provides the steel with particularly good mechanical properties, including good impact strength combined with good bendability.
  • the end temperature in direct quenching is preferably 100 0 C at the most, because this enables to obtain a planar strip with also planar and even edges after the quenching.
  • the steep strip is preferably direct quenched directly to the coiling temperature and coiled.
  • the processing of the steel strip is preferably thermome- chanical, and thus no tempering is carried out after the direct quenching. It has been observed that a steel product manufactured with the method has good mechanical properties although no tempering adding the costs is required on the product. Tempering does not significantly improve the mechanical properties of the product, and it complicates the process.
  • the major advantages of the method of the invention are that it allows a steel product with good mechanical properties, including bendability, and a predetermined composition to be manufactured in a simple and economical manner and with simple equipment.
  • the invention further relates to a product manufactured in method steps of the invention.
  • the steel strip product of the invention having a wall thickness of 2 to 12 mm and composed in percentage by weight of
  • Ni: ⁇ 0.5, the rest being iron and inevitable impurities, is characterized in that the micro structure of the steel is substantially low carbon ferritic and/or low carbon bain- itic, that upon bending the steel sustains a bending radius of R ⁇ 0.75 t without fractures or cracks visible to the eye, t being the thickness of the steel product, that its yield strength is 650 - 800 MPa and that its percentage of elongation after fracture is at least 12%.
  • High strength has been obtained although the microstructure of the steel mostly consists of a low carbon ferrite and/or bainite, without containing significant amounts of carbon-rich martensite or carbon-rich bainite.
  • the dominant phase consists of ferrite with an almost fully ferritic microstructure, as recommended, and small amounts of bainite and/or martensite and/or residue austenite in extremely small islands of enriched carbon content.
  • a significant reason for the obtained high strength is the use of niobium and titanium as micro-alloy elements in the steel produced with the method. Both niobium and titanium must be used.
  • the major advantages of the steel product of the invention are its excellent mechanical properties, including bendability and shear characteristics and impact strength values, in relation to its composition.
  • the steel is also well applicable in arctic conditions.
  • the steel of the invention is extremely useful due to its properties related to engineering works, because its weldabil- ity is good and its isotropic strength properties allow a very efficient optimization of its use.
  • the small bending radius particularly facilitates the work of bent product designers.
  • the steel strip product of the invention is specifically well suited for use as strong structure steel. BRIEF DISCLOSURE OF THE FIGURES
  • FIG 1 shows the method steps of the invention
  • Figure 2 is a schematic view of a V-bending in bending tests
  • Figure 3 illustrates an example of a successful bending test result
  • Figure 4 illustrates an example of a failed bending test result
  • Figure 5 presents transition curves for charpy-V obtained with the steel of the invention and a reference steel
  • Figure 6 illustrates the connection between yield strength isotropy and strip rolling
  • Figure 7 illustrates the connection between yield strength isotropy and coiling temperature.
  • Figure 1 shows the method steps of the invention for producing a steel strip product with a wall thickness of 2 to 12mm.
  • the manufacture starts with a work piece of steel whose composition in percentage by weight is
  • Ni ⁇ 0.5 and the rest iron and unavoidable impurities.
  • the steel has a low carbon content C of 0.04 to 0.08%, which is advantageous in view of the impact strength, bendability and weldabil- ity of the material.
  • Silicon, Si may be used in an amount of 0 to 0.50% as a killing agent (in addition to aluminium) and for ferrite reinforcement. If a particularly good surface quality is to be aimed at, the silicon content must be limited to below 0.25%.
  • the alloying content of manganese, Mn is 1.0 to 2.2%. Because of the low carbon content, steel is not prone to manganese and carbon segregation during casting, which enhances the homogeneity of the micro- structure also at relatively high contents of Mn. Preferably at least 1.3% of manganese is alloyed to achieve a high strength and to ensure a weldability of 2.0% at the most.
  • the steel of the invention may be cut into precisely dimensioned pieces both thermally (e.g. by laser and plasma) and mechanically. It has been observed that a piece with a relatively smooth cutting surface is obtained. This has an advantageous effect on fatigue strength. In addition, low carbon content prevents the cutting surface from becoming rough during thermal cutting and reduces maximum hardness, the cutting surface being less prone to brittle and crack during forming of the piece and in the conditions of use thereof.
  • the cutting gap may be set at a value of 10 to 15% of the sheet thickness, the cutting result being still smooth and non- fractured and hence separate grinding of the cutting surface or thermal cutting is not needed, which significantly reduces working allowances and decreases the number of manufacturing steps, thereby enhancing the manufacturing process.
  • the amounts of phosphor, P, (0.03% at the most) and sulphur, S, (0.015% at the most) present as impurities are to be restricted.
  • the maximum amount of P is preferably 0.015% and that of S preferably 0.005%.
  • the properties may be improved, when necessary, by treatment with molten Ca or CaSi.
  • As a killing agent aluminium Al 0.01 - 0.15% is used.
  • the amount of aluminium used is preferably 0.05% at the most.
  • the amount of nitrogen, N, used is 0.01% at the most, because when present in steel containing titanium, nitrogen forms hard titanium nitride particles that impair the bendability of the steel.
  • the preferred amount of nitrogen used is 0.006% at the most.
  • the content of copper, Cu is to be reduced to 0.3% at the most to ensure excellent surface quality for a hot-rolled strip. If the copper con- tent exceeds 0.3%, it is recommended to alloy also nickel, Ni, in an amount equal to at least 0.25 times the Cu content. Although steel achieves its good properties also without copper, it may be used, when necessary, to slightly increase strength.
  • the Cu content is 0.5% at the most.
  • An alloy 0.3 to 0.5% of copper and at least 0.1% of nickel is preferably used particularly for thick strips of 8 to 12 mm, for example.
  • Ni is restricted to 0.5% at the most. Although steel achieves its excellent strength properties also without the blending of Ni, it may slightly increase strength, when necessary.
  • Titanium, T may be alloyed to achieve a desired strength level. Typically 0.06 to 0.16%, although higher Ti levels could be used as well, but in that case its strength increasing effect is extremely small and may complicate the casting of the work piece. Lower Ti percentages are not used, because then high strength is difficult to obtain without using a more expensive alloying or increasing the carbon content to over 0.08%. Surprisingly the invention has shown that even at low temperatures, such as -40 0 C and -60 0 C, titanium does not lower significantly the impact strength of the basic agent, as shown by the measurement results of Table 3.
  • Chromium, Cr, and molybdene, Mo do not need to be alloyed. They are elements that increase hardening and have a disadvantageous effect on weldability, at least in higher amounts. For this reason Cr is restricted to a maximum content of 0.2% and, similarly, Mo to a maximum content of 0.2%.
  • the amount of chromium is preferably less than 0.1%.
  • Molybdene is preferably allowed in an amount of 0.10%, and most preferably 0.5%, at the most, because the mechanical properties of the steel of the invention are most preferably achieved by alloying titanium which provides more affordable alloying element costs than molybdene. Molybdene may even be harmful for strength in a direct quenched steel strip product of the invention. In any case, added molybdene does not significantly improve the strength of the steel strip product of the invention, when the product is produced by thermomechanical treatment.
  • Vanadine, V does not need to be alloyed. In addition, it increases unnecessary hardening and has a disadvantageous effect on weld- ability at least in high concentrations. For this reason, V is restricted to a maximum content of 0.1%.
  • Nb and Ti concentrations are restricted as follows: Nb: 0.04 - 0.06% and Ti: 0.06 - 0.10% for reducing the rolling forces and, at the same time, a vanadium concentration V of 0.06 - 0.10% may be selected to obtain high strength.
  • silicon may be advantageously added in an amount of Si: 0.30 - 0.50% to increase strength, as shown in Table 1 of the tests run with an experimental composition E1.
  • the sum of the niobium, titanium and vanadium concentrations is greater than 0.15%, i.e. Ti + Nb + V > 0.15%, the steel strip product being applicable as a particularly strong structural steel.
  • the steel strip product of the invention is excellent to bend (fold) and to weld e.g. by autogenous high frequency (HF) welding into a tube or a tube beam.
  • HF high frequency
  • the work piece of steel is 210 mm thick, for example, and heated to an austenizing temperature of 1280 0 C, where it is kept for about 3 hours.
  • the thickness of the steel work piece may differ from the one disclosed here and the austenizing temperature may be differently chosen, but a range of 1200 - 1350 0 C is recommended. If the austenizing temperature is below the lower limit given, there is a risk that the microalloying elements do not dissolve into the austenite, i.e. a homogenous austenite is not obtained.
  • the annealing time varies within a range of 2 to 4 hours.
  • the carbon equivalent C + Mn/6 + (Cr + Mo +V)/5 + Ni + Cu)/15 for steel is preferably not higher than 0.45, which guarantees a good weldability of the steel.
  • the steel work piece After austenizing, the steel work piece is hot-rolled at a temperature of 950 - 1250 0 C to a thickness which is typically 25 - 50 mm and then immediately transferred to a strip rolling mill to be rolled into a strip with a final thickness of 2 - 12 mm.
  • the recommended final thickness of the steel strip is at least 4 mm. It also recommended that the final thickness does not exceed 10 mm.
  • the number of passes in the strip roll mill is typically 5 to 7.
  • the last pass in the strip roll mill is carried out at a temperature range of 760 - 960 0 C, the recommendation being 780 - 850 0 C.
  • the direct quenching of the steel strip starts within 15 seconds.
  • the temperature of the steel strip must be at least 700 0 C.
  • the direct quenching is carried out as a water quenching at a quenching rate of 30 - 150°C/s, the recommended upper limit being 12O 0 CVs at the most.
  • the direct quenching continues up to a temperature of 300 0 C at the most, the recommended temperature being 100 0 C.
  • the steel is coiled.
  • the coiling temperature may fall within a temperature range of 30 - 300 0 C.
  • a recommended initial coiling temperature is 100 0 C at the most, because when steel is coiled at a temperature exceeding 100 0 C, a discontinuous steam cushion complicating the process may form onto the steel surface.
  • the micro- structure of the steel becomes homogenous and consists of a dominant phase, which is preferably low carbon ferrite and/or low carbon bainite.
  • the amount of the dominant phase is typically over 90%.
  • extremely low amounts of high carbon bainite and/or residual austenite and/or martensite is present in extremely high carbon groups.
  • the average grain size in the micro- structure is small, preferably approximately 2 - 4 micrometers. It is also essential that the microstructure does not contain big grains in the first place and therefore the steel has particularly good bending characteristics taking into consideration the strength of the steel.
  • the grain size must be as uniform and fine as possible, which is achieved by the method of the invention.
  • Tables 1 to 3 below provide examples of the concentrations and manufacturing parameters of the steel of the invention and of the strength and toughness values obtained with them. For the sake of comparison, Tables 2 and 3 also contain manufacturing parameters not belonging to the scope of the method of the invention, i.e. treatments not corresponding to the method of the invention. In Table 2 on the manufacturing parameters and in the table on the mechanical strength properties reference tests have been indicated with R.
  • a further topic of examination are the bending characteristics obtained with the treatments of the invention, these being compared with the bending characteristics obtained by manufacturing parameters remaining outside the scope of the method, see Tables 3 and 4, Steel B3Q23 (bending test a) according to the invention)and Steel A3M33 (bending test b) outside the invention).
  • Indication T_f in Table 2 denotes the temperature at the last rolling pass, indication T_c denoting the temperature at the start of the coiling, indication Th denoting the thickness of the steel strip and indication Wi denoting the width of the steel strip.
  • T denotes a sample whose strength and toughness have been determined in a direction transverse to the roll direction.
  • Ending L denotes a sample whose strength and toughness have been determined in the rolling direction.
  • Tables 2 and 3 show that the impact strength values are good and the strength is isotropically high, when direct quenching is carried out to a low temperature (50 0 C).
  • the yield strength of steels according to the invention is 635 - 829 MPa.
  • the percentage of elongation after fracture A5 is at least 12% and typically at least 15%.
  • the yield ratio (yield strength/break strength) of the steels is about 0.8 - 0.95.
  • said uniform quality is present in steels in which the final rolling temperature is low (below 890 0 C) and/or coiled at a low temperature (coiling temperatures 50 0 C).
  • Uniform quality is advantageous, because when a steel strip for different purposes is being designed, there is no need to take into account the fact that the steel strip has a higher strength in rolling direction than in the direction that is transverse to the rolling direction. Hence it is possible to take advantage of the high strength of the steel strip in all situations, i.e. also when cutting blanks that are processed into products which in use receive their greatest load in the direction that corresponds to the rolling direction of the steel strip. Further, the use of the steel strip may be optimized, because varia- tions in strength in relation to the loading direction do not need to be taken into account.
  • isotropic strength properties probably contribute to the formation of bends of uniform quality irrespective of the bending direction (longitudinal/transverse), which further improves the applicability of the steel strip product of the invention.
  • Table 4 shows that bendability in longitudinal bending, which is known to be problematic, is excellent.
  • Steel sample B5Q3 for example, in longitudinal bending allows an RfT value of 1.3 to be reached. Transverse bending of this steel still succeeds at R7t value 0.3.
  • the bending has been carried out by a prior art method as a V-bend between the upper and the lower tool, Figure 3 illustrating the principle.
  • the bending method used is free bending with a V-opening width V of 100 mm.
  • the test pieces were bent in both directions, whereby they were bent into Z-shapes.
  • steel B3Q23 (bending test a in Table 2) has a far better bendability than steel A3M33 (bending test b in Table 2).
  • the ratio of the bending radius to material strength (R/t) may be even 0.4, whereas the ratio achieved by conventionally manufactured reference steel is only about 1.6.
  • the conclusion drawn from Tables 1 to 4 and Figure 5 is that the in the method of the invention direct quenching is performed to a temperature of 300 0 C at the most.
  • the impact strength of the steel of the invention at a temperature of -20 0 C is at least 200 J/cm 2 and/or at a temperature of -40 0 C at least 190 J/cm 2 and/or at a temperature of -60 0 C at least 180 J/cm 2 .
  • Example 1 A strip rolling mill was used to roll a hot strip having a thickness of 5 mm and composition (A1) of Table 1.
  • the roll parameters (A1M33) are shown in Table 2.
  • the results (A1M33) are shown in Table 3.
  • the results show that when the strip is coiled at a coiling temperature of 600 0 C, an excellent strength is achieved, but impact strength, however, remains on a normal level only.
  • yield strengths are clearly different in different testing directions, which is normal for micro-alloy steels conventionally rolled thermomechanically. Elongation level is normal.
  • a strip rolling mill was used to roll a hot strip having a thickness of 5 mm and composition (A1) of Table 1.
  • the roll parameters (A1 M63) are shown in Table 2.
  • the results are shown in Table 3.
  • the results show that coiling at a relatively low coiling temperature (about 480 0 C) produces steel (A1M63) of a low strength but improved impact energy. Elongation level is normal. Cooling the strip to a still lower coiling temperature (about 250 0 C) increases the strength of steel (A1Q61) close to the normal level with clearly improved impact energy. Elongation remains below the normal level.
  • Example 3 A strip rolling mill was used to roll a hot strip having a thickness of 5 mm and composition (A1) of Table 1.
  • the roll parameters (A1 M83) are shown in Table 2.
  • the results (A1M83) are shown in Table 3.
  • the results show that coiling at a very low coiling temperature (about 50°C) raises strength to a good level close to normal with impact energy still clearly better than the normal level. Elongation remains below normal level.
  • IO0631 Example 4 A strip rolling mill was used to roll a hot strip having a thickness of 8 mm and composition (B4) of Table 1.
  • the roll parameters (B4Q23) are shown in Table 2 and the corresponding results in Table 3.
  • the results show that coiling at a very low coiling temperature (about 50 0 C) increases strength to a normal level and provides an impact energy that is clearly better than normal. Again, it is noteworthy that yield strengths in the rolling direction are nearly the same both crosswise and lengthwise. Elongation is slightly below normal.
  • IO0641 Example 5 A strip rolling mill was used to roll a hot strip having a thickness of 10 mm and composition (B2) of Table 1.
  • the roll parameters (B2L13) are shown in Table 2, the corresponding results in Table 3.
  • Example 6 A strip rolling mill was used to roll a hot strip having a thickness of 10 mm and composition (B3) of Table 1.
  • the roll parameters (B3Q25) are shown in Table 2, the corresponding results in Table 3.
  • the results show that at a very low rolling temperature (about 800 0 C) and a very low coiling temperature (about 50 0 C) yield strength increases to a normal level also for a thick strip, with impact energy still on a good level.
  • yield strengths in relation to the rolling direction are the same both crosswise and lengthwise. Elongation is slightly below the normal level.
  • Example 7 A strip rolling mill was used to roll a hot strip having a thickness of 5 mm and composition (D1) of Table 1.
  • the roll parameters (D1Q63) are shown in Table 2, the corresponding results in Table 3.
  • the results show that reduction of alloying elements (Ti, Nb in particular) decrease strength heavily when the steel is rapidly cooled to a temperature of 50 0 C. Elongation and impact strength are at a good level.
  • r00671 Example 8.
  • a strip rolling mill was used to roll a hot strip having a thickness of 7.7 mm and a composition (C1) of Table 1 , the strip being then used for manufacturing a HF-welded quadratic tube beam with dimensions of 100mm x 250mm.
  • the rolling parameters (C1Q35) are shown in Table 2 and the results measured from the tube beam in Table 3.
  • the measured strength values are strengths obtained after the formation of the tube beams. Because of cold forming taking place in the manufacture of tube beams, impact strength values typically drop a little. The results show that the steel according to the method is well suited also for manufacturing high-strength tube beams.
  • Example 9 A strip rolling mill was used to roll a hot strip having a thickness of 8 mm and compositions (A3 and B4) of Table 1.
  • the rolling parameters (A3M33 and B3Q23) are shown in Table 2 and the corresponding test results measured from the strip in Table 3.
  • Table 4 shows a comparison of the bending of these steels (A3M33 and B3Q23), whereby it is noted that a direct quenched steel B3Q23 sustains bending well even at R/t value 0.4.
  • Steel A3M33 cooled to a temperature of about 600 0 C can be successfully bent to R/t value 1.6.
  • Figure 5 compares the impact strength values of steels A2M33 and B4Q23 at different testing temperatures by a Charpy V impact test.
  • the compositions and manufacturing parameters of steels A2M33 and B4Q23 are shown in Tables 1 and 2.
  • Direct quenched steel B4Q33 proves to be clearly better, maintaining its strength also at extremely low temperatures.
  • Example 11 A strip rolling mill was used to roll hot strip having thicknesses of 5 and 6mm and composition (E 1) of Table 1.
  • the rolling parameters (E1Q11 and E1Q33) are shown in Table 2 and the corresponding test results measured from the strip in Table 3.
  • the results show that a steel strip product of the invention may be manufactured also in small thicknesses, for example by selecting the niobium, titan and vanadine contents of the steel as follows: Nb: 0.04 - 0.06%, Ti: 0.06 - 0.10% and V: 0.06 - 0.1%.
  • Example 12 A strip rolling mill was used to roll a hot strip having a thickness of 12 mm and compositions (F1 and F2) of Table 1.
  • the rolling parameters (F1Q23 and F2Q43) are shown in Table 2 and the corresponding test results measured from the strip in Table 3. The results show that a steel strip product of the invention can be manufactured also with thick dimensions. In addition, this example further proves that uniform quality is obtained by direct quenching carried out to a temperature below 100°C and/or by using a strip rolling end temperature that is below 890 0 C.

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Abstract

The invention relates to a method for manufacturing a hot-rolled steel strip product with a thickness of 2 - 12 mm from low-alloy steel having a carbon content of 0.04 - 0.08 in percentage by weight and containing niobium and titanium. In order to obtain good mechanical properties, with bending properties included, for the steel strip product, a work piece of steel is austenized at an austenizing temperature of 1200 - 13500C, the steel work piece is hot-rolled at a pre-rolling step, the pre-rolled steel work piece is rolled in a strip roll mill so that a rolling temperature of 760 - 9600C is achieved for the work piece in the last pass, and the steel strip is direct quenched after the last pass in the strip roll mill by a single-step cooling at a cooling rate of 30 - 150°C/s to a temperature of 3000C at the most, the direct quenching being carried out within 15s from the last pass. The invention also relates to a steel strip product.

Description

METHOD FOR MANUFACTURING HOT ROLLED STEEL STRIP PRODUCT, AND HOT ROLLED STEEL STRIP PRODUCT
BACKGROUND OF THE INVENTION
[0001] The invention relates to a method for manufacturing a hot rolled steel strip product having a wall thickness of 2 to 12 mm using steel whose composition in percentage by weight is
C: 0.04 - 0.08
Si: 0 - 0.5
Mn: 1 - 2.2
Nb: 0.04 - 0.09
Ti: 0.06 - 0.16
N: < 0.01
P: < 0.03
S: < 0.015
Al: 0.01 - 0.15
V: ≤ 0.1
Cr: < 0.2
Mo: < 0.2
Cu: < 0.5
Ni: < 0.5 and the rest iron and unavoidable impurities. Low carbon content is excellent for providing steel with good welding characteristics. Also the low carbon equivalent of steel has a positive effect to good weldability.
[0002] The invention further relates to a steel product with a wall thickness of 2 to 12 mm and a composition as described above.
[0003] EP 1319725 discloses a method for manufacturing a steel strip having the above composition. The strength of the steel strip thus manufactured is relatively high, its yield strength exceeding 690 MPa, combined with a relatively high percentage of elongation after fracture (12 to 21%). According to the publication these mechanical properties are arrived at by subjecting the steel to a two-step cooling. In the first cooling step an extremely fast cooling is carried out, the cooling rate being over 150°C/s after hot rolling, followed by a pause of 3 to 10 seconds without active cooling, after which a second cooling step is carried out to the coiling temperature of the steel strip to be manufactured, the temperature being chosen according to the desired strength. The recommended coiling temperature for yield strengths exceeding 690 MPa is 5800C. The high cooling rate of over 150°C/s at the first quenching step may be obtained only at low strip thicknesses, and the publication only discusses strip thicknesses lower than 4 mm. The cooling pause is meant to provide time for a phase change, during which the yield strength of the material in particular decreases and the yield strength/tensile strength value decreases compared with continued cooling. The publication does not disclose how a yield strength of over 690 MPa is obtained in the steel when the coiling temperature is below 5800C. The publication shows that the yield strength obtained in a coiling temperature of less than 5800C remains below 690 MPa.
[0004] Said two-step cooling is in practice more complicated to carry out than a one-step cooling and requires more complex production equipment. Moreover, the bendability of the steel strip obtained by two-step cooling is not particularly good, although the steel strip has relatively good values for percentage of elongation after fracture. Bendability means the ability of steel strip to bend to a small bending radius without surface damage emerging at the bending point. Two-step cooling has not succeeded in providing steel with particularly good impact strength values at low temperatures in combination with high strength.
SUMMARY OF THE INVENTION
[0005] An object of the invention is to overcome said drawbacks of the prior art and to provide a method that is easy to implement for manufacturing strip steel product, typically a steel strip, of high strength and a particularly good bendability, the strip steel product having a chemical composition as mentioned above. To achieve this, the method of the invention is characterized by
- austenizing a work piece of steel at an austenizing temperature of 1200 to 13500C;
- hot rolling the steel work piece in a pre-rolling step;
- rolling the pre-rolled steel work piece in a strip rolling mill so that a rolling temperature of 760 to 9600C for the work piece is achieved in the last pass; and
- direct quenching the steel strip after the last pass in the strip rolling mill by a single-step cooling at a cooling rate of 30 to 150°C/s to a maximum of 3000C, the parallel extinction being carried out within 15s the last pass. [0006] The invention has surprisingly shown that said steel composition is capable of producing high-strength steel which also has good bend- ability. Also surprisingly, it was discovered that the strength of the steel is isotropic, i.e. its yield strength does not vary considerably irrespective of whether it is measured lengthwise or crosswise in relation to the rolling direction.
[0007] The direct quenching rate is preferably 120 °C/s at the most, because this enables to obtain a steel microstructure that provides the steel with particularly good mechanical properties, including good impact strength combined with good bendability.
[0008] The end temperature in direct quenching is preferably 1000C at the most, because this enables to obtain a planar strip with also planar and even edges after the quenching.
[0009] The steep strip is preferably direct quenched directly to the coiling temperature and coiled.
[0010] The processing of the steel strip is preferably thermome- chanical, and thus no tempering is carried out after the direct quenching. It has been observed that a steel product manufactured with the method has good mechanical properties although no tempering adding the costs is required on the product. Tempering does not significantly improve the mechanical properties of the product, and it complicates the process.
[0011] The preferred embodiments of the invention are disclosed in the accompanying claims 2 to 6.
[0012] The major advantages of the method of the invention are that it allows a steel product with good mechanical properties, including bendability, and a predetermined composition to be manufactured in a simple and economical manner and with simple equipment.
[0013] The invention further relates to a product manufactured in method steps of the invention.
[0014] The steel strip product of the invention having a wall thickness of 2 to 12 mm and composed in percentage by weight of
C: 0.04 - 0.08
Si: 0 - 0.5
Mn: 1 - 2.2
Nb: 0.04 - 0.09
Ti: 0.06 - 0.16
N: < 0.01 P < 0.03
S: < 0.015
Al: 0.01 - 0.15
V: < 0.1
Cr: < 0.2
Mo: < 0.2
Cu: < 0.5
Ni: < 0.5, the rest being iron and inevitable impurities, is characterized in that the micro structure of the steel is substantially low carbon ferritic and/or low carbon bain- itic, that upon bending the steel sustains a bending radius of R < 0.75 t without fractures or cracks visible to the eye, t being the thickness of the steel product, that its yield strength is 650 - 800 MPa and that its percentage of elongation after fracture is at least 12%.
[0015] High strength has been obtained although the microstructure of the steel mostly consists of a low carbon ferrite and/or bainite, without containing significant amounts of carbon-rich martensite or carbon-rich bainite. As recommended, the dominant phase consists of ferrite with an almost fully ferritic microstructure, as recommended, and small amounts of bainite and/or martensite and/or residue austenite in extremely small islands of enriched carbon content. A significant reason for the obtained high strength is the use of niobium and titanium as micro-alloy elements in the steel produced with the method. Both niobium and titanium must be used.
[0016] The preferred embodiments of the invention are disclosed in the accompanying claims 8 to 19.
[0017] The major advantages of the steel product of the invention are its excellent mechanical properties, including bendability and shear characteristics and impact strength values, in relation to its composition. The steel is also well applicable in arctic conditions. The steel of the invention is extremely useful due to its properties related to engineering works, because its weldabil- ity is good and its isotropic strength properties allow a very efficient optimization of its use. Moreover, the small bending radius particularly facilitates the work of bent product designers. The steel strip product of the invention is specifically well suited for use as strong structure steel. BRIEF DISCLOSURE OF THE FIGURES
[0018] In the following the invention will be disclosed in greater detail and with reference to the accompanying drawing in which
Figure 1 shows the method steps of the invention;
Figure 2 is a schematic view of a V-bending in bending tests;
Figure 3 illustrates an example of a successful bending test result;
Figure 4 illustrates an example of a failed bending test result;
Figure 5 presents transition curves for charpy-V obtained with the steel of the invention and a reference steel;
Figure 6 illustrates the connection between yield strength isotropy and strip rolling; and
Figure 7 illustrates the connection between yield strength isotropy and coiling temperature.
DETAILED DISCLOSURE OF THE INVENTION
[0019] Figure 1 shows the method steps of the invention for producing a steel strip product with a wall thickness of 2 to 12mm. The manufacture starts with a work piece of steel whose composition in percentage by weight is
C: 0.04 - 0.08
Si: 0 - 0.5
Mn: 1 - 2.2
Nb: 0.04 - 0.09
Ti: 0.06 - 0.16
N: < 0.01
P < 0.03
S: < 0.015
Al: 0.01 - 0.15
V: < 0.1
Cr: < 0.2
Mo: < 0.2
Cu: < 0.5
Ni: < 0.5 and the rest iron and unavoidable impurities.
[0020] The steel has a low carbon content C of 0.04 to 0.08%, which is advantageous in view of the impact strength, bendability and weldabil- ity of the material. [0021] Silicon, Si, may be used in an amount of 0 to 0.50% as a killing agent (in addition to aluminium) and for ferrite reinforcement. If a particularly good surface quality is to be aimed at, the silicon content must be limited to below 0.25%.
[0022] The alloying content of manganese, Mn, is 1.0 to 2.2%. Because of the low carbon content, steel is not prone to manganese and carbon segregation during casting, which enhances the homogeneity of the micro- structure also at relatively high contents of Mn. Preferably at least 1.3% of manganese is alloyed to achieve a high strength and to ensure a weldability of 2.0% at the most.
[0023] The steel of the invention may be cut into precisely dimensioned pieces both thermally (e.g. by laser and plasma) and mechanically. It has been observed that a piece with a relatively smooth cutting surface is obtained. This has an advantageous effect on fatigue strength. In addition, low carbon content prevents the cutting surface from becoming rough during thermal cutting and reduces maximum hardness, the cutting surface being less prone to brittle and crack during forming of the piece and in the conditions of use thereof. In mechanical cutting the cutting gap may be set at a value of 10 to 15% of the sheet thickness, the cutting result being still smooth and non- fractured and hence separate grinding of the cutting surface or thermal cutting is not needed, which significantly reduces working allowances and decreases the number of manufacturing steps, thereby enhancing the manufacturing process.
[0024] In order for a good impact strength and bendability to be achieved, the amounts of phosphor, P, (0.03% at the most) and sulphur, S, (0.015% at the most) present as impurities are to be restricted. The maximum amount of P is preferably 0.015% and that of S preferably 0.005%. Further, the properties may be improved, when necessary, by treatment with molten Ca or CaSi. As a killing agent, aluminium Al 0.01 - 0.15% is used. The amount of aluminium used is preferably 0.05% at the most.
[0025] The amount of nitrogen, N, used is 0.01% at the most, because when present in steel containing titanium, nitrogen forms hard titanium nitride particles that impair the bendability of the steel. The preferred amount of nitrogen used is 0.006% at the most.
[0026] The content of copper, Cu, is to be reduced to 0.3% at the most to ensure excellent surface quality for a hot-rolled strip. If the copper con- tent exceeds 0.3%, it is recommended to alloy also nickel, Ni, in an amount equal to at least 0.25 times the Cu content. Although steel achieves its good properties also without copper, it may be used, when necessary, to slightly increase strength. The Cu content is 0.5% at the most. An alloy 0.3 to 0.5% of copper and at least 0.1% of nickel is preferably used particularly for thick strips of 8 to 12 mm, for example.
[0027] Even without copper in the alloy, Ni is restricted to 0.5% at the most. Although steel achieves its excellent strength properties also without the blending of Ni, it may slightly increase strength, when necessary.
[0028] Borium, B, is not alloyed at all, because it would unnecessarily increase hardening. Hence the borium content in the steel strip product of the invention is restricted to the impurity level, i.e. B < 0.0005%.
[0029] Titanium, T, may be alloyed to achieve a desired strength level. Typically 0.06 to 0.16%, although higher Ti levels could be used as well, but in that case its strength increasing effect is extremely small and may complicate the casting of the work piece. Lower Ti percentages are not used, because then high strength is difficult to obtain without using a more expensive alloying or increasing the carbon content to over 0.08%. Surprisingly the invention has shown that even at low temperatures, such as -400C and -600C, titanium does not lower significantly the impact strength of the basic agent, as shown by the measurement results of Table 3.
[0030] Chromium, Cr, and molybdene, Mo, do not need to be alloyed. They are elements that increase hardening and have a disadvantageous effect on weldability, at least in higher amounts. For this reason Cr is restricted to a maximum content of 0.2% and, similarly, Mo to a maximum content of 0.2%. The amount of chromium is preferably less than 0.1%.
[0031] Molybdene is preferably allowed in an amount of 0.10%, and most preferably 0.5%, at the most, because the mechanical properties of the steel of the invention are most preferably achieved by alloying titanium which provides more affordable alloying element costs than molybdene. Molybdene may even be harmful for strength in a direct quenched steel strip product of the invention. In any case, added molybdene does not significantly improve the strength of the steel strip product of the invention, when the product is produced by thermomechanical treatment.
[0032] Vanadine, V, does not need to be alloyed. In addition, it increases unnecessary hardening and has a disadvantageous effect on weld- ability at least in high concentrations. For this reason, V is restricted to a maximum content of 0.1%.
[0033] However, with low strip thicknesses t of 2 to 6 mm in particular, at high rolling forces, Nb and Ti concentrations are restricted as follows: Nb: 0.04 - 0.06% and Ti: 0.06 - 0.10% for reducing the rolling forces and, at the same time, a vanadium concentration V of 0.06 - 0.10% may be selected to obtain high strength.
[0034] With the low strip thicknesses t = 2 - 6 mm also silicon may be advantageously added in an amount of Si: 0.30 - 0.50% to increase strength, as shown in Table 1 of the tests run with an experimental composition E1.
[0035] According to a preferred embodiment of the invention the sum of the niobium, titanium and vanadium concentrations is greater than 0.15%, i.e. Ti + Nb + V > 0.15%, the steel strip product being applicable as a particularly strong structural steel.
[0036] At a lower carbon content limit in particular, the steel strip product of the invention is excellent to bend (fold) and to weld e.g. by autogenous high frequency (HF) welding into a tube or a tube beam. Manufacturing experiments have shown that the material suits excellently for producing HF- welded tube beams.
[0037] The work piece of steel is 210 mm thick, for example, and heated to an austenizing temperature of 12800C, where it is kept for about 3 hours. Naturally the thickness of the steel work piece may differ from the one disclosed here and the austenizing temperature may be differently chosen, but a range of 1200 - 13500C is recommended. If the austenizing temperature is below the lower limit given, there is a risk that the microalloying elements do not dissolve into the austenite, i.e. a homogenous austenite is not obtained. Most preferably the annealing time varies within a range of 2 to 4 hours.
[0038] The carbon equivalent C + Mn/6 + (Cr + Mo +V)/5 + Ni + Cu)/15 for steel is preferably not higher than 0.45, which guarantees a good weldability of the steel.
[0039] After austenizing, the steel work piece is hot-rolled at a temperature of 950 - 12500C to a thickness which is typically 25 - 50 mm and then immediately transferred to a strip rolling mill to be rolled into a strip with a final thickness of 2 - 12 mm. The recommended final thickness of the steel strip is at least 4 mm. It also recommended that the final thickness does not exceed 10 mm.
[0040] The number of passes in the strip roll mill is typically 5 to 7. The last pass in the strip roll mill is carried out at a temperature range of 760 - 9600C, the recommendation being 780 - 8500C.
[0041] After the last pass the direct quenching of the steel strip starts within 15 seconds. At the start of the direct quenching the temperature of the steel strip must be at least 7000C. The direct quenching is carried out as a water quenching at a quenching rate of 30 - 150°C/s, the recommended upper limit being 12O0CVs at the most. The direct quenching continues up to a temperature of 3000C at the most, the recommended temperature being 1000C. Immediately after the direct quenching the steel is coiled. Hence the coiling temperature may fall within a temperature range of 30 - 3000C. A recommended initial coiling temperature is 1000C at the most, because when steel is coiled at a temperature exceeding 1000C, a discontinuous steam cushion complicating the process may form onto the steel surface.
[0042] As a result of the thermomechanical treatment the micro- structure of the steel becomes homogenous and consists of a dominant phase, which is preferably low carbon ferrite and/or low carbon bainite. The amount of the dominant phase is typically over 90%. In other words, extremely low amounts of high carbon bainite and/or residual austenite and/or martensite is present in extremely high carbon groups. The average grain size in the micro- structure is small, preferably approximately 2 - 4 micrometers. It is also essential that the microstructure does not contain big grains in the first place and therefore the steel has particularly good bending characteristics taking into consideration the strength of the steel. The grain size must be as uniform and fine as possible, which is achieved by the method of the invention.
[0043] Tables 1 to 3 below provide examples of the concentrations and manufacturing parameters of the steel of the invention and of the strength and toughness values obtained with them. For the sake of comparison, Tables 2 and 3 also contain manufacturing parameters not belonging to the scope of the method of the invention, i.e. treatments not corresponding to the method of the invention. In Table 2 on the manufacturing parameters and in the table on the mechanical strength properties reference tests have been indicated with R.
[0044] A further topic of examination are the bending characteristics obtained with the treatments of the invention, these being compared with the bending characteristics obtained by manufacturing parameters remaining outside the scope of the method, see Tables 3 and 4, Steel B3Q23 (bending test a) according to the invention)and Steel A3M33 (bending test b) outside the invention).
[0045] Indication T_f in Table 2 denotes the temperature at the last rolling pass, indication T_c denoting the temperature at the start of the coiling, indication Th denoting the thickness of the steel strip and indication Wi denoting the width of the steel strip.
[0046] In the first column of Table 3 T denotes a sample whose strength and toughness have been determined in a direction transverse to the roll direction. Ending L denotes a sample whose strength and toughness have been determined in the rolling direction.
[0047] Tables 2 and 3 show that the impact strength values are good and the strength is isotropically high, when direct quenching is carried out to a low temperature (500C).
[0048] As seen from Table 3, the yield strength of steels according to the invention is 635 - 829 MPa. The percentage of elongation after fracture A5 is at least 12% and typically at least 15%. The yield ratio (yield strength/break strength) of the steels is about 0.8 - 0.95.
[0049] It may be further concluded from the results of Tables 1 to 3 that the yield strength values of the steel strip in the machine direction and cross machine direction of the steel strip do not differ significantly from one another in examples 3, 4, 6, 7, 9, 11 and 12. The yield strength in the machine direction is almost as high as the yield strength in cross machine direction, the ratio of the strengths being < 6.5%, even < 2%. According to the examples, strength variations as low as these are obtained by carrying out the quenching according to a preferred embodiment of the invention to a temperature of less than 1000C and/or by using the final strip rolling temperature of 8900C.
[0050] As shown in Tables 2 and 3, said uniform quality is present in steels in which the final rolling temperature is low (below 8900C) and/or coiled at a low temperature (coiling temperatures 500C).
[0051] Reference values from the table show for examples 1 , 2a and 5 that when the coiling temperature is well over 1000C, the isotropy of the steel strength values decreases to a value closer to 10%, this representing a usual variation in strength values for a conventional, thermomechanically produced steel. The same applies to break strength values.
[0052] The effect of final bending temperature T_f and coiling temperature T_c on the isotropy of yield strength is examined in greater detail in Figures 6 and 7, which show that a decrease in both the final bending temperature and the coiling temperature allow the yield strength of the steel of the invention to be improved.
[0053] The invention has also shown that yield strength isotropy may be evaluated using formula Rp(T-L)/Rp(L) = - 46.6 + 0.0576 T_f + 0.0103 T_c, where T_f is the final bending temperature and T_c the coiling temperature.
[0054] Uniform quality is advantageous, because when a steel strip for different purposes is being designed, there is no need to take into account the fact that the steel strip has a higher strength in rolling direction than in the direction that is transverse to the rolling direction. Hence it is possible to take advantage of the high strength of the steel strip in all situations, i.e. also when cutting blanks that are processed into products which in use receive their greatest load in the direction that corresponds to the rolling direction of the steel strip. Further, the use of the steel strip may be optimized, because varia- tions in strength in relation to the loading direction do not need to be taken into account. Moreover, isotropic strength properties probably contribute to the formation of bends of uniform quality irrespective of the bending direction (longitudinal/transverse), which further improves the applicability of the steel strip product of the invention. Table 4 shows that bendability in longitudinal bending, which is known to be problematic, is excellent. Steel sample B5Q3, for example, in longitudinal bending allows an RfT value of 1.3 to be reached. Transverse bending of this steel still succeeds at R7t value 0.3.
[0055] The bending has been carried out by a prior art method as a V-bend between the upper and the lower tool, Figure 3 illustrating the principle. The bending method used is free bending with a V-opening width V of 100 mm. The test pieces were bent in both directions, whereby they were bent into Z-shapes.
Table 4. Bending results. Bending with a square sheet having a side length of 300 - 400 mm, and the bent made crosswise to the rolling direction. In the table R represents the bending radius and t the sheet thickness. The bending tests were made transversally (T) to the rolling direction.
[0056] The results of the bending test have been analyzed visually. Figure 3 shows a successful bend (OK) with a round bend form and an intact surface. Rejecting result (Fail) is due to visible cracks, fissures or angularity in the area of the bending radius. Table 5 shows typical bending faults that lead to a rejecting result and Table 4 an example of a clearly failed bending (Fail).
Table 5. Typical bending faults
Name Descri tion
[0057] As shown in Figure 4, steel B3Q23 (bending test a in Table 2) has a far better bendability than steel A3M33 (bending test b in Table 2). In the steel of the invention the ratio of the bending radius to material strength (R/t) may be even 0.4, whereas the ratio achieved by conventionally manufactured reference steel is only about 1.6. The conclusion drawn from Tables 1 to 4 and Figure 5 is that the in the method of the invention direct quenching is performed to a temperature of 3000C at the most.
[0058] As shown in Table 3 and Figure 5, the impact strength values obtained for steel samples B4Q23 (transition curve d) are significantly better than those for steel samples A2M33 (transition curve c). The former steel samples have been direct quenched to a temperature of 500C (cf. Table 2), whereas the latter have been cooled to a temperature of 615°C. Table 3 also shows that cooling to a high temperature of about 6000C (examples 1 and 10) results only in impact strength values that are typical for steel of this strength grade. As is shown, the impact strength of the steel of the invention at a temperature of -200C is at least 200 J/cm2 and/or at a temperature of -400C at least 190 J/cm2 and/or at a temperature of -600C at least 180 J/cm2.
[0059] Lastly, the invention will be illustrated by a more detailed description of test examples and the information in Tables 1 to 4.
IO0601 Example 1. A strip rolling mill was used to roll a hot strip having a thickness of 5 mm and composition (A1) of Table 1. The roll parameters (A1M33) are shown in Table 2. The results (A1M33) are shown in Table 3. The results show that when the strip is coiled at a coiling temperature of 6000C, an excellent strength is achieved, but impact strength, however, remains on a normal level only. A noteworthy aspect is that yield strengths are clearly different in different testing directions, which is normal for micro-alloy steels conventionally rolled thermomechanically. Elongation level is normal. rOQβπ Example 2. A strip rolling mill was used to roll a hot strip having a thickness of 5 mm and composition (A1) of Table 1. The roll parameters (A1 M63) are shown in Table 2. The results are shown in Table 3. The results show that coiling at a relatively low coiling temperature (about 4800C) produces steel (A1M63) of a low strength but improved impact energy. Elongation level is normal. Cooling the strip to a still lower coiling temperature (about 2500C) increases the strength of steel (A1Q61) close to the normal level with clearly improved impact energy. Elongation remains below the normal level.
IO0621 Example 3. A strip rolling mill was used to roll a hot strip having a thickness of 5 mm and composition (A1) of Table 1. The roll parameters (A1 M83) are shown in Table 2. The results (A1M83) are shown in Table 3. The results show that coiling at a very low coiling temperature (about 50°C) raises strength to a good level close to normal with impact energy still clearly better than the normal level. Elongation remains below normal level.
IO0631 Example 4. A strip rolling mill was used to roll a hot strip having a thickness of 8 mm and composition (B4) of Table 1. The roll parameters (B4Q23) are shown in Table 2 and the corresponding results in Table 3. The results show that coiling at a very low coiling temperature (about 500C) increases strength to a normal level and provides an impact energy that is clearly better than normal. Again, it is noteworthy that yield strengths in the rolling direction are nearly the same both crosswise and lengthwise. Elongation is slightly below normal. IO0641 Example 5. A strip rolling mill was used to roll a hot strip having a thickness of 10 mm and composition (B2) of Table 1. The roll parameters (B2L13) are shown in Table 2, the corresponding results in Table 3. The results show that at a very high rolling temperature (9100C) and coiling at a coiling temperature of 3600C, yield strength lengthwise in the bending direction remains at a low level, but impact energy is still good. Elongation is approximately at a normal level.
IO0651 Example 6. A strip rolling mill was used to roll a hot strip having a thickness of 10 mm and composition (B3) of Table 1. The roll parameters (B3Q25) are shown in Table 2, the corresponding results in Table 3. The results show that at a very low rolling temperature (about 8000C) and a very low coiling temperature (about 500C) yield strength increases to a normal level also for a thick strip, with impact energy still on a good level. A noteworthy aspect is that yield strengths in relation to the rolling direction are the same both crosswise and lengthwise. Elongation is slightly below the normal level.
1O0661 Example 7. A strip rolling mill was used to roll a hot strip having a thickness of 5 mm and composition (D1) of Table 1.The roll parameters (D1Q63) are shown in Table 2, the corresponding results in Table 3. The results show that reduction of alloying elements (Ti, Nb in particular) decrease strength heavily when the steel is rapidly cooled to a temperature of 500C. Elongation and impact strength are at a good level. r00671 Example 8. A strip rolling mill was used to roll a hot strip having a thickness of 7.7 mm and a composition (C1) of Table 1 , the strip being then used for manufacturing a HF-welded quadratic tube beam with dimensions of 100mm x 250mm. The rolling parameters (C1Q35) are shown in Table 2 and the results measured from the tube beam in Table 3. The measured strength values are strengths obtained after the formation of the tube beams. Because of cold forming taking place in the manufacture of tube beams, impact strength values typically drop a little. The results show that the steel according to the method is well suited also for manufacturing high-strength tube beams.
IO0681 Example 9. A strip rolling mill was used to roll a hot strip having a thickness of 8 mm and compositions (A3 and B4) of Table 1. The rolling parameters (A3M33 and B3Q23) are shown in Table 2 and the corresponding test results measured from the strip in Table 3. Table 4 shows a comparison of the bending of these steels (A3M33 and B3Q23), whereby it is noted that a direct quenched steel B3Q23 sustains bending well even at R/t value 0.4. Steel A3M33 cooled to a temperature of about 6000C can be successfully bent to R/t value 1.6.
IO0691 Example 10. Figure 5 compares the impact strength values of steels A2M33 and B4Q23 at different testing temperatures by a Charpy V impact test. The compositions and manufacturing parameters of steels A2M33 and B4Q23 are shown in Tables 1 and 2. Direct quenched steel B4Q33 proves to be clearly better, maintaining its strength also at extremely low temperatures.
[0070] Example 11. A strip rolling mill was used to roll hot strip having thicknesses of 5 and 6mm and composition (E 1) of Table 1. The rolling parameters (E1Q11 and E1Q33) are shown in Table 2 and the corresponding test results measured from the strip in Table 3. The results show that a steel strip product of the invention may be manufactured also in small thicknesses, for example by selecting the niobium, titan and vanadine contents of the steel as follows: Nb: 0.04 - 0.06%, Ti: 0.06 - 0.10% and V: 0.06 - 0.1%. r00711 Example 12. A strip rolling mill was used to roll a hot strip having a thickness of 12 mm and compositions (F1 and F2) of Table 1. The rolling parameters (F1Q23 and F2Q43) are shown in Table 2 and the corresponding test results measured from the strip in Table 3. The results show that a steel strip product of the invention can be manufactured also with thick dimensions. In addition, this example further proves that uniform quality is obtained by direct quenching carried out to a temperature below 100°C and/or by using a strip rolling end temperature that is below 8900C.
[0072] In the above the invention has been illustrated by examples. On account of this it is to be noted that the details of the invention may be implemented in various ways within the scope of the accompanying claims.

Claims

1. A method for manufacturing a hot-rolled steel strip product having a thickness of 2 to 12 mm by using steel whose composition in percentage by weight is
C: 0.04 - 0.08
Si: 0-0.5
Mn: 1 -2.2
Nb: 0.04 - 0.09
Ti: 0.06-0.16
N: <0.01
P: < 0.03
S: < 0.015
Al: 0.01 -0.15
V: <0.1
Cr: < 0.2
Mo: < 0.2
Cu: <0.5
Ni: <0.5 the rest consisting of iron and unavoidable impurities, characterized by
- austenizing a work piece of steel at an austenizing temperature of 1200 to 13500C;
- hot rolling the steel work piece in a pre-rolling step;
- rolling the pre-rolled steel work piece in a strip rolling mill so that a rolling temperature of 760 to 9600C is achieved for the work piece in the last pass; and
- direct quenching the steel strip after the last pass in the strip rolling mill by a single-step cooling at a cooling rate of 30 to 150°C/s to 3000C at the most, the direct quenching being carried within 15s from the last pass.
2. A method according to claim 1, characterized in that the direct quenching rate is 12O0CVs at the most.
3. A method according to claim 1 or 2, characterized in that the end temperature of the direct quenching is 1000C at the most.
4. A method according to any one of the preceding claims, characterized in that the steel strip is direct quenched directly to a coiling temperature and coiled.
5. A method according to any one of the preceding claims, characterized in that the steel strip is handled thermomechanically, in which case direct quenching is not followed by annealing.
6. A method according to any one of the preceding claims, characterized in that the steel strip is formed into a tube product after the direct quenching.
7. A hot-rolled steel strip product having a thickness of 2 - 12 mm and a composition in percentage by weight of
C: 0.04 - 0.08
Si: 0-0.5
Mn: 1 -2.2
Nb: 0.04 - 0.09
Ti: 0.06-0.16
N: <0.01
P: < 0.03
S: < 0.015
Al: 0.01 -0.15
V: <0.1
Cr: < 0.2
Mo: < 0.2
Cu: <0.5
Ni: <0.5 the rest being iron and unavoidable impurities, characterized in that the microstructure of the steel is substantially low carbon ferritic and/or low carbon bainitic, that its yield strength is 650 - 800 MPa and percentage of elongation after fracture is at least 12%; and that its structure is isotropic in the sense that its yield strength in the rolling direction differs 6.5% at the most from its yield strength in the direction that is transverse to the rolling direction.
8. A steel strip product according to claim 7, characterized in that the substantially low-carbon ferrite and/or low-carbon bainite structure contains high-carbon islands.
9. A steel strip product according to claim 7 or 8, characterize d in that in crosswise bending the steel sustains a bending radius of 0.4 < R < 0.75 t, t being the wall thickness of the steel product, without cracks or fractures visible to the eye.
10. A steel strip product according to any one of the preceding claims 7 to 9, characterized in that its average grain size is 2 to 4 micrometres.
11. A steel strip product according to any one of the preceding claims 7 to 10, characterized in that its carbon equivalent is 0.45 at the most.
12. A steel strip product according to any one of the preceding claims 7 to 11, characterized in that its yield strength is over 680 MPa.
13. A steel strip product according to any one of the preceding claims 7 to 12, characterized in that its impact strength at a temperature of -200C is at least 200 J/cm2 and/or at a temperature of -400C at least 190 J/cm2 and/or at a temperature of -6O0C at least 180 J/cm2.
14. A steel strip product according to any one of the preceding claims 7 to 13, characterized in that it can be cut at a cutting gap of 10 - 15% of the sheet thickness without visually perceptible cracks.
15. A steel strip product according to claim 7 or 8, characterize d in that the steel composition also meets the requirement Ti + Nb + V > 0.15.
16. A steel strip product according to claim 15, characterized in that its thickness is 2 - 6 mm and the contents of alloying elements Nb, Ti and V in the steel are
Nb: 0.04 - 0.06 Ti: 0.06 -0.10 V: 0.06 -0.10.
17. A steel strip product according to claim 15, characterized in that the molybdene content of the steel is Mo < 0.10.
18. A steel strip product according to claim 7 or 18, characterize d in that the molybdene content of the steel is Mo < 0.05.
19. A steel strip product according to claim 7 or 8, characterize d in that its thickness exceeds 8 mm and that the copper and nickel content of the steel is 0.3 < Cu < 0.5 and Ni < 0.1%.
EP10727754.3A 2009-05-11 2010-04-16 Method for manufacturing hot rolled steel strip product, and hot rolled steel strip product Active EP2430199B1 (en)

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FI20095528A FI20095528A (en) 2009-05-11 2009-05-11 Process for producing a hot rolled strip steel product and hot rolled strip steel product
PCT/FI2010/050310 WO2010130871A1 (en) 2009-05-11 2010-04-16 Method for manufacturing hot rolled steel strip product, and hot rolled steel strip product

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Families Citing this family (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI122313B (en) * 2010-06-07 2011-11-30 Rautaruukki Oyj Process for the production of hot rolled steel product and hot rolled steel
WO2013007729A1 (en) 2011-07-10 2013-01-17 Tata Steel Ijmuiden Bv Hot-rolled high-strength steel strip with improved haz-softening resistance and method of producing said steel
FI20125379L (en) * 2012-04-03 2013-10-04 Rautaruukki Oyj Method for making high strength malleable continuous annealed steel strip and high strength malleable continuously annealed steel strip
FI124825B (en) * 2013-02-22 2015-02-13 Rautaruukki Oyj Process for producing a metal-coated and hot-worked steel component and metal-coated steel strip product
EP3097214B1 (en) * 2014-01-24 2021-02-24 Rautaruukki Oyj Hot-rolled ultrahigh strength steel strip product
SI2924140T1 (en) * 2014-03-25 2018-04-30 Thyssenkrupp Steel Europe Ag Method for manufacturing a high strength flat steel product
CN104526115B (en) * 2014-11-04 2017-01-18 南方增材科技有限公司 Electric smelting forming method for nuclear power station pressure vessel shell
WO2016198906A1 (en) 2015-06-10 2016-12-15 Arcelormittal High-strength steel and method for producing same
CN109414904B (en) 2016-05-10 2022-10-28 美国钢铁公司 High strength steel product and annealing process for manufacturing the same
US11560606B2 (en) * 2016-05-10 2023-01-24 United States Steel Corporation Methods of producing continuously cast hot rolled high strength steel sheet products
CN107236909B (en) * 2017-06-16 2019-06-18 武汉钢铁有限公司 It can be used for the high intensity, high tenacity corrosion resistant steel and its production method of -60 DEG C of low temperature environments
CN108300949B (en) * 2018-02-12 2020-01-17 天津理工大学 Method for orientationally distributing bundled bainite in steel
CN109100378B (en) * 2018-07-24 2021-01-01 华北理工大学 Method for analyzing residual austenite in low-carbon bainite steel
EP3653736B1 (en) * 2018-11-14 2020-12-30 SSAB Technology AB Hot-rolled steel strip and manufacturing method
CN109487163B (en) * 2018-12-13 2020-08-28 河钢股份有限公司 Direct quenching type 800 MPa-level yield structural steel plate and production method thereof
CN111349759B (en) * 2020-03-30 2021-09-28 武汉钢铁有限公司 Production method of thin-specification wear-resistant steel for DQ (data-on-demand) process
CN113172980B (en) * 2021-05-12 2023-01-03 北京科技大学 Preparation method of stainless steel/carbon steel composite sheet strip
CN114150215B (en) * 2021-10-19 2022-10-21 首钢集团有限公司 Low-alloy high-strength steel for automobiles and preparation method thereof

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5531842A (en) * 1994-12-06 1996-07-02 Exxon Research And Engineering Company Method of preparing a high strength dual phase steel plate with superior toughness and weldability (LAW219)
JP3425837B2 (en) * 1996-03-28 2003-07-14 株式会社神戸製鋼所 High-strength hot-rolled steel sheet, high-strength galvanized steel sheet excellent in pitting corrosion resistance and crushing properties, and methods for producing them
FR2757877B1 (en) * 1996-12-31 1999-02-05 Ascometal Sa STEEL AND PROCESS FOR THE MANUFACTURE OF A SHAPED STEEL PART BY COLD PLASTIC DEFORMATION
ATE346960T1 (en) * 1997-07-28 2006-12-15 Exxonmobil Upstream Res Co MANUFACTURING PROCESS FOR ULTRA-HIGH-STRENGTH, WELDABLE STEELS WITH EXCELLENT TOUGHNESS
FR2807068B1 (en) * 2000-03-29 2002-10-11 Usinor HOT ROLLED STEEL WITH VERY HIGH LIMIT OF ELASTICITY AND MECHANICAL STRENGTH FOR USE IN PARTICULAR FOR THE PRODUCTION OF PARTS OF MOTOR VEHICLES
DE10062919A1 (en) * 2000-12-16 2002-06-27 Thyssenkrupp Stahl Ag Process for producing hot strip or sheet from a microalloyed steel
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
FI114484B (en) * 2002-06-19 2004-10-29 Rautaruukki Oyj Hot rolled strip steel and its manufacturing process
JP4214006B2 (en) * 2003-06-19 2009-01-28 新日本製鐵株式会社 High strength steel sheet with excellent formability and method for producing the same
JP2006299415A (en) * 2005-03-24 2006-11-02 Jfe Steel Kk Method for producing hot-rolled steel sheet for low yield-ratio electric-resistance welded steel tube excellent in low temperature toughness
RU2292404C1 (en) * 2005-07-15 2007-01-27 Открытое акционерное общество "Северсталь" Strip making method for producing tubes

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2010130871A1 *

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RU2011149763A (en) 2013-06-20
EP2430199B1 (en) 2019-05-29
CN102439179A (en) 2012-05-02
TR201910938T4 (en) 2019-08-21
FI20095528A0 (en) 2009-05-11
CN102439179B (en) 2015-03-25
WO2010130871A1 (en) 2010-11-18
ES2738876T3 (en) 2020-01-27
RU2535890C2 (en) 2014-12-20
FI20095528A (en) 2010-11-12
PL2430199T3 (en) 2019-12-31

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