EP4206337A1 - Plate and thermomechanical processing method of a raw material for producing a plate - Google Patents

Abstract

A heavy plate and a thermomechanical treatment method of a starting material, in particular a slab, for the production of the heavy plate consisting of a steel alloy are shown. In order to be able to create advantageous mechanical parameters on the heavy plate, it is proposed that a multi-stage cooling with optionally at least one straightening takes place after the final forming, in which in a first stage (8a) after the second rolling (W2) with a first cooling rate (KR1) cooled from a second final rolling temperature, in particular ≥ Ar3, of the second rolling (W2) to a first temperature (T1) between Ar3 and Ar1 and in a subsequent second stage (8b) at a second cooling rate (KR2) from the first temperature (T1) is cooled to a second temperature (T2) < Ar1, where first cooling rate (KR1) < second cooling rate (KR2).

Description

The invention relates to a heavy plate and a thermomechanical treatment method of a starting material, in particular a slab, for the production of a heavy plate consisting of a steel alloy.

In order to increase the toughness, especially the low-temperature toughness, of a heavy plate made of a steel alloy, WO2011/079341A2 a thermomechanical treatment process is known in which the starting material is hot-rolled in several stages and accelerated between two hot-rolling passes to below the Ar3 temperature and then inductively heated to above the Ac3 temperature. After the last hot rolling pass, a two-stage cooling to room temperature takes place - first with an accelerated cooling rate by water quenching to a cooling stop temperature below Ar3 and finally with cooling at room temperature. Despite high low-temperature toughness, these heavy plates have the disadvantage of low uniform elongation Ag, which limits their use in earthquake zones, for example.

It is therefore the object of the invention to create a thermomechanical treatment process for the production of a heavy plate with which an improved uniform elongation Ag can be achieved reproducibly on the heavy plate despite high toughness values.

The invention solves the problem set by the features of claim 1.

• 0,01 bis 0,20 Kohlenstoff (C),
• 0,5 bis 2,50 Mangan (Mn),
• 0,05 bis 0,80 Silizium (Si),
• 0,01 bis 0,20 Aluminium (Al),
• < 0,05 Phosphor (P),
• < 0,01 Schwefel (S) und

als Rest Eisen (Fe) sowie herstellungsbedingt unvermeidbare Verunreinigungen, beispielsweise mit jeweils maximal 0,05 Gew.-% und gesamt höchstens 0,15 Gew.-%, kann daher im Gegensatz zum Stand der Technik reproduzierbar bei vergleichsweise hohen Zähigkeitswerten auch eine besonders hohe Gleichmaßdehnung aufweisen. Optional kann diese Stahllegierung auch einzeln oder in Kombination aus der Gruppe: 0 bis 1,5 Chrom (Cr) 0 bis 1,0 Molybdän (Mo) 0 bis 1,0 Kupfer (Cu) 0 bis 5,0 Nickel (Ni) 0 bis 0,30 Vanadium (V) 0 bis 0,20 Titan (Ti) 0 bis 0,20 Niob (Nb) 0 bis 0,005 Bor (B) 0 bis 0,015 Stickstoff (N) 0 bis 0,01 Kalzium (Ca) aufweisen.By in a multi-stage cooling in a first stage after the second rolling with a first cooling rate KR1 from a second final rolling temperature, in particular ≥ Ar3, the second rolling to a first temperature between Ar3 and Ar1 is cooled and, in a subsequent second stage, is cooled from the first temperature to a second temperature <Ar1 at a second cooling rate KR2, with the first cooling rate KR1 <second cooling rate KR2, in contrast to the prior art, a delayed microstructural transformation can be initiated leads to a significant improvement in the uniform elongation Ag of the heavy plate. It is assumed that due to the comparatively low first cooling rate KR1, ferrite can separate from the austenitic structure, which has a lower solubility for carbon (C) than is the case with austenite. Carbon can therefore shift from the ferrite to the remaining austenite and accumulate there. If a comparatively high second cooling rate KR2 is used for further cooling of the starting material, a multi-phase structure consisting of ferrite and bainite or ferrite and martensite (depending on the alloy, thickness of the heavy plate, cooling rate KR2 and first temperature for this cooling start) can form. A first cooling rate to a temperature between Ar3 and Ar1, which is reduced compared to the second cooling rate, allows precisely that structural transformation which is decisive for the uniform elongation. In the subsequent second stage, the starting material is cooled at an accelerated rate, for example by quenching, which can limit the loss of toughness on the heavy plate. Depending on requirements (i.e. optional), the multi-stage cooling can also include straightening or other process steps. The heavy plate according to the invention with a steel alloy, comprising (each in % by weight)

• 0.01 to 0.20 carbon (C),
• 0.5 to 2.50 manganese (Mn),
• 0.05 to 0.80 silicon (Si),
• 0.01 to 0.20 aluminum (Al),
• < 0.05 phosphorus (P),
• < 0.01 sulfur (S) and

the remainder iron (Fe) and impurities that are unavoidable due to production, for example with a maximum of 0.05% by weight each and a maximum of 0.15% by weight in total, can therefore be reproduced in contrast to the prior art at comparatively high toughness values also have a particularly high uniform elongation. Optionally, this steel alloy can also be used individually or in combination from the group: 0 to 1.5 Chromium (Cr) 0 to 1.0 Molybdenum (Mo) 0 to 1.0 copper (Cu) 0 to 5.0 Nickel (Ni) 0 to 0.30 vanadium (V) 0 to 0.20 Titanium (Ti) 0 to 0.20 niobium (Nb) 0 to 0.005 boron (B) 0 to 0.015 nitrogen (N) 0 to 0.01 Calcium (Ca) exhibit.

In a preferred embodiment, the steel alloy (in each case in % by weight)) 0.02 to 0.1 carbon (C), 1.0 to 2.0 manganese (Mn), 0.1 to 0.80 silicon (Si), 0.010 to 0.15 aluminum (Al), < 0.050 Phosphorus (P) and < 0.010 Sulfur (S) on.

Optionally, the steel alloy can be used individually or in combination from the group (each in % by weight): 0 to 0.75 copper (Cu) 0 to 3.0 Nickel (Ni) 0 to 0.20 vanadium (V) 0 to 0.003 boron (B) exhibit.

mit C1min = 0,5, C2min = 69,7, C3min = 0,02148 und Nmin = 0,3 und Dicke = Dicke des Grobblechs in Millimetern ist, kann mit dieser Untergrenze im Verfahren die gewünschte Gefügeausbildung, bestehend aus Ferrit, Bainit und gegebenenfalls Martensit, bei der erfindungsgemäßen Stahllegierung reproduzierbarer erzeugt werden, um hohe Gleichmaßdehnung Ag bei hoher Zähigkeit zu erreichen.For example, by setting the second cooling rate (KR2) in degrees Celsius $$\ge C1\mathit{at\; least}+\left(\frac{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="imgf0001.png"\; state="\{\{state\}\}">C</figure-callout>}2\mathit{at\; least}}{{\mathit{thickness}}^{\mathit{Nm}}}\right)\ast e^{\left(-\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="imgf0001.png"\; state="\{\{state\}\}">C</figure-callout>}3\mathit{at\; least}\ast \mathit{thickness}\right)}$$

with C1min = 0.5, C2min = 69.7, C3min = 0.02148 and Nmin = 0.3 and thickness = thickness of the heavy plate in millimeters, the desired microstructure consisting of ferrite, bainite and optionally martensite, can be produced more reproducibly in the steel alloy according to the invention in order to achieve high uniform elongation Ag with high toughness.

For example, the lower limit for the cooling rate KR2 of the starting material can be 16 °C/s for a heavy plate with a thickness of 25 mm. The lower limit for the cooling rate KR2 of the starting material can be 3.9 °C/s for a heavy plate with a thickness of 80 mm.

mit C1max = 1,5, C2max = 12294,5, C3max = 0,02264 und Nmax = 1,43 und der Dicke = Dicke des Grobblechs in Millimetern ist. Denn mit dieser Obergrenze kann im Verfahren die gewünschte Gefügeausbildung besonders reproduzierbar erzeugt werden, um hohe Gleichmaßdehnung Ag bei hoher Zähigkeit zu erreichen.It may turn out to be sufficient if the second cooling rate (KR2) is in degrees Celsius $$\le C1\mathit{Max}+\left(\frac{C2\mathit{Max}}{{\mathit{thickness}}^{\mathit{N\; max}}}\right)\ast e^{\left(-\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="imgf0001.png"\; state="\{\{state\}\}">C</figure-callout>}3\mathit{Max}\ast \mathit{thickness}\right)}$$

with C1max = 1.5, C2max = 12294.5, C3max = 0.02264 and Nmax = 1.43 and the thickness = thickness of the plate in millimeters. Because with this upper limit, the desired microstructure can be produced in the process in a particularly reproducible manner in order to achieve high uniform elongation Ag with high toughness.

An exemplary upper limit based on the above formula for cooling rates KR2 for a heavy plate with a thickness of 25 mm is 78.6 °C/s - for a heavy plate with a thickness of 80 mm this is 5.9 °C/s.

In combination, this means that in this example the range for the second cooling rate KR2 for the thinner heavy plate (starting material after final forming) is in the range from 16 °C/s to 78.6 °C/s and for the thicker heavy plate (starting material after the final forming) can be in the range from 3.9 °C/s to 5.9 °C/s according to the invention. For all formulas, the thicknesses are to be used in mm (millimeters) and the temperatures in °C and the cooling rates in °C/s.

If the ratio of the second cooling rate KR2 to the first cooling rate KR1 is at least 2:1, this can further increase the uniform elongation Ag if the toughness is sufficiently high. In particular, if the ratio of the second cooling rate KR2 to the first cooling rate KR1 is at least 3:1, this can lead to an optimum balance between toughness and uniform elongation Ag in the case of stressed steel alloys.

The first cooling rate (KR1) is preferably ≦5° C./s, particularly preferably ≦3° C./s, which makes it easier to handle the method and can also further improve the reproducibility for a high uniform elongation Ag with high toughness.

und $$\le \mathit{Ar}1+\mathrm{1,9}\ast \frac{\left(\mathit{Ar}3-\mathit{Ar}1\right)}{2}$$

Preferably, the first temperature is T1 in degrees Celsius $$\ge \mathit{are}1+0.1\ast \frac{\left(\mathit{are}3-\mathit{are}1\right)}{2}$$

and $$\le \mathit{are}1+1.9\ast \frac{\left(\mathit{are}3-\mathit{are}1\right)}{2}$$

A first temperature T1 in this range can, among other things, reproducibly lead to a maximum of uniform elongation Ag in the steel alloy according to the invention.

The second temperature T2 is preferably in the range from 450° C. to 100° C., preferably in the range from 400° C. to 150° C., particularly preferably in the range from 400° C. to 250° C., in order to set the structure for high toughness and in this way an optimum combination of high strength, uniform elongation and toughness can be set.

Cooling from the second temperature to room temperature in a third stage at a third cooling rate KR3, with the third cooling rate KR3<second cooling rate KR2, can further improve the mechanical characteristics of the steel alloy.

For example, the third cooling rate KR3 is ≦5° C./s, preferably ≦3° C./s, because—in terms of process technology—the cooling can be carried out unaccelerated in air.

It is preferable to heat to the second rolling start temperature for a second rolling at a heating rate of at least 12° C./min.

For example, the starting material can be inductively heated for this purpose, which can be advantageous for the overall duration of the production route, since this reduces both the cycle time and the heating rate can be set very high. Alternatively, heating can also take place via thermal radiation - this represents a particularly simple and robust method for heating.

End forming is preferably carried out to a thickness of the plate in the range from 8 to 150 mm (millimeters), in particular to a thickness of the plate in the range from 25 to 120 mm.

It is also the object of the invention to create a heavy plate which, despite high toughness values, has improved uniform elongation Ag.

The invention solves the problem set by the features of claim 14.

According to the invention, the heavy plate produced by the thermomechanical treatment process can have a yield strength ratio (R _p0.2 /R _m ) of <0.7. This heavy plate can preferably have a yield point ratio (R _p0.2 /R _m ) of <0.70. This heavy plate can preferably have a yield point ratio (R _p0.2 /R _m ) of <0.65.

For example, the heavy plate has a thickness in the range from 8 to 150 mm. In particular, the heavy plate can have a thickness in the range from 25 to 120 mm.

The heavy plate preferably has a yield point R _p0.2 >550 N/mm ² (Newton per square millimeter), in particular a yield point R _p0.2 (0.2% yield point) >590 N/mm ² , in order to have a comparatively high to guarantee strength.

This heavy plate can therefore be particularly suitable as a longitudinally welded pipe for a natural gas pipeline or as a construction material, especially in a seismically active region.

In general, it is mentioned that in the case of a starting material, due to its comparatively high thickness, a wide variety of cooling rates and/or heating rates develop over the thickness of the starting material. For example, a cooling rate on the outside of the starting material can be significantly higher than that cooling rate in its core. Therefore, the respective cooling rate (KR1, KR2, KR3) or heating rate from the initial temperature to the final temperature is an average value, namely a cooling rate or heating rate from the initial temperature to the final temperature averaged over the thickness of the starting material.

Fig. 1

Temperaturprofile von zwei thermomechanischen Behandlungsverfahren und

Fig. 2

ein Spannungs-Dehnungs-Diagramm zu zwei Grobblechen, hergestellt durch je ein thermomechanisches Behandlungsverfahren nach Fig. 1.

In the figures, for example, the subject of the invention is shown in more detail using an embodiment variant. Show it

1

Temperature profiles of two thermomechanical treatment processes and

2

a stress-strain diagram for two heavy plates, each produced by a thermomechanical treatment process 1 .

After 1 two temperature profiles 1, 2 of a thermomechanical treatment method for producing a heavy plate A, B from a steel alloy are shown. Both heavy plates A, B have the same steel alloy 0.04% by weight (C) carbon, 1.63% by weight (Mn) manganese, 0.34% by weight (Si) silicon, 0.04% by weight (Al) aluminum, 0.012% by weight (P) phosphorus, 0.001% by weight (S) sulphur, 0.17% by weight (Cr) chromium, 0.02% by weight (Mo) molybdenum, 0.035% by weight (Nb) niobium, 0.014% by weight (Ti)titanium, 0.0003% by weight (B) boron, 0.0045% by weight (N) nitrogen and the remainder iron (Fe) and impurities that are unavoidable as a result of production, each with a maximum of 0.05% by weight and a maximum of 0.15% by weight in total.

After 1 it can be seen that the first temperature profile 1 and the second temperature profile 2 differ at the end of the process, the multi-stage cooling 3 to room temperature. The previous steps are the same.

The primary material, namely the slab, of the respective heavy plate A, B is heated 4 to above the Ac3 temperature, namely 1100° C. (degrees Celsius), for example with a slab heating device.

The starting material is then partially formed by first rolling W1.

This is followed by accelerated cooling 5, namely quenching, preferably water quenching, with which the starting material is cooled from the first final rolling temperature, which is above Ac3, to below the Ar3 temperature, namely - as in 1 recognizable - the primary material is cooled or quenched to below the Ar1 temperature.

This is immediately followed by rapid, preferably inductive, heating 6 to above the Ac3 temperature, at which temperature the starting material is finally formed in a second roller W2 to a thickness of the heavy plate (final thickness of the starting material).

The starting material leaves the second rolling W2 with a second final rolling temperature EW2 ≥ Ar3, namely 830 °C. Instead of inductive heating, other heating sources are also conceivable, for example sources with radiant heat. This rapid heating, be it inductive or with radiant heat etc., takes place at a minimum of 12°C/min.

This second roll W2, which can also be referred to as end rolls, is followed by two different multi-stage coolings 3 to room temperature (which is usually between 0 and 60 degrees Celsius, for example 20 degrees Celsius in these processes).

Thus, in a first stage 7a of cooling 3 after the second rolling W2, the starting material of the heavy plate A is accelerated from the second final rolling temperature to a temperature below Ar1 by water quenching at 30° C./s, namely quenched. This is followed by cooling at 0.1° C./s in still air at ambient temperature as the second immediately following second stage 7b of cooling 3 to room temperature RT.

The multi-stage cooling 3 according to the invention can be seen from the starting material of the heavy plate B. Here, after the second rolling W2, in a first stage 8a, the starting material is cooled at a first cooling rate KR1, namely 0.6 °C/s, from the second final rolling temperature EW2 to a first temperature T1 between Ar3 and Ar1, namely 720 °C (Centigrade).

In an immediately following second stage 8b, the starting material is quenched from the first temperature T1 to a second temperature T2<Ar1, namely 150° C., at a second cooling rate KR2, namely 30° C./s. However, it can also be quenched to room temperature RT, which has not been detailed.

Like in the 1 it can be seen that the first cooling rate KR1<second cooling rate KR2, specifically by a factor of 3 less than the second cooling rate KR2.

After 1 a third stage 8c with a third cooling rate KR3 from the second temperature T2 to room temperature RT in still air at ambient temperature can be seen in the multi-stage cooling. The third cooling rate KR3 is preferably 0.1° C./s.

In general, it is mentioned that accelerated cooling can be understood to mean faster cooling than cooling at room temperature and still air, which is also often referred to as quenching.

A block or a billet is also conceivable as the starting material.

In addition, the first and/or second rolling can consist of one or more part-rolls with possibly several part-rolling steps (passes), which is possible, for example, by reversing rolling.

This process difference in the multi-stage cooling 3 leads to the mechanical characteristics listed in Table 2 for the heavy plates A, B. Stress σ and elongation ε were determined using a tensile test (tensile test according to the standard DIN EN 10002-1) and the toughness was determined using a notched bar impact test according to the standard DIN EN ISO 148-1. Table 1: Characteristics heavy plate _Rp0.2 R _{m Ag Rp0.2} / _Rm Impact work at -80 °C [J] [N/ ^mm2 ] [N/ ^mm2 ] [%] A 519 598 8.9 0.87 398 B 369 602 14.7 0.61 130

Like the table 1 and also the 2 can be seen, the uniform elongation A _g of the heavy plate B was increased from 8.9% to 14.7%, ie by 5.8% compared to heavy plate A. Heavy plate B therefore enables a significantly higher energy dissipation capacity, ie energy absorption capacity.

At low strains (cf. 0.2% yield strength R _p0.2 ), heavy plate B undergoes plastic deformation more quickly than heavy plate A (cf. 0.2% yield strength R _p0.2 ), but it still occurs with heavy plate B much later to failure (cf. A _g ).

This property is particularly advantageous when used in earthquake-prone regions or seismically active regions, where the dissipation capacity of the material is crucial.

The heavy plate B produced according to the invention can therefore be particularly suitable, for example, as longitudinally welded pipes for natural gas pipelines or in steel construction in seismically active regions. Due to the high uniform elongations, components made from this heavy plate B have a high energy dissipation capacity. It is also conceivable to use it as a building material in steel construction in the production of welded I-beams with advantageous behavior in the event of a hole reveal failure.

• Ac3: Temperatur, bei der die Umwandlung des Ferrits in Austenit bei einem Wärmen endet.
• Ar1: Temperatur, bei der die Umwandlung des Austenits in Ferrit oder in Ferrit und Zementit bei einem Abkühlen endet.
• Ar3: Temperatur, bei der die Bildung des Ferrits bei einem Abkühlen beginnt.

In general, it is mentioned that the following definitions exist according to DIN EN 10052:

• Ac3: temperature at which the transformation of ferrite into austenite ends on heating.
• Ar1: temperature at which the transformation of austenite into ferrite or into ferrite and cementite ends on cooling.
• Ar3: temperature at which the formation of ferrite starts on cooling.

Claims (17)

Thermomechanical treatment method of a starting material, in particular a slab, for the production of a heavy plate consisting of a steel alloy, each having in % by weight 0.01 to 0.20 carbon (C), 0.5 to 2.50 manganese (Mn), 0.05 to 0.80 silicon (Si), 0.01 to 0.20 aluminum (Al), < 0.05 phosphorus (P), < 0.01 sulfur (S), optionally individually or in combination from the group: 0 to 1.5 Chromium (Cr) 0 to 1.0 Molybdenum (Mo) 0 to 1.0 copper (Cu) 0 to 5.0 Nickel (Ni) 0 to 0.30 vanadium (V) 0 to 0.20 Titanium (Ti) 0 to 0.20 niobium (Nb) 0 to 0.005 boron (B) 0 to 0.015 nitrogen (N) 0 to 0.01 Calcium (Ca) and the remainder iron (Fe) as well as impurities unavoidable due to production, which treatment process comprises the following steps: heating to above Ac3 temperature and partial forming by a first rolling (W1), accelerated cooling after the first rolling (W1) from a first final rolling temperature to below the Ar3 temperature, in particular to below the Ar1 temperature, After this accelerated cooling, heating to a second rolling start temperature for a second rolling (W2) above the Ac3 temperature and final forming by this second rolling (W2) to a thickness of the plate and multi-stage cooling with optional at least one straightening after final forming by in a first stage (8a) after the second rolling (W2) at a first cooling rate (KR1) from a second final rolling temperature, in particular ≥ Ar3, of the second rolling (W2) to a first temperature (T1) between Ar3 and Ar1 and is cooled in a subsequent second stage (8b) at a second cooling rate (KR2) from the first temperature (T1) to a second temperature (T2) < Ar1, where first cooling rate (KR1)<second cooling rate (KR2). Thermomechanical treatment method according to claim 1, characterized in that the second cooling rate (KR2) in degrees Celsius $$\ge C1\mathit{at\; least}+\left(\frac{C2\mathit{at\; least}}{{\mathit{thickness}}^{\mathit{Nm}}}\right)\ast e^{\left(-C3\mathit{at\; least}\ast \mathit{thickness}\right)}$$

with C1min = 0.5 C2 min = 69.7 C3 min = 0.02148 Nmmin = 0.3
and Thickness = thickness of the plate in millimeters. Thermomechanical treatment method according to claim 1 or 2, characterized in that the second cooling rate (KR2) in degrees Celsius $$\le C1\mathit{Max}+\left(\frac{C2\mathit{Max}}{{\mathit{thickness}}^{\mathit{N\; max}}}\right)\ast e^{\left(-C3\mathit{Max}\ast \mathit{thickness}\right)}$$

with C1 max = 1.5 C2 max = 12294.5 C3 max = 0.02264 Nmax = 1.43 and Thickness = thickness of the plate in millimeters. Thermomechanical treatment method according to one of Claims 1 to 3, characterized in that the ratio of the second cooling rate (KR2) to the first cooling rate (KR1) is at least 2:1, in particular at least 3:1. Thermomechanical treatment method according to one of Claims 1 to 4, characterized in that the first cooling rate (KR1) is ≦5°C/s, particularly preferably ≦3°C/s. Thermomechanical treatment method according to any one of Claims 1 to 5, characterized in that the first temperature (T1) is in degrees Celsius $$\ge \mathit{are}1+0.1\ast \frac{\left(\mathit{are}3-\mathit{are}1\right)}{2}$$

and $$\le \mathit{are}1+1.9\ast \frac{\left(\mathit{are}3-\mathit{are}1\right)}{2}$$

is. Thermomechanical treatment method according to one of Claims 1 to 6, characterized in that the second temperature (T2) is in the range from 450 °C to 100 °C, in particular in the range from 400 °C to 150 °C, preferably in the range from 400 °C up to 250 °C. Thermomechanical treatment method according to any one of claims 1 to 7, characterized in that in a third stage (8c) with a third cooling rate (KR3) is cooled from the second temperature (T2) to room temperature, the third cooling rate (KR3)<second cooling rate (KR2). Thermomechanical treatment method according to Claim 8, characterized in that the third cooling rate (KR3) is ≤ 5 °C/s, preferably ≤ 3 °C/s. Thermomechanical treatment method according to one of Claims 1 to 9, characterized in that the second rolling start temperature for a second rolling (W2) is heated at a heating rate of at least 12°C/min. Thermomechanical treatment method according to one of Claims 1 to 10, characterized in that end-forming is carried out to a thickness of the heavy plate in the range from 8 to 150 mm, in particular to a thickness of the heavy plate in the range from 25 to 120 mm. Thermomechanical treatment method according to one of Claims 1 to 11, characterized in that the steel alloy in each case in % by weight 0.02 to 0.1 carbon (C), 1.0 to 2.0 manganese (Mn), 0.1 to 0.80 silicon (Si), 0.010 to 0.15 aluminum (Al), < 0.050 Phosphorus (P) and < 0.010 Sulfur (S) having. Thermomechanical treatment method according to one of Claims 1 to 12, characterized in that the steel alloy in each case in % by weight optionally individually or in combination from the group: 0 to 0.75 copper (Cu) 0 to 3.0 Nickel (Ni) 0 to 0.20 vanadium (V) 0 to 0.003 boron (B) having. Heavy plate produced by the thermomechanical treatment process according to one of Claims 1 to 13, characterized in that the heavy plate has a yield point ratio (R _p0.2 /R _m ) of <0.7, preferably <0.65. Heavy plate according to Claim 14, characterized in that the heavy plate has a thickness in the range from 8 to 150 mm, in particular in the range from 25 to 120 mm. Heavy plate according to Claim 14 or 15, characterized in that the heavy plate has a yield point R _p0.2 > 550 N/mm ² , in particular > 590 N/mm ² . Use of a heavy plate according to Claim 14, 15 or 16 as a longitudinally welded pipe for a natural gas pipeline or as a building material, in particular in a seismically active region.

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