DE1962334A1 - Rolled steel and method of making the rolled steel - Google Patents

Description

bill-: ".. ■ '..; ZJ ΜώθΙ 6138

b jr'rc:,: ..γλ α. M. 1 "

BETHLEHEM STEEL CORPORATION, Bethlehem, Pennsylvania, VStA

Rolled steel and method of making the rolled steel

The invention relates to a V / Alzstahl and a method for Manufacture of the same. For the sake of simplicity, the process is also referred to below as "continuity rolling".

Usually, the steel is heated to one temperature during hot rolling heated, at which it is completely austenitic, and then the steel becomes as fast as possible with as little as possible Heat loss rolled to the final dimensions, the final rolling temperature above the transformation point Ar ·, is. This method takes advantage of the fact that it is easier to process at a high temperature, but you do not get the advantageous properties that you get with a rolled Can form steel. ·

Investigations have shown that there is a higher strength of the steel can be achieved if a low finishing rolling temperature is used applies. In this process, the steel is heated and then its cross-section is partially reduced for as long the steel is still in the austenitic state, as in hot rolling. A further reduction in cross section is then delayed to bring the rolling stock below a normal temperature Allow to cool, and then the rolling stock is finish-rolled in one or more passes to the final caliber. In this known method, the cross-sectional

009133 / 11-18

area of the rolling stock in a sequence of rolling passes up to the final dimension and the final shape are reduced. These stitches can be of two types, one of which is primarily to reduce the cross-sectional area of the rolling stock and the other is mainly used for shaping, with the Cross-sectional area only slightly reduced. For economic reasons, a rolling program should include as few passes as as it is possible or practical. Any stitch that is primarily used to reduce the cross-section should therefore use the Reduce the cross-sectional area as much as possible or practically. It is also known that to form the mentioned higher strength by roller burnishing at low temperature, a reduction in cross section of about 15% or more the temperature below normal temperature is required is.

It is known that at low finishing or finish rolling temperatures the strength of the steel increases and its shock transition temperature reduced by placing the closing temperature below the transformation point Ar. It is also known that you get an even higher strength by lowering it even further achieve the finishing temperature below the transformation point Ar ^ can, but that then the shock transition temperature rises. In contrast, it has now been found that the continuity rolling not only increases the strength, but the shock transition temperature is also reduced. This meeting high strength and low impact temperature is an unexpected and highly desirable combination of Properties. .

ι The rolled steels according to the invention are characterized, therefore

a) by higher strength and lower impact transition temperature compared to steels of the same composition, which are produced by hot rolling, and b) by lower impact transition temperature compared to steels of the same composition and the same strength, as they are obtained at low finishing or finishing rolling temperatures . The method according to the invention consists essentially in that

009830 / tttt

1) the rolling stock is heated to a temperature "at which it is almost completely austenitic.

2) the rolling stock during cooling in the temperature range between the Transformation points Ar, and Ar ^ is rolled,

3) the rolling of the rolled stock is continued while it _{cools in the temperature range between the transformation point Ar 1} and a temperature of 316 ⁰ C (600 ⁰ F), and

4) preventing complete recrystallization at any temperature after the completion of the second step.

The advantages of the invention result mainly in Stäh- len μ, with not more than 0.35% of carbon and not more than a total of 3% other elements, with the exception of iron.

Fig. 1 is a diagram showing the relationship between typi- ' see cooling curves of steel plates and curves showing different percentages of recrystallization or represent crystal transformation.

FIG. 2 shows one possible continuity rolling program that a A recrystallization diagram similar to that of FIG. 1 is superimposed.

Figure 3 is a graph showing surge transition temperatures and yield points or yield stresses I (yield points or yield points or yield stresses) of steel of a certain composition that passes through Continuity rolls are compared with those of steel of the same composition, which, however, firstly by hot rolling and secondly by Rolling at low finishing or finishing temperatures has been made.

The method according to the invention differs from known methods in that a) the steel must be rolled in two temperature ranges, namely between the transformation points Ar ^ and Ar ₁ and between the transformation point Ar ₁ and the

009830/1118

Temperature of 316 ⁰ C (600 ⁰ F) and preferably in three temperature ranges, namely the two first mentioned temperature ranges and the hot rolling temperature range and that b) a complete recrystallization or crystal transformation at any point in time after the completion of the rolling in the temperature range Ar, - Ar. must be avoided.

The rolling stock to be rolled in the temperature range Ar, - Ar ^ has a temperature at which it is almost entirely austenitic. There are various methods of obtaining such a rolling stock, but it is preferable to obtain this rolling stock or Workpiece by hot rolling. The amount of contraction in hot rolling is not critical, but it is practical Considerations out expedient, the cross-section because of the easier machinability as much as possible. The rolling in the temperature range of Ar, - Ar ^ must during the Cooling of the rolling stock can be carried out in this area and one or more stitches including at least one reduction stitch. The term "reduction stitch" intended both a single stitch, in which the reduction of the cross-sectional area of the rolling stock at least 15%, as well as zv / ei or several stitches, a cross-sectional increase of the same amount, cause and run in such quick succession, that between the Stitches no recrystallization occurs.

After rolling in the temperature range of Ar, - Ar ;, rolling in the temperature range of Ar ₁ - 316 ⁰ C must be continued with simultaneous cooling of the rolling stock and include one or more rolling passes and at least one cross-sectional reduction pass in this area.

After rolling in the temperature range Ar, - Ar ^ the conditions must be such that at no time after the last cross- reduction stitch a complete recrystallization of the deformed structure takes place, which in this last cross-section sverringerungsstich in this temperature range · formed

* 009830/1118

was, and they must preferably be chosen so that the degree of recrystallization does not exceed 60% at any time after this last reduction in section.

Under the degree of recrystallization or percentage recrystallization, the ratio of the cross-sectional area is intended to be recrystallized Grains to the total cross-sectional area lying in a plane transverse to the direction of greatest extension of the Workpiece or rolling stock runs during rolling, to be understood as a percentage.

Fig. 1 uses diagrams to illustrate the principle ^ after | which the cross-section reduction in the temperature range Ar, - ^ and in the temperature range Ar ^ -316 ⁰ C takes place. On the abscissa, the time is shown on a logarithmic scale, the point in time zero being placed on the point in time at which a cross-sectional reduction stitch is completed. The ordinate represents the temperature, with the crystal transition points Ar ^ and Ar ^ being indicated. Lines 1, 2 and 3 represent the times and temperatures for the beginning of a 60% and 100% recrystallization or crystal transformation. Lines 4, 5, 6, 7 and 8 represent the cooling process of steel workpieces. The values shown in Fig. 1 are for explanation only. The true values depend on the type of rolling stock used and can be determined using known methods.

As already mentioned, the workpiece or rolling stock initially measured in the range of Ar, -Ar ,. ⁰ -316 C and then be rolled in the range of Ar ,, and such conditions are met, .that a complete recrystallization is avoided and exceeds 60% at any time after completion of the last stitch cross-sectional reduction in the first-mentioned roller follower. The point A in FIG. 1 on the line 8 ° corresponds to a temperature to which a steel workpiece has cooled and which is in the temperature range Ar, -Ar ^. The line 5 represents the course of the temperature of the workpiece during cooling after a cross-sectional

009830/1118

ringing stitch at the temperature corresponding to point A. It can be seen that when the workpiece or rolling stock is accordingly cools down the course of line 5, it completely recrystallizes before it cools down to a temperature that below the temperature Ar ^, so that it is suitable for the subsequent Cross-section reduction in the area of Ar., -316 C unsuitable is. There are several ways to prevent this from happening. One possibility is to start the cooling process by spraying on water, blowing on with air or on to accelerate similar V / s, so that the rolling stock on a temperature below the temperature Ar ^ cools down before it is completely recrystallized, as shown for example by line 4. There is a second possibility therein, the rolling stock (reduced in cross-section) accordingly the course of the line 5 to cool down to a temperature that corresponds to point B, for example, and then a second cross-sectional reduction stitch in the area Ar-z-Ar ^ to subdue. As can be seen from line 6, if it cools down twice with regard to its cross-section Workpiece or rolling stock down to a temperature that is below the temperature Ar ^, namely at a temperature below 60% lying degree of recrystallization. There is a third possibility in allowing the rolling stock mentioned to cool to a lower temperature after line 8, - as they are for example corresponds to point C and then a reduction stitch to be subdivided in the area of Ar, -Ar ^. Of the Course of the temperature of this workpiece with reduced cross-section is also represented by line 6.

As already mentioned, a complete recrystallization of the steel must be prevented at any point after the last cross-section reduction pass in the area Ar, -Ar. In FIG. 1, line 7 shows the course of the temperature of the steel workpiece during cooling after a cross-section reduction stitch at a temperature below the transformation point Ar. It can be seen that during the cooling of the workpiece with reduced cross-section no Recrystallization occurs. However, if the temperature at which:

0098 30/1118

a cross-sectional reduction stitch is carried out and the _v cooling and recrystallisation of the resulting reduced cross-section workpiece is chosen so that it would recrystallize "before a further cross-sectional reduction stitch is carried out or before it is cooled to a temperature which is so low that no recrystallization is possible then the cooling of this workpiece of reduced cross-section must be accelerated by spraying on water or blowing air or in a similar manner in order to prevent complete recrystallization and preferably to prevent the degree of recrystallization from exceeding 60%

Fig. 2 diagrammatically illustrates one possible rolling sequence for producing a plate 1.27 cm (1/2 inch) thick by continuous rolling. The time is plotted on the abscissa on a logarithmic scale, the time zero being placed at the end of a cross-sectional reduction stitch. The ordinate shows the temperature on a linear scale, with the crystal transition points Ar and Ar ^ being shown. Lines 1 through 3 represent the times and temperatures for the start of a $ 60 and. 100 years of recrystallization. The (horizontal) dashed lines represent an immediate return to time zero. In this example, an approximately 67 mm thick slab was rolled from an approximately 102 mm thick slab at temperatures above the transformation point Ar, and, as shown in Fig. 2, cooled in about two minutes by air cooling to about 938 G ^0. The 67 mm thick slab is rolled in two passes at temperatures above the transformation point Ar, first down to 54 mm (A) and then down to 44 mm (B). After each of these stitches, the plate is cooled for about two minutes in air where it cools to about 752 ⁰ C after the last stitch, a temperature which is slightly below the transformation point Ar, is located.

009830/11 ta

In the temperature range of Ar ^ -Ar ₁ , the steel is reduced in two passes, first to 35 mm (C) and then to 25 mm (D). After each of these stitches, the plate is cooled for about two minutes in air from where it cools to about 626 ⁰ C after the last stitch, which is below the transformation point Ar ^ liegt-, The percent recrystallization after the first pass is somewhat low, while after the second stitch there is no recrystallization.

In the temperature range between Ar ₁ and 316 ⁰ C, three stitches ^ are carried out, first up to 19 mm (E), then up to 16 mm (F) and finally up to 13 mm (G). After each of the first two stitches, the plate cools down in air for about two minutes, while after the last stitch it cools down in air to room temperature. Recrystallization does not take place after any of these stitches.

All stitches in this sequence are cross-sectional reduction stitches, and it is understood that other required stitches may be included in this sequence, provided that the degree of recrystallization is adhered to in the manner described. The cooling time of two minutes in the air was chosen for convenience, Wk for the recrystallization can be controlled in accordance with any other cooling time and other cooling methods.

The following are examples of plates that are made by Continuity rolls and manufactured by known methods. . *

Thirteen steel plates were produced with the following percentage composition:

C Mn. PS Si Al Cb N ₂

0.052 1.08 0.01 0.015 0.02 0.005 0.03 0.002 The rest consists essentially of iron.

009830/1118

About 102 mm thick slabs of this steel were heated to a temperature of about 1204 ⁰ C and rolled in the following rolling result in an approximately 13 mm thick plate: - -

Stitch no. Thickness after each stitch (mm) Reduce the thickness

1 89 12.5% 2 76 16.7% 3 76 * - 4th 67 12.5% 5 54 19.1% 6th 44 17.6% 7th 35 21.4% 8th 25th 27.2% 9 19th 25.0% 10 16. 16.7% 11th 13th 20.0%

* Box stitch (box caliber) for widening.

The transformation points Ar- ^ and Ar. were respectively 816 ⁰ C and 716 ⁰ C at a cooling rate of about 538 ⁰ C per hour.

Table I 'shows the temperature ranges in which this rolling program was carried out. The plates AH are examples of plates made by known methods, while the plates JN are examples of plates made by continuous rolling. The recrystallization properties of the steel and the cooling rates and intervals between the passes were chosen so that the degree of recrystallization when rolling the plates JN after rolling in the temperature range Ar ^ -Ar ₁ never exceeded 50%.

009830/1118

In Table II are the finishing rolling temperature, the pour point or the yield point (also called yield stress), the Tensile strength, elongation, and Charpy V-15 impact transition temperature of all thirteen panels A-N.

FIG. 3 shows for all thirteen plates how the impact transition temperature changes with the strength depending on the rolling process used. Points A, B and C represent plates which have been produced by V / arm rolling, points D and E represent plates which have been finish-rolled or coated at temperatures between the transformation points Ar and Ar ^ by rolling at low finishing or finish-rolling temperatures , Points F, G and H represent plates produced by rolling at temperatures below the transformation temperature Ar ^, and points J, K, L, M and N represent plates produced by continuity rolling . Both Figure 3 and Table II clearly show that the panels made by continuity rolling have higher strengths and lower impact transition temperatures than the panels made by hot rolling. Moreover, it can be seen from Table II that the completion of rolling is below the transformation temperature Ar ₁ temperatures lying opposite that increases in either by rolling low, the finish rolling temperature or by continuity of rolling, the strength of the steel, which can zen by final Wal at above the transformation temperature Ar ^ maintains lying temperatures. However, both the table and the figure show that the essential difference is that when the strength is increased by rolling at a low finishing temperature, the joint transition temperature rises with increasing strength, and when the strength is increased by continuous rolling, the joint transition temperature also increases increasing strength decreases. This difference is essential. The dashed lines in Fig. 3 show that one can produce a plate with a 'flow limit of 5 250 kp / cm and a shock transition temperature of about +26 ^{0 C by rolling with a low finishing temperature, while}

009830/1118

rend can be produced by rolling a continuity plate with the same strength at a lower by about 112 ⁰ C impact transition temperature, namely about -82 ⁰ C.

In Table III are the percentages seven other steels are given from which specific examples of plates have been made by continuity rolling and by known processes. In all of these steels there is the remainder of the composition consists essentially of iron. Included varieties are semi-pacified, pacified, carbon, low alloy, bainitic and precipitation hardening steels.

The crystal transition _{temperatures Ar 1 and Ar 1 of} the steels according to Table III at cooling rates of about 538 ^° C. per hour are given in Table IV.

No.

1 2 3 4

TABEL IV Ar 3 826 ⁰ C ■ 826 ⁰ C 826 ⁰ C 782 ⁰ G 760 ⁰ C 760 ⁰ C 616 ⁰ C

Ar r 760 ° c 716 ⁰ C 704 ⁰ C 660 ⁰ G 648 ⁰ C 626 ⁰ C 516 ⁰ C

One or more slabs, each with the in Table III compositions indicated were rolled by continuity rolls to about 13 mm thick plates. For comparison were also one or more slabs each with the same composition according to known Y / alz method also except for rolled to a thickness of 13 mm. The details of the rolling processes and the resulting yield strengths (also yield strength or called yield points), tensile strengths and Charpy's

00-9830 / 1 1V8

V-15 impact temperatures are given in Tables V through XI.

With regard to the data given in Tables V-XI, to say that it is of course known that the strength and impact transition temperature of a steel both depend on its composition as well as the manner in which it was treated. For example, Tables V-XI contain one wide range of strengths and shock transition temperatures: of steels with seven different compositions, the all rolled by known processes or by one or more examples of a continuity rolling process, while Table II covers a wide range of strengths and impact transition temperatures for a steel with a given Composition shows that in various ways, including various examples of a continuity— rolling process, was rolled. Each through continuity rollers The panel produced has an unexpectedly good strength and impact transition temperature combination, but it is off For the reasons given above, a steel plate made by continuity rolling cannot be modified by specific values to identify these properties. As mentioned earlier, plates made by continuity rolling are what distinguishes them in the rolled state a) due to greater strength and lower joint transition temperature than steels of the same composition, which were produced by hot rolling, and b) due to a lower impact temperature than steels of the same composition, which were produced with the same strength by rolling at a low sizing or finishing temperature.

Although the method according to the invention has been described with reference to the rolling of plates, this method is not limited to the rolling of these shapes, but can be used for rolling other objects such as bars, bolts, rods, profile rods and so on.

The percentages given here for the composition of the steels are all percentages by weight.

009830/1118

- 13 ■ I. 102 13th 1962334 with low finishing rolling temperature 102
16 16
13th Continuity rollers 102
35
19th 35
19th
13th 84.3
20.0 TABEL 102 13th 1204-982
• 810 102
25th 25th
13th 1204-816
816-716
716-652 102
44
25th 44
25th
13th 75.0
50.0 plate Number of temperature
the stitches area, C 102 13th reduction 1204-816
816-763 102
16 16
13th 1204-816
816-716
716-582 102
54
35 54
35
13th . " 84.3
20.0 - Reduction · '^
the iJicke (mm)
from ... to 1204-982
710 102
16 16
13th 1204-816
816-716
716-482 102
67
44 67
44
13th 84.3
20.0 A. 11th Hot rolling 87.5 1204-982
610 102
16 16
13th 1204-816
816-716
716-388 102
67
44 67
44
13th 84.3
20.0 B. 11th 1204-1004 87.5 1204-982
488 1204-816
816-716
716-330 C. 11th 1204-938 87.5 65.6
45.4
33.3 Rollers 1204-832 56.2
42.8
50.0 D. 10
1 • 46.8
. 35.3
63.6 Ξ 8th
3 34.4
33.3
71.5 E. 10
1 34.4
33.3
71.5 G 10
1 H 10
1 J '7
2
2 K 6th
2
3 L. 5
2
4th M. 4th
2.
5 N ■ 4
2
5

009830/1118

Complete-
rolling
tempe-
rature • - 14 - Percentage
renewal
(Stretching) 4850 38 24 31 Continuity rollers 5000 18th 1962334 ⁰ C TABLE 'II 51 now 203 mm 4450 26th 4560 5850 26 14 Plat
te Flow
Point train
firm
speed 5200 25th 5500 * 6070 23-10 Charpy
V-15 butt
transitional
temperature 1004 (kp / cm ² ; ) (kp / cm ² ) 21 5320 5890 * 7546 16 ⁰ C 938 Hot rolling 21 5860 - 7532 * 7959 15th A. 832 3250 4620 24 7917 * +10 B. Rollers 3890 4760 with low finishing rolling temperature -9.4 C. 810 3780 4330 4100 -37.2 763 4070 D. 710 4160 0 E. 610 4700 * -34.4 F. 488 5420 * -20.6 G + 4.4 H 625 +32.2 582 J 482 -65 K 388 -95.6 L. 330 -120.6 M. -128.1 'N -101.1

* Pour point (0.2% offset)

009830/1118

No. Art C. Mn P. S. • TABEL Cr III sammer
Cu final
Al V Cb B. N Very low
alloyed
C-Mn-V 0.002 1.06 0.009 0.018 Si 0.01 0.01 <0.005 0.06 N11 N11 0.002 1 Low
C-Mn 0.051 1.03 0.008 0.015 0.02 Ni 0.01 TO £
Mon 0.01 <0.005 0.002 N11 N11 0.001 2 Low
C-Mn-VN 0.050 1.08 0.009 0.015 0.02 0.01 0.01 0.008 0.01 <0.005 0.07 N11 N11 0.008 3 Low
alloy 0.10 0.69 0.083 0.025 0.02 0.02 0.57 0.002 0.24 <0.005 0.003 N11 N11 0.007 4th C-Mn 0.28 1.11 0.020 0.032 0.30 0.03 0.04 0.008 0.05 0.043 0.002 N11 N11 0.005 O
O 5 V / o copper 0.24 1.08 0.014 0.015 0.20 0.71 0.01 N11 1.00 0.079 0.003 N11 N11 0.008 983G 6th Bainitic 0.12 1.05 0.011 0.014 0.33 0.03 0.50 N11 0.02 0.039 0.003 N11 0.003 0.007 7th 0.26 0.02 N11 -Jk 0.04 0.50 ΰΰ

K) CO Cx)

TABLE V

Steel No. 1 - Very low alloyed with C-Mn-V

Rolling process

number

the temperature stitch range

thickness
(mm)

rings point

Charpy
Tensile V-15 impact resistance transition temperature

(kp / cm ² ) (kp / cm ² ) ⁰ C

Flowing

V / arm rollers

11th
11th

4th
2
5

* Yield point (O, 2? O offset)

° V / arm rollers
co

^ζ * ^> continuity of salt

1204-932 102

1204-843 102

1204-827 102

827-760 67

760-471 44

13th 87.5 1890 3100 13th 87.5 1680 2050 67 34.4 44 33.3 13th 71.5 4340 * 4850

-15
- 6.7

-162

CD CD NJ CjO CO

TABLE VI

Steel # 2 Low C-I-In

Rolling process

number

the temperature stitch range

thickness
(mm)

Flow reduction point

Tensile strenght

Charpy V-15 shock transition temperature

(kp / cnr) (kp / cnT)

Y / arm rollers

ο continuity sv / alz en

^ Continuity Rollers

1204-426 102

6 1204-827 102

2 827-716 44

2 716-593 25

4 1204-827 102 2 827-716 67

5 716-477 44

13th
44

13th

67

44

13th

87.5

56.2 42.8 50.0

34.4 33.3 71.5

2270

3460

4450 * 4950

-23.3

-78.9

4845 * 5410

-176

Positive limit (0.2% offset)

OJ CjO

TABLE VII
Steel No. 3 Low C-Mn-VN

Rolling process

number

the temperature stitches area thickness
(mm)

Flow reduction point

Tensile strenght

Charpy

y-15-butt-

transition temperature

(kp / cm ² ) (kp / cm ² )

Hot rolling

ο hot rolling

** · Continuity rollers
ο

11th
10

6th
2

1204-877 1204-818

1204-815 815-704 704-652

-> 13

44

87.5 87.5

56.2} 25 42.8 > 13 50.0

3450 3850

4320 4325

5010 *

5360

-31.7 -48.3

-120.6

* Yield point (0.2% offset (

Vi'alzvorfohrcn

V / arm rollers
Warmv / alzen

V / alzen at

low

Extreme temperature

Continuity rollers

TABKIXK VIII
Steel No. 4 Low alloyed

Number

the ^ Touperatur-

Stitches' area

thickness
(mm)

Flow rings tion point

Charpy tensile V-15 impact resistance transition temperature

(kp / cra ² ) (kp / cia ² )

11 1204-926 127

11 1204- 810 127

10 1204-1010 127

1 '716 16

5 1204-788 127

3 782-660 54

1 599 21

13th

13th

- ^ 54
-> 21

90.0 90.0

87.5 20.0

57.5 61.0 39.8

3620 3960

4130

5090 5150

5410

-23.3 -56.7

-29.2

6550 * 6980

-128.9

■ * Yield point ($ 0.2 offset)

co σ> ro to co

TABLE IX

Steel No. 5 C-Mn (calmed)

Rolling process

\ / armv: alzen

ο hot rolling
co

ω rolls at

° lower

^ Finished temperature

Continuity rollers

number

the temperature

Stitches "boroich

thickness
(mm)

11 1204-949 152

9 1204-815 152

10 1204-1010 152

1 710 16

5 1204-760 152

2 760-649 54

2 649-593 35

Flows

wrestling point

Charpy tensile V-15 butt

solidity transition temperature

95

91.7 91.7

89.5 20.0

64.6 35.3 63.6

Qp / cm ² ) (kp / crn ² )

-3300 3750

·. 3820

5320 5380

5520

-37.2

-48.3

-20.6

6180 *

676O

-117.8

* Yield point (0.2? Α offset)

TABLE X
Steel No. 6 V / o copper

Rolling process

number

the temperature stitch range

Hot rolling

Salting continuity

5
3
3

12Ö4-760

760-627. 627-504

thickness
(mm)

Flow reduction point

Charpy's marriage
Tensile V-15 impact resistance transition tnneratur

1204-989 '102

■>

87.5

46.8

53.0

50.0

(kp / cm ² ) (kp / cm ² )

4225

6410

-6.7

7500 * 8320

-120.6

* Yield point (0.2% offset)

TABLE XI
Steel No. 7 bainite table

• · Charpy

Number. Pull - V-15 push-

the temperature · Ver. Flow strength transitional

Valz method stitches area thickness reduction point speed temperature

⁰ C (mm) ° / o ■ (kp / cm ² ) (kp / cm ² ) ⁰ C

Hot rolling 10 1204-815 102> 13 87.5 2880 5550 -20.6

Hot rolling 10 x 1204-738 102 ^ 13 87.5 x 2760 5920 -59.5

Continuity rollers 7 1204-615 102> 35 65.6

2,615-515 35 >> 21 39.6

1,493 21 ^ 13 39.8 6900 * 8190. -13.1

Yield point (0.2 ^ offset)

Claims (8)

Claims 1. ) Process for rolling a steel mill piece with a carbon content of not more than 0.35 percent by weight and, apart from iron, a total content of other elements not exceeding 3 percent by weight, characterized in that the workpiece is heated to a temperature, "at which it is nearly fully austenitic, that the workpiece is then in one or more passes, including at least one cross-sectional reduction stitch, with simultaneous cooling down λ lung in the temperature range between the crystal transition points Ar, and Ar * is rolled, that then the rolling of the workpiece is rolled in one or more passes, including at least one cross-sectional reduction pass, with simultaneous cooling in the temperature range between the crystal transition temperature Ar., And a temperature of about 316 ⁰ C and such conditions are constantly maintained, that at no point in time after the last cross-sectional reduction stitch in the temperature range between the crystal transition temperatures Ar, and Ar ^ does a complete recrystallization occur. 2. The method according to claim 1, I. characterized in that the workpiece in one or more passes with simultaneous cooling from a temperature at which it is austenitic, but which is still above the Kristallumwandlungstem-. temperature Ar, is rolled and then the rolling of the workpiece is continued in the temperature range between the crystal transformation temperatures Ar ^ and Ar ^ and in the temperature range between the crystal transformation temperature Ar ^ and the temperature of 316 ^° C. 009830/1118 3. The method according to claim 1 or 2,
characterized in that the percentage recrystallization does not exceed at any point in time after the last cross-sectional reduction stitch in the temperature range between the crystal transition temperatures Ar 1 and -60%. 4. Rolled steel with a carbon content of not more than 0.3596 and, with the exception of iron, a content of other elements of not more than 3 percent by weight, characterized in that it has a Charpy V-15 impact transition temperature in the rolled state , which is lower than that of steel with the same composition, which was produced by a rolling process with a low finish or finish rolling temperature _t . 5. rolled steel according to claim 4, characterized in that that it has a Charpy V-15 impact transition temperature in the as-rolled condition which is lower than that of steel of the same composition and strength, which is through a rolling process with low finish or finish rolling temperature was established. 6. rolled steel according to claim 4, characterized in ', that in the rolled state it has a lower Charpy V-15-, Impact transition temperature and a higher strength than steel of the same composition, which is produced by hot rolling became. 7. rolled steel according to claim 4,. · characterized, that it has a Charpy V-15 joint in the rolled state; transition temperature, which is higher than about -73 ⁰ C , and a flow stress (also called Flieiigr-Snze) , which is lower than 5250 kilopond / cm ² .. 003330 / 1118- 8. rolled steel according to claim 7,
-dadurch in that it comprises a deformed structure in the rolled state or grain, a Charpy'sche V-15 impact transition temperature which is not higher than about -46 ⁰ C, and a yield point is not lower than 4550 kgf / cm . K / Gu 009830/1118 Blank page