Method for calculating the combination of properties being established for a deformable lightweight steel

Abstract

A method is disclosed for calculating the combination of properties of phase components and of mechanical properties being established of a predefined alloy composition for a deformable lightweight steel having the elements in percent by weight C 0.02 to 1.0, Al 2.5 to 8.0, Si 0.0 to 1.5, Mn 5.0 to 35.0, Cr >1.0 to 14.0, total content of N, S, P 0.1, the remainder iron and other steel-accompanying elements with some contents of Cu, Mo, Ni, and Zn of up to 1.0 wt % in total by using specific formulas on the basis of the manganese content, wherein, in the formulas, the alloy contents are used as absolute numbers without dimensions, and the calculated, dimensionless values are assigned the units MPa for Rm and Rp and % for A80.

Claims

1. A method for producing a formable lightweight steel with the elements in weight % TABLE-US-00004 C 0.02 to 1.0 Al 1 to 9 Si 0.0 to 1.5 Mn 6.0 to 35.0 Cr >1.0 to 14.0 With N, S, P in sum together 0.1, remainder iron and other steel accompanying elements, and optionally Cu, Mo, Ni and Zn in sum together up to 1.0 weight %, wherein the lightweight steel is made of a phase mixture of austenite and ferrite (A/F) with an austenite proportion between 100% and 5%, a strength Rm between 600 and 1200 MPa, a yield strength Rp0.2 between 300 and 1120 MPa, and a elongation at break A80 between 5 and 40% said method comprising: for a first given alloy composition of said formable lightweight steel in which Mn: 5 to maximal 11%, calculating a strength Rm and Rp in MPa and an elongation at break A80 in % of the formable lightweight steel according to the formulas:
Rm=3182{C}+1224{Si}+847.6{Cr}+633.2{Al}3354.8140.7{Al}{Cr}482.5{Cr}{C}1372.3{Si}.sup.2
Rp=2509.2{C}+947{Si}+538{C}+367.8{Al}2168.178.1{Al}{Cr}381.9{Cr}{C}923.2{Si}.sup.2
A80=267.4+48{Al}{C}2.6{Cr}16.8{Si}41.1{Al}275.4{C} Wherein the following content limits are to be observed: C: 0.2 to 0.7, Si: 1.0%, and a sum of Al+Cr: 12%; for a second given composition of said formable lightweight steel in which 22%Mn>11%, calculating the strength Rm and Rp in MPa and the elongation at break A80 in % of the formable lightweight steel according to the formulas:
Rm=322.7{C}+103{Si}+847.6{Cr}+55{Al}+195.8{Cr}{C}15{C}{Cr}.sup.2
Rp=132{Si}101.8{Cr}+60.6{Al}+91{Cr}{C}11.9{Cr}.sup.2
A80=24+46.5{Si}+48{C}.sup.27.9{Cr}{C}8.8{Al}{Si}, wherein the following content limits are to be observed: C <0.6%, Si >0.4 to 1.2, Al: 1 to <9% and Cr: 10%; for a third given composition of said formable lightweight steel in which Mn: >22% to 35%, calculating the strength Rm and Rp in MPa and the elongation at break A80 in % of the formable lightweight steel according to the formulas:
Rm=104.3{Cr}+2766.6{Si}.sup.2+11.7{Al}2172.8{Cr}{Si}282.3{Al}{Si}.sup.2
Rp=3269{Si}+234.2{Cr}335.6{Al}{C}1266.5188.4{Al}{Si}1391.6{Cr}{Si}{C}
A80=33.5+88.7{Si}{C}2.1{Cr}4.5{Al}{C}36{Si}.sup.2 wherein the following content limits are to observed: C: 0.2 to 0.7%, Si: 0.3 to 1.5%, and a sum of Al+Cr: 12%, wherein absolute numbers without dimension are inserted into the formulas and the unit MPa for Rm and Rp and % for A80 are assigned to the dimensionless values; and producing a hot strip with any of the first, second and third given composition by casting a melt in a horizontal strip casting system in the absence of bending into a pre-strip with a thickness in the range between 6 and 30 mm, and rolling the pre-strip into a hot strip with a degree of deformation of at least 50%.

2. The method of claim 1, wherein a speed of a supply of the melt is equal to the speed of the rotating conveyor belt.

3. The method of claim 1, wherein approximately same cooling conditions result for all surface elements of a strip shell of the strip that forming at a beginning of solidification of the strip and extending over a width of the conveyor belt.

4. The method of claim 1, wherein the melt applied onto the conveyor belt is fully solidified to the most part at the end of the conveyor belt.

5. The method of claim 4, further comprising after full solidification and prior to a further processing, passing the pre-strip through a homogenization zone.

6. The method of claim 5, wherein the further processing comprises cutting the pre-strip into plates.

7. The method of claim 6, further comprising after the cutting of the pre-strip into plates, heating the plates to a rolling temperature and are then subjected the plates to the rolling process.

8. The method of claim 5, wherein the further processing comprises coiling the pre-strip.

9. The method of claim 8, further comprising after the coiling up the pre-strip is coiling the pre-strip, heating the pre-strip to rolling temperature and subjecting the pre-strip to the rolling process.

10. The method according of claim 8, further comprising preheating the pre-strip prior to the uncoiling.

11. The method of claim 1, wherein the pre-strip is subjected to the rolling process in-line and is then wound up.

12. The method of claim 1, wherein the degree of deformation during the hot rolling is >70%.

13. The method of claim 1, wherein the degree of deformation during the hot rolling is >90%.

14. The method of claim 1, wherein the hot strip is reheated and is cold rolled after the cooling.

15. The method of claim 1, further comprising an annealing process performed in a decarburizing atmosphere.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The sole FIGURE shown in the appendix schematically shows a method sequence according to the Invention for the condition casting speed=rolling speed.

(2) Prior to the hot rolling process the casting method is performed with a horizontal strip casting system 1, consisting of a rotating conveyor belt 2 and two deflection rolls 3, 3. Also a lateral sealing 4 can be seen which prevents the applied melt 5 from flowing off the conveyor belt 2 to the right and left. The melt 5 is transported to the strip casting system 1 by means of a ladle 6 and flows through an opening 7 arranged on the bottom into a supply container 8, which is constructed as an overflow container.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(3) Not shown are the devices for intensive cooling of the bottom side of the upper scaffold of the conveyor belt 2 and the complete housing of the strip casting system 1 with corresponding protective gas atmosphere.

(4) After application of the melt 5 onto the rotating conveyor belt 2 the intensive cooling leads to solidification and formation of a pre-strip 9, which at the end of the conveyor belt 2 is fully solidified to the most part.

(5) For temperature compensation and tension reduction a homogenization zone 10 adjoins the strip casting system 1. The homogenization zone consists of a heat-insulated housing 21 and a here not shown roller table.

(6) The scaffold 12 following thereafter is either configured only as a pure driver aggregate optionally with a small reduction, or as a rolling aggregate with a predetermined reduction.

(7) Following is an intermediate heating, advantageously here configured as an inductive heating for example in the form of a coil 13. The actual hot forming takes places in the following scaffold series 14, wherein the first three scaffolds 15, 15 15 cause the actual thickness reduction, while the last scaffold 16 is configured as smoothing rolls.

(8) After the last pass a cooling zone 17 follows in which the finished hot strip is cooled down to coiling temperature.

(9) Between the end of the cooling zone 17 and the coil 19, 19 a cutter 20 is arranged. The cutter 20 has the purposed to divide the hot strip 18 transversely as soon as one of the two coils 19, 19 is completely wound up. The beginning of the following hot strip 18 is then conducted to the second freed coil 19, 19, this ensures that the strip tension is maintained over the entire strip length. This is particularly important for generating thin hot strips.

(10) Not shown in the FIGURE are the system components for reheating the pre-strip 9 prior to the hot rolling and for cold rolling the hot strip.