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, Mn5.0 to 35.0, Cr>1.0 to 14.0, total content of N, S, P0.1, 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.-19. (canceled)

20. Method for calculating property combinations of phase proportions and mechanical properties of a given alloy composition for a formable lightweight steel with the elements in weight %: TABLE-US-00005 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 with N, S, P in sum together 0.1, remainder iron and other steel accompanying elements, and optionally containing Cu, Mom Ni and Zn in sum together up to 1.0 weight %, wherein the lightweight steel consists 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: 511%, 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 Mn: >11%22%, 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: 19% and Cr: 10%; for a third given composition of said formable lightweight steel in which Mn: >22%35%, calculating the strength Rm and Rp in MPa and the elongation at beak A80 in % of the formable lightweight steel according to the formulas:
Rm=104.3{Cr}+2766.6{Si}2+11.7{Al}.sup.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 be observed: C: 0.2 to 0.7%, Si: 0.3 to 1.5%, and a sum of Al+Cr12%, wherein absolute numbers without dimension are inserted into the formulas and the units MPa for Rm and Rp and % for A80 are assigned to the dimensionless values.

21. The method of claim 20, wherein the steel at a Mn content of 5 to <=11 weight % has an austenite content between 30 and 85%, in which a strength Rm of at least 850 MPa, a yield strength Rp of at least 700 MPa and an elongation at break A80 between 4 and 20% results.

22. The method of claim 20, wherein the steel has a Mn content of <=22 weight %, an austenite phase content of 20 to 99% in which a strength of Rm of 600 to 850 MPa, a yield strength of at least 350 MPa and a elongation at break A80 between 8 and 60% results.

23. The method of claim 20, wherein the steel at a Mn content of <=weight % to 35 weight % has an austenite phase content between 20 and 60%, in which a strength of 820 MPa, a yield strength of at least 450 MPa and a elongation at break between 10 and 30% results.

24. A method for producing a formable lightweight steel with the elements in weight % TABLE-US-00006 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 with N, S, P in sum together 0.1, remainder iron and other steel accompanying elements, and optionally containing Cu, Mom Ni and Zn in sum together up to 1.0 weight %, wherein the lightweight steel consists 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: 511%, 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 Mn: >11%22%, 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: 19% and Cr: 10%; for a third given composition of said formable lightweight steel in which Mn: >22%35%, calculating the strength Rm and Rp in MPa and the elongation at beak A80 in % of the formable lightweight steel according to the formulas:
Rm=104.3{Cr}+2766.6{Si}2+11.7{Al}.sup.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 be observed: C: 0.2 to 0.7%, Si: 0.3 to 1.5%, and a sum of Al+Cr12%, wherein absolute numbers without dimension are inserted into the formulas and the units 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 under calm flow conditions and 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%.

25. The method of claim 24, wherein a speed of a supply of the melt is equal to the speed of the rotating conveyor belt.

26. The method of claim 24, 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.

27. The method of claim 24, wherein the melt applied onto the conveyor belt is fully solidified to the most part at the end of the conveyor belt.

28. The method of claim 27, further comprising after full solidification and prior to a further processing, passing the pre-strip through a homogenization zone.

29. The method of claim 28, wherein the further processing comprises cutting the pre-strip into plates.

30. The method of claim 29, 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.

31. The method of claim 28, wherein the further processing comprises coiling the pre-strip.

32. The method of claim 31, 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.

33. The method according of claim 31, further comprising preheating the pre-strip prior to the uncoiling.

34. The method of claim 24, wherein the pre-strip is subjected to the rolling process in-line and is then wound up.

35. The method of claim 24, wherein the degree of deformation during the hot rolling is >70%.

36. The method of claim 24, wherein the degree of deformation during the hot rolling is >90%.

37. The method of claim 24, wherein the hot strip is reheated and is cold rolled after the cooling.

38. The method of claim 24, further comprising an annealing process performed in a decarburizing atmosphere.

Description

[0037] The sole FIGURE shown in the appendix schematically shows a method sequence according to the Invention for the condition casting speed=rolling speed.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] After the last pass a cooling zone 17 follows in which the finished hot strip is cooled down to coiling temperature.

[0045] 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.

[0046] 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.

LIST OF REFERENCE SIGNS

[0047]

TABLE-US-00004 Nr Designation 1 Strip casting system 2 Conveyor belt 3, 3 Deflecting roller 4 Lateral insulation 5 Melt 6 Ladle 7 Opening 8 Supply container 9 Pre-strip 10 Homogenization zone 11 Housing 12 First scaffold 13 Induction coil 14 Scaffold series 15, 15 15 Roiling scaffold 16 Smoothing scaffold 17 Cooling path 18 Finished hot strip 19, 19 Coil 20 Cutter