Non-scaling heat-treatable steel and method for producing a non-scaling component from said steel

Abstract

A non-scaling heat-treatable steel with particular suitability for producing hardened or die-hardened components is disclosed, characterized by the following chemical composition in % by weight: C 0.04-0.50; Mn 0.5-6.0; Al 0.5-3.0; Si 0.05-3.0; Cr 0.05-3.0; Ni less than 3.0; Cu less than 3.0; Ti 0.010-0.050; B 0.0015-0.0040; P less than 0.10; S less than 0.05; N less than 0.020; remainder iron and unavoidable impurities. Further disclosed is a method for producing a non-scaling hardened component from the steel and a method for producing a hot strip from a steel.

Claims

1. A method for producing a component from steel comprising: heating a pre-product comprising a following chemical composition in weight %: C: 0.04-0.50 Mn: 0.5-6.0 Al: >1.5-3.0 Si: 0.05-3.0 Cr: 0.05-3.0 Ni: less than 3.0 Cu: less than 3.0 Ti: 0.010-0.050 B: 0.0015-0.0040 P: less than 0.10 S: less than 0.05 N: less than 0.020, remainder iron and unavoidable impurities, in a nitrogen-containing atmosphere to austenizing temperature; lowering an oxygen content or humidity in the nitrogen-containing atmosphere to a level sufficient to keep a dew point at below 0 C. and to form a layer of Al.sub.2O.sub.3 on a surface of the heated pre-product and thereby effectively inhibit scaling of iron in the pre-product; and quenching the pre-product.

2. The method of claim 1, wherein the level of the oxygen content or humidity in the nitrogen-containing atmosphere is such as to keep the dew point below 10 C.

3. The method of claim 1, wherein the level of the oxygen content or humidity in the nitrogen-containing atmosphere is such as to keep the dew point below 20 C.

4. The method of claim 1, wherein the level of the oxygen content or humidity in the nitrogen-containing atmosphere is such as to keep the dew point below 30 C.

5. The method of claim 1, wherein the heating to austenizing temperature is realized through induction, conduction, or radiation.

6. The method of claim 1, Fan hot or cold rolling a sheet metal to produce the pre-product.

7. The method of claim 1, further comprising seamlessly hot rolling a tube to produce the pre-product.

8. The method of claim 1, further comprising: casting a melt to a pre-strip in a horizontal strip casting system; and hot rolling the pre-strip to form the pre-product with a deformation degree of at least 50%.

9. The method of claim 8, further comprising supplying the melt onto a rotating conveyor belt of the horizontal strip casting system at a speed which equals a speed of the rotating conveyor belt.

10. The method of claim 8, further comprising evenly cooling all surface areas of the pre-strip, across a width of the conveyor belt so as to substantially fully solidify the ore-strip when exiting the conveyor belt.

11. The method of claim 10, further comprising after full solidification of the pre-strip, passing the pre-strip through a homogenization zone.

12. The method of claim 11, further comprising cutting the pre-strip into plates after undergoing homogenization.

13. The method of claim 12, further comprising after cutting the pre-strip to plates, heating the plates to rolling temperature and subsequently rolling the plates.

14. The method of claim 11, further comprising coiling the pre-strip after undergoing homogenization.

15. The method of claim 14, further comprising after the coiling uncoiling the pre-strip, heating the pre-strip to rolling temperature and rolling the pre-strip.

16. The method of claim 15, wherein the pre-strip is reheated prior to the uncoiling.

17. The method of claim 8, further comprising subjecting the pre-strip to the rolling process in-line and subsequently coiling the pre-strip.

18. The method of claim 8, wherein the deformation degree during rolling is >70%.

19. The method of claim 8, wherein the deformation degree during rolling is >90%.

20. The method of claim 10, further comprising cold rolling the pre-strip after the cooling.

21. The method of claim 1, wherein the nitrogen containing atmosphere contains H.sub.2, CO and CO.sub.2.

Description

BRIEF DESCRIPTION OF THE DRAWING

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

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(2) The casting method with a horizontal strip casting system 1 is located upstream of the hot rolling process, and is composed of a rotating conveyor belt 2 and two deflector rolls 3, 3. A lateral sealing 4 can also be seen which prevents that the applied melt 5 flows off the conveyor belt to the right hand or left hand side. The melt 5 is transported to the strip casting system 1 by means of a pan 6 and flows through an opening 7 provided in the bottom of the pan into a supply container 8. This supply container 8 is constructed in the manner of an overflow.

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

(4) For temperature compensation and tension reduction a homogenization zone 10 adjoins the strip casting system 1. The homogenization zone includes a heat insulating housing 11 and a here not shown roller table.

(5) The first stand 12 following thereafter is either configured only as pure drive unit optionally with a small pass or a roller unit with a predetermined pass.

(6) Following is an intermediate heating, here preferably as inductive heating for example configured in the form of a coil 13. The actual hot forming occurs in the subsequent stand array 14, wherein the first three stands 15, 15, 5 cause the actual pass reduction, while the last stand 16 is configured as smoothening stand.

(7) Following the last pass is a cooling zone 17, in which the hot strip is cooled down to coiling temperature.

(8) Between the end of the cooling distance 17 and the coiling 19, 19 a scissor 20 is arranged. This scissor 20 has the purpose to separate the hot strip 18 transversely as soon as the one of the two coils 19, 19 is fully wound up. The beginning of the following hot strip 18 is then guided onto the second released coil 19, 19. This ensures that the tension on the strip is maintained over the entire strip length. This is particularly important when producing thin hot strips.

(9) Not shown in the FIGURE are the system components for cold rolling of the hot strip.

(10) TABLE-US-00001 No. Designation 1 Strip casting system 2 Conveyor belt 3, 3 Deflector roller 4 Lateral sealing 5 Melt 6 Pan 7 Opening 8 Supply container 9 Pre-strip 10 Homogenization zone 11 Housing 12 First stand 13 Induction coil 14 Stand array 15, 15, 15 Roller stand 16 Smoothing stand 17 Cooling distance 18 Finished hot strip 19, 19 Coil 20 Scissor