WO1998006881B1 - Steel, method for its manufacture, its use and product made from steel - Google Patents

Abstract

Steel in the form of sheet or strip having the above chemical composition, balance Fe and inevitable impurities, wherein 0.4≤B/N≤1.2.

Claims

AMENDED CLAIMS

[received by the International Bureau on 06 February 1998 (06.02.98); original claims 1-16 replaced by new claims 1-15 (4 pages)]

1. Steel in the form of cold reduced, annealed and optionally further cold reduced sheet or strip having a chemical composition:

Element Min* Max*

C 40

Mn 140 250

P 20

S 20

Si 30

N ppm 30

Al ** 50

B ppm 5 50

Cu 40

Sn 10

Cr 40

Ni 40

Mo 10

* in 0.001 % wt. unless otherwise stated

** acid soluble

balance Fe and inevitable impurities, wherein 0.4 < B / N < 1.2, wherein the grain size in an edge region of the strip Gs-edge and the grain size in a centre region of the strip Gs-centre differ less than 0.5 ASTM units.

15

Steel according to claim 1 having a chemical composition:

Element Min* Max*

C 10 40

Mn 140 200

P 20

S 20, preferably 10

Si 30

N ppm 25

AJ ** 15 35

B ppm 8 25

Cu 40

Sn 10

Cr 40

Ni 40

Mo 10

* in 0.001 % wt. unless otherwise stated

** acid soluble

Steel in accordance with Claim 1 or Claim 2, wherein for the following elements the following standard values are respected:

16

4. Steel in accordance with any one of the preceding claims in the form of cold reduced, annealed and optionally further cold reduced strip or sheet wherein the r-value in an edge region of the strip r-edge and the r-value in a centre region of the strip r-centre differ less than 0.2 units, preferably less than 0.1 units.

5. Steel in accordance with any one of the preceding claims in the form of cold reduced, annealed and optionally further cold reduced strip or sheet wherein the Yield Point in an edge region of the strip Rp-edge and the Yield Point in a centre region of the strip Rp-centre differ less than 20 N/mm².

6. Steel in accordance with any one of the preceding claims in the form of cold reduced, annealed and optionally further cold reduced strip or sheet wherein the average r-value is at least 1.3.

7. Method for manufacturing an annealed steel strip from the steel according to any one of claims 1-6, comprising the stages: - hot-rolling comprising finish-rolling at a finish-rolling temperature and coiling at a coiling temperature; pickling; cold-rolling; annealing, preferably, continuous annealing, and optionally further cold rolling, preferably with a reduction of at least 0.6 % wherein the finish-rolling temperature is selected above \τ₃-10 °C and the coiling temperature is selected below 700 °C.

8. Method according to claim 7, wherein the finish-rolling temperature is selected above 825 °C and the coiling temperature below 690 °C. 17

9. Method according to claim 7 or claim 8, wherein the finish-rolling temperature is selected at 900 ± 30 °C and the coiling temperature at 670 °C ± 20 °C.

10. Method according to claim 7, 8 or 9 wherein the total cold reduction before annealing is 85 % or more.

1 1. Method in accordance with anyone of claims 7-10, wherein further cold rolling after annealing is carried out with a reduction of > 5 %.

12. Method in accordance with claim 1 1 wherein further cold rolling after annealing is carried out with a reduction of 10-20 %.

13. Use of the steel in accordance with anyone of claims 1-6, or a steel strip obtained in the method in accordance with anyone of claims 7-12 for stretching, deep-drawing and drawing and wall-ironing applications.

14. Steel in accordance with anyone of claims 1-6, or obtained in a method in accordance with anyone of claims 713, provided with one or more coatings selected from the group of coatings comprising Sn, Cr, lacquer, organic coating, polymer and combinations thereof on one or both sides of the strip or sheet.

15. Stretched, deep drawn or drawn and wall ironed product made from steel according to any one of claims 1-6 or claim 14 or from steel obtained by the method or use according to any one of claims 7-13.