AU2006201550B2

AU2006201550B2 - Structural steel

Info

Publication number: AU2006201550B2
Application number: AU2006201550A
Authority: AU
Inventors: Jim Williams
Original assignee: BlueScope Steel Ltd
Current assignee: BlueScope Steel Ltd
Priority date: 2005-04-15
Filing date: 2006-04-12
Publication date: 2012-03-22
Anticipated expiration: 2026-04-12
Also published as: AU2006201550A1

Abstract

- 17 A structural steel and a method of manufacturing the structural steel are disclosed. The structural steel 5 has the following steel composition, in wt%: C: < 0.35, Mn: < 0.5, Ti: at least 0.01, Si: < 0.8, Nb: < 0.1, Al: < 0.1, Ni: < 0.5, Cr: < 1.0, Mo: < 0.5, Cu: < 0.35, Ca: < 0.005, B: < 0.005, P: < 0.040, V: < 0.10, S: < 0.01, Fe: balance, and incidental impurities. H;\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06 BIS 450 tempering curve 0 20% P S 0 200 400 600 800 Tempering Temperature (*C) BIS 450 tempering curve .......... ........ 400 " I 300 -0 200 - 1 5 0 . .. ............. 0 100 200 300 400 500 600 700 800 Tempering Temperature BIS 450 tempering curve IT10 10 20 30 40 50 60 70 80 Tempering Temperature (*C)

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: BLUESCOPE STEEL LIMITED Invention Title: STRUCTURAL STEEL The following statement is a full description of this invention, including the best method of performing it known to us: -2 STRUCTURAL STEEL 5 The present invention relates to structural steel and a method of manufacturing the structural steel. The term "structural steel" is understood herein to mean a steel that is suitable for use as structural 10 components, for example beams. The present invention is based on the realisation that a steel composition developed initially by the applicant for use as plate for applications requiring 15 substantial abrasion resistance such as dump truck wear liners, chutes, earth moving buckets, and ground engaging tools is also suitable for use as structural steel. Australian provisional application 2004904074 20 describes the initial quenched and tempered steel plate invention of the applicant. Australian provisional application 2005900794 describes the subsequent coil plate invention of the applicant. The disclosure in the provisional applications is incorporated herein by cross 25 reference. The present invention provides a structural steel and a method of manufacturing the structural steel. 30 According to the present invention there is provided a structural steel having the following composition, in wt%: C: < 0.35 35 Mn: < 0.5 Ti: at least 0.01 Si: < 0.8 H:\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06 -3 Nb: < 0.1 Al: < 0.1 Ni: < 0.5 Cr: < 1.0 5 Mo: < 0.5 Cu: < 0.35 Ca: < 0.005 B: < 0.005 P: < 0.040 10 V: < 0.10 S: < 0.01 Fe: balance, and incidental impurities. 15 The term "incidental impurities" is understood herein to mean impurities that are the result of the steelmaking process and the feed materials used in the steelmaking process and are not deliberate additions to the composition and are not already in the list of 20 elements. Sn is one such element. Typically the composition includes less than 0.3 wt.% C. 25 Preferably the composition includes less than 0.25 wt.% C. Typically the composition includes at least 0.02 wt.% C. 30 Typically the composition includes less than 0.4 wt.% Mn. Preferably the composition includes less than 0.3 35 wt.% Mn. H:\angelal\keep\GRM Speci\Bluescope\BluescopeStructura1 Steel Final.doc 12/04/06 - 4 Typically the composition includes at least 0. 1 wt.% Mn. Typically the composition includes at least 0. 2 5 wt.% Mn. Typically the composition includes at least 0.02 wt.% Ti. 10 Typically the composition includes less than 0.05 wt.% Ti. Preferably the composition includes less than 0.04 wt.% Ti. 15 Typically the composition includes 0.010-0.030 wt.% Ti. Typically the steel composition includes at least 20 0.005 wt.% Si. Typically the steel composition includes less than 0.08 wt.% Nb. 25 Typically the steel composition includes at least 0.001 wt.% Nb. Preferably the steel composition includes at least 0.01 wt.% Nb. 30 Typically the steel composition includes less than 0.10 wt.% V. Typically the steel composition includes at least 35 0.001 wt.% V. Preferably the steel composition includes at H:\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06 -5 least 0.01 wt.% V. Typically the steel composition includes less than 0.05 wt.% Al. 5 Typically the steel composition includes at least 0.01 wt.% Al. Typically the composition includes less than 0.3 10 wt.% Ni. Preferably the composition includes less than 0.2 wt.% Ni. 15 Typically the composition includes less than 0.8 wt.% Cr. Preferably the composition includes less than 0.7 wt.% Cr. 20 Typically the composition includes less than 0.3 wt.% Mo. More preferably the composition includes less 25 than 0.2 wt.% Mo. Typically the composition includes less than 0.001 wt.% Ca. 30 Typically the steel composition includes less than 0.012 wt.% S. Typically the steel composition includes less than 0.01 wt.% S. 35 Typically the steel composition includes at least 0.005 wt.% S. H:\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06 -6 Typically the composition has a Carbon Equivalent (CET) value of less than 0.32%. This formula provides a measure of the weldability of the steel. 5 More preferably the Carbon Equivalent (CET) is less than 0.30%. According to the present invention there is 10 provided a method of manufacturing the above-described structural steel which includes the steps of treating pattern plate or coil plate made from the above-described steel composition by: 15 (a) heating the pattern plate or the coil plate to the austenitising temperature range and holding the plate in the temperature range for a predetermined time; (b) quenching the plate, typically with water 20 sprays; and (c) tempering the quenched plate as required at a predetermined temperature and for a predetermined time. 25 Typically the method also includes manufacturing the pattern plate and the coil plate by casting slabs of steel having the required composition and thereafter processing the slabs and forming pattern plate or coil plate having a required thickness, typically 10-80 mm or 30 coil plate having a required thickness, typically 5-8mm. Typically, the method includes tempering the quenched pattern plate or coil plate at a temperature of at least 6000C. 35 Preferably the tempering temperature is 650 0 C. H:\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06 - 7 Typically, the method includes selecting the temperature and/or the time for tempering step (c) to produce the structural steel having a required combination of properties, such as tensile strength and yield 5 strength, for use as a structural steel. In addition to tensile strength and yield strength, the properties of particular interest are elongation and toughness. 10 Preferably the method includes selecting the temperature and/or the time for tempering step (c) to produce the structural steel having a minimum tensile strength of 800 MPa and a minimum yield strength of 690 15 MPa. Typically, the method includes tempering the quenched pattern plate or coil plate for at least 20 minutes for each 10mm of plate thickness. 20 According to the present invention there is also provided structural products made from the above-described structural steel. 25 The products include, by way of example, fabricated I-beams and other structural beams. The applicant has found in test work that the above-described structural steel has comparable or 30 superior toughness, hardness, weldability, and formability to currently available structural steel in Australia. Typically the toughness of the above-described structural steel after tempering at 650 0 C and as measured 35 in a Charpy impact test in a longitudinal direction with a 10 mm x 10 mm test sample is about 180 J at a test temperature of -40C. H;\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06 -8 Typically the hardness of the above-described structural steel after tempering at 650*C is 260-270 Brinell. 5 Typically, the tensile strength of the above described structural steel after tempering at 650*C is about 880 MPa. 10 Typically, the yield strength of the above described structural steel after tempering at 650 0 C is about 820 MPa. Typically, the elongation of the above-described 15 structural steel after tempering at 650 0 C is about 18%. Typically the through thickness tensile reduction of area after tempering at 650 0 C is above 45%. 20 The above values of toughness, hardness, tensile strength, yield strength, and elongation of the above described structural steel were determined by the applicant on test work carried out on quenched plate having the composition, in wt.%, set out below: 25 C: 0.195 Mn: 0.29 Ti: 0.030 Si: 0.51 30 Ni: 0.15 Cr: 0.81 Mo: 0.10 Ca: 0.001 B: 0.001 35 P: 0.010 V: 0.043 S: 0.003 H:\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06 -9 Fe: balance, and incidental impurities More particularly, the test work was carried out 5 on samples of the above-mentioned quenched plate that were tempered at 10 selected temperatures, namely 25*C, 200*C, 300 0 C, 400 0 C, 450 0 C, 500 0 C, 550 0 C, 600 0 C, 650 0 C, and 700 0 C and were then tested to determine the tensile strength, yield strength, hardness, and toughness of the samples. 10 Figures 1 to 3 are graphs of tensile strength and yield strength versus tempering temperature (Figure 1), hardness versus tempering temperature (Figure 2), and toughness versus tempering temperature (Figure 3) 15 generated in the test work. The results presented in Figures 1 to 3 indicate that tempering the structural steel at a temperature of 650 0 C produces a combination of properties, summarized 20 below, that is particularly well-suited for use as a structural steel: e Toughness: 180 J measured in a Charpy impact test in a longitudinal direction with a 10 mm x 10 mm test sample 25 at a test temperature of -40*C. * Hardness: 260-270 Brinell. " Tensile strength: 880 MPa. 30 e Yield strength: 820 MPa. In addition to providing the above-quoted specific values of toughness, hardness, tensile strength, 35 yield strength, and elongation at a tempering temperature of 650 0 C and at other tempering temperatures in the experimental range, the test results are a guide to the H,\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06 - 10 heat treater as to what temperature range they should temper the material to achieve required mechanical properties, such as a minimum tensile strength of 800MPa and a minimum yield strength of 690MPa with appropriate 5 values of elongation and toughness. Many modifications may be made to the present invention described above without departing from the spirit and scope of the invention. H:\angelal\keep\GRM Speci\Bluescope\BluescopeStructural Steel Final.doc 12/04/06

Claims

1. A structural steel having the following steel composite ion, in wt%: 5 I C: 0.35 Mn: 0.1-0.5 Ti: > 0.01 Si: 0.005-0.8 10 Nb: < 0.1 Al: < 0.1 Ni: < 0.5 Cr: < 1.0 Mo: < 0.5 15 Cu: < 0.35 Ca: < 0.005 B: - 0.005 P: 0.040 V:- 0.10 20 ;: 0.01 Fe: balance, and inc dental impurities.

2. The structural steel defined in claim 1 wherein 25 the composition includes less than 0.3 wt.% C.

3. The structural steel defined in claim 1 or claim 2 wherein the composition includes at least 0.02 wt.% C. 30

4. The structural steel defined in any one of the preceding claims wherein the composition includes less than 0.4 wt.% Mn.

5. The structural steel defined in any one of the 35 preceding claims wherein the composition includes at least 0.2 wt% Mn. 3..97201_1 (GHMatters) P56575.Al 06/03/12 - 12

6. The structural steel defined in any one of the preceding claims wherein the composition includes at least 0.02 wt.% Ti. 5

7. The structural steel defined in any one of the preceding claims wherein the composition includes less than 0.05 wt.% Ti.

8. The structural steel defined in any one of the 10 preceding claims wherein the composition includes less than 0.0)4 wt.% Ti.

9. The structural steel defined in any one of the preceding claims wherein the composition includes 0.010 15 0.030 wt.% Ti.

10. The structural steel defined in any one of the precedihg claims wherein the composition includes at least 0.001 wt.% Nb. 20

11. The structural steel defined in any one of the preceding claims wherein the composition includes at least 0.001 t.% V. 25

12. The structural steel defined in any one of the preceding claims wherein the composition includes at least 0.01 wt,.% Al.

13. The structural steel defined in any one of the 30 preceding claims wherein the composition includes at least 0.005 t.% S.

14. The structural steel defined in any one of the preceding claims wherein the composition has a Carbon 35 Equivalent (CET) value of less than 0.32%. 1197201 1 {GHMtter) P5657S.M.1 06/03/12 - 13

15. A method of manufacturing the structural steel defined in any one of the preceding claims which includes the steps of treating pattern plate or coil plate made from the above-described steel composition by: 5 (a) heating the pattern plate or the coil plate to the austenitising temperature range and holding the plate in the temperature range for a predetermined time; 10 (b) quenching the plate, typically with water sprays; and (c) tempering the quenched plate at a temperate ure of at least 600 0 C and for a predetermined time 15 to produce the structural steel having a required combination of properties, such as tensile strength and yield strength, for use as a structural steel.

16. The method defined in claim 15 includes manufacturing 20 the pattern plate and the coil plate by casting slabs of steel having the required composition and thereafter processing the slabs and forming pattern plate or coil plate having a required thickness, typically 10-80 mm or coil plate having a required thickness, typically 5-8mm. 25

17. The method defined in claim 15 or claim 16 wherein the tempering temperature is 650 0 C.

18. The method defined in any one of claims 15 to 17 30 includes selecting the temperature and/or the time for tempering step (c) to produce the structural steel having a minimum tensile strength of 800 MPa and a minimum yield strength of 690 MPa. 35

19. The method defined in any one of claims 15 to 18 includes tempering the quenched pattern plate or coil 319S201_1 (GHatters) 356575.AU.1 06/03/12 - 14 plate for at least 20 minutes for each 10mm of plate thickness.

20. A structural product made from the structural 5 steel defined in any one of claims 1 to 14. 31S7201_1 (GHMatters) P56515,AU.1 06/03/12