JEFORMA TM. High-Strength Steel Sheets with Excellent Formability

Transcription

1 JEFORMA TM High-Strength Steel Sheets with Excellent Formability

2 Introduction In recent years, ever-higher expectations have been placed on automotive high-strength steel sheets for improvement of automobile fuel consumption and crashworthiness. As a leading manufacturer of automotive steel sheets, JFE Steel has continued to develop automotive high-strength steel sheets over many years up to the present. Because high-strength steel sheets generally have lower formability, such as elongation, stretch-flange formability, etc., in comparison with mild steel sheets, there were limits on the parts in which these materials could be applied. To overcome this problem, JFE Steel studied the possibility of expanding the applicable range of high-strength steels by enabling users to select the optimum steel sheet for specific part shapes and forming methods. In other words, we supply high performance steel sheets that are the optimum match for the properties, such as elongation, stretch-flange formability, etc., required in each automotive part... JEFORMA TM is a series of highstrength steel sheets with excellent formability which was developed based on this concept. JFE Steel not only supplies outstanding steel sheets, but also conducts research and development of forming technologies and welding technologies for high tensile strength products. By providing these application technologies to users, we are cooperating with auto makers in realizing even more stable production of high-strength lightweight parts. JEFORMA stands for JFE Excellent Formability. CONTENTS Introduction Advantages and Production Process... 1 Product Line-Up and Features... 2 Mechanical Properties... 4 (1) Cold-rolled steel sheets (CR)... 4 (2) Galvannealed steel sheets (GA)... 5 Formability (Examples of Applied Parts)... 6 Available Product Size Range... 8 JFE Technical Solution for Application of High Tensile Strength Steel Sheets... 9 JEFORMA is a registered trademark of JFE Steel Corporation in Japan.

3 Advantages JEFORMA In every TS grade, customers can select the most suitable formability grade from 4 featured types, including the conventional grade. A line-up based on a uniform concept is available in strength grades 590, 780, 980 and 1180 MPa for both cold-rolled (CR) and galvannealed (GA) steel sheets. Material design considers weldability and resistance to delayed fracture. JEFORMA products are produced in a wide range of sheet thicknesses. Production Process Limestone Coke Iron ore Vacuum degasser Reheating furnace Converter Continuous caster Blast furnace Hot finishing mill Rougher Scale breaker Pickling line Continuous cold strip mill Cold-rolled steel product (CR) Continuous annealing line Galvannealed steel product (GA) Hot-dip galvanizing line JEFORMA 1

4 Product Line-Up and Features JEFORMA is available in a line-up of high formability steel sheets with 3 types of formability features (Type 1: High El, : High El-high λ, Type 3: Super high El). These products are available as both cold-rolled steel sheets and galvannealed steel sheets with strength levels of 590, 780, 980 and 1180 MPa class. This wide line-up allows users to select the optimum steel sheet for the specific forming method and part shape. Name Type Formability features Suitable parts Conventional high strength steel (HSS) Conventional DP (comparison) Good bendability for stamping to simple shapes. (CR) Bumper, Door impact beam, etc. Type 1 High El (DP) Suitable for stretch-forming or drawing parts due to high elongation. (CR) Center pillar upper, Front pillar upper, Front member, etc. JEFORMA High El-high λ Suitable for severe stretchflange-forming parts (forming involving shearing working) (CR) Rail outer, Roof cross member, etc. (GA) Center pillar lower, Front pillar lower, Side sill outer/ inner, Front /rear side member, Floor cross member, etc. Type 3 Super high El (TRIP) Suitable for more severe stretchforming or drawing parts due to extra-high elongation; provides a higher degree of freedom when forming parts. (GA) Center pillar (Integrated type), Front pillar (Integrated type), etc. El: Elongation. λ: Hole expanding ratio; index of stretch-flangeability. DP: Dual Phase steel. TRIP: TRansformation Induced Plasticity. Roof Cross Member CR Suitable Parts for JEFORMA Type 1 Front Pillar Upper CR Front Side Member GA Type 3 Front Pillar (Integrated type) GA Front Pillar Lower GA 2

5 JEFORMA Stretch-flangeability Conventional DP Excellent stretchflangeability and burring properties High El and high λ Type 1 High El DP Type 3 Super high El TRIP Excellent stretch-formability and drawability Elongation Rail Outer CR Rear Side Member GA Type 1 Center Pillar Upper CR Type 3 Center Pillar (Integrated type) GA Center Pillar Lower GA Side Sill Outer/Inner GA Floor Cross Member GA JEFORMA 3

6 Mechanical Properties 1 Cold-Rolled Steel Sheets (CR) JEFORMA The JEFORMA Series is a line-up of high formability steel sheets which is available with 3 types of formability features in each strength grade. Users can select the optimum steel sheet for the forming method and part shape, including conventional DP steel sheets. Strength grade Type Name YS (MPa) TS (MPa) Total elongation El (%) Hole expanding ratio λ (%) Development stage Conventional DP (comparison) JSC590Y Commercial production 590 High El (DP) 590CR-type Commercial production Super high El (TRIP) 590CR-type Commercial production Conventional DP (comparison) JSC780Y Commercial production 780 High El (DP) 780CR-type Commercial production High El-high λ 780CR-type Developed Super high El (TRIP) 780CR-type Commercial production Conventional DP (comparison) JSC980Y Commercial production 980 High El (DP) 980CR-type Commercial production High El-high λ 980CR-type Developed Super high El (TRIP) 980CR-type Commercial production Conventional DP (comparison) JSC1180Y Commercial production 1180 High El (DP) 1180CR-type Commercial production High El-high λ 1180CR-type Developed Super high El (TRIP) 1180CR-type Commercial production JSCxxxY: Low yield ratio type cold-rolled steel in the Japan Iron and Steel Federation standard. El: Elongation. λ: Hole expanding ratio; index of stretch-flangeability. DP: Dual Phase steel. TRIP: TRansformation Induced Plasticity. Conventional 1320 and 1470 grades (Martensite), which are under commercial production, are also available. Continuous cold strip mill Continuous annealing line 4

7 Mechanical Properties 2 Galvannealed Steel Sheets (GA) JEFORMA Strength grade Type Name YS (MPa) TS (MPa) Total elongation El (%) Hole expanding ratio λ (%) Development stage Conventional DP (comparison) JAC590Y Commercial production 590 High El (DP) 590GA-type Commercial production High El-high λ 590GA-type Developed Conventional DP (comparison) JAC780Y Commercial production 780 High El (DP) 780GA-type Commercial production High El-high λ 780GA-type Developed Super high El (TRIP) 780GA-type Commercial production Conventional DP (comparison) JAC980Y Commercial production 980 High El (DP) 980GA-type Commercial production High El-high λ 980GA-type Commercial production 1180 Conventional DP (comparison) JAC1180YL Commercial production High El (DP) 1180GA-type Developed JACxxxY: Low yield ratio type hot-dip galvannealed steel in the Japan Iron and Steel Federation standard. Conventional 1320 and 1470 grades (Martensite), which are already developed, are also available. Hot-dip galvanizing line (cooling tower section) Product coil multi-level warehouse (automated warehouse) JEFORMA 5

8 Formability Examples of Applied Parts JEFORMA is available in a line-up of 3 types, Type 1 (High El), (High El-high λ) with high elongation and a high hole expanding ratio and Type 3 (Super high El) with even higher elongation than Type 1. By selecting the optimum steel sheet for the product forming method and product shape, users can improve stretch-forming cracking and stretch flange-forming cracking, which are frequently problems in press forming. 980 MPa GA Type 1 (High El) Crack caused by stretchforming of conventional 980 MPa class steel High El JEFORMA steel sheets are advantageous for drawn and stretch-formed parts. In the bag-shaped bottom part of the center pillar, satisfactory forming is possible even with part shapes that require severe stretch-formability. 590 MPa GA (High El-high λ) Crack caused by stretch-flange-forming of conventional 590 MPa class steel High El-high λ JEFORMA has excellent properties for stretch-flange forming, which involves shearing working. Satisfactory forming can be realized in forming of the upper part of the center pillar, even with part shapes that require severe stretch-flangeability. 6

9 JEFORMA 1180 MPa GA Type 3 (Super high El) Super high El Type 3 is effective for forming drawn and stretch-formed parts. In the front pillar lower, Type 3 enables satisfactory forming of part shapes that require deep drawing formability. Crack caused by drawing of conventional 1180 MPa class steel Formability and Its Evaluation Press-forming of sheet materials is classified into the basic elements of 1. Deep drawing, 2. Stretch-forming, 3. Stretchflange-forming and 4. Bending, and can be considered to be a combination of these 4 elements. Although bending is the simplest form of press-forming of steel sheets, actual parts are often formed to more complex shapes. Therefore, the elements of stretch-forming and stretchflange-forming become necessary. If the formability of a material has inadequate performance in these types, this will become a cause of pressing cracks. The stretch-formability of a material is controlled by the uniformity of the strain distribution during forming (strain dispersion capacity) and the deformation limit strain, and is generally said to have a close correlation with total elongation, El in the tensile test (Fig.1). On the other hand, because stretch-flangeability is controlled by the deformation capacity of the flange edge, the hole expanding ratio (λ) in the hole expanding test is an index of this property. The hole expanding ratio used in these technical materials was measured by a method (Fig.2) conforming to JIS Z 2256: In obtaining the hole expanding ratio (λ), a hole with a diameter of 10 mmφ is punched in process (1). Then, in process (2), the punched hole is expanded by using a conical punch with a tip angle of 60 until a through-crack occurs at the edge of the hole, and the diameter (d) of the hole when the crack occurred is measured. The hole expanding ratio (λ) is then calculated by the following equation. d 10 Hole expanding ratio λ (%) = 10 Nominal stress YS TS Fracture (1) Punching Test piece Die Punch Uniform deformation Diffused neck (necking in width direction) Local neck (necking in thickness direction) (2) Hole expanding Punch U-El (uniform elongation) L-El (local elongation) El (total elongation) Nominal strain (%) Die Fig.1 Schematic diagram of stress-strain curve in tensile test Fig.2 Hole expanding test method JEFORMA 7

10 Available Product Size Range JEFORMA Product type Strength grade Type Name Sheet thickness (mm) Conventional DP JSC590Y 590 High El 590CR-type1 Super high El 590CR-type3 Conventional DP JSC780Y 780 High El 780CR-type1 Cold-rolled (CR) Super high El 780CR-type3 Conventional DP JSC980Y 980 High El 980CR-type1 Super high El 980CR-type3 Conventional DP JSC1180Y 1180 High El 1180CR-type1 Super high El 1180CR-type3 590 Conventional DP JAC590Y High El 590GA-type1 Galvannealed (GA) Conventional DP JAC780Y High El 780GA-type1 Super high El 780GA-type3 Conventional DP JAC980Y High El 980GA-type1 High El-high λ 980GA-type Conventional DP JAC1180Y Please inquire concerning product types not shown in the table. : Possible production range : Consultation range Resistance spot welding robot 8

11 JFE Technical Solutions for Application of High Tensile Strength Steel Sheets JEFORMA JFE Steel puts great effort not only into development, production and sales of products, but also development of application technologies for those products. We are contributing to the development of advanced automobiles by proposing total technical solutions through EVI (Early Vender Involvement) activities, which match JFE s accumulated Material technology, Automotive body design technology and Forming & joining technology and the needs of the customer at a high level. Evaluation of collision performance of part Material technology Material performance and evaluation techniques Automotive material development Welding & joining techniques Remote laser welding Automotive body performance Stiffness Crashworthiness Outer panels Elemental technologies and technical solutions for auto body development Press-forming & new forming techniques Automotive body design technology Functional analysis of auto body structure Corrosion performance evaluation techniques Press-forming simulation techniques (CAE) Forming & joining technology Evaluation of auto body stiffness performance Z-Displacement (mm) Analysis of springback of pressed parts JEFORMA 9

12 Cat.No.B1E HEAD OFFICE Hibiya Kokusai Building, 2-3 Uchisaiwaicho 2-chome, Chiyodaku, Tokyo , Japan Phone: (81) Fax: (81) ASIA PACIFIC SEOUL JFE Steel Korea Corporation 16th Floor, 41, Chunggyecheon-ro, Jongno-gu, Seoul, 03188, Korea (Youngpung Building, Seorin-dong) Phone: (82) Fax: (82) BEIJING JFE Steel Corporation Beijing 1009 Beijing Fortune Building No.5, Dongsanhuan North Road, Chaoyang District, Beijing, , P.R.China Phone: (86) Fax: (86) SHANGHAI JFE Consulting (Shanghai) Co., Ltd. Room 801, Building A, Far East International Plaza, 319 Xianxia Road, Shanghai , P.R.China Phone: (86) Fax: (86) GUANGZHOU JFE Consulting (Guangzhou) Co., Ltd. Room 3901 Citic Plaza, 233 Tian He North Road, Guangzhou, , P.R.China Phone: (86) Fax: (86) MANILA JFE Steel Corporation, Manila Office 23rd Floor 6788 Ayala Avenue, Oledan Square, Makati City, Metro Manila, Philippines Phone: (63) Fax: (63) HO CHI MINH CITY JFE Steel Vietnam Co., Ltd. Unit 1704, 17th Floor, MPlaza, 39 Le Duan Street, Dist 1, HCMC, Vietnam Phone: (84) Fax: (84) HANOI JFE Steel Vietnam Co., Ltd., Hanoi Branch Unit 1501, 15th Floor, Cornerstone Building, 16 Phan Chu Trinh Street, Hoan Kiem Dist., Hanoi, Vietnam Phone: (84) Fax: (84) BANGKOK JFE Steel (Thailand) Ltd. 22nd Floor, Abdulrahim Place 990, Rama IV Road, Silom, Bangrak, Bangkok 10500, Thailand Phone: (66) Fax: (66) SINGAPORE JFE Steel Asia Pte. Ltd. 16 Raffles Quay, No.15-03, Hong Leong Building, , Singapore Phone: (65) Fax: (65) JAKARTA JFE Steel Corporation, Jakarta Office 6th Floor Summitmas II, JL Jendral Sudirman Kav , Jakarta 12190, Indonesia Phone: (62) Fax: (62) NEW DELHI JFE Steel India Private Limited 806, 8th Floor, Tower-B, Unitech Signature Towers, South City-I, NH-8, Gurgaon , Haryana, India Phone: (91) Fax: (91) MUMBAI JFE Steel India Private Limited, Mumbai Office , A Wing, 215 Atrium Building, Andheri-Kurla Road, Andheri (East), Mumbai , Maharashtra, India Phone: (91) Fax: (91) CHENNAI JFE Steel India Private Limited, Chennai Office No.86, Ground Floor, Polyhose Towers(SPIC Annexe), Mount Road, Guindy, Chennai , Tamil Nadu, India Phone: (91) Fax: (91) BRISBANE JFE Steel Australia Resources Pty Ltd. Level28, 12 Creek Street, Brisbane QLD 4000 Australia Phone: (61) Fax: (61) EUROPE and MIDDLE EAST LONDON JFE Steel Europe Limited 15th Floor, The Broadgate Tower, 20 Primrose Street, London EC2A 2EW, U.K. Phone: (44) Fax: (44) DUBAI JFE Steel Corporation, Dubai Office P.O.Box LOB , Jebel Ali Free Zone Dubai, U.A.E. Phone: (971) Fax: (971) NORTH, CENTRAL and SOUTH AMERICA NEW YORK JFE Steel America, Inc. 600 Third Avenue, 12th Floor, New York, NY 10016, U.S.A. Phone: (1) Fax: (1) HOUSTON JFE Steel America, Inc., Houston Office 750 Town & Country Blvd., Suite 705 Houston, Texas 77024, U.S.A. Phone: (1) Fax: (1) MEXICO CITY JFE Steel America, Inc., Mexico Office Ruben Dario #281, 1404 Col. Bosque de Chapultepec, C.P , Mexico, D.F. Mexico Phone: (52) Fax: (52) RIO DE JANEIRO JFE Steel do Brasil LTDA Praia de Botafogo, 228 Setor B, Salas 508 & 509, Botafogo, CEP , Rio de Janeiro-RJ, Brazil Phone: (55) Fax: (55) Notice While every effort has been made to ensure the accuracy of the information contained within this publication, the use of the information is at the reader s risk and no warranty is implied or expressed by JFE Steel Corporation with respect to the use of information contained herein. The information in this publication is subject to change or modification without notice. Please contact the JFE Steel office for the latest information. Copyright JFE Steel Corporation. All Rights Reserved. Any reproduction, modification, translation, distribution, transmission, uploading of the contents of the document, in whole or in part, is strictly prohibited. 1708N JTR Printed in Japan