High-strength plated steel sheet having excellent plating properties, workability, and delayed fracture resistance, and method for producing same

Inactive Publication Date: 2017-12-28
KOBE STEEL LTD
View PDF0 Cites 4 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a hot-dip galvanized and galvannealed steel sheet that has a strength of 980 MPa or higher, excellent formability in bendability and balance between strength and ductility, as well as delayed fracture resistance. The steel sheet has a unique structure that includes an internal oxide layer, a soft layer, and a hard layer, which works as a hydrogen trap site to effectively suppress hydrogen embrittlement. The average depth of the internal oxide layer and the relationship between it and the soft layer are controlled, which further enhances bendability and delayed fracture resistance. Overall, the invention provides a high-quality plated steel sheet that meets various demands.

Problems solved by technology

However, Si and Mn are readily oxidizable elements, and hot-dip galvanizing wettability is significantly impaired by Si oxides, Mn oxides, and complex oxides of Si and Mn, that are formed on the surface.
This poor wettability gives rise to problems such as bare spots and the like.

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • High-strength plated steel sheet having excellent plating properties, workability, and delayed fracture resistance, and method for producing same
  • High-strength plated steel sheet having excellent plating properties, workability, and delayed fracture resistance, and method for producing same
  • High-strength plated steel sheet having excellent plating properties, workability, and delayed fracture resistance, and method for producing same

Examples

Experimental program
Comparison scheme
Effect test

examples

[0122]Slabs having the component composition given in Table 1, the balance being iron and inevitable impurities, were heated to 1250° C., and were hot-rolled down to 2.4 mm at a finish rolling temperature of 900° C., followed by coiling at the temperature given in Table 2.

[0123]Some of the examples, i.e. Nos. 26 to 28, 37 to 39 and 41, were placed thereafter in a ceramic fiber heat-insulating apparatus, where the temperature was kept under the conditions given in Table 2. The keeping time at a temperature of 500° C. or higher was measured using a thermocouple attached to the outer periphery of the coil.

[0124]Each hot-rolled steel sheet thus obtained was then pickled under the conditions below, and was thereafter cold-rolled at a cold rolling ratio of 50%. The sheet thickness after cold rolling was 1.2 mm.

[0125]The pickling solution was 10% hydrochloric acid, the temperature was 82° C. and the pickling time as given in Table 2.

[0126]Next, annealing (oxidation, reduction) and cooling ...

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

PUM

PropertyMeasurementUnit
Temperatureaaaaaaaaaa
Temperatureaaaaaaaaaa
Lengthaaaaaaaaaa
Login to view more

Abstract

A high-strength plated steel sheet has a plated layer on the surface of a base steel sheet and contains predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t / 4 of the base steel sheet, where t is a sheet thickness of the base steel sheet; and a hard layer containing martensite and bainite, and ferrite in predetermined ranges. The average depth D of the soft layer is 20 μm or greater, and the average depth d of an internal oxide layer is 4 μm or greater and smaller than D.

Description

TECHNICAL FIELD[0001]The present invention relates to a high-strength plated steel sheet having a tensile strength of 980 MPa or higher and having excellent platability, excellent formability in terms of both bendability and balance between strength and ductility, and excellent delayed fracture resistance, and also relates to a method for producing the steel sheet. The term plated steel sheet of the present invention denotes both of a hot-dip galvanized steel sheet and a hot-dip galvannealed steel sheet.BACKGROUND ART[0002]Hot-dip galvanized steel sheets and hot-dip galvannealed steel sheets that are widely used in the fields of automobiles, transport aircrafts and the like, are required to have, in addition to high strength, also excellent formability in terms of both bendability and balance between strength and ductility, and to exhibit moreover excellent delayed fracture resistance.[0003]Adding a substantial amount of strengthening elements such as Si or Mn into steel is effectiv...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

Application Information

Patent Timeline
no application Login to view more
IPC IPC(8): C21D9/46C21D8/02C23C2/06C23C2/02C22C38/32C22C38/28C22C38/22C22C38/18C22C38/16C22C38/14C22C38/12C22C38/08C22C38/06C22C38/04C22C38/02C22C38/00C23C2/40C23F17/00
CPCC21D9/46C23F17/00C21D8/0226C21D8/0236C21D8/0278C23C2/02C23C2/06C23C2/40C22C38/32C22C38/28C22C38/22C22C38/18C22C38/14C22C38/12C22C38/16C22C38/08C22C38/06C22C38/04C22C38/02C22C38/002C22C38/001C21D8/0205C23G1/06C23G1/08C23C2/0222C23C2/024C23C2/0224C23C2/28C23C2/29C21D1/76C21D8/0257C22C38/58C21D2211/005C21D2211/001C21D2211/009
Inventor IKEDA, MUNEAKIFUTAMURA, YUICHINAKAYA, MICHIHARU
Owner KOBE STEEL LTD
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Try Eureka
PatSnap group products

Browse by: Latest US Patents, China's latest patents, Technical Efficacy Thesaurus, Application Domain, Technology Topic.

© 2024 PatSnap. All rights reserved.Legal|Privacy policy|Modern Slavery Act Transparency Statement|Sitemap