Thick steel plate having excellent toughness and reduced softening in weld heat-affected zone

A technology for welding heat-affected, thick steel plates, which is applied in the field of thick steel plates, can solve the problems of HAZ toughness reduction, no consideration, etc., and achieve excellent toughness, excellent mechanical properties, and the effect of inhibiting HAZ softening

Inactive Publication Date: 2008-06-04
KOBE STEEL LTD
View PDF4 Cites 14 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, according to this method, even if the softening of the HAZ is suppressed, there is still a problem that the toughness of the HAZ is lowered because a coarse bainite structure is formed at the welding lin

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
  • Thick steel plate having excellent toughness and reduced softening in weld heat-affected zone
  • Thick steel plate having excellent toughness and reduced softening in weld heat-affected zone
  • Thick steel plate having excellent toughness and reduced softening in weld heat-affected zone

Examples

Experimental program
Comparison scheme
Effect test

Example Embodiment

[0029] The inventors of the present invention conducted intensive research in order to provide a thick steel plate that has excellent HAZ toughness and suppressed HAZ softening even if a large heat input welding with a heat input exceeding about 60 kJ / mm is performed on a thick steel plate with a thickness of about 60 mm or more. . As a result, it was found that in order to coexist these characteristics, Ti, N, and B are used in the steel components, and the form of the old γ grains should be controlled to a flat shape as the pre-structure of the base material. In detail, it was found that: (a) Mainly, the miniaturization of austenite grains (γ grains) caused by TiN and the formation of intragranular ferrite with BN as the nucleus in TiN maximize To limit the enhancement of the HAZ toughness effect of the fine TiN; and (b) For N, excessive addition of Ti and B (in addition, Nb as needed) to ensure hardenability, and suppression of ferrite transformation to maximize Limit the softe...

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
Plate thicknessaaaaaaaaaa
Plate thicknessaaaaaaaaaa
Login to view more

Abstract

A thick steel plate which has superior HAZ(heat-affected zone) toughness(specifically, toughness of a bonding part) and suppressed HAZ softening(specifically, deterioration of hardness at the position that is distanced from the bonding part) at the same time is provided. A thick steel plate having superior toughness and reduced softening in a weld heat-affected zone comprises, by mass percent, 0.030 to 0.080% of C, 1.0% or less(excluding 0%) of Si, 0.8 to 2.0% of Mn, 0.01 to 0.10% of Al, not less than 0.015% to less than 0.030% of Ti, greater than 0.0055% to not more than 0.0100% of N, not less than 0.0015% to less than 0.0035% of B, and 0.015% or less(including 0%) of Nb with the balance of Fe and inevitable impurities, wherein the thick steel plate has 1.5 or more of a flatness ratio(major axis/minor axis) of spherical austenite grains, and satisfies the mathematical expression 1, 2.0<=[Ti]/[N[<=4.0, and the mathematical expression 2, 0<P value<23.0 and P value=2000x[B]+300x([Ti]-3.42x[N])+1000x[Nb], wherein [ ] means the content(mass%) of each element.

Description

technical field [0001] The present invention relates to a thick steel plate suitable for welded structures such as ships and marine structures, and particularly relates to a thick steel plate having excellent toughness in a heat-affected zone (HAZ) after welding and suppressed softening. Background technique [0002] In recent years, thick steel plates used in welded structures such as ships and marine structures have to be welded under stricter conditions than before as the size of welded structures increases. For example, for thick steel plates with a plate thickness of about 60mm or more, Perform ultra-large heat input welding with heat input exceeding 60kJ / mm. Under the above-mentioned heat input conditions, the welding wire (bond) part will be subjected to a thermal cycle in which the thick steel plate is heated to 1400°C and held for 50 seconds, and then cooled from 780°C to 500°C for 500 seconds. . [0003] Then, if such super heat input welding is carried out, sinc...

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): C22C38/14C22C38/42C22C38/44C22C38/46C22C38/52
CPCC22C38/001C22C38/002C22C38/005C22C38/02C22C38/04C22C38/06C22C38/12C22C38/14C22C38/18
Inventor 高冈宏行冈崎喜臣
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