Development and Production of Ultra-High Strength Linepipes With Dual-Phase Microstructure for High Strain Application

2007 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Mitsuru Okatsu ◽  
Junji Shimamura ◽  
Shigeru Endo ◽  
Nobuo Shikanai ◽  
...  
Keyword(s):  
Base Material ◽  
High Strength ◽  
Controlled Rolling ◽  
Accelerated Cooling ◽  
Heating Process ◽  
Dual Phase ◽  
Low Carbon ◽  
Cooling Process ◽  
Bainite Microstructure ◽  
Microstructural Control

Extensive studies to develop high strength linepipes with higher deformability have been conducted. One of the key technologies for improving deformability is dual-phase microstructural control. Steel plate with ferrite-bainite microstructure can be obtained by applying Thermo-mechanical controlled processing, TMCP, made up with controlled rolling and accelerated cooling process. Low carbon-boron free steels were used to enable the ferrite formation during cooling after controlled rolling, and the accelerated cooling process with ultimate cooling rate enabled to achieve high strength of up to X120 grade. On-line heating process by induction device was also applied subsequently after accelerated cooling in order to improve Charpy energy of the base material and homogeneity of material properties in the plate. Trial production of X120 high deformability linepipe was also conducted by applying dual-phase microstructural control. Microstructural and mechanical properties of X120 linepipe are introduced in this paper.

Development of 780MPa Grade Steel Plate by Microstructural Control Containing M-A through the On-Line Heating Process

2010 ◽  
Vol 638-642 ◽  
pp. 3555-3560 ◽  
Author(s):  
Keiji Ueda ◽  
Shinichi Suzuki ◽  
Shinji Mitao ◽  
Nobuo Shikanai ◽  
Takayuki Ito
Keyword(s):  
Heating Temperature ◽  
Bainitic Ferrite ◽  
High Strength ◽  
Steel Plates ◽  
Accelerated Cooling ◽  
Heating Process ◽  
Line Heating ◽  
On Line ◽  
Grade Steel ◽  
Microstructural Control

High strength steel plates with 780MPa in tensile strength, suitable for building construction use, have been developed. The steel plates provide excellent combination of high strength, toughness, deformability and weldability. The key technology to obtain the excellent combination in mechanical properties of the steel is the microstructural control of M-A (martensite-austenite constituent) and the bainitic ferrite dual-phase structure, through the on-line heat treatment immediately after the accelerated cooling in Thermo-mechanical control process (TMCP). The developed steel plates have microstructure of fine M-A dispersed in the bainitic ferrite matrix. Basic metallurgical research revealed that the transformation behavior and microstructural morphologies were varied with the cooling stop temperature before the on-line heating, and the on-line heating temperature itself. Trial production of the developed 780MPa grade steel plates was also carried out with the plate mill. The obtained plates showed the satisfactory combination of high strength, low yield ratio, toughness.

Investigations of Microstructure of Resistance Spot-Welded Joints Made of HSLA340 and DP600 Steels / Badanie Mikrostruktury Złączy Zgrzewanych Punktowo Ze Stali HSLA340 I DP600

2012 ◽  
Vol 57 (4) ◽  
pp. 1081-1086 ◽  
Author(s):  
A. Ignasiak ◽  
M. Korzeniowski ◽  
A. Ambroziak
Keyword(s):  
Welded Joints ◽  
High Strength Steel ◽  
Hsla Steel ◽  
High Strength ◽  
Dual Phase ◽  
Low Carbon ◽  
Spot Welds ◽  
Bainite Microstructure ◽  
Martensite Microstructure ◽  
Carbon Martensite

The paper presents results of metallographic investigations of spot welds made of high-strength steel HSLA340 and dual-phase DP600 steel. Low-carbon martensite microstructure was found in the weld nugget of HSLA steel. The DP600 steel shows martensite and bainite microstructure. For both steels, no carbides of microadditives were found because they dissolved in liquid nugget and could not precipitate again because of rapid heat abstraction. Moreover, no transcrystallisation was found in both steels, which proves good mixing of the materials within the weld.

MITTAL DI-FORM T700, HF80Y100T

Alloy Digest ◽  
2007 ◽  
Vol 56 (2) ◽  
Keyword(s):  
Automotive Industry ◽  
High Strength ◽  
Martensite Phase ◽  
Carbon Steels ◽  
Ferrite Phase ◽  
Dual Phase ◽  
Low Carbon ◽  
Advanced High Strength Steel ◽  
Dp Steels ◽  
Soft Ferrite

Abstract MITTAL DI-FORM T700 and HF80Y100T are low-carbon steels with a manganese and silicon composition. Dual-phase (DP) steels are one of the important advanced high-strength steel (AHSS) products developed for the automotive industry. Their microstructure typically consists of a soft ferrite phase with dispersed islands of a hard martensite phase. The martensite phase is substantially stronger than the ferrite phase. The DI-FORM grades exhibit low yield-to-tensile strengths, and the numeric designation in the name corresponds to the tensile strength. This datasheet provides information on microstructure and tensile properties as well as deformation and fatigue. It also includes information on forming. Filing Code: SA-561. Producer or source: Mittal Steel USA Flat Products.

MITTAL DI-FORM T590, T600

Alloy Digest ◽  
2007 ◽  
Vol 56 (1) ◽  
Keyword(s):  
Tensile Strength ◽  
Automotive Industry ◽  
High Strength ◽  
Martensite Phase ◽  
Ferrite Phase ◽  
Dual Phase ◽  
Bend Strength ◽  
Low Carbon ◽  
Advanced High Strength Steel ◽  
Soft Ferrite

Abstract MITTAL DI-FORM T590 and T600 are low-carbon dual-phase steels containing manganese and silicon. Dual-phase (DP) steels are important advanced high-strength steel (AHSS) products developed for the automotive industry. Their microstructure typically consists of a soft ferrite phase with dispersed islands of a hard martensite phase. The martensite phase is substantially stronger than the ferrite phase. The DI-FORM grades exhibit low yield-to-tensile strength ratios. The numeric designation in the grade name corresponds to the tensile strength in MPa. This datasheet provides information on microstructure, tensile properties, and bend strength as well as fatigue. It also includes information on forming. Filing Code: SA-558. Producer or source: Mittal Steel USA Flat Products.

scholarly journals Assessment of the Hardening Behavior and Tensile Properties of a Cold-Rolled Bainitic–Ferritic Steel

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6662
Author(s):  
Emilio Bassini ◽  
Antonio Sivo ◽  
Daniele Ugues
Keyword(s):  
Strain Hardening ◽  
High Strength ◽  
Dual Phase ◽  
Low Carbon ◽  
Soft Phase ◽  
Bending Tests ◽  
Ductile Materials ◽  
Hardening Behavior ◽  
Material State ◽  
Cold Rolled

The automotive field is continuously researching safer, high-strength, ductile materials. Nowadays, dual-phase (DP) steels are gaining importance, since they meet all these requirements. Dual-phase steel made of ferrite and bainite is the object of a complete microstructural and mechanical characterization, which includes tensile and bending tests. This specific steel contains ferrite and bainite in equal parts; ferrite is the soft phase while bainite acts as a dispersed reinforcing system. This peculiar microstructure, together with fine dispersed carbides, an extremely low carbon content (0.09 wt %), and a minimal degree of strain hardening (less than 10%) allow this steel to compete with traditional medium-carbon single-phase steels. In this work, a full pearlitic C67 steel containing 0.67% carbon was used as a benchmark to build a comparative study between the DP and SP steels. Moreover, the Crussard–Jaoul (C-J) and Voce analysis were adopted to describe the hardening behavior of the two materials. Using the C-J analysis, it is possible to separately analyze the ferrite and bainite strain hardening and understand which alterations occur to DP steel after being cold rolled. On the other hand, the Voce equation was used to evaluate the dislocation density evolution as a function of the material state.

scholarly journals Impact of Cold-Rolling and Heat Treatment on Mechanical Properties of Dual-Phase Treated Low Carbon Steel

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Le Van Long ◽  
Dinh Van Hien ◽  
Nguyen Truong Thanh ◽  
Nguyen Chi Tho ◽  
Van Thom Do
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Low Carbon Steel ◽  
High Strength ◽  
Processing Parameters ◽  
Dual Phase ◽  
Low Carbon ◽  
Forming Process ◽  
Good Ductility ◽  
Rolling Deformation

The low carbon steel has good ductility that is favorable for forming process, but its low strength leads to limiting their application for forced structures. This paper studied improving strength of low-carbon steel via rolling deformation and dual-phase treatment. The results showed that the dual-phase treated steel had a combination of high strength and good ductility; its tensile ultimate strength reached 740 MPa with elongation at fracture of over 15%, while that of the cold-rolled steel only reached 700 MPa with elongation at fracture of under 3%. Based on the obtained results, relationships between mechanical properties and dual-phase processing parameters were established to help users choose suitable-processing parameters according to requirements of products.

Microstructure and Mechanical Properties of X80/X100 High Deformability Pipeline Steel

2011 ◽  
Vol 399-401 ◽  
pp. 139-143
Author(s):  
Dian Xiu Xia ◽  
De Liang Meng ◽  
Shou Yong An ◽  
Yong Lin Kang
Keyword(s):  
Pipeline Steel ◽  
Large Strain ◽  
High Strength ◽  
Longitudinal Direction ◽  
Granular Bainite ◽  
Dual Phase ◽  
Cooling Process ◽  
Bainite Structure ◽  
Lath Bainite ◽  
High Deformability

In the present study, X80 and X100 grade high deformability pipeline steels have been processed by using TMCP and followed two-stage cooling process. The microstructures of the X80HD (HD, high deformability) and X100HD steels were both characterized by ferrite-bainite dual phase. The grains sizes of ferrite were mostly less than 5μm and the volume fractions were about 20~25% in X80HD and 10~15% in X100HD steel. The bainite structure in X80HD steel was granular bainite (GB); while in X100HD steel large amounts of lath bainite (LB) were also formed besides GB, and bainite grains were much finer. Ferrite-bainite dual phase microstructure has large strain hardenability that resulting high strength and high deformability combination. Both the steels exhibit high strength/toughness in transverse direction and high deformability in longitudinal direction. The X100HD steel with more volume of LB and less volume of PF has higher strength but lower deformability than that of X80HD steel.

Refinement of Cementite in High Strength Steel Plates by Rapid Heating and Tempering

2007 ◽  
Vol 539-543 ◽  
pp. 4720-4725 ◽  
Author(s):  
A. Nagao ◽  
K. Hayashi ◽  
K. Oi ◽  
S. Mitao ◽  
N. Shikanai
Keyword(s):  
Rapid Heating ◽  
High Strength ◽  
Average Diameter ◽  
Carbon Steels ◽  
Steel Plates ◽  
Heating Process ◽  
Low Carbon ◽  
Precipitation Behavior ◽  
Heating Rates ◽  
Extraction Replica

The precipitation behavior of cementite in low carbon steels at various heating rates from 0.3 to 100 K/s has been studied using a high-frequency induction heating apparatus. The materials used in this study were steel platesfor welded structures: 610 and 780 MPa class steel plates with a mixed microstructure of bainite and martensite.Cementite was observed using a carbon extraction replica method and the hardness and toughness were also examined. When heated at the conventional slow rate of 0.3 K/s, relatively large cementite particles with an average diameter of 72 nm precipitated at the lath boundaries, whereas when heated at a rapid rate over 3.0 K/s, cementite precipitated both within the laths and at the lath boundaries, and the cementite was refined down to an average diameter of 54 nm. With such refinement of the cementite, the toughness was improved. On the other hand, the hardness was irrespective of the heating rate and was dependent on the tempering parameter. TEM observations of the cementite precipitation behavior during the rapid heating process revealed that cementite begins to precipitate at the lath boundaries at about 773 K and within the laths at about 873 K. It is concluded that rapid heating especially from 773 to 873 K contributes to the cementite refinement and consequently the improvement in toughness. The effect of alloying elements such as chromium, molybdenum or silicon on the cementite growth during the rapid heating and tempering treatment is also discussed.

Development of Grade X80 High Charpy Energy Linepipe by MA Formation Control

2016 ◽  
Author(s):  
Hideyuki Kimura ◽  
Tomoyuki Yokota ◽  
Nobuyuki Ishikawa ◽  
Shinichi Kakihara ◽  
Joe Kondo
Keyword(s):  
Ductile Fracture ◽  
Formation Control ◽  
Single Phase ◽  
Void Nucleation ◽  
Controlled Rolling ◽  
Accelerated Cooling ◽  
Dual Phase ◽  
Long Distance ◽  
Dual Phase Steels ◽  
Homogeneous Microstructure

Higher grade linepipes such as grade X80 have been developed and applied to long distance pipelines in order to reduce the cost of pipeline construction by using thinner pipes than is possible with conventional grades. Service pressures have also been increased in recent years for efficient gas transportation. In addition to the requirement of higher strength, running ductile fracture should be prevented in long distance and high pressure pipelines. Resistance to ductile fracture, as evaluated by Charpy energy, is an important material property for higher grade linepipes. It has been reported that bainite single-phase steel tends to show higher Charpy energy than ferrite-bainite or bainite-MA (martensite-austenite constituent) dual-phase steels, since void nucleation is suppressed in single-phase steels compared with dual-phase steels. However, in higher grade steels with a bainite single phase, a small amount of MA grains generally remains due to the chemical stability of MA. Therefore, further reduction of MA is key to improving Charpy energy for higher grade linepipe steels. In order to achieve high Charpy energy by MA formation control, the optimum conditions of the plate manufacturing process were investigated. As a result, a high Charpy energy was achieved by the combination of controlled rolling and precise control of the accelerated cooling conditions, by which the MA phase was minimized. Based on the above investigation, grade X80 high Charpy energy linepipes were trial-produced by applying JFE Steel’s optimized accelerated cooling (ACC) system with a high cooling rate and homogeneous temperature profile. Stable higher Charpy energy was achieved by minimizing MA formation and achieving a homogeneous microstructure by advanced cooling control.

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