Effects of Niobium on Microstructure and Hardness of Base Plate and Coarse Grained HAZ of High Strength X70 Grade UOE Linepipe Steel

2020 ◽  
Author(s):  
Taro Kizu ◽  
Ryutaro Sakai ◽  
Hiroshi Imoto ◽  
Shigeru Endo ◽  
Frank Barbaro
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Weld Zone ◽  
Low Carbon Steel ◽  
Coarse Grained ◽  
Microstructural Development ◽  
Chemical Compositions ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Niobium Content

Abstract The present study systematically evaluated base plates and Coarse Grained Heat Affected Zone (CGHAZ) properties of linepipe steels by using the controlled addition of increasing levels of niobium in a low carbon steel for comparison with other alloying combinations of Mn, Ni, Mo and V using laboratory melts and processed under simulated production conditions. The effects of niobium and other alloying elements on the mechanical properties and microstructural development, have been quantified with the intention of maintaining constant CGHAZ hardness in order that specific compositional effects can be directly compared. Characteristics of martensite and austenite (M-A) constituents in terms of size, shape and chemical composition has also been assessed. It is demonstrated that niobium additions up to 0.1 mass% in a low carbon steel design provide opportunities to improve pipeline mechanical properties, service performance and safety. For the CGHAZ, austenite grain size was limited as the niobium content increased. Weld HAZ microstructures were relatively similar with little influence of niobium content on MA character, although the hardness was noted to increase with increasing niobium content, which would be beneficial to ensure adequate resistance to weld zone softening. Bainite and small volume fractions of MA (nearly equal 2%) was a characteristic feature of CGHAZ of the materials having constant CGHAZ hardness, irrespective of chemical compositions examined. Other MA characteristics, such as size and cementite fraction, were also very similar among the steels.

Prediction of the Mechanical Properties of Hot-Rolled Low Carbon Steel Strips in Correlation to Chemical Compositions and Rolling Conditions

2011 ◽  
Vol 462-463 ◽  
pp. 401-406 ◽  
Author(s):  
Jiratthanakul Noppon ◽  
Somrerk Chandra-ambhorn
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Steel Strip ◽  
Low Carbon Steel ◽  
Chemical Compositions ◽  
Low Carbon ◽  
Coiling Temperature ◽  
Empirical Formulas ◽  
The Difference ◽  
Hot Rolled

Seven thousand sets of data consisting of mechanical properties, chemical compositions, and rolling parameters of industrial hot-rolled coils were analysed using multiple regression. This was to establish empirical formulas to predict mechanical properties of steel as a function of chemical compositions and rolling parameters. The empirical formulas predicting yield strength (YS), ultimate tensile strength (UTS) and percentage of elongation (EL) of low carbon steel strip were obtained, e.g. YS = 461+ 418 C + 61.6 Mn + 796 P ¬– 303 S + 159 Si + 146 Cu + 204 Ni + 49.7 Cr + 1127 V + 1072 Ti + 3674 Nb – 266 Mo – 6299 B – 76.3 Al – 557 Sn – 3.54 THK – 0.00758 WID – 0.114 FT – 0.223 CT. The rolling parameters in equation included finishing temperature (FT), coiling temperature (CT), thickness (THK) and width (WID) of strip. R-Square values for the formulas predicting YS, UTS, and EL were 82.3%, 90.1%, and 75.8% respectively. These equations were validated by using another 120 hot-rolled coils. The averages of absolute values of the difference between the predicted and actual values of YS, UTS, and EL were 9.6 MPa, 7.8 MPa, and 2.7 % respectively. Correlation of chemical compositions and rolling conditions with mechanical properties was discussed in the paper.

Effect of Niobium on the Microstructure and Mechanical Properties of Low Carbon Steel Plate with Intercritical Quenching

2010 ◽  
Vol 152-153 ◽  
pp. 1382-1386
Author(s):  
De Hui Zou ◽  
Zhi Fang Peng ◽  
Ping He Li ◽  
Ai Min Guo
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Low Temperature ◽  
Low Carbon Steel ◽  
Yield Ratio ◽  
Steel Plates ◽  
Low Carbon ◽  
Niobium Content ◽  
Microstructure And Mechanical Properties ◽  
Low Temperature Toughness

The microstructure and mechanical properties of the low carbon steel plates containing Niobium content of 0.038%, 0.063% and 0.082% with intercritical quenching were studied by SEM, TEM, tensile and impact tests. The results showed that the intercritical quenching steel with high Niobium content can gain the fine microstructure , but also easily obtain the martensite, which made the strength very high but low temperature toughness very low, however, the steel with low Niobium content can not reach enough austenitization level, which caused both low temperature and yield ratio high relatively. So in the given rolling and heat treatment process, there was suitable Niobium content can contribute to obtain the optimal austenization level resulting in the good combination of strength, yield ratio, elongation and low temperature toughness after intercritical quenching in the low carbon steel.

Microstructure and Mechanical Properties of Cooled and Tempered Cu and Nb-Bearing Ultra-Low Carbon Steels

2010 ◽  
Vol 638-642 ◽  
pp. 3242-3247 ◽  
Author(s):  
Hui Guo ◽  
Zhi Qiang Yao ◽  
Shan Wu Yang ◽  
Xin Lai He
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Low Carbon Steel ◽  
Carbon Steels ◽  
Steel Plates ◽  
Low Carbon ◽  
Niobium Content ◽  
Low Carbon Steels ◽  
Microstructure And Mechanical Properties ◽  
Ultra Low Carbon Steel

To improve the toughness and weldability, the carbon content of the steels has to be deduced, and more and more attention has been attracted to the low carbon and ultra-low carbon steels. To strengthen the microstructure Cu and Nb-bearing steels are developed. However, the knowledge on influence of combined addition of Cu and Nb is still in lack. The microstructure and mechanical properties are studied in the 6-mm thick as-rolled and tempered ultra-low carbon steel plates with varied copper and niobium content. The microstructure and mechanical properties are studied in the 6-mm thick as-rolled and tempered ultra-low carbon steel plates with varied copper and niobium content. The experimental results show that if niobium is added without copper, the increase of niobium addition does not have a significant influence on the phase transformation and mechanical properties before tempering. The strength and toughness of those copper-free niobium steels do not vary significantly after tempered at different temperatures, while the strength of niobium steels with 1.8% copper added increases after tempered in the range of 450-650°C and reaches a peak at 500-550°C. If combined with 1.8% copper, the increase of niobium addition from 0.08% to 0.16% improves the hardenabililty and strength significantly, and the strength peak after tempering moves to a lower temperature. The strength of air-cooled niobium steels with 1.8% copper added is usually higher than those water-cooled, while after tempered at a proper temperature, the strength of the latter becomes higher than the former.

Influence of laser surface hardened layer on mechanical properties of re-engineered low carbon steel sheet

2017 ◽  
Vol 685 ◽  
pp. 168-177 ◽  
Author(s):  
Badirujjaman Syed ◽  
Sulthan Mohiddin Shariff ◽  
Gadhe Padmanabham ◽  
Shaumik Lenka ◽  
Basudev Bhattacharya ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Steel Sheet ◽  
Low Carbon Steel ◽  
Hardened Layer ◽  
Laser Surface ◽  
Low Carbon ◽  
Carbon Steel Sheet ◽  
Surface Hardened Layer

Microstructure and Mechanical Properties of a Low-Carbon Steel Treated by One-Step Quenching and Partitioning Process

2014 ◽  
Vol 1082 ◽  
pp. 202-207 ◽  
Author(s):  
Shu Yan ◽  
Xiang Hua Liu
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Microstructural Evolution ◽  
Retained Austenite ◽  
Uniform Elongation ◽  
Low Carbon Steel ◽  
Total Elongation ◽  
Low Carbon ◽  
Quenching And Partitioning ◽  
Partitioning Time

A low carbon steel was treated by quenching and partitioning (Q&P) process, and a detailed characterization of the microstructural evolution and testing of mechanical properties were carried out. The resulted mechanical properties indicate that with the partitioning time increasing, the tensile strength decreases rapidly first and then remains stable, and the total elongation increases first then decreases. The investigated steel subjected to Q&P process exhibits excellent products of strength and elongation (17.8-20.6 GPa•%). The microstructural evolution of martensite matrix during the partitioning step was observed, and the morphology and content of retained austenite were characterized. The working hardening behavior of the samples was analyzed, and the retained austenite with higher carbon content contributes to the uniform elongation more effectively.

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