scholarly journals Metallurgical Effects of Niobium and Molybdenum on Heat-Affected Zone Toughness in Low-Carbon Steel

2019 ◽  
Vol 9 (9) ◽  
pp. 1847 ◽  
Author(s):  
Hardy Mohrbacher
Keyword(s):  
Heat Treatment ◽  
Heat Affected Zone ◽  
High Strength ◽  
Post Weld Heat Treatment ◽  
Coarse Grained ◽  
Accelerated Cooling ◽  
Low Carbon ◽  
Structural Applications ◽  
Steel Grades ◽  
Weld Heat

Modern weldable high strength steel grades are typically based on low-carbon alloy concepts using microalloying for obtaining a good strength-toughness balance. Such steel grades having a yield strength in the range of 420 to 690 MPa are very commonly used in pipelines, heavy vehicles, shipbuilding and general structural applications. Thermomechanical processing during hot rolling combined with accelerated cooling is an established means of producing such steel grades. Considering the alloying concepts, the use of niobium and molybdenum, and in selected cases boron, is very efficient to achieve high strength and good toughness. However, all targeted applications of such high strength steels involve extensive welding. Thus, heat affected zone properties are of particular importance. The present paper investigates the effects of Nb, Mo and Ti on the heat affected zone properties. Variations of the Mn and Si contents are considered as well. Additionally, the influence of post-weld heat treatment in the coarse-grained heat-affected zone (HAZ) is considered. In this approach, HAZ subzones were generated using laboratory weld cycle simulations in combination with systematic variation of alloying elements to scrutinize and interpret their specific effects. The results indicate that Mo and Nb, when alloyed in the typical range, provide excellent HAZ toughness and guarantee sufficiently low ductile-to-brittle transition temperature. An alloy combination of Nb, Mo and Ti improves performance under hot deformation conditions and toughness after post-weld heat treatment.

Effect of Post-Weld Heat Treatment on Carbide Precipitation and Impact Properties of Coarse-Grained Heat-Affected Zone of Q690 Steel

2014 ◽  
Vol 989-994 ◽  
pp. 576-580 ◽  
Author(s):  
Zhen Shun Li ◽  
Sheng Li Li ◽  
Lei Tian ◽  
Xiang Hai Zhang ◽  
Ji Zhi Liu
Keyword(s):  
Heat Treatment ◽  
Grain Boundaries ◽  
Heat Affected Zone ◽  
Unit Area ◽  
Carbide Precipitation ◽  
Post Weld Heat Treatment ◽  
Coarse Grained ◽  
Impact Properties ◽  
Carbide Particles ◽  
Weld Heat

The effect of post-weld heat treatment (PWHT) on carbide precipitation and impact properties of coarse-grained heat-affected zone (CGHAZ) of Q690 Steel was studied in this paper. Carbide particles precipitated primarily at prior austenite grain boundaries and martensitic lath boundaries. When the PWHT temperature is 520–570 °C, temper embrittlement occurs. This temperature range is also where the number of carbide particles per unit area at grain boundaries reaches its maximum. The high number of particles per unit area increases the rate of crack initiation at grain boundaries under rapid loading; linking of microcracks along grain boundaries which are already weakened by impurity segregation results in TE and intergranular fracture.

scholarly journals Performance Evaluation of the Effects of Post Weld Heat Treatment on the Microstructure, Mechanical and Corrosion Potentials of Low Carbon Steel

2019 ◽  
Vol 44 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Isiaka Oluwole Oladele ◽  
Davies Babatunde Alonge ◽  
Timothy Olakunle Betiku ◽  
Emmanuel Ohiomomo Igbafen ◽  
Benjamin Omotayo Adewuyi
Keyword(s):  
Heat Treatment ◽  
Carbon Steel ◽  
Low Carbon Steel ◽  
Welding Process ◽  
Post Weld Heat Treatment ◽  
Welding Parameters ◽  
Low Carbon ◽  
Corrosion Properties ◽  
Mechanical And Corrosion Properties ◽  
Weld Heat

The effect of Post Weld Heat Treatment (PWHT) on the microstructure, mechanical and corrosion properties of low carbon steel have been investigated. The welding process was conducted on butt joint using Manual Metal Arc Welding (MMAW) techniques at a welding voltage of 23 V and welding current of 110 A with the use of E6013 and 3.2 mm diameter as filler material. Heat treatment through full annealing was carried out on the welded low carbon steel. The mechanical properties (hardness, impact toughness and tensile properties) of the AW and PWHT samples were determined. The microstructure of the AW and PWHT samples was characterized by means of an optical microscopy. Corrosion behavior of the sample was studied in3.5 wt.% NaCl environment using potentiodynamic polarization method. The results showed that the AW samples has good combination of mechanical and corrosion properties. The microstructure revealed fine grains of pearlite randomly dispersed in the ferrite for the AW base metal (BM) sample while agglomerated and fine particle of epsilon carbide or cementite randomly dispersed on the ferritic phase of the heat affected zone (HAZ) and weld metal (WM), of the AW, respectively. The PWHT samples shows that the annealing process allow diffusion and growth of the fine grains into partial coarse grains of ferrite and pearlite which did not encourage improvement of the properties. Therefore, it was concluded that the welding parameters put in place during welding of the low carbon steel are optimum for quality weld.

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