Comparison of the Effects Metal Inert Gas and Laser Beam Welding on Duplex Stainless Steel Properties

In this study


‫المزدوج‬ ‫للصدأ‬ ‫المقاوم‬ ‫الفوالذ‬ ‫خصائص‬ ‫على‬ ‫بالليزر‬ ‫واللحام‬ ‫التقليدي‬ ‫اللحام‬ ‫تأثيرات‬ ‫مقارنة‬
Introduction reh e ehT In recent years, with the continuous expansion of the application fields of duplex stainless steel, the demand for welding technology has increased which has accelerated the development of welding technology there has been an ever increasing necessitate for investigates the constitute and approximately come to fractions of ferrite (α) and austenite (γ) phases, 50/50 by volume.This microstructure can be achieved by balancing the alloying elements, heat treatment and/or thermomechanical processes.The change in the balance of phases during the welding process can induce the material mechanical properties with the possible formation of intermetallic compounds [1].The quality of welded joints was assessed mainly metallographically (including optical microscopy).The consequences of ferrite content measurement in weld metal and in base metal show, that application of suitable post heat made possible to reduce the ferrite content in weld metal by 12 %.These results suggest that such a procedure leads to positive results [2].The weld zone area grows as laser power increases.By concentrating the laser beam, a higher ferrite/austenite ratio for the joint samples was produced.Furthermore, the biggest elongation from strength test has been observed for the joint samples prepared with laser power 2.0kW [3].Heat input affects straight on the cooling rate of the weld and there by ferrite-austenite ratio.Laser welding of duplex grades has been associated with excessively high ferrite contents, due to the low heat input and rapid cooling rate.The heat inputs can be modified by welding speed, focus point of laser beam and by additional materials.[4].Slight changes in duplex stainless steel composition exert a great effect on the mutual proportion of austenitic and ferritic phases [5].Due to the low heat input and rapid cooling rate, laser welding of duplex grades has been associated with excessively high ferrite contents.Insufficient time for adequate austenite reformation can result in considerable chromium nitride precipitation, which in turn may have a detrimental effect on toughness [7].Those also have twice of the yield strengths compared to that of austenitic grades while holding worthy ductility and toughness.The thermal expansion coefficient and the heat transfer properties of the DSS are intermediate between its constituent.The cost of duplex stainless is less sensitive to nickel price as it contains smaller amount of nickel compare to that of common austenitic stainless steel [8].In recent years, with the continuous expansion of the application fields of duplex stainless steel, the demand for welding technology has increased which has accelerated the development of welding technology there has been an ever increasing necessitate for investigates the constitute and approximately come to fractions of ferrite (α) and austenite (γ) phases, 50/50 by volume.This microstructure can be achieved by balancing the alloying elements, heat treatment and/or thermomechanical processes.The change in the balance of phases during the welding process can induce the material mechanical properties with the possible formation of intermetallic compounds [1].The quality of welded joints was assessed mainly metallographically (including optical microscopy).The consequences of ferrite content measurement in weld metal and in base metal show, that application of suitable post heat made possible to reduce the ferrite content in weld metal by 12 %.These results suggest that such a procedure leads to positive results [2].The weld zone area grows as laser power increases.By concentrating the laser beam, a higher ferrite/austenite ratio for the joint samples was produced.Furthermore, the biggest elongation from strength test has been observed for the joint samples prepared with laser power 2.0kW [3].Heat input affects straight on the cooling rate of the weld and there by ferrite-austenite ratio.Laser welding of duplex grades has been associated with excessively high ferrite contents, due to the low heat input and rapid cooling rate.The heat inputs can be modified by welding speed, focus point of laser beam and by additional materials.[4].Slight changes in duplex stainless steel composition exert a great effect on the mutual proportion of austenitic and ferritic phases [5].
Due to the low heat input and rapid cooling rate, laser welding of duplex grades has been associated with excessively high ferrite contents.Insufficient time for adequate austenite reformation can result in considerable chromium nitride precipitation, which in turn may have a detrimental effect on toughness [7].Those also have twice of the yield strengths compared to that of austenitic grades while holding worthy ductility and toughness.The thermal expansion coefficient and the heat transfer properties of the DSS are intermediate between its constituent.The cost of duplex stainless is less sensitive to nickel price as it contains smaller amount of nickel compare to that of common austenitic stainless steel [8].

Result and Discussion
The (MIG) and (LB) welding process revealed no visible welding flaws, such as porosity, undercuts, outside cracks, incompetent penetration, a lack of fusion, when using MIG welding parameters as following ranges; 85A, 45V and 26cm/min and 98%Ar, 2% CO2 and used filler metal ER2209 was found to be the good result, simultaneously, when used 5kW of laser power, welding speed at 0.75/min and shielding gas argon was found to be a good result of the laser parameters.The structure of 2507 duplex stainless steel is composed of ferrite (α) phase (dark region) and austenite (γ) phase, the austenite is distributed on the ferrite matrix and is distributed in strips as white phase the interface between the austenite and ferrite is not smooth when observed at higher magnification, but is jagged, which shows that during the cooling process after cooling, austenite is formed by nucleation and growth at the ferrite interface as shown in Figure 1.The (MIG) and (LB) welding process revealed no visible welding flaws, such as porosity, undercuts, outside cracks, incompetent penetration, a lack of fusion, when using MIG welding parameters as following ranges; 85A, 45V and 26cm/min and 98%Ar, 2% CO2 and used filler metal ER2209 was found to be the good result, simultaneously, when used 5kW of laser power, welding speed at 0.75/min and shielding gas argon was found to be a good result of the laser parameters.The structure of 2507 duplex stainless steel is composed of ferrite (α) phase (dark region) and austenite (γ) phase, the austenite is distributed on the ferrite matrix and is distributed in strips as white phase the interface between the austenite and ferrite is not smooth when observed at higher magnification, but is jagged, which shows that during the cooling process after cooling, austenite is formed by nucleation and growth at the ferrite interface as shown in Figure 1.Ferrite and austenite phases are seen in micrographs of welding fusion zones (FZ), but in the MIG welding zone, the filler is affected in these amounts by consisting of a ferrite phase rather than an austenite phase are given in Figures 2. On the other hand, the microstructure of the welds increscent austenite (γ) to the leaser welding is mainly composed of acicular ferrite with abundant dispersion of on microstructure of fusion zone, its grain size is finer observed in LB than MIG welds in HAZ.As a results as solidification of 2507duplex stainless steel, the low heat input associated with high cooling rate 12 leads to form a microstructure with a higher volume fraction of austenite than ferrite.On the other hand, the low heat input associated with high cooling rate leads to form a microstructure with a higher volume fraction of austenite than ferrite.The small volume fraction of ferrite presented here should be from inhibiting ferrite to austenite transformation due to this last condition.Ferrite content in all welds of tested variants is higher in the root zone of penetration runs, as compared to surface and center.This is perhaps related to the fact that the root area was heated less than the surface during post-heat treatment runs and the root was shielded with the Ar gas [ 6 ].  .1 shown the composition obtained from EDX microscopic analysis of the main alloying element for the base metal, MIG and LB welds of BM microstructure has slightly different structure in welding bool area zone (fusion zones (FZ) in MIG welded suggesting the filler changing the amount of Fe element in chemical composition and C are Carbone was apparent in composition which caused brittleness by presented some amount of ferrite rather than austenite phase.The primary solidification of the used duplex stainless steel occurs as delta ferrite and that the structure is completely ferritic at completion of solidification.[9].Table 1: EDX microanalysis of used 2507DSS for the base metal, MIG and LB welds at (FZ) Figure 4 shown as a micro hardness of (BM, HAZ and WM) of both MIG and laser welded joints both welding processes exhibit similar profiles.The hardness profiles reveals that there is no significant difference between hardness of BM and that of WM or HAZ (i.e.265, 289) regardless of welding process, inspite of variation in ferrite/austenite ratio.Suggestions as hardness of 2507DSS, in general, are not remarkably affected by such variation.

Conclusion
The results obtained from present study are as follows: 1. Microstructure of fusion zone, its grain size is finer observed in LB than MIG welds in HAZ A microstructure with a greater volume proportion of austenite than ferrite is formed as a result of the 2507duplex stainless steel's solidification due to the low heat input and rapid cooling.2. The microstructure observed that columnar regular structure appears in case of laser beam welding without additional material.The quantity of fine dispersed austenite island (light) inside of ferrite grains (darken) matrix increased.
3. The balance between ferrite/austenite in the MIG welding metal is closer from the balance of the base metal and compared to the laser welding process.4. The hardness profiles reveals that there is no significant difference between hardness of MIG and LB in the welding bool area zone were equaled (265-289Hv) respectively.

Fig 1 :
Fig 1: Microstructure of base metal of 2507 duplex stainless steel

Fig 2 :
Fig 2: Heat affected zone microstructures of samples joined by (a) MIG (b) LB Microchemical Analysis Balanced composite compound microanalysis 2507DSS.Figures. 3 and Table.1 shown the composition obtained from EDX microscopic analysis of the main alloying element for the base metal, MIG and LB welds of BM microstructure has slightly different structure in welding bool area zone (fusion zones (FZ) in MIG welded suggesting the filler changing the amount of Fe element in chemical composition and C are Carbone was apparent in composition which caused brittleness by presented some amount of ferrite rather than austenite phase.The primary solidification of the used duplex stainless steel occurs as delta ferrite and that the structure is completely ferritic at completion of solidification.[9].Table1: EDX microanalysis of used 2507DSS for the base metal, MIG and LB welds at (FZ)

Fig 3 :
Fig 3: EDX microanalysis of (a) MIG and (b) LB welding Comparisons of the promoting elements for the presence of ferrite phases in the weld metal, which are represented by the elements of chromium and manganese (Cr, Mn), which help in the formation of austenite in the MIG welding are given in Table1and Figures 4a.It is highest percentage of nickel and manganese (Ni, Mn) element compared to the laser welding process as in Figure 4b.It can be concluded that the balance between ferrite/austenite in the MIG welding metal is closer from the balance of the base metal and

Fig 4 :
Fig 4: Hardness profiles of WM, HAZ and BM of MIG and laser welded jointsThe Figure5and Table2 representation the tensile results of MIG and LB welding on different samples.It is observed the tensile strength and ductility at samples welded with MIG and laser beam welding were increased in the HAZ as a Good detected of homogeneous weld metal samples where laser welded specimens had the highest ductility and strength.

Fig 5 :
Fig 5: Tensile properties of BM, MIG and laser welded joints together with those of standard 2507DSS

Table : 2
Tensile of 2507DSS for the base metal MIG and LB welded joints

α FN γ HAZ α γ
5. The autogenously laser welded specimens had the highest ductility and strength. .No big differences were observed in tensile strength