The welding of heat exchange tube and tubesheet is the key point of heat exchanger quality control.The goal of duplex stainless steel welding is to obtain the balance of ferrite(δ)and austenite(γ).The S32205 heat exchange tube and tubesheet specimens of Φ25 mm×2 mm were welded by manual TIG with Φ1.6 mm ER2209 and 0.54 kJ/mm heat input.After sampling and testing,the average thickness of fillet weld is 2.88 mm;average vickers hardness of weld 255.8 HV;According to ASTM E562,the average ferrite content of weld was 59.3%,tube side fusion line 57.3%,tube side HAZ 58%,plate side fusion line 58.7%,plate side HAZ 58.2%.According to ASTM A923 method A test,the phase boundary and grain boundary of the five zones were smooth,no harmful phase is precipitated,and assessed as unaffected metallographic structure.According to GB/T 4334 method E test,no intergranular corrosion phenomenon.The above test indicators are in line with the corresponding standards and technical agreement requirements,indicating that the welding process is applicable.
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