Microstructure and Properties of Surface-Modified Plates and Their Welded Joints

Area of Science:

• Materials Science
• Metallurgical Engineering
• Corrosion Science

Background:

• Q235 low carbon steel has limitations in certain industrial applications.
• Surface modification and welding are crucial for enhancing material properties.
• 304 stainless steel offers improved characteristics over carbon steel.

Purpose of the Study:

• To improve the properties of Q235 low carbon steel through surface modification.
• To evaluate the performance of surface-modified Q235 steel after keyhole tungsten inert gas (K-TIG) welding.
• To analyze the microstructure, hardness, and corrosion resistance of the modified material and welded joints.

Main Methods:

• Surface modification of Q235 steel using metal inert-gas welding (MIG) with 304 stainless steel.
• Welding of surface-modified plates using keyhole tungsten inert gas (K-TIG) welding.
• Microstructural analysis, elemental distribution, micro-hardness testing, and electrochemical corrosion tests.
• Hydrochloric acid immersion tests and surface morphology studies after corrosion.

Main Results:

• Defect-free surface-modified plates and welded joints were achieved.
• The surfacing layer microstructure comprised austenite, martensite, and ferrite; the weld microstructure was predominantly martensite.
• The surfacing layer exhibited superior hardness and corrosion resistance compared to Q235 base steel.
• The weld's micro-hardness exceeded that of the surfacing layer and base material.
• The surfacing layer demonstrated the best corrosion resistance, with the weld also outperforming the base material.

Conclusions:

• Surface modification of Q235 steel with 304 stainless steel via MIG welding significantly enhances its properties.
• Subsequent K-TIG welding produces defect-free joints with improved hardness and corrosion resistance.
• The combined approach offers a viable method for improving the performance of Q235 steel in demanding applications.