12Cr1MoV (manual arc welding) metallographic diagram

12Cr1MoV Is a type of weldable low and medium alloy steel, the corresponding American steel grades are A387 and SA537 Grade 11, and its Chinese grade is 12Cr1MoV, which is equivalent to ASTM A335 P11. 12Cr1MoV steel is mainly used for boiler and pressure vessels, as well as pipelines with elevated temperatures.

12Cr1MoV has good weldability and it can be welded by traditional welding methods such as manual arc welding, CO2 gas shielded welding, and plasma welding. It can also be welded with gas shielded tungsten arc welding, but preheating is required before welding. After that, the surface of the base metal should be cleaned and no oxide, impurities and coating should remain on the surface. During welding, the maximum allowable heat input is 0.95KJ/mm, and the maximum welding speed is 4mm/s.

After welding, the surface of the weld should be inspected by visual inspection and non-destructive testing. Moreover, for large-scale girth welds, the excess weld reinforcement should be removed. If a large residual heat affects the welding quality, then a coolant should be used to dissipate the heat after welding.

The macrostructure of 12Cr1MoV steel produced by manual arc welding has a large amount of ferrite content, and the grain size increases slightly with increasing welding current.

The microstructure consists of acicular ferrite, polygonal ferrite and small amounts of carbides. The carbide forms are mainly M3C, M7C3, M3C3 and MC type carbides. The addition of titanium and boron can change the proportion of polygonal ferrite, thereby increasing the impact toughness and fatigue strength of the weldment at the same time. At the same time, the microstructure also contains small amounts of oxides, sulfides and other non-metallic inclusions, which have an adverse effect on the performance of the weld.

The hardness of 12Cr1MoV steel produced by manual arc welding is generally not very high, the hardness of the welded part is about 200HV, and the hardness of the HAZ part is about 250HV. The hardness of the weld is lower, so the hardness needs to be improved during welding through preheating, post weld heat treatment and other treatment methods.

In conclusion, manual arc welding can be used to weld 12Cr1MoV steel, and the welding performance of the welded part reaches the requirements of the welded structure. The post-weld treatment can improve the service performance of the welded structure, such as impact toughness and fatigue strength.

12Cr1MoV weldments can be made by Manual Metal Arc (MMA) welding. The material itself is a low alloy steel which contains Chromium (Cr) and Molybdenum (Mo). It also contains 1.0 % Vanadium (V) which increases its creep properties when used at elevated temperatures. This type of material is widely used in power plants and chemical engineering due to its excellent resistance to corrosion, oxidation and creep.

The weldments of this material can be successfully made by using Manual Metal Arc (MMA) welding process. Manual Metal Arc welding uses a consumable electrode coated with flux along with an electrical current which is used to generate the arc. This process is also referred as shielded metal arc welding (SMAW) and stick welding. When welding this material, the welding parameters like current and voltage should be set accurately to obtain a quality weldment. The preparation of the joint requires that the joint is properly prepared and cleaned. Uneven surfaces should be grinded down to create a even weldment surface.

The use of too high current setting for welding this material can lead to the production of excessive heat which in turn causes welding defects such as cold cracks and warping. The correct welding temperature, heat input and travel speed should also be maintained to obtain a quality weldment.

The weld bead of the weldment can be inspected by macro-etch testing. This type of testing provides a better image of the weld structure and it is used to detect surface and sub-surface defects in the weldment. The micrograph and pictures of the weldment sample can also be taken to have better understanding of the weldment’s structure.

In conclusion, welding of 12Cr1MoV material can be done successfully by using Manual Metal Arc (MMA) welding process. The weldment should be accurately prepared and cleaned prior to welding for a quality weldment. Parameters like current, voltage, heat input and travel speed should be maintained to avoid any cold cracking and warping. To inspect the weldment, macro-etch testing and micrographs should be used to gain a better understanding of the weldment’s structure.