Talking about the common failure analysis on the surface quality of titanium plate products
Titanium plate has excellent performance, high specific strength, good medium temperature performance, non-magnetic and other advantages, and it is widely used in civilian fields. In the production, we found that the surface quality of titanium plate products are common faults
There are several kinds of corrosion, dusting, unremoved oxide scale and streaky mottling.
1. Over-corrosion: Over-corrosion refers to the appearance of pits or uneven defects on the surface of the titanium plate after pickling, which is different from the material structure. -Generally, the cause of over-corrosion defects is the imbalance of the ratio of hydrofluoric acid and nitric acid. Too high concentration of hydrofluoric acid or insufficient concentration of nitric acid can cause this defect. Another reason is that the pickling time is too long. It is 1mm ~ 4min, and the process parameters can be adjusted according to the operation site to appropriately shorten the pickling time.
2. Hanging ash: Hanging ash refers to the oxide attached to the surface of the titanium plate after pickling. During the pickling, the dry titanium alloy and the acid liquid undergo a chemical reaction, and the generated oxide accumulates on the surface, preventing the reaction from proceeding.
One step occurs. The defects of ash hanging are generally caused by excessive ash deposition during pickling and insufficient washing after pickling. During pickling, the parts should be shaken constantly to make the reacted product fall off the surface of the titanium alloy. After pickling, spraying or washing should be strengthened to remove the ash. Our country generally adopts the water flow of compressed air and tap water to wash the parts, and the effect is good.
3. The oxide scale is not removed: There are many reasons for this defect, and all processes are possible. It is possible that the oil removal is not good, or the molten salt treatment time is not enough, or the pickling solution is invalid. When this defect occurs, all possible factors should be eliminated one by one, and when necessary, sandblasting can be added to the pre-treatment.
4. Striped mottling: The cause of this defect is generally due to uneven reaction. It can be eliminated by moving parts during pickling and lowering the temperature of the pickling liquid. In addition to the above shortcomings
Sometimes it is found that the titanium plate products that have passed the inspection after pickling will have mottling on the surface after a period of time. There are relatively few studies on this phenomenon. It may be caused by the presence of residual acid on the surface after pickling or the presence of corrosive media brought in by subsequent production. The difference, generally speaking, does not affect its performance, and can be removed by pickling again, but the stressed parts should be strengthened to remove hydrogen after the second pickling.
