Titanium and titanium alloys are extremely important lightweight structural materials. They are widely used in aerospace, vehicle engineering, biomedicine and other fields, and have always been a hotspot in materials research. With the development of economy and technology, more and more applications of titanium plates have appeared, but the surface quality problems have become more prominent accordingly.
The surface defects of titanium plates are classified into two types: conventional defects and unconventional defects. The conventional defects are:
Cause: The guide plate, roller table, tools and rollers are not smooth, there are adhesions or angular burrs, etc., and the scratched surface is rolled; the operation is not careful, so that they collide with each other to form a scratched surface.
Measures: Before rolling, check the tools, guide plates, roller table and rollers, etc., and find the problem in a timely manner; clear the operation carefully, do not pull and bump.
- Metal indentation
Reason: The burr on the edge of the rolled product and the dross on the tail are pressed into the surface of the product.
Measures: Eliminate burrs and foreign objects on the surface of the slab in time. Cracked edges, cut off in time.
- Non-metallic indentation
Reasons: Poor environmental hygiene, dust and foreign objects fall on the surface of rolled parts; after pickling, cleaning is not clean.
Measures: Do a good job of sanitation, and remove the adhesion on the surface of the rolled piece in time.
- Pit pits
Reason: During pressing orthopedic annealing, there are dust and foreign objects on the surface of the pressing plate or the backing plate.
Measures: Remove the surface of the pressure plate and backing plate in time before entering the furnace.
- Roll marks
Cause: The surface of the roller is seriously worn, with pits, pits, scratches, etc.; the surface of the roller is pressed out of the pits by the plate corners.
Measures: If roll marks are found, it is necessary to sharpen or replace the rolls.
Unconventional defects are:
- Surface crack
Reasons: The incoming material is unqualified, the surface crack is not cleared, or the brittle getter layer of the incoming material is not cleared, and the reduction procedure is unreasonable, the pass processing rate is small, the pass is too much, or the pass processing rate is not evenly distributed.
Measures: Strictly control the surface quality of incoming materials, reasonably allocate the processing rate of passes, ensure uniform annealing temperature of the slab, and enhance rolling lubrication.
- Acid spots
Reason: One is that the residual acid is not rinsed out during pickling, and the board is dried. One is the uneven oxidation of the surface of the sheet during stacking annealing, resulting in inconsistent surface corrosion after pickling.
Measures: Pickling must be clean to ensure that there is no residual acid on the surface of the plate before drying; reduce the thickness of the stack to ensure that the plate is evenly annealed; sanding treatment can also be used to save the treatment later.