Grinding and polishing titanium alloy
Sanding: in painting, friction media such as sandpaper, pumice and fine stone powder are used to rub the coated object or film surface, which is called Sanding.Painting is an important step in the process, usually manual work, can also be used for air or electric equipment.Burnish runs through in whole besmear process, not only white billet, base or blow be bored with child to need burnish, also want burnish after besmear topcoat.Its function is to remove burr, floating rust, oil, dust on the surface of the substrate;Remove the coarse particles and impurities on the coating surface to obtain a smooth surface;The smooth coating surface should be polished to a certain roughness to enhance the adhesion of the coating.There are two types: dry sanding and wet sanding, which are lubricated with water or other wetting agents to give a smoother surface and wash away the powder.
Almost "polished".In fact, artificial is the same, the difference lies in the use of abrasive thickness, the smaller the number, the finer the particle size, the larger the number is thicker, 8000# is the most fine.Grind and polish the jade. Grind with the coarse size. The fine size polished jade is very bright.Polished glass, gem, jade, stainless steel, stone, can achieve mirror effect.
Polishing refers to the use of mechanical, chemical or electrochemical action, the workpiece surface roughness reduction, in order to obtain a bright, flat surface processing method.Is the use of polishing tools and abrasive particles or other polishing media on the workpiece surface modification processing.
Polishing does not improve the size or geometry of the workpiece, but is for the purpose of obtaining a smooth surface or mirror gloss, and is sometimes used to eliminate gloss (extinction).
The polishing wheel is usually used as a polishing tool.Polishing wheel is generally made of multilayer canvas, felt or leather, both sides are clamped with metal round plate, and its rim is coated with the polishing agent which is mixed evenly by micro powder abrasive and grease.
When polishing, the high-speed rotating polishing wheel (the circumference speed is more than 20 meters/second) is pressed to the workpiece, so that the abrasive produces rolling and micro-cutting on the workpiece surface, thus obtaining a bright processing surface, the surface roughness generally up to Ra: 0.63 ~ 0.01 micron;When non-grease matting polishes are used, bright surfaces can be matted to improve appearance.
Roller polishing is often used in mass production of bearing steel balls.
A large number of steel balls, lime and abrasive are put in the inclined canister drum during rough throwing. When the drum is rotating, steel balls and abrasive are made to roll and collide randomly in the drum to achieve the purpose of removing the surface convex edge and reducing the surface roughness. The residual of about 0.01 mm can be removed.
In the finishing process, the wooden barrel is filled with steel balls and pieces of fur.The polishing of precision linear ruler is carried out by immersing the processed surface in the polishing fluid, which is composed of chromium oxide powder with particle size of W5 ~ W0.5 and emulsion.
The polishing wheel is made of evenly fine degreased wood or specially made fine felt, and its movement track is a uniform dense network. The polished surface roughness is no more than Ra: 0.01 micron, and no surface defects can be observed under a microscope with a magnification of 40 times.In addition, there are electrolytic polishing and other methods.
Difficulties in grinding and polishing titanium alloy
The metallography sample preparation of titanium and titanium alloy is more difficult than that of steel. Its polishing and polishing efficiency is low. Excessive severe cutting and polishing process will produce deformation twins in alpha phase.
Cold inlay is more suitable for pure titanium than thermal pressure inlay, which may change the content and distribution of hydrogen in pure titanium.It is very difficult to remove scratch and plastic rheology of pure titanium during sample preparation.
Development of polishing technology for titanium alloy
Early mechanical polishing processes were time-consuming, and almost all mechanical polishing methods used a polishing fluid containing an erosive agent during the last or two steps of the polishing process.Electrolytic polishing method can often get a better polishing surface, but in the process of electrolytic polishing electrolyte has a certain risk, these electrolyte also has some role in chemical polishing.
In the 1970s and 1980s, the mechanical polishing methods of titanium and titanium alloys continued with the old polishing methods. Springer and Ahmed first published a paper on the polishing methods of titanium and titanium alloys in 1984.
This is the three-step method of sample polishing. Suppose the sample is polished with 320grit paper, but this may not always be the case.If the sample is cut with ultra-thin cutting pieces or the grinding wheel cutting pieces with suitable bonding strength, the cutting surface is smooth and the damage layer is minimal. In this case, 320grit paper can be used to finish the grinding process of the sample.If the cut surface is rough and the damage layer is large.For example, using a band saw to cut may result in the use of coarser sandpaper and the time required to remove the damaged layer.
The difference between manual polishing and mechanical polishing
1. Manual polishing requires experience. The strength, time and speed of the hand all require long-term experience to master these key parameters.For the novice, often impetuous, there are insufficient polishing or throwing over the first class problems.
2. The principle of mechanical polishing and manual polishing is consistent.Most of the domestic metallographic work is still based on manual polishing, manual polishing needs metallographic staff have greater patience, throwing over the need to repeat throwing, but as long as there is patience, many attempts and summary, can also get a good metallographic polishing effect, so need to seriously summarize experience, pay sweat will be harvested.