If the steel plate with high hardness is used for “printing with a planeâ€, if it is not ground, it will cause the edges of the pattern to be rough and have a large amount of residual ink after plate printing. Grinding by hand is a chore.
The author has solved this problem by combining electrolytic polishing technology with the electrolysis grinding principle.
The principle of electrolytic grinding is to place steel parts in a specific electrolyte and energize them to form a thin oxide film on the surface. The surface hardness immediately drops, and it can be easily ground, and then oxidized and then ground to make oxidation. The grinding proceeds synchronously until it is satisfied.
As a non-specialized processing enterprise, it is not possible to invest heavily in the purchase of electrolytic grinding machine tools. However, the use of electrolytic grinding wheels alone is not suitable for manual grinding of flat steel plates due to its bowl shape. Therefore, you have to make your own block. There are three ways to make it.
1. A 1:1 blend (volume ratio) of the resin composition and corundum was added, and a curing agent was added. The cast was cast on an iron plate having a thickness of 5 mm and an area of ​​150 mm×300 mm. After solidification, a diamond milling cutter is used to regularly slot the groove in a certain geometric shape so that it can see the iron bottom so as to achieve the purpose of circulation of the electrolyte and conduction. Then level with a surface grinder.
2. The square strips or ladder strips of the whetstone were adhered regularly, at regular intervals, to an iron plate of 300 mm×150 mm in thickness and 5 mm in thickness, pressed with a thick flat glass, and set aside for use.
3. Graphite plates are used as electrolytic grinding blocks because of their dual role of electrolytic grinding and EDM grinding, so their speed is extremely fast. But it is also easy to wear, so it is necessary to always trim
Grinding electrolyte formula:
NaNO2 9.6%
NaNO3 0.3%
NaHPO4 0.3%
K2Cr2O7 0.1%
The current density is 5 to 10 A/cm2. The solution does not corrode the device at room temperature.
Operation: Put the grinding block facing up--in the pot welded by the PVC plate, connect the cathode of the rectifier. The electrolyte was poured so that the liquid surface was parallel to the surface of the grinding block and was about 1 mm higher. Adjust the four corners of the block to achieve parallelism. Put the steel plate to be ground into a fixture made of PVC plate, and connect the anode of the rectifier to face the grinding block. When the rectifier is turned on and the steel plate moves back and forth, the voltage is increased step by step, and after the current is increased to a predetermined value, the steel plate moves randomly. At this time, the oxide film is formed and the oxide film is removed simultaneously. Then, gradually reduce the voltage and stop the power supply. Grind a few more times and then take out the observation. If you do not meet the requirements, repeat the steps until you are satisfied. The ideal result is: a gray surface, a fine silky texture, a delicate touch, and mechanical scratches that disappear when flattened.
Electrolytic polishing is the principle of electrochemical anodic dissolution: the workpiece (anode) is placed in an extremely thick electrolyte. Due to the difference in resistance between the two poles, the resistance at the bulge is low and the current density is high. This process continues until the surface is leveled to achieve a bright effect.
formula:
H3PO4 70%
H2SO4 20%
The rest is water
Temperature: 60～70°C
Current density: 30 A/dm2
Time: 1～2 min
Cathode: Lead
Operation: Pour the measured water first into the trough, and then pour the two acids. Stir and measure the specific gravity. Normally it should be between 1.69 and 1.70. Warm to 60°C. The ground steel plate was placed in a fixture made of PVC hard board. Pick up the positive pole and hang people slot. Facing cathode lead plate, power on.
Precautions:
1. Rising during electrolysis; liquid temperature will automatically
2. Do not bring water to people's tanks easily. The specific gravity of the solution must be between 1.69 and 1.7.
3. When mounting, the surface of the steel plate should be in the same plane as the fixture surface. The surface of the steel plate should not be lower than the jig surface, otherwise the edges will not be bright. The surface of the steel plate should not be higher than the clamp surface, otherwise the edge effect is serious;
4. When the distance between poles is more than 30mm, during electrolysis, do not move the workpiece and let it stand still.
The final effect: the workpiece is semi-bright silver gray, observed under the microscope, fine grain. The entire surface is free of any mechanical scratches and feels smooth.
The surface of steel plates produced by Sino-foreign joint ventures are all in this state, and the surface treatment process is roughly the same.