Metallographic cutting is the use of high-speed rotating sheet grinding wheel to intercept metallographic samples,which is widely used in metallographic laboratory cutting of various metal materials.Next,you will quickly understand the key points of gold cutting.
1.Determination of the sampling location:
Sampling is the first process in the preparation of metallographic samples.If the sampling is not appropriate,the purpose of inspection can not be achieved.Therefore,the parts,quantity,grinding surface direction of the samples should be carried out in strict accordance with the corresponding standards,so that the cut samples are representative.
Traditional steel selection generally follows these principles:
1)When observing the surface defects,such as grinding cracks,heat treatment cracks,etc.,select the outer surface of steel or steel products for metallographic sampling;
2)During the sampling inspection,the samples should be cut at both ends of the steel respectively;
3)In the analysis and detection of the ingot and billet,a longitudinal plane and two or three(both ends of the ingot or billet or upper,middle and lower)cross sections should be selected.For example,white spots of steel,segregation,subcutaneous bubbles,loose,residual shrinkage,intercrystalline cracks along the axis can be observed in cross section;the strip organization in steel can be observed in longitudinal samples.
In summary,the selected samples must be representative of the metallographic observations.
Generally speaking,for materials with low hardness,saw,car,plane and other processing methods can be used;for materials with high hardness,grinding wheel slicer cutting or electric spark cutting methods can be used.The specific cutting methods are:
1,the plasma arc cutting
A processing method in which the heat of high temperature plasma arc can melt the metal locally,and eliminates the molten metal by high speed plasma momentum.The depth of the deformation layer is about 1,500 mm.
2,the laser beam cutting
The energy released when the laser beam hits the surface to melt the piece and evaporate the piece for cutting purposes.The depth of the deformation layer is about 500mm.
3,Electric spark line cutting
Using continuously moving fine wire(called electrode wire)as the electrode,the workpiece is pulse spark discharge metal,cutting and forming.The depth of the deformation layer is about 50mm.
4,wet grinding wheel cutting
Cut with a high-speed rotating grinding wheel sheet.Including wet grinding wheel cutting,precision wet grinding wheel cutting.The wet grinding wheel cutting deformation layer depth is about 15mm,while the precision wet grinding wheel cutting can be as low as 5mm.
Wet grinding wheel cutting is the best cutting method for gold-phase test samples.Because the high pressure cooling water is added in the cutting process,it can prevent the damage caused by the surface overheating.And electric spark line cutting,saw or laser cutting and other ways will lead to poor material cutting quality.
Note:1.In order to better cut the sample,the workpiece must contact with the cutting sheet with the minimum contact surface.
2.The grinding wheel cutting sheet of the metallographic cutting machine should be selected according to the recommendation of the grinding wheel cutting machine manufacturer.