By metallographic and hardness measurement shows that the cutter body by high strength after quenching, high frequency welding process in martensite with high hardness to Soxhlet size of pearlite and chunky ferritic low strength and hardness. In this transformation, the hardness and strength of the cutter body is greatly reduced. This shift is due to the cutter body high-frequency welding head, welding temperature is higher, generally 900 to 950 DEG C; this high temperature quenching after the knife body near the weld are normalized, resulting in the hardness, greatly reduced strength. From the crater near the area because of heat conduction welding, the region temperature, high temperature caused by tempering in the region, and also makes the area of strength, hardness decreased. The tool is used, the tool damage is also the most easy to appear in the welding position that the cutter body hardness welding, strength degradation is the tool Important cause of damage.

In order to find out the knife body first and then quenching on the cutter body causes high-frequency welding method of making hard alloy knife head has the above defects, we do the following test: first made the test to determine the shape and size of milling cutter, the test principle is easy to test metallographic sampling. The cemented carbide insert head at 900 DEG C the heating and cooling, the cutter head hardness does not change significantly.

cemented carbide insert in quenching, if the quenching medium is saline,cemented carbide insert and cracking due to rapid cooling; if the medium is oil, cooling, heating at 900 DEG C, cemented carbide insert without cracking. It is proved that the welding tool used in quenching, the knife should be used in alloy steel oil cooling can be hardened, but can not use oil quenching hard, carbon steel hardened to water, such as a knife body made of 45 steel or high carbon steel welding tool, after quenching, the knife body material should be changed into alloy steel.

In order to prevent the solder melting at the heating process of the cutter body position change welding, solder flow or the cutter head and the cutter, quenching temperature should not exceed 900 degrees, 850 degrees below the best quenching temperature. Most of the alloy steel are near 850 DEG C, and in general, high alloy steel quenching temperature is over 900 DEG C, so the whole appliance when quenching, the knife body material should be selected in small, high alloy steel, such as forming the previously mentioned flat drill, cutter body material is W18Cr4V, quenching temperature above 900 DEG C, the overall quenching cannot.

According to the above three, we first test for quenching cutter, cutter body materials, milling and quenching test before quenching after welding is the same as that of quenched from the knife body weld 1mm metallographic test, microstructure of martensite ferrite, hardness 52 ~ 54HRC metallographic cutter body quenching and when the cutter head weld hardness. Milling cutter, drill the whole quenching test and into the formal production and achieved good results.

Note that the whole milling cutter when quenching, the knife head is welded on the cutter body, and the cemented carbide hard and brittle, a little bump will cause the scrap off angle, quenching, tempering and sandblasting after all must be careful not to bump.With the overall quenching of the cutter, the hardness of the cutter body at the welding seam has been greatly improved compared with that of the original quenching tool.

Posted by: hannahgwendolyn at 09:23 AM | No Comments | Add Comment
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