Analysis on the causes of forging defects of titanium bar

Titanium bar and titanium alloy is an important metal structure material which rose in the 1950s. TC4 alloy is a+ lu titanium alloy which is widely used at home and abroad. Due to its high specific strength, good corrosion resistance and superior comprehensive performance, it is widely used in aerospace, chemical machinery, medical engineering and other industries. Common defects of TC4 alloy of titanium rod manufacturer include segregation and inclusion of alloy elements, residue of casting structure, embrittlement layer, hydrogen embrittlement, brittleness and forging crack, etc.

A unit found a 4.3mmx0.68mm crack on the surface of a product processed by TC4 titanium alloy bar during machining. In order to analyze the cause of the defect and avoid the occurrence of similar defects, various physical and chemical inspection methods were used to analyze the TC4 titanium alloy product.

TC4 bar change ring forging process are the two fire heating at 950 ° C, forging into bread, cake material flaring cyclization material, maybe it's because of the defect formation change caused by improper forging technology craze, it is possible that the bar itself exists the metallurgical defects such as inclusions, segregation, porosity, etc., and in the subsequent change caused by metallurgical defect in the process of forging cracking.

Through the theoretical calculation, it is concluded that the design of this set of special jig for the computer horizontal machine flyover fully conforms to the theoretical design requirements. So the author produced the actual object of this set of jig and installed it on the work table of vcentei-70 high precision CNC machining center for actual machining verification. Then the finished products of the processed horizontal machine flyover parts are put into the CMM for accurate measurement, and the Angle error of the two included angles is obtained within the range of 0.2° ~ 0.6°, which meets the technical requirements. Because this jig can be very convenient to quickly achieve the processing of the bridge parts positioning, and do not need to find through other ways, so it is suitable for the mass production of the bridge parts.

Combined with the left and right characteristics of the defect, it can be concluded that the defect is formed in the smelting process of oxidized titanium sponge. The weak oxidation melting of titanium sponge leads to the formation of low-density segregation defect area, and the serious oxidation melting of titanium sponge leads to the formation of oxygen-rich inclusion, which is a metallurgical defect. Defect area rich oxygen carbon and small amounts of nitrogen can make this area increased hardness and brittle, sometimes T ^ Al brittle phase formation, in the process of hot forging, the regional deformation ability and the coordinated ability is very poor, melting of thick sheet a and bright piece of hard to broken, organizational performance for bulky, also easy to produce cracks, is the larger defects on the material harm.

According to the smelting process, such defects are easy to appear at the bottom of the ingot, when the arc is melted, the instability of the arc current is easy to make the titanium sponge spread at the bottom oxidation and incomplete melting, the formation of inclusion and segregation zone, it is not easy to find out. In order to prevent damage to the product caused by this defect, the bottom of the ingot should be sawed off 6 to 8 percent of the nominal diameter.

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