Chemical composition of industrial pure titanium and its brands

Titanium is a polycrystalline metal. Below 882 ℃, it is a crystal form. Its atomic structure is a close packed hexagonal lattice. From 882 ℃ to the melting point, it is B crystal form and a body centered cubic lattice. Industrial pure titanium presents a phase in the metallographic structure. If the annealing is complete, it is an equiaxed single lattice with basically equal size. Due to the existence of impurities, there is also a small amount of B phase in industrial pure titanium. It is basically distributed along the grain boundary.

Industrial pure titanium according to GB / t3620 There are nine brands in the new standard of ta1-2007, three of TA1 and two of ta2-ta4. The difference between them is the purity.

From the table, we can see that from TA1 to TA4, each brand has a brand with suffix Eli, which is the abbreviation of low gap element in English, that is, high purity.

Because Fe, C, N, h and O exist as interstitial elements in a-ti, their content has a great impact on the corrosion resistance and mechanical properties of industrial pure titanium. The solid solution of C, N and O in titanium can greatly distort the lattice of titanium and make titanium strongly strengthened and brittle. The existence of these impurities is brought in by raw materials in the production process, mainly the quality of sponge titanium. If you want to produce high-purity industrial pure titanium ingot, you have to use high-purity sponge titanium.

In the standard, the brand with Eli has the highest content of these six elements, which is lower than the brand without Eli. The revision of these standards is based on the international or Western standards (our national standards are trying to move closer to the western countries, because many basic industries in our country are still behind them, and many old standards follow the former Soviet Union). In particular, in terms of impurity content and room temperature mechanical properties, the indexes of various brands are basically consistent with those in the international and Western countries. This new standard mainly refers to ISO (International Standard) surgical implants and American ASTM material standards (b265, B338, b348, b381, b861, b862 and b863). It also corresponds to ISO and ASTM standards in the United States. For example, TA1 corresponds to GR1, TA2 corresponds to Gr2, TA3 corresponds to GR3, and TA4 corresponds to GR4. This is conducive to clarifying the reference of national standards in material selection and application in various industries, and is also conducive to international exchanges in technology and commerce.

There are two problems worthy of attention on this new standard pure titanium watch. One is GB / t3620 And GB t36201-1994 1-2007 in contrast, the original TA0 is changed to TA1, the original TA1 is changed to TA2, the original TA2 is changed to TA3, the original TA3 is changed to TA4, and the original TA4 is changed to ta28. Second, with the increase of brand number, the content of these five impurity elements is also increasing, which means that the strength increases and the plasticity decreases gradually. It should also be noted here that Fe exists as an impurity, not deliberately added as an alloy element. From GB / t3620 1-2007 standard, we can see that the content of TA1 ~ TA4 impurity elements increases gradually, but the increment of Fe and O is obvious, and the increase of C, N and H is not obvious.

Industrial pure titanium is different from chemical pure titanium. Chemical pure titanium is used for scientific research on some characteristics of pure metal in scientific research institutions. Industrial pure titanium is a material directly applied in various industries. At the same time, it contains more of the above five impurities than chemical pure titanium. The characteristics of industrial pure titanium are that it has low strength, good plasticity, easy processing and molding, and can be stamped, Welding and machining performance are also good, and it has good corrosion resistance in various oxidation and corrosion environments. Therefore, more than 70% of the plate is industrial pure titanium, which is mainly used in the processing and forming of reaction kettle and pressure vessel in the chemical industry. Among these pure titanium brands, TA1 is the most widely used, followed by TA2. When it comes to industrial pure titanium, one thing we must make clear is that industrial pure titanium cannot improve its strength by heat treatment. If the mechanical properties of a batch of pure titanium are low, don’t fantasize about how to deal with it to make it qualified, it’s in vain.