Comparison of Chinese and Foreign Titanium Alloys

    We mentioned in the previous article that the grade of titanium alloy is actually not that mysterious. TA, TB, TC, understand the initial letters, and you can first judge which category it probably belongs to. Today I will continue to talk about a more heady problem. The same titanium alloy, why is it called TC4 by the Chinese, Grade 5 by the Americans, Ti-6Al-4V by the international community, and the Russians are also called А-6? What kind of "charades" are these engineers playing?

I. A dialect chaos of "material language"
    Imagine this procurement site. The Chinese engineer asked, "Has this TC4 arrived yet?" The American supplier replied, "Grade 5? No problem, it will be shipped next week." The German customer wrote in the email, "Wir brauchen Ti-6Al-4V." Meaning, we need Ti-6Al-4V. The Russian colleague added another sentence: "BT6, д а?" Means, VT6, right? What the four people said is likely to be the same classic titanium alloy. But it sounds like decrypting a telegram. It's not someone who misremembered. But different countries, different standard systems, have different "material languages". Today we will put these sets of "dialects" on the table to see how to match them.

II. Chinese team, GB standard, logical classification school
    The common grades of titanium and titanium alloys in China are the easiest to understand first. The basic rule is:T, for titanium; A/B/C for approximate type; The following number indicates the serial number or system number of the grade.
Something like:TA2, common industrial pure titanium; TC4, typical α β titanium alloy;  TC11, one of the common heat-resistant titanium alloys.
    The advantage of this set of nomenclature is that the classification is clear. When you see TA, you probably know that it is partial to titanium, corrosion resistant and stable. When you see TC, you probably know that it is partial to comprehensive performance and engineering applications. The drawbacks are also obvious. If foreign engineers are not familiar with Chinese standards, they may not know which titanium alloy you are talking about when they see TC4. Therefore, when it comes to international trade, drawing conversion, and procurement acceptance, "translation" is required.

III. Team USA, ASTM/AMS standard, numbering faction
    In the American system, the most common is the Grade number. Grade 1, Grade 2, Grade 5, simply Gr1, Gr2, Gr5. Of which:
    Grade 1, which often corresponds to high-purity industrial pure titanium;
    Grade 2, which is a very widely used industrial pure titanium; 
    Grade 5 is the famous Ti-6Al-4V.
    In the Chinese context, Grade 5 usually corresponds to TC4. The United States also has a set of UNS numbers, the full name is Unified Numbering System, Unified Numbering System. For example, Ti-6Al-4V/Grade 5 common UNS number is R56400. UNS numbers are more like "file numbers" for materials, often appearing in standards, warranties, and engineering documents. The advantage of this system in the United States is that it has a high degree of international commonality. ASTM and AMS standards are often cited especially in, medical, chemical equipment, and international procurement. The downside is that it's less intuitive. Why TC4 corresponds to Grade 5? There is no logic that is particularly easy to remember. It was in that standard system that it was compiled into this number.

IV. International common writing method, speak according to the composition
    There is also the most straightforward way to write it, which is to write the main elements directly. For example: Ti-6Al-4V. These few characters have made the main components clear:
    Ti, titanium;
    6Al, approximately 6% aluminium;
    4V, approximately 4% vanadium.
    Another example is Ti-3Al-2.5 V, the meaning is also very intuitive. It contains about 3% aluminum, 2.5% vanadium, and the rest is mainly titanium. The advantage of this writing is transparency. People who know a little about element symbols can know at a glance what is probably added to it. The downside is that the name is longer. When engineers communicate verbally, they still prefer to say short names such as TC4 and Gr5. So you will see a very interesting phenomenon: Ti-6Al-4V is often used when writing papers, standards, and technical materials. In factory site, procurement communication, and industry oral communication, everyone prefers to talk about TC4 or Gr5.

V. Russian team, GOST standard, self-contained school
    Russia and the former Soviet Union are important forces in the world's titanium industry. They have their own GOST standard system, and their titanium alloy grades are also of their own. Common beginnings include the northern version, which is also often transcribed as VT. Something like: 
    BT1-0, common industrial pure titanium grades; 
    BT6, the same is true for classic titanium alloys such as Ti-6Al-4V, which corresponds roughly to Ti-6Al-4V;
    BT8, is one of the common heat-resistant titanium alloys.
    The Russian system is characterized by a long history, strong military industry and color. The disadvantage is that for Chinese, American and European engineers, it is difficult to directly correspond without looking up the table. Therefore, as long as Russian materials, import substitution, and old model equipment maintenance are involved, one thing is often encountered: don't rush to talk about performance, and translate the brand name clearly first.

VI. A table to understand common "multi-national dialects"
    The following table is only for introductory reference. When engineering use, be sure to go back to specific standards and technical protocols.

    There is a special explanation here. "Corresponding" is not equal to "exactly the same". Different national standards may have different requirements for element range, impurity control, mechanical properties, heat treatment status, and testing. Therefore, the form can only help you get started with identification, and cannot directly replace project acceptance.

VII. Why are there so many "dialects"?
    The reason is simple and realistic. Standards don't fall from the sky. It is the result of a national industrial system. The titanium industry in the United States started early and has mature medical applications, so ASTM and AMS standards have a great impact on international trade. The former Soviet Union and Russia had strong demand for military industry, as well as their own resources and production systems, so they formed an independent serial system. China's titanium industry learned from the Soviet system in the early days, and later continued to connect with international standards. At the same time, it produced its own domestic high-end titanium alloys. So there is today's situation. The same or similar material will have different names in different systems. Just like a person has a Chinese name, an English name, an ID number and a unit number. You can't say which name is wrong. But you need to know which name to use on what occasion.

VIII. When buying materials, I am most afraid of only looking at the name
    Finally, a reminder to non-professional readers and material purchasers. Grade is only the first step. There are many details that really determine whether the material can be used or not. For example, also speaking of TC4, the following information is very important: 
which standards are implemented; 
    the range of chemical composition; 
    To what level of interstitial elements such as oxygen, nitrogen, and hydrogen are controlled;  whether it is bar, plate, forging or powder; 
    Whether it is annealed or solution-aged; 
    Whether there are reports on ultrasonic testing, flaw detection and mechanical properties; 
    Used in, medical or ordinary industrial scenarios.
    Even if it is the same TC4, there is a difference between ordinary TC4 and TC4 ELI. ELI is Extra Low Interstitial, which means Ultra Low Gap Element. By controlling interstitial elements such as oxygen, nitrogen, and carbon, it makes materials more suitable for high-safety scenarios in terms of toughness and biocompatibility, such as medical implants. Therefore, when buying titanium alloy, you can't just say "I want TC4". A more professional question would be: What standard TC4 do I want? What form? What state? What testing requirements? What scenario is it used in? This is the real engineering language.

IX. Remember three sentences today
    First, the same titanium alloy may have multiple names in different countries and standard systems.

    Second, TC4, Ti-6Al-4V, and Grade 5 often refer to the same classic titanium alloy, but the engineering still depends on the standard rules.

    Third, the grade comparison table can only help you "recognize people", and cannot complete material acceptance for you.

    The Smash Bros. of titanium alloy grades are not chaos in essence. It is a language trace left by different industrial systems. Only by reading these "dialects" can you truly understand the communication rules of the material world.