3.4 misunderstanding on titanium materials and titanium bike frames, here to clarify for you!
Misleading 3: The thicker the titanium alloy frame is welded, the more solder joints the more reliable.
Welding of metals is based on the principle that the contact point between metals can reach or even exceed the melting point instantaneously by using high heat energy so that the welding parts can be combined instantaneously.
Look at the table below to see the respective melting points of the three metals.
It can be said that the larger the welding area, the greater the heat demand for welding, excessive heat accumulation will change the arrangement of metal molecules, the change of the arrangement of metal molecules will produce the internal stress changes of metal. If the stress cannot be eliminated, the hardening and embrittlement of the welded surface will probably occur.
It seems a bit deep. To put it simply, the thermal effect and heat treatment of titanium and other metals are totally different. Welding at high melting point and completely anaerobic state must reduce the heat energy accumulation on the weld as much as possible. Only in this way can the stress of metal be reduced. So when welding, let the weld better fusion, do not pursue large area welding.
The practice has proved that the more complex welding, the more reinforced titanium frame, the greater the probability of problems. Of course, this is not absolute, some companies have advanced titanium alloy products heat treatment equipment, will reduce this risk through special heat treatment technology.
In order to add a point here, we must be alert that the grinding of welding scars (fish scales on the welded surface) can not eliminate the stress inside the metal. More grinding, especially on the welded joints of titanium alloys, may reduce the welding strength. This must be noted that it is better not to buy the grinding of welding scars when buying titanium frames.
Misleading 4:6-4ti frame is the best titanium frame.
Many people compare titanium frame with another material frame in general. They have love and hate. This is human nature.
In fact, it is necessary to classify the titanium frame first, just like the same steel frame, some are carbon steel, some are manganese steel, some are molybdenum steel, the price is also very different. Good steel frame also has ten thousand yuan grade, this is not a new topic. The same is true of aluminium frames. The price difference between the two frames will be quite striking due to the differences in aluminium alloy materials, frame manufacturers, models, manufacturing processes and surface treatment processes. The same is true of the titanium frame. There are hundreds of titanium frames passed by me in recent years. The price difference is still quite large. So it is not the same quality as a frame of similar material. We must talk about things separately.
There was a time when it was said that the 6-4 titanium frame was the best titanium frame. I've also asked about it. It turned out that this was not the case.
First of all, let's talk about 6-4 titanium alloy.
According to the national standard GB/T 3602.1-2007, the alloy brand TC4 is Ti-6Al-4V, the nominal chemical composition of Ti-6Al-4V titanium alloy, which is commonly known as 6-4 titanium. Aluminum (Al) and vanadium (V) components account for 5.5%-6.5% and 3.5%-4.5% respectively. The impurities of titanium and other elements are the remainder after 100% reduction of these two components.
The addition of two metals of this proportion in titanium makes titanium alloy have better mechanical properties, and its application scope is expanding. The biggest advantage is that the hardness is improved. The hardness of a bicycle made of this material is quite ideal.
However, in fact, no country in the world can produce 6-4 titanium alloy seamless tubes in large quantities. Rolling such seamless tubes requires several times more advanced equipment and technology than large steel mills. Undoubtedly, this restricts the production of 6-4 seamless tubes. This is also the reason why there are almost 6-4 seamless pipe materials in the world. (Pipes in some locations, such as five-way and head pipes, can be made into tubular shapes by means of a 6-4 titanium alloy bar middle punch truck, which is not counted here as tubing)
So why do people say that their frame is 6-4 titanium alloy? Why did several manufacturers stop producing 6-4 titanium alloy frame in Europe and America when it was noisy?
The reason is very simple. The forming process of those pipes is welded by coiled pipes (seamed pipes). How many cases of so-called 6-4 titanium tube frame cracking, what manufacturer happened and so on, I do not open up the topic. Everyone knows it's OK. Aluminum is inelastic, the proportion of adding is higher, more like the road feel of aluminum frame, which has been proved by practice.
In other words, 3-2.5 titanium alloy was developed about 30 years ago and is the best material for a bicycle frame. This has been proven by countless practices in the past, now and in the future.