Titanium alloy fasteners have many advantages. How to determine whether a screw is made of titanium?

 

Eight advantages of titanium alloy fasteners

 

(1) Low density. The density of titanium alloy is significantly lower than that of steel, so titanium alloy fasteners are lighter than steel fasteners.

 

(2) High specific strength. Titanium alloy is a metal material with higher specific strength among common metal materials. Taking advantage of the high specific strength, titanium alloy can also be used to replace lighter aluminum alloy materials. When the external load is the same, the geometric dimensions of titanium alloy parts are smaller, which can effectively save space. This material utilization concept is of great significance to the aerospace field.

 

(3) High melting point. The melting point of titanium alloy is significantly higher than that of steel, so the heat resistance of titanium alloy fasteners is better than that of steel fasteners.

 

(4) Small thermal expansion coefficient and elastic modulus. The thermal expansion coefficient and elastic modulus of titanium alloy materials are smaller than those of nickel alloy and steel materials. In the same temperature change range, the thermal stress generated by titanium alloy is very small, so titanium alloy has higher thermal fatigue performance.

 

(5) Non-magnetic. The magnetic permeability of titanium alloy is very small and almost negligible, so titanium alloy fasteners are non-magnetic and can effectively prevent the interference of magnetic fields. Austenitic stainless steel is also non-magnetic, but subsequent cold processing will increase its magnetism, while hot or cold processing of titanium alloy does not change its magnetism, which makes titanium alloy applicable to avionics equipment.

 

(6) High yield strength ratio. The critical strength standard for the design of fasteners under tensile load is yield strength, followed by tensile strength, because once the fastener yields, it will lose its fastening effect.

 

(7) The electrode potential matches that of carbon fiber composite materials. An important reason why titanium alloy is used in large quantities in fasteners is that the electrode potential of titanium alloy matches that of carbon fiber composite materials, which effectively prevents the occurrence of galvanic corrosion.

 

(8) Titanium alloy also has the advantages of excellent corrosion resistance and high creep resistance.

 

Titanium alloy materials used in fasteners

 

Titanium alloy materials used in fasteners are mainly divided into three categories: industrial pure titanium, (α+β) type and β type titanium alloy. Industrial pure titanium is mainly TA1 and TA2; (α+β) type titanium alloys mainly include TC4, TC6 and Ti-662; β type titanium alloys are mainly metastable β type titanium alloys, because the molybdenum equivalent of metastable β type titanium alloys is generally around 10%.

 

To determine whether a screw is made of titanium, you can refer to the following methods:

 

1. Appearance identification: Observe the appearance of the screw. Pure titanium screws and titanium alloy screws are similar to traditional stainless steel, copper, and iron screws, but high-end series of titanium screws can reach a higher level. It has a beautiful appearance and sometimes emits a cool light like a handicraft. Compared with iron screws and copper screws, titanium screws will appear brighter and have a cool light.

 

2. Scratch test: If you are unsure, you can gently scratch the screw on white ceramic. If the screw is made of titanium, it will leave a gray scratch on white porcelain. Stainless steel will not leave scratches on white porcelain. But it should be noted that some titanium products now have special hardening treatment on the head of the product for a better user experience, so that it is no longer easy to leave scratches.

 

3. Chemical testing: This is a more accurate method. Through chemical reactions, the composition of the material can be determined. For example, using nitric acid test, pure titanium will produce bubbles in an instant.

 

4. Price judgment: Since titanium is relatively expensive as a raw material for screws, price is also a basis for judgment. If the price of the screw is found to be abnormally low, then it may not be a real titanium screw.

 

It should be noted that there are mainly two types of titanium screws on the market: pure titanium and titanium alloy. Pure titanium has good flexibility and oxidation resistance. Titanium alloy is a mixture of titanium and other metals to enhance its specific properties. When selecting and using screws, you should determine the appropriate material according to your actual needs.