Why is machining titanium parts difficult?
Titanium alloys are widely used in the aerospace and medical industries because of their excellent properties. Despite its popularity, titanium is notorious for being one of the most difficult materials to process, with numerous stories of broken tools and damaged workpieces. This article will help demystify the challenges encountered in processing this material and provide some insights into techniques that can improve the success rate of titanium processing.
The development history of titanium
Titanium is an important structural metal developed in the 1950s. Titanium alloy is widely used in various fields because of its high strength, good corrosion resistance and high heat resistance. Many countries in the world have realized the importance of titanium alloy material, and have successively researched and developed it, and obtained practical application.
Types of titanium alloys
Like all other metals titanium has numerous different alloys available, each with its own special set of properties and behaviour. Here is a summary of the different types:
Pure titanium – As the name suggests, pure titanium consists of no alloying elements and is the easiest type of titanium to machine
Alpha alloys – This refers to titanium alloys that contain aluminium, oxygen and/or nitrogen
Beta alloys – This refers to titanium alloys that contain molybdenum, iron, vanadium, chromium and/or manganese
Mixed – This is a mixture of both alpha and beta titanium alloys
Benefits of using titanium
Why even bother using titanium if it is so difficult to use?
The main advantages of titanium as a manufacturing material are that it is highly corrosion resistant, has exceptional bio-compatibility and has the best strength to weight ratio of any metal. These qualities make it an especially sought after material in the aerospace and medical industries.
Disadvantages of using titanium
Due to titanium’s affinity to other elements it cannot be found naturally occurring and therefore requires complex and energy-intensive processes to refine it. This means that it is very expensive compared to other common materials. Another major disadvantage of titanium is its degree of difficulty when machining processes are required.
WHY TITANIUM IS SO POPULAR
While aluminum and aluminum alloys were previously the preferred materials of the aerospace industry, newer aircraft designs are increasingly making use of titanium and titanium alloys. These materials are also used in the biomedical industry. The reasons for their popularity include light weight, high strength, excellent fatigue performance and high resistance to aggressive environments, remaining free of rust and degeneration. Titanium parts last longer and provide better performance and results than other metals and materials.
WHY TITANIUM IS SO DIFFICULT TO MACHINE
The very properties that make titanium such a beneficial and high-performance metal are also the properties that can make it difficult to machine. Just as when using aluminum and aluminum alloys, up to 90% of the material may need to be milled and turned away to produce the final part.
Titanium alloys have a low Young’s modulus, which causes spring back and chatter during machining. This can create poor surface quality in the finished product.
Because of titanium’s high work hardening tendency and the stickiness of the alloy, long continuous chips are formed during turning and drilling, which can entangle the tool and impede function. This almost eliminates the possibility of automating titanium machining.
Despite these setbacks, there are techniques that make machining titanium easier.
HOW TO MACHINE TITANIUM
Machining titanium requires coated carbide tools that will resist the stickiness of the alloy and break up the long chips. The tool coating also helps to manage the heat produced with machining.
Keeping radial engagement low is important to counteract the effects of heat generation and work hardening tendency. Increasing the number of flutes in the end mills can help to counteract the lower feed per tooth to increase productivity.
Application of high pressure coolant helps to reduce heat and damage to the tool. Currently, ultrasonic assisted machining is in R&D. The goal is to reduce the contact time of the tool, and prolong tool life.
The technique used when machining titanium can also help to improve results. By using ‘climb milling’, arcing in, ending on a 45-degree chamfer, using a secondary relief tool design, altering the axial depth, and using a tool at least 70% smaller than the tool pocket, you can reduce tool damage and get better results when machining titanium.
By carefully examining the unique properties of titanium and adjusting machining appropriately, you can get the best results for your tool and your finished piece. For more assistance in machining titanium, talk to the experienced engineers at Guten for a custom titanium solution for you.
Frequently Asked Questions about Titanium Alloy Parts Machining
How difficult is it to cut titanium?
Titanium cutting is difficult due to the reactive nature of the material. Because the material is sensitive to heat, it must be cut at a relatively low temperature to prevent warping, discoloration, and contamination.
How easy is it to machine titanium?
Titanium is a widely used material in the aerospace and medical industries due to its exceptional properties. Despite its popularity, titanium is notorious for being one of the most difficult materials to machine, and tales of broken tools and ruined workpieces are abundant.
How hard is it to CNC titanium?
When it comes to pliability, both metals are quite hard, but titanium has the ability to flex or bow repeatedly in CNC conditions. Steel will often rupture when flexed too far. The challenge most people have with titanium is that it is incredibly unforgiving when it comes to CNC tool wear, feeds and speeds, etc
What is the hardest metal to machine?
1. Tungsten (1960–2450 MPa) Tungsten is one of the hardest metals you will find in nature. Also known as Wolfram, the rare chemical element exhibits a high density (19.25 g/cm3) as well as a high melting point (3422 °C/ 6192 °F).
What is the best way to cut titanium?
Since titanium alloys are a stronger and harder material, they pose a unique cutting challenge best solved by carbide blades. Using a carbide-tipped band saw blade not only allows for the successful cutting of titanium alloys, but it simultaneously offers longer blade life and faster cutting as well.
Can a CNC cut titanium?
Titanium has desirable material properties, and it is also relatively easy to work with. It is weldable (in an inert atmosphere) and it can be CNC machined like stainless steel.
Titanium is certainly not an easy material to use, but its material properties mean it's here to stay. It is very important to process in the right way if you have any questions. Please contact our engineers for expert advice on milling materials such as titanium.