Is the cost of heat treatment for metal 3D printing high?

一, The main role of heat treatment in 3D printing metal
Metal 3D printing makes complicated structures by melting metal powder one layer at a time, but this process has three big problems:
Residual stress: Rapid heating and cooling with a laser can change the shape of the lattice, which can cause parts to crack or bend.
Organizational flaws: Non-equilibrium solidification creates coarse features like columnar crystals and dendrites, which make materials less strong.
Uneven performance: weak interfaces can easily form at interlayer junctions, which shortens the life of the material.

Stress relief: Annealing treatment gets rid of leftover stress and makes the dimensions more stable.
Organizational optimization: Getting a uniform and fine equiaxed crystal structure by using solid solution and aging treatment.
Improving performance: Controlling the shape of the precipitating stages to find a balance between strength and toughness.
For instance, SLM technology was used to make a specific aviation engine blade, which was then treated with a solution at 1050 ℃ and aged at 550 ℃. The tensile strength went from 850MPa to 1200MPa, and the fatigue life went up by three times.
2, A multidimensional look at the cost breakdown of heat treatment
1. Cost of equipment: the cost of precise control
To heat treat metal 3D printed objects, you need special tools:
A vacuum furnace stops active metals like titanium alloys from rusting. It costs two to three times as much as a regular furnace.
Laser heat treatment system: used to change the surface of a small area, and the equipment costs more than 5 million yuan.
An intelligent control system needs to include infrared temperature measurement, atmosphere control, and other modules. The worth of a single system is over one million yuan.
A certain company says that the depreciation of heat treatment equipment makes up 18% to 25% of the unit cost, and this percentage goes up quickly as the accuracy of the equipment improves.
2. Energy cost: High temperatures create a long-term energy consumption black hole.

Solution treatment: 4 to 6 hours of insulation at 1000–1050 ℃
Time treatment: keep the insulation at 160–180 ℃ for 8–12 hours.
Stress relieving annealing: Keep it at 300–400 ℃ for 2–4 hours.
For example, it takes 120–150 kWh of energy to heat treat one piece of Ti6Al4V that was made using SLM. The cost of power is more than 15% if you use an electric heating furnace. If you utilize a gas heating furnace, you will save 40% on energy costs, but you will need to spend more on equipment to clean up the exhaust gases.
3. Material Cost: The Efficiency Game of Recycling Powder

Oxidation burn: When metal is heated to high temperatures, oxidation skin occurs on its surface. The loss rate is 0.5% to 1.2%.
Loss of volatile substances: Metals with low boiling points, such magnesium alloys, evaporate at high temperatures, losing more than 2% of their weight.
Supporting structure: Designing complex internal flow channel parts with removable supports raises the material waste rate by 5% to 8%.
The powder recycling system can raise the utilization rate to 92%–95%, however the issue of recycled powder losing its effectiveness still needs to be fixed. A study found that after three uses, the oxygen concentration of Ti6Al4V powder went up by 0.03%, which caused the components' fatigue strength to go down by 12%.
4. Time cost: the process chain has an efficiency bottleneck

Before treatment: cleaning, unsupported, sandblasting (2–4 hours)
Heating, insulating, and cooling (8 to 24 hours) are all part of heat treatment.
Post-processing: cutting the wire, polishing it, and testing it (3–6 hours)
A certain automotive parts firm says that the heat treatment procedure makes up 60% to 70% of the whole 3D printing production cycle. This is a major reason why deliveries are slow.
3, Technical path for lowering costs
1. Change the way things are done: make the heat treatment cycle shorter.
Rapid annealing technique uses high-power density heating to cut the time it takes to treat a solution from 6 hours to 2 hours.
Graded aging process: By controlling the temperature in several stages, the overall insulating time is cut down while still making sure the performance is good.
Induction heating local treatment: Only the most important parts are heated, which cuts energy use by more than 70%.
A certain aircraft company used quick annealing technology to cut the cost of heat treating Ti6Al4V parts by 35% and make the microstructure more consistent by 20%.
2. Upgrade equipment: Make better use of energy
Vacuum low-pressure carburizing furnace: Keep the pressure in the air between 10 and 100 Pa to use less gas.
Waste heat recovery system: using the waste heat from cooling water to warm new parts, which cuts overall energy use by 18%.
Smart temperature control system: uses machine learning to improve the heating curve and cut down on the need for repeated processing caused by changes in temperature.
After a certain equipment maker started using an intelligent temperature management system, the heat treatment qualification rate went up from 82% to 95%, and the cost per unit went down by 22%.
3. Improving materials: Making alloy systems that are cheap
Partial printing technology: employing aluminum alloy in parts that don't have to hold a lot of weight and titanium alloy in parts that must, which cuts material prices by 40%.
Nano modified powder: Adding 0.5% nanoparticles lowers the heat treatment temperature by 50 degrees Celsius and cuts energy use by 30%.
Using regenerated powder: Create a model for how the powder's performance will change over time so that production stays stable after at least five uses.
The Mg Zn Ca stainless magnesium alloy created by a certain research team worked just as well as aluminum alloy in salt spray tests, and it cut surface treatment expenses by 60%.
4. Process reengineering: bringing together manufacturing and heat treatment
Integrated equipment for printing heat treatment: an induction heating module is built inside the printing chamber to allow for in-situ annealing.
Digital twin technology: Using simulation to find the best process parameters and cut down on trial and error costs.
Automated production line: combining modules like cleaning, heat treatment, and detection to cut labor expenses by half.
A specific company built a smart factory that cut the total cost of 3D printed parts by 42% by changing the way they are made. The cost of heat treatment went down from 25% to 14%.