When you think of titanium and titanium alloys, you might picture their crucial role in aerospace or their "bio-friendly" properties in medical implants. But did you know that this "star material," combining high strength, corrosion resistance, and low density, is far more difficult to process than traditional metals? Today, we'll break down the four core processes of titanium forming to see how it overcomes processing challenges and supports high-end equipment manufacturing!
1). Bending Forming:
Finding a Balance Between Elasticity and Plasticity As a frequent component in titanium equipment manufacturing, the key to bending forming is controlling the springback and deformation limits of titanium materials. During cold bending, the minimum bending radius of titanium tubes must be three times the tube diameter. Tubes with a diameter less than 50mm require stress-relieving annealing at 450-550℃ for one hour after cold bending. Hot bending is even more demanding. Heating pure titanium to 177-350℃ and titanium alloys to 427℃ can reduce the yield strength by 25%-50%, and the springback angle can be controlled within 1°. More importantly, hot bending must be carried out in an inert gas or vacuum environment to avoid the formation of oxide scale that affects performance. For example, the titanium tubes of a certain deep-sea exploration device achieved a 180° bend at 250℃ with a springback of only 0.5° and a surface oxide layer thickness of less than 0.1mm, firmly withstanding the high pressure of the deep sea.
2). Stamping:
Controlling Deformation "Freedom" Through Temperature. Stamping titanium plates is significantly more difficult than stamping steel and aluminum, making temperature a crucial control method. Cold forming is suitable for thin-walled parts with a wall thickness <2mm and deformation <15%, such as thin-walled shells. After stamping, these require annealing at 600-650℃ for 2 hours to prevent cracking. Low-temperature hot forming (200-350℃) can handle medium-thickness slabs with a deformation of 40%, a process commonly used for chemical equipment heads. High-temperature hot forming (600-800℃) is even more powerful, with deformation exceeding 50%, making it ideal for thick plates (>10mm) or complex parts such as aircraft engine nacelles. An aviation company uses 750℃ high-temperature hot forming to manufacture titanium alloy wing panels, achieving a single deformation of 60%, a surface roughness Ra <0.8μm, and a 40% weight reduction compared to traditional steel panels, perfectly meeting the lightweight requirements of the aviation industry.
3). Spin forming:
Material-saving and precision-maintaining. Spin forming is a "cost-saving master" in titanium processing. By rotating the tool and the blank through localized continuous deformation, material utilization can be increased by 20%-50%, making it particularly suitable for precious metals like titanium. Moreover, the processed products have a surface roughness Ra < 0.4μm and dimensional accuracy of ±0.1mm, requiring virtually no subsequent machining. Ordinary spin forming is suitable for thin-walled cylindrical parts with a wall thickness < 5mm, where shape can be controlled through multiple deformation passes; high-strength spin forming is for thick-walled parts with a wall thickness > 10mm, where single-pass deformation can reach 50%, but work hardening must be carefully controlled. The titanium alloy gas cylinders of a certain satellite propulsion system were reduced from a wall thickness of 15mm to 8mm using spin forming, resulting in a 47% weight reduction, while the burst pressure reached 1.5 times the design value.
4). Expansion Joint Process:
Enhancing the Reliability of Titanium Tube Connections. In shell-and-tube heat exchangers, the connection between titanium tubes and the tube sheet relies entirely on the expansion joint process. During expansion jointing, the inner diameter expansion rate of pure titanium needs to be controlled at 1%-3%, while that of titanium alloys is 4%-6%, and the tube wall thinning rate is maintained at 5%-8%. Finite element analysis is also required to optimize the parameters. Different expansion joint methods have their advantages: mechanical expansion joints are low-cost and suitable for conventional operating conditions; flexible expansion joints use hydraulic or rubber expansion heads, improving sealing performance by 30%, making them the preferred choice for high-pressure scenarios; explosive expansion joints rely on instantaneous impact and can handle thick-walled tubes (>5mm) or connections between dissimilar materials. A petrochemical company's titanium tube heat exchanger using the flexible expansion joint process operated continuously for 5 years without leakage under conditions of 3.5MPa and 200℃, with a lifespan three times longer than traditional welded structures.
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