Will a vape cartridge set off a metal detector?

It's possible, but there is no unified answer. Since the internal structure of e-cigarette cartridges necessarily involves the use of metals, they are not the focus of attention for public security inspection systems such as those at airports. Therefore, the situation is rather complicated.
To help you understand this issue more clearly, the following provides specific explanations based on several key factors.
⚙️ Key Influencing Factors
Device Construction: All e-cigarette cartridges contain metal components, which is the basis for detection. The most crucial parts include the lithium battery serving as the energy source, the metal heating core that generates the vapor, and the circuit containing metal wires and connectors. Some device casings are also made of metal. It should be noted that even if the casing is made of plastic, the necessary metal components inside are generally difficult to avoid detection.
Detector sensitivity: The sensitivity setting of the detector is also crucial. The sensitivity can be adjusted up to detect tiny metals, or down to avoid frequent false alarms from small items such as keys. Additionally, whether it undergoes additional scanning is also relevant. Even if it passes through the door-type detector smoothly, security personnel may use handheld detectors for local scanning, at which point the possibility of detection will significantly increase.
✈️ Analysis of Common Public Security Checkpoints
Air Travel (Airport Security Check):

Will it be detected? : It is highly likely. But since you are allowed to carry compliant e-cigarette products on board, simply placing them in the tray for X-ray security check can avoid the unnecessary hassle caused by triggering the metal detector alarm due to concealed carrying.
Key regulations: Electronic cigarette devices (including batteries) must be carried with you or placed in your carry-on luggage. They are strictly prohibited from being checked in. E-cigarette liquid must comply with liquid carry-on regulations (within 100ml, placed in a transparent bag), and it is strictly forbidden to use or charge them on the plane.
Other public places (concerts, courts, etc.):
The rules in such places are far more important than whether they can be detected. If you are not allowed to carry any electronic devices anyway, then even if an e-cigarette is detected, the result will generally be that it will be required to be stored or confiscated.
?? Practical Tips for Smooth Security Check
Self-declaration: Before going through the security check, actively place your e-cigarette devices along with your mobile phones, keys, and other metal items into the security basket/tray.
Get familiar with the regulations in advance: Before traveling or participating in an event, be sure to review the official regulations of the relevant venue.
Overall, as long as you follow the instructions of the security personnel and actively place the e-cigarette on the tray for inspection, you usually won't encounter too many obstacles.