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heating

PROCESSES


Annealing

Bonding

Brazing

Forging

Fusing

Hardening

Heat Staking

Heat Setting

Pre-Tinning

Susceptor Heating

Pre-Heating for Welding


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Brazing Stainless Steel to Brass

Research Objective

To braze a stainless steel valve seat to a brass plumbing fixture in an oxygen atmosphere and improve assembly reliability.

Parts & Materials Description

Stainless steel valve, 0.25” ID threaded brass plumbing fixture, black flux, braze ring preforms

Temperature Required

1325°F

Induction Heating Equipment

5 kW RF power supply, two-turn helical inductor (coil)

Operating Frequency

220 kHz Heating

Procedure

The testing was done in an open air atmosphere. A specially-designed, two turn helical inductor was used to provide optimal heating to the joint area of the plumbing assembly. Initial tests were conducted with bare parts and temperature sensing paints to establish time-to-temperature and heating profiles. Next the parts were placed in position with a joint clearance of .002” to .003”. The braze ring preform was positioned and black flux was applied to the assembly. RF heat was applied with the RF power supply for 7 seconds to reach the brazing temperature of 1325°F. At this temperature the braze alloy flowed into the joint and formed a strong bond.

Conclusion

Consistent, repeatable results were achieved at 1325°F within 7 seconds. The braze flowed well. Induction brazing produces a strong, clean joint which is ideal for this type of consumer product.

inductor positioned over brass fixture

The parts were heated with a two-turn helical inductor coil.