Soldering methods with standard solder do work reliabalyreliably long term but take extra effort to implement.
Solders tailored for this type of application make soldering easier.
Acid fluxes tailored for difficult materials are available. These are totally unsuited to PCB level soldering but are acceptable for wire termination such as this as long as instructions are properly followed. (This requirement is not unique to acid flux - anything can cause problems if instructions are not properly followed).
Crimp methods are common and work "well enough" in many cases. Crimps on even standard wiring in demanding environments can be extremely unreliable longer term if not carried out correctly. In this case "correctly" may be specified by a manufacturer for Nichrome use with a given connector but, if not, then enthusiastic "works well for me" advice which is not based on long representative experience or manufacturers advice may led to longer term disasters.
Be careful with crimping: Crimp connection is a widely used solution for wiring termination and in many cases works well. In demanding situations it can often produce poor reliability.
Procedure:
Degrease joint area.
Place All-State Duzall liquid flux on joint area.
Use any heat source that will produce 430°F (221°C)in the base metal.
If torch is used,heat heat indirectly and avoid burning flux.
Apply solder when flux starts to bubble.
Allow to cool slowly.
Remove flux residue with hot water.
When soldering stainless steel types 430, 316, 321 or 347, use All-State No. 430 Acid Flux.