"氨合成法" can be translated into English as "ammonia synthesis method" or more specifically, depending on the context, "Haber-Bosch process" (if referring to the industrial method for synthesizing ammonia from nitrogen and hydrogen, developed by Fritz Haber and Carl Bosch).
Ammonia synthesis method is a general term for any process used to synthesize ammonia.
Haber-Bosch process is the specific and most widely known industrial method for ammonia production.
Choose the appropriate term based on the specific context of your discussion.