What is up with the title? Nowhere in this play is there of a mention of the word "crucible." What the heck is a crucible anyway? Well, it's a piece of laboratory equipment used to heat chemical compounds to very high temperatures or to melt metal. It's a little container full of violent reactions. Seems like a pretty good metaphor for the violent hysteria that the little village of Salem contained during the witch trials.
Yes, Salem became a “crucible” for many people living there when they were brought before the religious court and accused falsely of being witches. If an accused person did not confess, she was hanged. If she did confess, she was spared death but marked for life as a person who worshipped the Devil. Under such conditions, several characters in this play, especially the central characters, John and Elizabeth Proctor, are forced to face their own internal demons, a process that ultimately leads to internal, spiritual transformation.
The title (and the entire play) is also a metaphor for the anti-communist craze of America's Red Scare, led by Sen. Joe McCarthy. Thanks to the efforts of McCarthy's House Un-American Activities Committee, the whole United States became a "crucible."