Leaving withoout a deal would mean tarrifs on UK steel going to the EU, which would probably wipe out that market. Even if UK industry was "encouraged" to buy UK produced product would that be enough to support the company, I think not. The EU is trying to protect domistically produced steel with the tarrifs in imposed on China a couple of years ago. If the UK goes it alone would it impose the same tarrifs on China? Not a good start to the new global UK.

https://www.theguardian.com/business...rt-talbot-tata