When did Warsaw Pact countries switch from brass to steel cases?

As the title says, when did WP countries switch from producing brass to steel cases? For 7,62x39, 7,62x54R, 12,7x108 and 14,5x114.

I only know that Romania transitioned for 7.62x39 from 1968 to 1970 (there are both brass and steel cases from those years) Before 68 there were only brass cases in this caliber, after 1970 only laquered steel.

I think it is no particular year that is to be named here as countries switched when they had the need or chance to do so.
Also most countries for example never switched from brass to steel with their 12.7x108.
The only 2 making (made) steel cases are Romania and Czechoslovakia. As you sure know Romania still makes steel and Czechoslovakia never made brass and ceased 12.7x108 production long ago.

Also Czechoslovakia for example made brass cases 14.5x114 but no steel cases.

So basically you will need to look at every single manufacturer and at every single caliber and there narrow down the years when a switch occured.
And saying this I remember that there were also cases when factories switched back and forth between brass and steel.

Which leads me to the next question. Steel casings were introduced as a cost (and strategic materials such as copper) saving measure, right? That is why Germans introduced them in the later part of WW2, while the Soviets started using copper plated steel in 54R since the 30s, and by the end of WW2 was the only type of case in that caliber.

Well, than why the Soviets (and later Russians) never switched from brass to steel in the case of 12,7x108? Especially considering how much material (brass) is contained in the larger cases? Could the reason be because that (maybe, my speculation) laquered steel performs badly in high rate of fire systems such as Berezin UB, Afanasev A-12,7, Yak-B aviation machine guns?

I mean by the 1970s and until today all mass made Soviet ammo ranging from 22LR to 30x165 is steel cased, except for 12,7x108. I dont understand why.

Vic, Germany made steel cases back in WW1 already.
Not as a cost saving measure but to replace the missing brass.
Actually making steel cases is more expensive than brass since it requires more machinery and has a higher wear.

The Soviets actually made their first 12.7x108 steel cases in 1941 and as per them they had problems with the guns digesting these. More attempts wer emade at least arond 1974 but this also did not go anywhere.
The surprising thing is that Czechoslovakia, Romania and China seem not to have this problem.

We would need to as a Russian engineer about the steel case mystery in 12.7x108.

Besides this Russia tested and also used many steel cases which are way less commonly known in the west.