The first official strike by West German steel workers in 50 years hit eight plants in the Ruhr iron and steel heartland this morning as some 37,000 persons walked off their jobs in support of a 35-hour week.

The walkout is widely viewed as the spearhead of a union drive to gradually cut the work week for most of West Germany's unionized labor. As such, it could have major implications both for West Germany and other major industralized nations.

The steel companies bitterly oppose, and decline to even negotiate, such a reduction from the current 40-hour standard and in so doing enjoy the general support of companies in many other industries that believe similar demands might soon confront them.

In a counterproposal, the steel companies have offered a six-week vacation to workers, another aspect of this labor battle which extends the kinds of benefits being discussed well beyond those in most other countries.

Perhaps most importantly, however, the strike reflects the growing aggressiveness in labor movement demands in a country where the virtual absence of strikes and days lost due to labor disputes in the postwar years has been a major factor catapulting West German industry and society into unprecedented prosperity.

The long-term antagonisms brewed by this strike will almost certainly be increased by an industry decision taken yesterday to respond to the walkout by locking out some 28,000 other workers beginning on Friday. This same tactic, which doubles the cost of strike benefits to the unions, was used in two strikes earlier this year and is despised by labor leaders.

Aside from the extra vacation - which would amount to between three and nine days more annually beyond what is already granted - the employers have offered a three percent wage increase, roughly equal to the official rise in cost-of-living.

The steel workers have asked for a five percent pay raise but say privately that this is negotiable.

The key demand, union officials say, is the 35-hour week, which they say is necessary to bring an eventual halt to the loss of jobs that union leader Eugen Loderer estimates at 1,000 a month. The West German steel industry is hard pressed, as are others in Europe these days, by foreign competition, especially from Japan. Loderer predicts a "catastropine" if the shorter work week is not introduced.

Loderer says he is counting on support from metal working unions in other countries and the union demand for the shorter week also drew important backing today from the local parliamentary group of the ruling Social Democratic Party and other opposition politicians, thus increasing pressure on industry.

Support for the strike is not universal, however.

Although the stakes are very high for both labor and management, some labor specialists and even some workers milling around union headquarters here suggest this particular strike is "a little bit foolish," as one worker here put it.

In this view, as one striker sipping beer in a local tavern put it, the walkout is "half hearted," since union management has asked only 37,000 out of some 220,000 steel workers in the Ruhr area to strike. The idea is not to deal the entire industry too harsh a blow. Only the healthiest companies, especially the big Thyssen Steel Works here, are being hit.

Yet, as one labor specialist says, those companies can afford the longest strike. A worker here adds, "It was a foolish time to strike. Just before Christmas doesn't help us and the companies don't mind not having to pay for what would have been holiday time off anyway."

Most importantly, some labor specialists believe that the steel workers were the wrong union to carry the ball on such a crucial issue as the 35-hour week. In this view, that job should have been left to the auto workers, who are vital to West Germany's most thriving and most important industry.

The steel strike is aimed eventually at auto industry supplies. But the strike has been anticipated for so long that on hand stocks are said to be sufficient that a stoppage of two-three weeks would not cause much of a problem. Arrangements are apparently being made with outside suppliers should it last longer.

The union involved, I. G. Metal, is the biggest in West Germany, with some 2.6 million members in several fields and possibly the biggest single union in the world. Loderer has not said exactly how he would like to get the 35-hour week but has hinted that a one-hour reduction annually over a five-year period would be acceptable.

Industry leaders, particularly in steel where six shifts of seven hours each are viewed as crucial for efficient operation, view the 35-hour week as simply a way to force the companies to hire a whole additional shift.

Aside from additional hiring costs, fringe and social benefits have made the West German worker the most highly paid in the world, with the exception of those in a few smaller countries such as Sweden, Belgium and Holland.

This has been a factor in driving West German industrialists to set up shop lately in other countries, especially the United States. That, in turn, has angered West German unions and is also a factor contributing to the growing labor demands here.

Thus far, at least, West Germany has been able to keep its exports high despite the growing value of the West German currency and cost of labor in this country. On the other hand, a key fact or in maintaining those exports has been German ability to deliver products on time and service them. And that is a direct result of what has for many generations here been a peaceful labor-management relationship.

If West German unions are becoming more aggressive, there is no sign they are becoming more physical. Outside the big Thyssen plant here this morning, there were very few pickets. The first snow of the season had driven more workers into local headquarters and taverns.

One woman worker complained privately that German men had become lazy. "They all have their wives working so a strike doesn't mean much to them," she said.

The strike also comes at a time when West German industry is challenging in court a controvedsial law passed in 1976 that is supposed to give workers an equal share in management of large firms. The iron and steel industry has had such laws for generations and at least part of the decision to strike, some here believe, was union annoyance at the industrial court action.