After six days, 41 witnesses and a rebuke by the judge about wasting time, defense attorneys for Sen. Harrison A. Williams Jr. (D-N.J.) late today began playing tapes they claim show government agents trying to manipulate a legitimate titanium mine venture into criminal activity.

In a June 7, 1979, tape secretly recorded by undercover FBI informer Melvin Weinberg, for instance, Williams' co-defendant, Alexandria Feinberg, said the senator had no intention of hiding his share in the mine. "He [williams] said put it in my own name. The hell with it. I am going to report it," Feinberg said.

Weinberg replied immediately that Williams couldn't put the stock in his name. "He can't report. . . . If he reports then he can't do nothing for us."

Feinberg: "That is correct, right."

Weinberg: "I mean that what the hell we got him in there for?"

Williams and Feinberg are charged with conspiracy and bribery in a scheme in which the senator allegedly agreed to help get government contracts for titanium in return for a $100 million loan from an Arab "sheik." The loan was to be used to develop the mine, in which Williams would hold hidden interest, the indictment charged.

The prosecution has played videotapes showing the senator agreeing to help get contracts, and hide his share in the mine. William's attorney, George J. Koelzer, started playing the series of audiotapes today to attack the credibility of government witness Henry A. (Sandy) Williams III and show that it was Weinberg who brought up the idea of government contracts and insisted that the senator hide his share in the mine.

While Koelzer has never used the word entrapment to describe his defense strategy, he seemed to be laying the groundwork for such a defense with the witnesses he has called and the tapes he played today.

Sandy Williams, who is not related to but was a longtime friend of the senator, testified last week that the senator used his influence in return for a hidden interest in other ventures long before Abscam.

Sandy Williams is an alleged co-conspirator who testified for the government to gain immunity from prosecution. Several tapes the defense played today had informer Weinberg calling Sandy Williams a liar and a con man who had stolen $200,000 in a recent deal.

On the last tape played for the record before the jury was sent home for the Easter weekend, defendant Feinberg is heard telling informer Weinberg how the senator spent part of his Thanksgiving and Christmas holidays each year preparing holiday "meals on wheels" for poor people in Jersey City.

Koelzer quickened his pace noticeably today after U.S. District Court Judge George C. Pratt lectured him, without the jury present, about wasting time by calling witnesses who testified "in endless detail about irrelevancies."

Pratt had made similar comments to Koelzer Wednesday after the jury left for the day, and apparently lost his patience about 12:30 this afternoon while Koelzer was laboriously questioning a foreign service officer who accompanied the senator on a trip to China in 1978.

Koelzer apparently called Robert A. Perito to show that the senator was deferential in his treatment of foreigners.

In his secretly videotaped meetings with the FBI agents, one of whom posed as an Arab sheik, Williams appeared quite deferential. At the final meeting he turned down a cash bribe offer, but added that he was still interested in the loan for the titanium mine.