WASHINGTON—The Federal Reserve launched a high-risk effort Wednesday to tame the worst inflation since the 1970s, raising its benchmark short-term interest rate and signaling potentially up to seven rate hikes this year. The Fed’s quarter-point hike in its key rate, which it had pinned near zero since the pandemic recession struck two years ago, marks the start of its effort to curb the high inflation that has followed the recovery from the recession. The rate hikes will eventually mean higher loan rates for many consumers and businesses. The central bank’s policymakers expect inflation to remain elevated and to end 2022 at 4.3 percent, according to updated quarterly projections they released Wednesday. That’s far above the Fed’s 2 percent annual target. The officials also now forecast much slower economic growth this year, of 2.8 percent, down from its 4 percent estimate in December. Chair Jerome Powell is steering the Fed into …