BERLIN—Social Democrat Olaf Scholz became Germany’s chancellor on Wednesday, ending 16 years of conservative rule under Angela Merkel and launching his three-way coalition that has pledged to boost green investment and strengthen European integration. Scholz, 63, who over the past four years served as vice chancellor and finance minister in coalition with Merkel, won a majority of 395 votes from lawmakers in the lower house of parliament, Bundestag President Baerbel Bas said. Wearing a black face mask, Scholz waved as he received a standing ovation from lawmakers and accepted bouquets of flowers and a basket of apples from leading members of parliament. After being formally nominated by President Frank-Walter Steinmeier in the nearby Bellevue Palace, Scholz returned to the historic Reichstag building in the heart of the German capital to take the oath of office in front of lawmakers and become Germany’s ninth chancellor since the end of World War …