Welter was born in Cologne-Lindenthal on 25 February 1916. He joined the military service of the Luftwaffe in 1934 and was trained as a pilot. He showed a strong natural ability as a pilot and was subsequently selected for flight instructor training and served many years as a flight instructor. In 1943 Welter transferred to an operational night fighter unit flying contemporary piston engine fighter aircraft. On 18 October 1944, after 40 combat missions, Welter was awarded the Knight's Cross of the Iron Cross. In early 1945, Welter transferred to an experimental jet night fighter unit flying the Messerschmitt Me 262. On 11 March 1945 he was awarded the Knight's Cross of the Iron Cross with Oak Leaves for 48 aerial victories. Welter survived the war and was killed in an accident at a railroad crossing on 7 March 1949.