The invention relates to a 135 steel-level
drill rod connector and a heat treatment process thereof. The
drill rod connector comprises the following components in percentage by weight: 0.25-0.32 percent of C, 0.30 percent of or less Si, 0.35-0.80 percent of Mn, 0.015 percent of or less P, 0.008 percent of or less S, 0.15-0.80 percent of Mo, 0.00-1.00 percent of Ni, 0.90-1.50 percent of Cr, 0.30 percent of or less Al, 0.05 percent of or less Nb, 0.10 percent of or less V and the balance of Fe and unavoidable trace elements. The heat treatment process comprises the steps of: heating a roughly processed connector blank to 920-960 DEG C from the
room temperature, preserving heat for 0.5-1.5 hours, putting the connector blank into a high-grade oil base
quenching medium at 30-50 DEG C, fully cooling the connector blank, then heating the connector blank to 550- 620 DEG C from the
room temperature for 50-70 minutes, preserving heat for 1.5-2.5 hours, and then discharging the connector. After heat treatment, the mechanical performances are as follows: the yield strength is 140-160 Ksi (965-1100 MPa), the elongation percentage is larger than or equal to 17 percent, the
drill rod connector is longitudinal and is at 20 DEG C below zero and has full size, and the charpy
impact energy is higher than or equal to 100 Joules.