The connecting rod materials of Dalian marine parts shall have high fatigue strength and impact toughness, and generally adopt medium carbon alloy steel or high-strength alloy steel. The blank is formed by die forging. The fiber direction of the metal macro structure in the longitudinal section of the connecting rod shall be along the center of the connecting rod and consistent with the shape of the connecting rod, and the microstructure shall be uniform fine grain structure.

Connecting rod bolt is an important connecting bolt connecting the big end of connecting rod and connecting rod cap. Connecting rod bolts shall be subject to the pre tightening force during assembly. The pre tightening force shall ensure the close fitting between the two split surfaces, so that they will not separate under the tensile action of large reciprocating inertia force.

At present, there are two structural types commonly used for marine ultra-low temperature breakaway valves: breakaway bolt type and cable breakaway type. The breakaway bolt type is widely used. The two ends of the breakaway valve are equipped with one-way valves, which are connected by breakaway bolts. When the tension received by the breakaway valve is greater than the set tension value of the breakaway bolt, the breakaway bolt will be disconnected instantly, and the one-way valve will be closed instantaneously under the force of the spring to ensure that the breakaway valve will not leak

Causes of surface porosity:

(1) The amount of resin added is too large, resulting in too much gas evolution;

(2) The mold is manually baked by blowtorch, which is difficult to achieve uniform drying;

(3) The pouring temperature of molten iron is low, and it is difficult to discharge air once pouring;

(4) The speed of molten iron entering the mold is too fast, so that the gas in the mold cavity cannot be discharged.