Fine crystal non-quenched and tempered steel for connecting rod

Abstract

The invention discloses fine crystal non-quenched and tempered steel for a connecting rod and belongs to the technical field of special alloy steel. The fine crystal non-quenched and tempered steel is characterized by being prepared from the following elements in percentage by weight: 0.10-0.20% of (Ti+Nb), 0.35-0.45% of C, 0.60-0.70% of Si, 0.75-0.9% of Mn, 0.08-0.10% of P, 0.05-0.07% of S, 0.10-0.20% of Cr, 0.05-0.25% of V, 0.0005-0.001% of B and the balance of Fe. The metallographic structure of the alloy steel is upper bainite. On the premise that the expansion fatigue property of the connecting rod is ensured, the alloy steel is good in cutting processing property and expansion property.

Description

technical field [0001] The invention relates to a micro-alloyed non-quenched and tempered steel, and in particular provides a fine-grained non-quenched and tempered steel used for connecting rods, which has good cutting performance and good swelling performance on the premise of ensuring the fatigue performance of the connecting rod when it expands. break performance. The invention belongs to the field of special alloy steel. Background technique [0002] The connecting rod of automobile engine is an important part of the engine. It bears the effect of cyclic stress in the working process, and its failure mode is mainly fatigue damage, so the fatigue performance directly affects the application range of the connecting rod. The performance stability of the engine requires that the connecting rod should have high stiffness and fatigue strength. Due to the complex traditional machining process and high precision requirements, especially the big head hole of the connecting rod...

AI Technical Summary

Problems solved by technology

However, due to the good toughness of the ferrite in the traditional ferrite + pearlite structure, the ferrite region at the root of the notch is prone to ductile fracture, resulting in poor bursting properties

In recent years, the research and development of related materials has also been carried out in China. The most typical one is a non-quenched and tempered steel for medium-carbon expansion connecting rods, which has good expansion properties, but due to the addition of up to 0.25% of microalloying elements V , the cost of steel increases, which weakens the economy of the steel; at the same time, too high Si content (2%) also deteriorates the surface quality of the forging and affects the fatigue performance of the part; in addition, in order to improve the machinability, the steel is added The harmful element Pb of about 0.1% is not conducive to environmental protection, which limits the application of the steel

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