4140 Round Steel: Find the Right Hardness and Strength

We all know that as a high-strength low-alloy structural steel, 4140 steel has very good comprehensive properties, high hardness, high hardness, as well as good toughness and plasticity.

In practical applications, for 4140 steel, is the higher the hardness and strength, the better? Obviously not, with high hardness, 4140 also becomes brittle and more likely to break. How to match the appropriate strength and hardness of 4140 steel must be adjusted through appropriate heat treatment processes.

First, let’s talk about 4140 steel in the annealed condition. As we all know, one of the purposes of annealing is to soften the material, which means that after annealing, 4140 steel will become softer, so the surface hardness is very low, and its strength will certainly not be very high.

Condition	No.	1	2	3	4	5	6	7
Annealed	Hardness，HBW	244	229	232	238	181	168	159
Annealed	Tensile strength,Mpa	735	680	680	675	665	535	550

From the actual test data table above, it can be seen that the hardness of annealed 4140 steel is very low, and the corresponding strength is not high either, which makes it difficult to meet actual application requirements.

A large number of experiments have shown that as the hardness of 4140 steel material increases, its strength also increases, that is, there is an obvious positive correlation between them.This feature can help us provide guidance and reference for actual production.

Taking into account the needs of actual production, 4140 steel needs to improve its own strength to meet the application, which requires 4140 steel to complete the transformation through quenching and tempering heat treatment.

Condition	No.	1	2	3	4	5	6
QT	Hardness，HBW	294	293	285	282	279	278
QT	Tensile strength,Mpa	965	945	935	920	920	915

It can be seen from the data in the above table that after quenching and tempering heat treatment, 4140 steel not only obtains a very high hardness, but also greatly improves its own strength, which can fully match various industrial applications.