How to improve hardness for solid steel SCM440

By heat treatment, we can increase SCM440 properties. Join us to learn more about methods to improve the hardness of solid steel SCM440.

It can be said that SCM440 steel is an upgraded version of ordinary carbon steel such as S45C, S50C, S55C, ... SCM440 steel is a specialized steel grade used as a shaft, bearing parts need high abrasion resistance. Thanks to the addition of Chromium - Molybdenum component, SCM440 is resistant to oxidation corrosion, good heat resistance, very good tensile strength.
And to increase SCM440 steel properties, people often use a number of methods. The most popular method is SCM440 steel hardness treatment - Heat treatment. SCM440 heat treatment is used to increase the surface hardness of machine parts that are an integral part of the mechanical processing industry. The surface hardness is directly proportional to the abrasion resistance of the product. The basic principle for increasing surface hardness is to produce a layer of hard-stressed material underneath the surface where the hardness needs to be increased.

                                                      SCM440 solid steel rebar raising method
The following article will help you understand more about methods to improve the hardness of solid steel SCM440 so that you have more knowledge about this steel when buying and choosing to use for your needs.
1. Composition determining steel hardness SCM440
For ordinary carbon steel, its main component is carbon, which plays a role in determining the hardness of steel. The amount of carbon in the steel decreases, the higher the ductility. Increased carbon content in steel will also increase hardness, durability but will also reduce ductility and weldability.

Tiêu chuẩn





Lưu huỳnh



JIS G4052

0,28 - 0,43

0,15 - 0,35

0,6 – 0,85



0,9 - 1,2

0,15 - 0,3

SCM440 steel has a carbon content from 0.28% to 0.43%, which is an average. So the hardness of SCM440 is not the highest but the heat treatment effect is very good.
The difference between SCM440 steel and ordinary carbon steel grades is that the content of Chromium and Molybdenum will give SCM440 steel a balance between hardness and ductility suitable for shaft applications or machine parts requiring intensity. high. In addition, abrasion resistance is a special feature of SCM440 that S45C, S50C, S55C steel lines can hardly meet.
2. The method of improving the hardness of solid steel SCM440
There are usually 2 methods to increase SCM440 hardness: mechanical processing and heat treatment. We are pleased to introduce some of the following methods:
- Volume heating - Volume heat treatment (HQ): This method helps to increase the hardness to prevent abrasion. Steel is heated to a certain temperature and then suddenly cold to change the fixed state of carbon in the steel.

Solid steel hardness SCM440
- Surface heating - Surface heat treatment (FHA / HQI): Under the effect of (dielectric current) surface of hot materials continuously, then suddenly cooled to increase hardness. The depth of hardness is 0.5 mm - 2 mm.
- Carbon permeation heating (HC): Heat in the atmosphere of Carbon permeable atmosphere, conducting heat to carbon permeate into the surface of materials 1500C - 2000C.
- Nitriding heating (HN): Heat in the condition of gas or liquid nitrogen to put nitrogen sheets on the product surface. 5000C - 6000C. The depth of hardness is 0.1 mm - 0.2mm.
- Heating and tempering: If handled only by sudden heating and cooling, the material will be hard but brittle. To improve this situation, after heating the product will be annealed, the hardness is reduced but the properties of SCM440 solid steel such as high strength, tensile strength, ductility, elongation, mechanical properties But the impact is improved, it becomes hard and ductile steel.

Mác thép tương đương

Độ cứng sau nhiệt luyện










20 – 30





35 – 40





50 – 55





56 - 58

     Table of SCM440 steel hardness and other grades of steel in the same line after heat treatment
  Hopefully the above information will solve the problems that readers are having. If you want more detailed advice on the type of industrial steel, readers can contact 0332 91 61 61 or chat online with us.
Sevit is pleased to answer all questions from readers!