When looking for 42CrMo4 material, you need to know that 42CrMo4, as a European grade, is one of the most commonly used steel grades. In the face of many quality uneven 42CrMo4 steel suppliers, how to select high-quality 42CrMo4 steel? A lot of people find it hard to understand, but it's really simple.
Through this guide, you can understand some of the necessary technical indicators of 42CrMo4 steel, so as to help you have confidence and ability to choose high-quality 42CrMo4 materials.
So, let's start learning!
What is 42CrMo4 steel?
42CrMo4 steel, refers to DIN 1.7225 steel. As one of the widely used Cr-Mo series typical alloy steels, it has been adopted and included by major European standards, such as EN10083 and EN10250 standards.
From the letters we can guess that it contains Cr and Mo, so what do the other numbers stand for? To understand this, we first need to understand naming conventions.
We can see Table 13 below from EN10027 Standard:Designation systems for steels.
Key
1 = primary symbol
2 = additional symbol for steel
3 = Additional symbol for steel products
an = numeric character, a = alphabetic character, an = alphanumeric character.
b To distinguish between two similar steel grades, the number representing the carbon content can be increased by 1.
The order of c symbols should be arranged in descending order of the average percentage content value; When two or more elements have the same content value, the corresponding symbol should be represented in alphabetical order.
From the above information, "42" in 42CrMo4 means that its average carbon content is 0.42%. This is the same as the last two '40s' in the US grade 4140, representing a carbon content of 0.4%. The final number 4 indicates that the average content of Cr is 4/4=1%, and the Mo content is not mentioned.
Is 42CRMO4 steel the same as EN19 steel?
The 42CrMo4 is mainly a European grade of the EN10083 and EN10250 standards, while the EN19 is a British grade of the BS970-1955 standards. Although the chemical composition is very close, it belongs to different grades and can be considered equivalent grades. Through technical adjustments, you can adjust their brand. Components to the corresponding valid ranges in the following table so that they can be used instead.
Other equivalent
China /GB 3077:42CrMoA
United States /ASTM A29:4140/4142
Japan /JIS G4105:SCM440
42CRMO4 steel FAQ
42CrMo4 steel is low carbon alloy steel?
From the above content, it can be seen that the average carbon content of 42CrMo4 is 0.42%, and the specific range is 0.38-0.45%, which does not belong to the low-carbon class (C≤0.25%), so 42CrMo4 steel belongs to the carbon-carbon low alloy steel.
What is 42CrMoS4 steel?
42CrMoS4, can be seen as the control of sulfur 42CrMo4,
So the question is, why add sulfur? As a harmful element, isn't the lower the better? As we all know, sulfur will increase the thermal brittleness of steel, reduce the strength and toughness of steel, and cause cracking.
However, steel with appropriate sulfur content can form more MnS with Mn element. In cutting, MnS can play the role of chip breaking and improve the cutting performance of steel. This is the beneficial side of sulfur, and free-cutting steel is a typical application.
How hard is 42CrMo4 steel?
42CrMo4 steel is generally supplied in hot rolled or annealed state, and its hardness is usually lower than 241HB. Such hardness is difficult to have a good performance in the application of the product.
If you want to use the characteristics of 42CrMo4 steel, it needs to be tempered to obtain satisfactory comprehensive performance. Its hardness is optional in the range of 28-58HRC, but is usually used between 28-34HRC.
Higher hardness applications of 42CrMo4 steel can be achieved by nitriding, with surface hardness up to 550-700HV3 and nitriding depth of 0.1-0.6mm.
Can 42CrMo4 steel be processed?
Generally speaking, the higher the hardness, the more difficult it is to process. Therefore, the 42CrMo4 steel without heat treatment has low hardness and is relatively easy to process. After softening annealing, 42CrMo4 steel is easier to work.
The hardness of 42CrMo4 steel after tempering is generally 300HB. Such hardness is still very common for machining. As long as you choose a reasonable speed and tools, you can still rest assured of processing.
Can 42CrMo4 steel be carburized?
42CrMo4 steel can be carburized, but it is not necessary. The average carbon content of 42CrMo4 is 0.42%, and as an alloy structural steel, it is suitable for tempering treatment to obtain good comprehensive mechanical properties.
42CrMo4 steel and 50CrMo4 steel
The strength and hardenability of 50CrMo4 steel is better than that of 42CrMo4 steel, but it is relatively poor in terms of weldability and toughness.
In terms of application, 50CrMo4 steel can be used for forgings with higher strength or larger cross-section than 42CrMo4 steel, such as large gear for locomotive traction, turbocharger transmission gear, rear axle, engine cylinder, 1200~2000m oil deep well drill pipe joints and other fishing gear. Sometimes 50CrMo4 can be used to replace tempered steel with higher nickel content.
How to make 42CRMO4/DIN1.7225 steel?
The process of manufacturing high-quality 42CrMo4 steel is a strict quality control process, and every step of the connection requires sufficient experience and strict quality control. From the picture below, we can roughly see a production flow chart.
The following is mainly about the following points of 42CrMo4 steel manufacturing.
Fusion casting technology
There are two main methods of smelting and casting, one is electric arc furnace smelting, secondary refining and vacuum degassing, and the other is the continuous casting technology of converter steelmaking used by large steel mills.
The difference is that electric arc furnace steelmaking is suitable for small batch production, and the composition of molten steel is greatly affected by scrap steel. The converter steelmaking is suitable for mass production and the purity of molten steel is high. Compared with electric arc furnace steelmaking, the smelting cycle is shorter and the power consumption is lower.
Hot working
Corresponding to smelting and casting processes, 42CrMo4 ingot produced by EAL+LF+VD is mainly used in hot forging processes, including free forging and die forging.
42CrMo4 billets produced by the converter + continuous casting process are usually used as hot-rolled products with extremely high production efficiency.
Finally, it should be noted that they can be applied to each other, but must match the size of the blank to ensure an adequate compression ratio.
Preliminary heat treatment process selection
For 42CrMo4 steel, after hot rolling or hot forging, it is usually delivered without heat treatment. However, sometimes considering the machinability of the material, 42CrMo4 steel is usually selected for softening annealing treatment.
42CrMo4 normalizing is often selected to improve processing performance, eliminate internal stress, and prepare a good metallurgical structure for final heat treatment.
What is the gas content of 42CRMO4 steel?
The gas in steel is a general term for oxygen, nitrogen, hydrogen and other gases in the medium absorbed during chemical and electrochemical reactions on the surface of steel in smelting, welding or steel. The gas in steel has an adverse effect on the properties of steel, and its content should be strictly controlled
Oxygen in steel
Steelmaking itself is an oxidation process. Although the deoxidizers such as ferromanganese, ferrosilicon and aluminum are added in the late period of steelmaking, some oxygen is still dissolved in the steel.
Oxygen is generally dissolved in ferrite, or the formation of FeO, SiO2, MnO, Al2O3 and other oxides (that is, non-metallic inclusions in steel), so that the tensile strength, plasticity and toughness of 42CrMo4 steel are reduced. Especially in the presence of inclusions, the fatigue strength of 42CrMo4 steel decreases and the cold and hot workability deteriorates.
Therefore, oxygen control technology such as VD deoxidation must be strictly used to make the oxygen content of 42CrMo4 steel less than 20ppm, or even lower.
Nitrogen in steel
In steelmaking, molten steel absorbs nitrogen from the air. Some dissolve in ferrite and some become nonmetallic inclusions. When 42CrMo4 steel does not contain Al, Ti, Zr and other elements, most of the nitrogen and iron form a needle-like compound Fe4N. Although the presence of Fe4N improves the strength of 42CrMo4 steel, it greatly reduces its plasticity and toughness.
By preventing LF nitrogen absorption technology and improving the VD denitrification rate, these two methods can effectively reduce the nitrogen content, which can effectively control the nitrogen content below 90ppm.
Hydrogen in steel
The solubility of hydrogen in steel decreases significantly with decreasing temperature. When hydrogen is present in its atomic state, it dissolves into the Spaces of iron. When the dissolved hydrogen in the steel exceeds 3 ml per 100 grams, it will exist in a molecular state, and hair-like cracks appear in the internal cross section of the ingot or forging, which is called cracking. They look like oval silvery white spots, so they are also called white spots.
White spots make steel hydrogen brittle. Low carbon steel is not easy to form white spots, but medium carbon alloy steel (such as AISI 1045 steel, C55 steel), especially medium carbon nickel chromium molybdenum steel (such as 34CrNiMo6 steel, 30CrNiMo8 steel, AISI 4340 steel), the most sensitive to hydrogen embrittling. For 42CrMo4 steel, it is also easy to form white spots, resulting in material cracking.
The VD vacuum degassing technology can effectively remove hydrogen. In order to avoid embrittleness, 42CrMo4 steel can also be annealed at about 650 ° C to diffuse hydrogen from the steel, eliminate the susaturated state, and achieve the purpose of removing hydrogen. Generally, the hydrogen content can be controlled below 2.0ppm
42CRMO4/DIN 1.7225 Heat treatment
42CrMo4/DIN 1.7225 Normalizing and annealing of steel
When 42CrMo4 steel needs to improve its overall performance, it is usually achieved by heat treatment. Before the final heat treatment, we first consider the preliminary heat treatment, the conventional methods include normalizing and annealing. Let's talk about the differences and characteristics of 42CrMo4 annealing and normalizing to help us choose when facing different requirements.
Different effects and purposes
42CrMo4 normalizing is mainly to refine the grain, homogenize the structure, and prepare the structure for the final heat treatment. The annealing time of 42CrMo4 steel is generally arranged after forging, hot rolling and welding, mainly to reduce the internal stress of the organization. Material, soften the structure, improve the turning performance.
