What are the performance differences between steel plates and forgings?
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Our company manufactures a certain type of product, one of the components of which is made from material S22253III (in accordance with standard NB/T47010-2017). The final product is obtained after machining this material, but the downside is that the cost of this material is very high, as a large amount of material is removed during the machining process. By referring to standard GB/T24511-2017, it is possible to find steel plates made from material S22253. The comparison table of chemical elements and mechanical properties between the two standards is as follows: C Si Mn Cr Ni Mo N P S – For forgings: 0.30 1.0 2.0 21-23 4.5-6.5 2.5-3.5 0.08-0.20 0.03 0.015; C Si Mn Cr Ni Mo N P S – For steel plates: 0.03 1.0 2.0 21-23 4.5-6.5 2.5-3.5 0.08-0.20 0.03 0.015. Rm, Rp0.2, A, HB, WHRC: 620, 450, 25 / / 620, 450, 25, 293, 31. By comparing the chemical elements and mechanical properties, it can be seen that there is little difference between forgings and steel plates; the only additional requirement for steel plates is regarding hardness. In my opinion, the other requirements specified in the standards also have little impact on the performance of the material. So, is it possible to use steel plates instead of forgings? Using steel plates of a certain thickness for machining results in significantly lower raw material costs. Additionally, the steel plates can be subjected to cold working before machining, which helps to give them a shape more suitable for processing and thus reduces the amount of work required during machining, saving more costs. Theoretically, forging can eliminate defects such as cast porosity that occur during metal smelting, and it improves the microstructural integrity of the metal; moreover, since the complete metal flow patterns are preserved, forgings should possess better mechanical properties. However, according to standard requirements, these superior properties of forgings are not reflected. I would appreciate some guidance from those who are more experienced
Due to processing methods, the fibers in the steel plate material have a directional structure, resulting in certain differences in properties depending on the direction； The material fibers in forged parts are uniform throughout, and the material has no directional properties; as a result, its formability strength may be slightly lower. However, its mechanical properties are significantly better than those of steel plates, which is why forged parts are used in applications that require high pressures, thick components, or critical structural elements. But the price using forgings will be higher. For thin sheet parts, steel plates are often chosen.
The biggest difference lies in the processing method: steel plates are produced by rolling, while forgings are created through forging. In terms of mechanical properties, forgings exhibit better isotropy, whereas steel plates can only ensure uniform mechanical properties in the plane of the plate.
Steel plates are mostly produced by rolling, and the final straightening process results in localized high residual stresses on the surface of the plate. During straightening, the elongation rate is approximately 0.25–1%, with about half of the volume undergoing plastic deformation. To achieve uniform deformation, a deformation rate of at least 5% is required; this is also why standards specify that heat treatment is necessary when the deformation rate exceeds a certain threshold. Forgings have a requirement regarding the forging ratio; this is an indicator designed to ensure uniform deformation of the material when it is in a hot state, thereby reducing local residual stresses. The other requirements are mostly related to controlling the material’s composition, while the hardness requirement for sheets is also an additional constraint based on strength considerations.
Simply put, on a microscopic level, in the thickness direction, you can consider a forged piece as a single entity, whereas steel plates are layered. There will be differences in mechanical properties between layers. Of course, the overall structure of a forging also tends toward integrity; the higher the grade of the forging, the more it moves in this direction of integrity.
Thin ones are mostly made of steel plates, while only thick ones can be forged. Why do I feel that steel plates are more expensive?
You should probably ask the customer base that uses your products about this
The original poster has a really creative mind. The standard mechanical properties seem similar, but the actual differences are significant. The mechanical properties of steel plates in the direction of rolling are similar to those of forgings, but they are much lower in the direction perpendicular to rolling and in the Z-direction. Some money can be saved, while some cannot! Use the standard.