Production process of 20CrMnTi ultra-fine grain forge piece

Abstract

The invention provides a production process of a 20CrMnTi ultra-fine grain forge piece, which sequentially comprises the working procedures of medium-frequency heating, forging forming, air cooling and annealing, the forging forming working procedure adopts warm forging forming, a heated bar is extruded and formed in a 800T press, the deformation rate during extrusion is 0.66 * s <-1 >-0.78 * s <-1 >, the deformation amount of the cross section after forming is greater than 40%, and the deformation amount of the cross section after forming is greater than 40%. A continuous push rod type annealing furnace is adopted in the annealing process, a room-temperature product is conveyed into the continuous push rod type annealing furnace, the annealing temperature is set to be 800 DEG C, heat preservation is conducted for 2 hours, and after slow cooling is conducted to 640 DEG C, the product is discharged out of the furnace and air-cooled to the room temperature. According to the method, grains are refined through dynamic recrystallization in the forging process, the structure form is optimized through a specific annealing process, and the grain size is uniform while the thin-sheet pearlite is obtained.

Description

Technical Field

[0001] The invention relates to the field of steel forging production and manufacturing, and in particular to a production process of 20CrMnTi ultrafine grain forgings. Background Art

[0002] Fine grain strengthening can achieve both strength and toughness, and is a current research hotspot for automotive steel materials. In industry, ultrafine grain steel refers to steel with an actual grain size of micrometers. With the continuous advancement of metallurgical technology and production processes, my country's steel mills can already mass-produce certain ultrafine grain steels. Compared with traditional steels of the same strength, ultrafine grain steels have low carbon and low carbon equivalent and low impurities, which is not only beneficial to its weldability, but also has good fatigue resistance and high strength, as well as good low-temperature toughness and other advantages. At the same time, under the same chemical composition, the mechanical properties of ultrafine grain steel are far superior to those of ordinary fine grain steel.

[0003] In the prior art, the production process of ultrafine grain steel mainly involves adding microalloying elements such as Cu, Nb, V, and Ti during smelting to prevent grain growth by using the pinning effect of the compounds. This requires special preparation during smelting and then a specific rolling process.

[0004] At present, the application of ultrafine grain steel in industry is mainly concentrated in the field of plate, and there is no relevant introduction in the field of steel forging production.

[0005] Therefore, it is necessary to provide a new technical solution. Summary of the invention

[0006] In order to solve the technical problems existing in the prior art, the present invention discloses a production process of 20CrMnTi ultrafine grain forgings, and the specific technical scheme is as follows:

[0007] The invention provides a production process of 20CrMnTi ultrafine grain forgings, which sequentially comprises medium frequency heating, forging, air cooling and annealing processes.

[0008] Furthermore, the medium frequency heating process includes preheating the rod to 150-200°C in a medium frequency heating furnace, coating the surface of the rod with a graphite coating, and heating to 680-700°C.

[0009] Furthermore, the forging process adopts warm forging, and the heated bar is extruded in an 800T press, and the deformation rate of the bar during extrusion is 0.66·s -1 ~0.79·s -1 , the deformation of the cross section of the bar after forming is greater than 40%.

[0010] Furthermore, in the forging process, the upsetting ratio of the height of the bar before and after forming is 1.97, the deformation time of the bar is 2.5-3s, and the deformation of the cross section of the bar after forming is the difference between the cross-sectional area of ​​the bar before and after deformation divided by the cross-sectional area of ​​the bar before deformation.

[0011] Furthermore, the air cooling process includes air cooling the forged product to room temperature via a conveyor belt.

[0012] Furthermore, the annealing process uses a continuous push-rod annealing furnace, and the room temperature product is sent to the continuous push-rod annealing furnace. The annealing temperature is set to 800°C, and it is kept warm for 2 hours. After slowly cooling to 640°C, it is taken out of the furnace and air-cooled to room temperature, and an ultrafine ferrite + lamellar pearlite structure can be obtained.

[0013] The present invention has the following beneficial effects:

[0014] 1. The production process of 20CrMnTi ultrafine-grained forgings provided by the present invention utilizes specific forging conditions to dynamically recrystallize and refine the grains of traditional fine-grained steel during the forging process, and optimizes the organizational morphology through a specific annealing process to achieve ultrafine crystallization of the forging organization, obtain fine lamellar pearlite and uniform grain size.

[0015] 2. The production process of 20CrMnTi ultrafine grain forgings provided by the present invention can obtain forgings with an actual grain size of up to 12 levels and a grain size of about 5-10 μm. The forgings have a uniform structure of ferrite + fine lamellar pearlite.

[0016] 3. The production process of 20CrMnTi ultrafine grain forgings provided by the present invention can obtain steel forgings with ultrafine grain size, and improve the mechanical properties of forgings by grain refinement. Compared with ordinary forgings, the yield strength of forgings obtained by the present invention is greatly improved. For forgings with higher service strength, the application of the present invention can greatly improve the service life of parts.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1This is a metallographic photograph of a 20CrMnTi low-carbon alloy steel ultrafine grain forging, magnification: 100 times.

[0020] Figure 2 This is a metallographic photograph of a 20CrMnTi low-carbon alloy steel ultrafine grain forging, magnification: 500 times. DETAILED DESCRIPTION

[0021] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In the description of the present invention, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0023] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] The invention discloses a production process of a 20CrMnTi ultrafine grain forging, which sequentially comprises medium frequency heating, forging, air cooling and annealing processes.

[0025] The medium frequency heating process includes preheating the rod to 150-200°C through a medium frequency heating furnace, coating the surface of the rod with a graphite coating, and heating to 680-700°C.

[0026] The forging process adopts warm forging, and the heated bar is extruded in an 800T press. The deformation rate of the bar during extrusion is 0.66·s -1 ~0.79·s -1 , the deformation of the cross section of the bar after forming is greater than 40%.

[0027] The deformation speed of the bar is the upsetting ratio of the bar divided by the deformation time. In the forging process of the present application, the upsetting ratio of the height of the bar before and after forming is 1.97, and the deformation time of the bar is 2.5-3s. The deformation amount of the cross section of the bar after forming is the difference between the cross-sectional area of ​​the bar after deformation and before deformation divided by the cross-sectional area of ​​the bar before deformation.

[0028] The air cooling process includes air cooling the forged product to room temperature via a conveyor belt.

[0029] The annealing process adopts a continuous push-rod annealing furnace, and the room temperature product is sent to the continuous push-rod annealing furnace. The annealing temperature is set to 800°C, and it is kept warm for 2 hours. After slowly cooling to 640°C, it is taken out of the furnace and air-cooled to room temperature, and an ultrafine ferrite + lamellar pearlite structure can be obtained.

[0030] refer to Figure 1 and Figure 2 According to the process of the present invention, ultrafine grains with an actual grain size of 5-10 μm can be obtained, and the forging structure is ferrite + fine lamellar pearlite. While improving the mechanical properties of the forging, the excellent mechanical processing properties of the material itself are not damaged.

[0031] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0032] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify and vary the above embodiments within the scope of the present invention.

Claims

1. A production process for 20CrMnTi ultrafine grain forgings, characterized in that: It includes medium frequency heating, forging, air cooling and annealing processes in sequence.

2. The production process of 20CrMnTi ultrafine grain forgings according to claim 1, characterized in that: The medium frequency heating process includes preheating the rod to 150-200°C through a medium frequency heating furnace, coating the surface of the rod with a graphite coating, and heating to 680-700°C.

3. The production process of 20CrMnTi ultrafine grain forgings according to claim 2, characterized in that: The forging process adopts warm forging, and the heated bar is extruded in an 800T press. The deformation rate of the bar during extrusion is 0.66·s -1 ~0.79·s -1 , the deformation of the cross section of the bar after forming is greater than 40%.

4. The production process of 20CrMnTi ultrafine grain forgings according to claim 3, characterized in that: In the forging process, the upsetting ratio of the height of the bar before and after forming is 1.97, the deformation time of the bar is 2.5-3s, and the deformation of the cross section of the bar after forming is the difference between the cross-sectional area of ​​the bar before and after deformation divided by the cross-sectional area of ​​the bar before deformation.

5. The production process of 20CrMnTi ultrafine grain forgings according to claim 1, characterized in that: The air cooling process includes air cooling the forged product to room temperature via a conveyor belt.

6. The production process of 20CrMnTi ultrafine grain forgings according to claim 1, characterized in that: The annealing process adopts a continuous push-rod annealing furnace, and the room temperature product is sent to the continuous push-rod annealing furnace. The annealing temperature is set to 800°C, and it is kept warm for 2 hours. After slowly cooling to 640°C, it is taken out of the furnace and air-cooled to room temperature, and an ultrafine ferrite + lamellar pearlite structure can be obtained.

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