CN111633166B - Pre-cooling forging process for 38MnVS6 steel - Google Patents
Pre-cooling forging process for 38MnVS6 steel Download PDFInfo
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- CN111633166B CN111633166B CN202010466958.5A CN202010466958A CN111633166B CN 111633166 B CN111633166 B CN 111633166B CN 202010466958 A CN202010466958 A CN 202010466958A CN 111633166 B CN111633166 B CN 111633166B
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- forging
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
- B21J5/02—Die forging; Trimming by making use of special dies ; Punching during forging
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
- B21J1/06—Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K29/00—Arrangements for heating or cooling during processing
Abstract
The invention relates to the technical field of non-quenched and tempered steel hot forging, in particular to a 38MnVS6 steel precooling forging process, which is a new improved process, wherein the forging is not carried out after the heating is finished, but the forging is started when the forging blank is cooled for a period of time and the temperature is reduced to 850-900 ℃. After the pre-forging, the temperature of the forging stock is further reduced to about 800-850 ℃, and then the finish forging is carried out. The deformation is well distributed between the pre-forging and the final forging, and 30% -50% of deformation is generally reserved for the final forging, so that the structure after the final forging still has enough energy storage to realize recrystallization to refine the structure, but the grain size of a grain growth structure is not refined from 6 grade to about 8-9 grade, the impact toughness is greatly increased, the required appearance is obtained, the required performance is obtained, and the forming integrity is realized.
Description
Technical Field
The invention relates to the technical field of non-quenched and tempered steel hot forging, in particular to a pre-cooled forging process for 38MnVS6 steel.
Background
The 38MnVS6 steel is a non-quenched and tempered steel, and the contents of alloy elements are as follows: 0.34-0.41% of C, 0.15-0.8% of Si, 1.2-1.6% of Mn, 0.025% or less of P, 0.02-0.06% of S, 0.3% or less of Cr, 0.08% of Mo, 0.08-0.2% of V, 0.01-0.02% of N, and strengthening the steel by solid solution and precipitation, and can be used in a rolled state or a normalized state.
The non-quenched and tempered steel is prepared by adding vanadium, titanium and niobium microalloying elements on the basis of medium carbon manganese steel, so that the vanadium, titanium and niobium microalloying elements are dissolved in austenite in the heating process, and because the solid solubility of the vanadium, titanium and niobium in the austenite is reduced along with cooling, the microalloying elements vanadium, titanium and niobium are precipitated in the form of fine carbides or nitrides in ferrite and pearlite which are precipitated in advance, and the precipitates and a parent phase keep a coherent relationship, so that the steel is strengthened; the steel can obtain good mechanical properties in a hot rolling state, a forging state or a normalizing state, thereby shortening the production period and saving energy; the 38MnVS6 steel is one of the steels, is beneficial to machining due to the addition of the S element, and is the steel grade with better formability and performance.
At present, the forging process for 38MnVS6 steel is generally to heat to 1180 ℃ to make alloy solid-dissolve in a matrix, and then forging is carried out at a higher temperature, wherein the forging force is lower, the mold filling capacity is better, but the finish forging temperature is higher due to higher pre-forging temperature; the high finish forging temperature still enables the 38MnVS6 steel to have larger energy storage for the austenite grains to continue growing after the dynamic recrystallization caused by deformation begins, and in the subsequent cooling phase transformation, the coarser austenite grains also cause the ferrite grains and the pearlite grains after the phase transformation to be coarser, and the general grain size is grade 6; in 38MnVS6 steel, at a proper cooling rate, the particles precipitated from the solid solution alloying elements strengthen the matrix, and the toughness is reduced while the particle precipitation strengthening occurs, and particularly, the toughness is reduced more severely when the crystal grains are large.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the invention provides a 38MnVS6 steel precooling forging process, which is a new improved process, and aims to solve the problems that the existing non-quenched and tempered steel is high in finish forging temperature due to high heating temperature, and the excessive temperature can cause grain growth after recrystallization, so that austenite grains are coarse, ferrite grains and pearlite grains are coarse after phase transformation, and the impact toughness is damaged. After the pre-forging, the temperature of the forging stock is further reduced to about 800-850 ℃, and then the finish forging is carried out. The deformation is well distributed between the pre-forging and the final forging, and 30% -50% of deformation is generally reserved for the final forging, so that the structure after the final forging still has enough energy storage to realize recrystallization to refine the structure, and the crystal grains are not grown. The grain size can be thinned from 6 grades to about 8-9 grades, so that the impact toughness is greatly increased, the required appearance is obtained, the required performance is obtained, the formation integration is realized, and the problems are effectively solved.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a pre-cooling forging process for 38MnVS6 steel comprises
1) Blanking bar stock;
2) heating the bar to 1150-1200 ℃ to complete the solid solution process of the alloy elements;
3) the bar stock is placed in a transition area for pre-cooling after being discharged from the furnace, and the cooling temperature is controlled at 850-;
4) after cooling to 850-;
5) placing the blank after the pre-forging piece into a finish forging cavity, and performing finish forging when the temperature of the blank is reduced to 800-850 ℃ due to heat transfer, and ensuring that the finish forging has 30-50% of deformation;
6) after finishing forging, trimming;
7) after the edge cutting is finished, the forged part is placed into a controlled cooling device, the controlled cooling process is carried out at the cooling speed of 70 ℃/min, and the part is cooled to room temperature after the temperature reaches 400 ℃, so as to obtain fine grains.
Further, the fine crystal grains are 8-9 grades.
Further, in step 2), the bar is heated to 1150-.
Further, in step 3), the cooling temperature is controlled at 850-.
Further, in the step 7), the cooling speed in the controlled cooling process is 70 ℃/min.
The invention has the beneficial effects that: the invention provides a pre-cooling forging process for 38MnVS6 steel, which is a new improved process and is characterized in that forging is not performed after heating is finished, but the forging is started when a forging blank is cooled for a period of time and the temperature is reduced to 850-900 ℃. After the pre-forging, the temperature of the forging stock is further reduced to about 800-850 ℃, and then the finish forging is carried out. The deformation is well distributed between the pre-forging and the final forging, and 30% -50% of deformation is generally reserved for the final forging, so that the structure after the final forging still has enough energy storage to realize recrystallization to refine the structure, and the crystal grains are not grown. The grain size of the structure is thinned from 6 grades to about 8-9 grades, so that the impact toughness is greatly increased, the required appearance is obtained, the required performance is obtained, and the formation integration is realized.
Detailed Description
The invention provides a 38MnVS6 steel precooling forging process which comprises the following specific steps
1) Blanking bar stock;
2) heating the bar to 1150-1200 ℃ to complete the solid solution process of the alloy elements;
3) the bar stock is placed in a transition area for pre-cooling after being discharged from the furnace, and the cooling temperature is controlled at 850-;
4) after cooling to 850-;
5) placing the pre-forged blank into a finish forging cavity, wherein the temperature of the blank is reduced to 800-;
6) after finishing forging, trimming;
7) after the edge cutting is finished, the forged part is placed into a controlled cooling device, the controlled cooling process is carried out at a cooling speed of about 70 ℃/min, and the part is cooled to room temperature after the temperature reaches 400 ℃ so as to obtain the required structure and high impact toughness.
According to the principle that deformation at a proper low temperature is beneficial to improving the phase change nucleation rate to refine grains and fine grains are beneficial to improving the toughness, the general forging process parameters are adjusted: after heating, firstly, forging is not carried out, but forging is started when the forging stock is cooled for a period of time and the temperature is reduced to 850-900 ℃, wherein the precooling stage is always in an austenite single-phase region, and the structure does not change except the temperature reduction; after the pre-forging, the temperature of the forging is further reduced to about 800-850 ℃, and then the finish forging is carried out. The deformation is well distributed between the pre-forging and the final forging, and 30% -50% of deformation is generally reserved for the final forging, so that the structure after the final forging still has enough energy storage to realize recrystallization to refine the structure, and the crystal grains are not grown. The refined structure provides a large number of nucleation positions for subsequent phase transformation, and the deformation-induced defects can also increase the nucleation rate, so that the ferrite and pearlite grain structures after the phase transformation are further refined. Under a proper cooling speed, the structure grain size is thinned from 6 grades to about 8-9 grades, so that the impact toughness is greatly increased, the required appearance is obtained, the required performance is obtained, and the forming integration is realized.
The reason why the 38MnVS6 steel needs high temperature heating is that the matrix structure contains trace alloying elements which will precipitate in the controlled cooling process after forging to form strengthening particles, and the strength of the structure is improved by precipitation strengthening without going through a heat treatment process again. However, the alloying elements are dissolved into the matrix at a high temperature to precipitate fine particles in subsequent cooling, so as to achieve the purpose of strengthening, the high temperature is generally above 1050 ℃, and the heating temperature before forging is generally increased to about 1150-. When forging is started at the temperature, due to the fact that the pre-forging temperature is too high, the temperature is still quite high after finish forging, then recrystallized grains continue to grow, the nucleation rate of subsequent phase change is reduced, the obtained grains are also relatively large, and the impact toughness is damaged by the large grains;
in order to eliminate the adverse effect of high-temperature forging, a bar heated before forging is precooled to a lower temperature, then forging is started at the cooled temperature, 30-50% of deformation is reserved for final forging deformation, a relatively fine grain structure can be obtained after final forging, meanwhile, grain growth does not occur due to the lower temperature, more deformation defects are reserved due to the lower temperature, more nucleation positions are provided for subsequent phase transformation, and a high nucleation rate is obtained through a proper cooling control process, so that the grain structure is refined. The key of the process is precooling cooling and reasonable finish forging deformation, and the technology of precooling cooling to proper temperature and then forging and ensuring proper finish forging deformation is called precooling forging process.
Compared with the prior art, the process does not perform forging after heating, but starts forging after cooling to a certain temperature, and ensures that the final forging has 30-50% of deformation, so that an austenite structure obtains fine recrystallized grains at a lower temperature without growing up, and the fine grain structure is obtained by controlling the subsequent cooling process, thereby improving the impact toughness and realizing the integration of formability.
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (2)
1. A pre-cooling forging process for 38MnVS6 steel is characterized in that: comprises that
1) Blanking bar stock;
2) heating the bar to 1150-1200 ℃ to complete the solid solution process of the alloy elements;
3) the bar stock is placed in a transition area for pre-cooling after being discharged from the furnace, and the cooling temperature is controlled at 850-;
4) after cooling to 850-;
5) after the pre-forging is finished, the temperature of the blank is reduced to 800-850 ℃ due to heat transfer, the blank is placed into a finish forging cavity for finish forging, and the deformation of 30-50% of the finish forging is ensured;
6) after finishing forging, trimming;
7) and after the edge cutting is finished, placing the forged part into a controlled cooling device, carrying out a controlled cooling process at a cooling speed of 70 ℃/min, and cooling to room temperature after the temperature reaches 400 ℃ to obtain fine crystal grains, wherein the fine crystal grains are 8-9 grades.
2. The pre-cooling forging process of 38MnVS6 steel according to claim 1, wherein: in the step 7), the cooling speed in the controlled cooling process is 70 ℃/min.
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| CN111633166B true CN111633166B (en) | 2022-03-11 |
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| CN112501505A (en) * | 2020-11-13 | 2021-03-16 | 江苏联峰能源装备有限公司 | Preparation method of non-modulated steel 38MnVS6 |
Citations (4)
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| CN101492787A (en) * | 2009-03-05 | 2009-07-29 | 芜湖三联锻造有限公司 | Medium-high-carbon microalloy non-hardened and tempered steel and controlled forging and cooling process |
| CN104060132A (en) * | 2014-07-23 | 2014-09-24 | 卢德强 | Novel aluminum alloy and method for manufacturing aluminum foil with high deep-drawing performance by continuous cast-rolling |
| CN107470852A (en) * | 2016-06-07 | 2017-12-15 | 南京工程学院 | A kind of Micro Alloying semiaxis and its manufacture method |
| CN107475501A (en) * | 2016-06-07 | 2017-12-15 | 江苏恒力制动器制造有限公司 | A kind of Micro Alloying brake camshaft and its manufacture method |
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2020
- 2020-05-28 CN CN202010466958.5A patent/CN111633166B/en active Active
Patent Citations (4)
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| CN101492787A (en) * | 2009-03-05 | 2009-07-29 | 芜湖三联锻造有限公司 | Medium-high-carbon microalloy non-hardened and tempered steel and controlled forging and cooling process |
| CN104060132A (en) * | 2014-07-23 | 2014-09-24 | 卢德强 | Novel aluminum alloy and method for manufacturing aluminum foil with high deep-drawing performance by continuous cast-rolling |
| CN107470852A (en) * | 2016-06-07 | 2017-12-15 | 南京工程学院 | A kind of Micro Alloying semiaxis and its manufacture method |
| CN107475501A (en) * | 2016-06-07 | 2017-12-15 | 江苏恒力制动器制造有限公司 | A kind of Micro Alloying brake camshaft and its manufacture method |
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| 重型汽车用非调质钢曲轴的质量控制概述;纪同圣;《重型汽车》;20180228(第1期);第33-34页 * |
| 非调质钢在汽车零部件上应用的可行性分析;魏元生;《热加工工艺》;20140731;第43卷(第14期);第78-82页 * |
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Address after: 213164 No.26 Longyu West Road, Wujin high tech Zone, Changzhou City, Jiangsu Province Applicant after: Jiangsu Longcheng Precision Forging Group Co.,Ltd. Address before: 213164 No.26 Longyu West Road, Wujin high tech Zone, Changzhou City, Jiangsu Province Applicant before: JIANGSU LONGCHENG PRECISION FORGING Co.,Ltd. |
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