CN115449607B - Method for determining isothermal gas quenching process parameters for prolonging service life of cold working die material - Google Patents
Method for determining isothermal gas quenching process parameters for prolonging service life of cold working die material Download PDFInfo
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- 238000010791 quenching Methods 0.000 title claims abstract description 174
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- 238000000034 method Methods 0.000 title claims abstract description 89
- 239000000463 material Substances 0.000 title claims abstract description 64
- 238000005482 strain hardening Methods 0.000 title claims abstract description 49
- 238000012360 testing method Methods 0.000 claims abstract description 69
- 238000009863 impact test Methods 0.000 claims abstract description 28
- 238000004321 preservation Methods 0.000 claims abstract description 19
- 238000005299 abrasion Methods 0.000 claims abstract description 14
- 238000009864 tensile test Methods 0.000 claims abstract description 13
- 238000013461 design Methods 0.000 claims abstract description 8
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- 238000007550 Rockwell hardness test Methods 0.000 claims description 5
- 238000007542 hardness measurement Methods 0.000 claims description 5
- 238000005259 measurement Methods 0.000 claims description 5
- 238000005303 weighing Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 149
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- 238000005261 decarburization Methods 0.000 description 1
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- 230000007613 environmental effect Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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Abstract
The invention relates to a method for determining isothermal gas quenching process parameters for prolonging the service life of a cold working die material. The technical proposal is as follows: 5 factors of quenching temperature, heat preservation time, gas quenching pressure, isothermal temperature and isothermal time are selected to carry out 3-level orthogonal test design, and L is established 18 (3 5 ) An orthogonal test table; taking 18 multiplied by 3 mould materials as original samples, carrying out isothermal gas quenching according to a scheme in an orthogonal test table, and measuring the hardness of each group of samples after isothermal gas quenching (hereinafter referred to as samples); the room temperature impact test, the abrasion resistance test and the tensile test were sequentially performed on 3 samples in each group, respectively. According to the Rockwell hardness Hi, the impact toughness alpha ki, the abrasion loss Mi and the tensile strength YSi, obtaining the comprehensive performance index delta i of the sample, and selecting the isothermal gas quenching process parameter corresponding to the maximum value of delta i as a basis for determining the parameters in the production of the cold working die material. The invention can greatly improve various performances and prolong the service life of the cold working die material after isothermal gas quenching.
Description
Technical Field
The invention belongs to the technical field of vacuum isothermal quenching methods. In particular to a method for determining isothermal gas quenching process parameters for prolonging the service life of cold working die materials.
Background
Isothermal gas quenching refers to an isothermal quenching process of a mold using inert gas in a vacuum gas quenching furnace in order to achieve smooth quenching of the mold material. The method is characterized by no decarburization, no oxidation, small deformation, high surface smoothness and environmental protection after the die is quenched. When the isothermal gas quenching process parameters are not matched with the corresponding die materials, the problems that the die materials are uneven in tissue distribution and unqualified in performance after quenching, easy to crack in subsequent treatment and the like can occur, and the service life of the die materials is seriously influenced. Therefore, each mold material needs the corresponding isothermal gas quenching process parameters, so that the performance of the material is improved and the service life of the mold is prolonged through the isothermal gas quenching process.
Wang Lijun et al (Wang Lijun, miao Bin, meng Xian New. Hardness and metallographic structure analysis of Cr12MoV steel under different heat treatment conditions [ J ]. Mould industry, 2005 (09): 52-56.) studied hardness changes after quenching and tempering at different temperatures with Cr12MoV cold work mould steel as the subject of investigation. Studies have shown that: the quenching temperature is 1010-1040 ℃, and the obtained die steel has better performance. However, the conventional heat treatment process adopted in the literature is easy to form irregular netlike carbide, cracking and peeling are easy to form at the stress part of the die, and the service life of the die is poor.
Su Liwu et al (Su Liwu. Vacuum heat treatment Process for DIEVAR die Steel [ J ]. Heat treatment, 2017,32 (1): 36-39.) the effects of different quench temperatures on DIEVAR die steel were studied with the conclusion that: under the condition of the same quenching pressure, the higher the quenching temperature is, the higher the hardness of the steel is, and the optimal technological parameter of the diear die steel is that the quenching temperature is 1020 ℃, and the quenching pressure is 4.5bar. However, the process parameters provided herein are not comprehensive, cannot be used for actual production, and do not give a standard and complete method of determining optimal process parameters.
A technology of vacuum heat treatment technology (CN 202010933061.9) for CrWMn die steel, which discloses quenching temperatures, heat preservation time and quenching pressures of cold working dies with different sizes. However, isothermal time and isothermal temperature among the process parameters are not disclosed, nor are methods for determining the process parameters, the specific values of which are only applicable to CrWMn cold work die steels.
Disclosure of Invention
The present invention aims to overcome the drawbacks of the prior art. Aims to provide a method for determining isothermal gas quenching process parameters for prolonging the service life of cold working die materials; the method is suitable for determining isothermal gas quenching process parameters of various cold-working die materials, and the determined process parameters can be used as the basis for determining the isothermal gas quenching process parameters of the cold-working die materials in industrial production, so that the performance and the service life of the cold-working die materials can be improved.
In order to achieve the above purpose, the steps of the technical scheme adopted by the invention are as follows:
step 1, selecting 5 factors of quenching temperature, heat preservation time, gas quenching pressure, isothermal temperature and isothermal time to perform 3-level orthogonal test design, and establishing L 18 (3 5 ) Orthogonal test table, 18 sets of orthogonal test protocols were obtained.
The 5 process parameters range: quenching temperature is 950-1050 ℃, heat preservation time is 10-40 min, gas quenching pressure is 3-9 bar, isothermal temperature is 200-280 ℃, and isothermal time is 1-3 h.
And 2, selecting 18X 3 cold-working die materials produced in the same batch as 18 groups of original samples, wherein each group of the cold-working die materials comprises 3 blocks.
And 3, selecting 3 original samples of the 1 st group, and carrying out isothermal gas quenching according to the 1 st orthogonal test scheme in the 1 st group to obtain 3 isothermal gas quenched samples of the 1 st group.
And 3 original samples of the 2 nd group are selected, isothermal gas quenching is carried out according to the 2 nd orthogonal test scheme in the step 1, and 3 isothermal gas quenched samples of the 2 nd group are obtained.
And so on;
and 3 original samples of the 18 th group are selected, isothermal gas quenching is carried out according to the 18 th orthogonal test scheme in the step 1, and 3 isothermal gas quenched samples of the 18 th group are obtained.
Step 4, according to the requirements of GB/T230.1-2004 Rockwell hardness test method, hardness measurement is carried out on 18 groups obtained in the step 3 and 3 isothermal gas-quenched samples thereof respectively:
firstly, 7 points are selected on the upper surface of a sample after isothermal gas quenching of the 1 st block of the first group to measure hardness, and the hardness value of the sample after isothermal gas quenching of the 1 st block is an average value of 5 hardness values after the maximum value and the minimum value are removed; obtaining the hardness values of the other 2 samples in the 1 st group according to the measurement; further, an average value H1 of the hardness of the samples after isothermal gas quenching of group 1 and 3 was obtained.
And so on;
the average value Hi of the hardness of the samples after isothermal gas quenching of 3 pieces per group was obtained.
And 5, taking one piece from the 1 st group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into four room temperature impact test samples with the length of 10mm multiplied by 55mm, respectively performing room temperature impact tests according to GB/T229-2007 Charpy pendulum impact test method for metal materials, measuring the impact toughness of the four room temperature impact test samples of the 1 st group, and obtaining the impact toughness average value alpha k1 of the four room temperature impact test samples of the 1 st group.
And so on;
the average value αki of the impact toughness of each group of the samples after isothermal gas quenching was obtained.
And 6, firstly, taking one sample from each group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into wear samples, then performing room-temperature wear tests on a friction and wear tester according to ASTM standard D3702-94 (1999), and measuring by adopting a weighing method to obtain the wear quantity Mi of each group of wear samples.
And 7, respectively performing linear cutting on the last sample in each group of isothermal gas quenched samples obtained in the step 4 according to the specification in GB 228-2002 'room temperature tensile test method for metal materials', processing the last sample into tensile samples with specified sizes, and sequentially performing tensile tests to obtain the tensile strength YSi of each group of tensile samples.
Step 8, obtaining the comprehensive performance index delta i of the isothermal gas quenched sample according to the Rockwell hardness Hi, the impact toughness alpha ki, the abrasion loss Mi and the tensile strength YSi measured in the steps 4 to 7
In the formula (1):
hi represents the average hardness of any group of samples after isothermal gas quenching, and the unit is HRC;
αki represents the average value of the impact toughness of any group of samples after isothermal gas quenching, and the unit is J/cm 2 ；
Mi represents the abrasion loss of any group of samples after isothermal gas quenching, and the unit is mg;
YSi represents the tensile strength of any group of samples after isothermal gas quenching, and the unit is MPa;
δi represents the comprehensive performance index of any group of samples after isothermal gas quenching.
In steps 4 to 8, i represents the serial number of the sample group corresponding to any one of the 18 orthogonal test schemes, and i is a natural number of 1 to 18.
And 9, selecting isothermal gas quenching process parameters corresponding to a group of test schemes with the maximum delta i value from the comprehensive performance index delta i obtained in the step 8, and taking the isothermal gas quenching process parameters as the basis for determining isothermal gas quenching process parameters of the cold working die material in industrial production.
By adopting the method, compared with the prior art, the invention has the following positive effects:
1. the invention determines the range of quenching temperature, heat preservation time, gas quenching pressure, isothermal temperature and isothermal time, carries out orthogonal test design according to the level of 5 factors and 3, and establishes L 18 (3 5 ) The orthogonal test table, after carrying out isothermal gas quenching according to the established test scheme, carries out hardness test, room temperature impact test, wear resistance test and tensile test on each group of samples after isothermal gas quenching,the comprehensive performance index delta i of the sample after isothermal gas quenching is obtained, a group of isothermal gas quenching process parameters corresponding to a test scheme with the largest delta i value are selected as the basis for determining the isothermal gas quenching process parameters of the cold-working die materials in industrial production by comparing the delta i values, and the method is suitable for determining the isothermal gas quenching process parameters of various cold-working die materials, and can improve the performance of the cold-working die materials and prolong the service life of the cold-working die.
2. According to the invention, 5 technological parameters of isothermal gas quenching of the cold-working die material are reasonably configured, isothermal gas quenching treatment is carried out on the cold-working die material under the technological parameters, and test results show that: the hardness, impact toughness, wear resistance and tensile strength of the die material are all improved, the toughness nest density degree in the die material is improved after the fracture of steel is detected, and the die material is observed through a scanning electron microscope image: compared with the conventional heat treatment, the strip-shaped carbide of the cold-work die material subjected to isothermal gas quenching by adopting the process parameters determined by the invention disappears, the carbide is uniformly distributed, and the metal grains are finer. Therefore, the determined technological parameters of the invention can improve the performance of the cold-work die material after quenching, thereby prolonging the service life of the die.
Therefore, the invention is suitable for determining the isothermal gas quenching process parameters of various cold-working die materials, and the determined process parameters can be used as the basis for determining the isothermal gas quenching process parameters of the cold-working die materials in industrial production, thereby improving the performance and the service life of the cold-working die materials.
Drawings
FIG. 1 is a scanning electron microscope image of cold work die steel after isothermal gas quenching using the process parameters determined in the present invention;
fig. 2 is a scanning electron microscope image of a cold work die steel after conventional heat treatment.
Detailed description of the preferred embodiments
The invention is further described in connection with the drawings and the detailed description which follow, without limiting the scope thereof.
A method for determining isothermal gas quenching process parameters for prolonging service life of cold working mold materials. The determination method in the specific embodiment is as follows:
step 1, selecting 5 factors of quenching temperature, heat preservation time, gas quenching pressure, isothermal temperature and isothermal time to perform 3-level orthogonal test design, and establishing L 18 (3 5 ) Orthogonal test table, 18 sets of orthogonal test protocols were obtained.
The 5 process parameters range: quenching temperature is 950-1050 ℃, heat preservation time is 10-40 min, gas quenching pressure is 3-9 bar, isothermal temperature is 200-280 ℃, and isothermal time is 1-3 h.
And 2, selecting 18X 3 cold-working die materials produced in the same batch as 18 groups of original samples, wherein each group of the cold-working die materials comprises 3 blocks.
And 3, selecting 3 original samples of the 1 st group, and carrying out isothermal gas quenching according to the 1 st orthogonal test scheme in the 1 st group to obtain 3 isothermal gas quenched samples of the 1 st group.
And 3 original samples of the 2 nd group are selected, isothermal gas quenching is carried out according to the 2 nd orthogonal test scheme in the step 1, and 3 isothermal gas quenched samples of the 2 nd group are obtained.
And so on;
and 3 original samples of the 18 th group are selected, isothermal gas quenching is carried out according to the 18 th orthogonal test scheme in the step 1, and 3 isothermal gas quenched samples of the 18 th group are obtained.
Step 4, according to the requirements of GB/T230.1-2004 Rockwell hardness test method, hardness measurement is carried out on 18 groups obtained in the step 3 and 3 isothermal gas-quenched samples thereof respectively:
firstly, 7 points are selected on the upper surface of a sample after isothermal gas quenching of the 1 st block of the first group to measure hardness, and the hardness value of the sample after isothermal gas quenching of the 1 st block is an average value of 5 hardness values after the maximum value and the minimum value are removed; obtaining the hardness values of the other 2 samples in the 1 st group according to the measurement; further, an average value H1 of the hardness of the samples after isothermal gas quenching of group 1 and 3 was obtained.
And so on;
the average value Hi of the hardness of the samples after isothermal gas quenching of 3 pieces per group was obtained.
And 5, taking one piece from the 1 st group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into four room temperature impact test samples with the length of 10mm multiplied by 55mm, respectively performing room temperature impact tests according to GB/T229-2007 Charpy pendulum impact test method for metal materials, measuring the impact toughness of the four room temperature impact test samples of the 1 st group, and obtaining the impact toughness average value alpha k1 of the four room temperature impact test samples of the 1 st group.
And so on;
the average value αki of the impact toughness of each group of the samples after isothermal gas quenching was obtained.
And 6, firstly, taking one sample from each group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into wear samples, then performing room-temperature wear tests on a friction and wear tester according to ASTM standard D3702-94 (1999), and measuring by adopting a weighing method to obtain the wear quantity Mi of each group of wear samples.
And 7, respectively performing linear cutting on the last sample in each group of isothermal gas quenched samples obtained in the step 4 according to the specification in GB 228-2002 'room temperature tensile test method for metal materials', processing the last sample into tensile samples with specified sizes, and sequentially performing tensile tests to obtain the tensile strength YSi of each group of tensile samples.
Step 8, obtaining the comprehensive performance index delta i of the isothermal gas quenched sample according to the Rockwell hardness Hi, the impact toughness alpha ki, the abrasion loss Mi and the tensile strength YSi measured in the steps 4 to 7
In the formula (1):
hi represents the average hardness of any group of samples after isothermal gas quenching, and the unit is HRC;
αki represents the average value of the impact toughness of any group of samples after isothermal gas quenching, and the unit is J/cm 2 ；
Mi represents the abrasion loss of any group of samples after isothermal gas quenching, and the unit is mg;
YSi represents the tensile strength of any group of samples after isothermal gas quenching, and the unit is MPa;
δi represents the comprehensive performance index of any group of samples after isothermal gas quenching.
In steps 4 to 8, i represents the serial number of the sample group corresponding to any one of the 18 orthogonal test schemes, and i is a natural number of 1 to 18.
And 9, selecting isothermal gas quenching process parameters corresponding to a group of test schemes with the maximum delta i value from the comprehensive performance index delta i obtained in the step 8, and taking the isothermal gas quenching process parameters as the basis for determining isothermal gas quenching process parameters of the cold working die material in industrial production.
Example 1
1. A method for determining isothermal gas quenching process parameters for prolonging service life of cold working mold materials. The method in this embodiment comprises the following steps:
step 1, the cold working mold material in this embodiment is Cr12MoV. According to practical experience and a phase change curve of Cr12MoV cold-work die steel, 3-level orthogonal test design is carried out by selecting 5 factors of quenching temperature, heat preservation time, gas quenching pressure, isothermal temperature and isothermal time, and L shown in table 1 is established 18 (3 5 ) Orthogonal test table, 18 sets of orthogonal test protocols were obtained.
The 5 process parameters range: the quenching temperature is 950-1050 ℃; the heat preservation time is 10 min-40 min; the gas quenching pressure is 3-9 bar; isothermal temperature is 200-280 ℃; isothermal time is 1-3 h.
Five factors and three levels were valued: quenching temperature is 950 ℃, 1000 ℃ and 1050 ℃; the heat preservation time is 10min, 25min and 40min; the gas quenching pressure is 3bar, 6bar and 9bar; isothermal temperature is 200 ℃, 240 ℃ and 280 ℃; isothermal time is 1h, 2h and 3h.
Table 1L 18 (3 5 ) Orthogonal test meter
And 2, selecting 18X 3 Cr12MoV cold-working die materials produced in the same batch as 18 groups of original samples, wherein each group of the original samples comprises 3 blocks. Each set of original samples: the length is 75mm; a width of 25mm; the height is 20mm.
And 3, selecting 3 original samples of the 1 st group, and carrying out isothermal gas quenching according to the 1 st orthogonal test scheme in the 1 st group to obtain 3 isothermal gas quenched samples of the 1 st group.
And 3 original samples of the 2 nd group are selected, isothermal gas quenching is carried out according to the 2 nd orthogonal test scheme in the step 1, and 3 isothermal gas quenched samples of the 2 nd group are obtained.
And so on;
and 3 original samples of the 18 th group are selected, isothermal gas quenching is carried out according to the 18 th orthogonal test scheme in the step 1, and 3 isothermal gas quenched samples of the 18 th group are obtained.
Step 4, according to the requirements of GB/T230.1-2004 Rockwell hardness test method, hardness measurement is carried out on 18 groups obtained in the step 3 and 3 isothermal gas-quenched samples thereof respectively:
firstly, 7 points are selected on the upper surface of a sample after isothermal gas quenching of the 1 st block of the first group to measure hardness, and the hardness value of the sample after isothermal gas quenching of the 1 st block is an average value of 5 hardness values after the maximum value and the minimum value are removed; obtaining the hardness values of the other 2 samples in the 1 st group according to the measurement; further, an average value H1 of the hardness of the samples after isothermal gas quenching of group 1 and 3 was obtained.
And so on;
the average value Hi of the hardness of the samples after isothermal gas quenching for each group of 3 pieces shown in table 2 was obtained.
Table 2 average Hi units of hardness of samples after isothermal gas quenching of 3 pieces per group: HRC (high-resolution imaging)
And 5, taking one piece from the 1 st group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into four room temperature impact test samples with the length of 10mm multiplied by 55mm, respectively performing room temperature impact tests according to GB/T229-2007 Charpy pendulum impact test method for metal materials, measuring the impact toughness of the four room temperature impact test samples of the 1 st group, and obtaining the impact toughness average value alpha k1 of the four room temperature impact test samples of the 1 st group.
And so on;
the average value αki of the impact toughness of each group of the samples after isothermal gas quenching as shown in table 3 was obtained.
Table 3 impact toughness average units for each set of samples after isothermal gas quenching: j/cm 2
And 6, firstly, taking one sample from each group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into wear samples with phi of 6 multiplied by 20, and then performing room-temperature wear tests on a friction and wear tester according to ASTM standard D3702-94 (1999), wherein 400-mesh water-based abrasive paper is adopted as the abrasive, the external load of 20N is 20, and the test duration is 10min. The wear Mi was then measured by weighing to obtain the wear values for each set of wear samples shown in Table 4.
Table 4 the wear amount Mi unit for each wear sample: mg of (mg)
And 7, respectively performing wire cutting on the last sample in each group of isothermal gas quenched samples obtained in the step 4 according to the specification in GB 228-2002 'room temperature tensile test method for metal materials', processing the last sample into tensile samples with specified sizes, and sequentially performing tensile tests to obtain the tensile strength YSi of each group of tensile samples shown in Table 5.
Table 5 tensile strength YSi units for each set of tensile samples: mpa (Mpa)
Step 8, obtaining the comprehensive performance index delta i of the isothermal gas quenched sample according to the Rockwell hardness Hi, the impact toughness alpha ki, the abrasion loss Mi and the tensile strength YSi measured in the steps 4 to 7
In the formula (1):
hi represents the average hardness of any group of samples after isothermal gas quenching, and the unit is HRC;
αki represents the average value of the impact toughness of any group of samples after isothermal gas quenching, and the unit is J/cm 2 ；
Mi represents the abrasion loss of any group of samples after isothermal gas quenching, and the unit is mg;
YSi represents the tensile strength of any group of samples after isothermal gas quenching, and the unit is MPa;
δi represents the comprehensive performance index of any group of samples after isothermal gas quenching.
The hardness average value Hi, the impact toughness average value αki, the abrasion loss Mi and the tensile strength YSi obtained in the steps 4, 5, 6 and 7 are respectively carried into the formula (1), and the comprehensive performance index of each group of samples shown in table 6 is obtained.
Table 6 comprehensive Performance index of each group of samples
In steps 4 to 8, i represents the serial number of the sample group corresponding to any one of the 18 orthogonal test schemes, and i is a natural number of 1 to 18.
Step 9, selecting isothermal gas quenching process parameters corresponding to a group of test schemes with the largest δi value from the comprehensive performance indexes δi obtained in table 6 of step 8, namely the optimal isothermal gas quenching process parameters of the Cr12MoV cold working mold material corresponding to test scheme 9, wherein the optimal isothermal gas quenching process parameters are as follows: the quenching temperature is 1050 ℃, the heat preservation time is 40min, the gas quenching pressure is 3bar, the isothermal temperature is 280 ℃, and the isothermal time is 2h, and the method is used as the basis for determining the isothermal gas quenching process parameters of the cold working die material in industrial production.
Example 2
1. A method for determining isothermal gas quenching process parameters for prolonging service life of cold working mold materials. The method in this embodiment comprises the following steps:
step 1, the cold working mold material shown in the embodiment is SKD11. According to practical experience and the phase change curve of SKD11 cold-working die steel, 5 factors of quenching temperature, heat preservation time, gas quenching pressure, isothermal temperature and isothermal time are selected to carry out 3-level orthogonal test design, and L shown in table 1 is established 18 (3 5 ) Orthogonal test table, 18 sets of orthogonal test protocols were obtained.
The 5 process parameters range: the quenching temperature is 950-1050 ℃; the heat preservation time is 10 min-40 min; the gas quenching pressure is 3-9 bar; isothermal temperature is 200-280 ℃; isothermal time is 1-3 h;
five factors and three levels were valued: quenching temperature is 950 ℃, 1000 ℃ and 1050 ℃; the heat preservation time is 10min, 25min and 40min; the gas quenching pressure is 3bar, 6bar and 9bar; isothermal temperature is 200 ℃, 240 ℃ and 280 ℃; isothermal time is 1h, 2h and 3h.
Table 1L 18 (3 5 ) Orthogonal test meter
And 2, selecting 18 multiplied by 3 SKD11 cold-working die materials produced in the same batch as 18 groups of original samples, wherein each group of the raw samples comprises 3 blocks. The original sample: the length is 75mm; a width of 25mm; the height is 20mm.
And 3, selecting 3 original samples of the 1 st group, and carrying out isothermal gas quenching according to the 1 st orthogonal test scheme in the 1 st group to obtain 3 isothermal gas quenched samples of the 1 st group.
And 3 original samples of the 2 nd group are selected, isothermal gas quenching is carried out according to the 2 nd orthogonal test scheme in the step 1, and 3 isothermal gas quenched samples of the 2 nd group are obtained.
And so on;
and 3 original samples of the 18 th group are selected, isothermal gas quenching is carried out according to the 18 th orthogonal test scheme in the step 1, and 3 isothermal gas quenched samples of the 18 th group are obtained.
Step 4, according to the requirements of GB/T230.1-2004 Rockwell hardness test method, hardness measurement is carried out on 18 groups obtained in the step 3 and 3 isothermal gas-quenched samples thereof respectively:
firstly, 7 points are selected on the upper surface of a sample after isothermal gas quenching of the 1 st block of the first group to measure hardness, and the hardness value of the sample after isothermal gas quenching of the 1 st block is an average value of 5 hardness values after the maximum value and the minimum value are removed; obtaining the hardness values of the other 2 samples in the 1 st group according to the measurement; further, an average value H1 of the hardness of the samples after isothermal gas quenching of group 1 and 3 was obtained.
And so on;
the average value Hi of the hardness of the samples after isothermal gas quenching for each group of 3 pieces shown in table 2 was obtained.
Table 2 average Hi units of hardness of samples after isothermal gas quenching of 3 pieces per group: HRC (high-resolution imaging)
And 5, taking one piece from the 1 st group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into four room temperature impact test samples with the length of 10mm multiplied by 55mm, respectively performing room temperature impact tests according to GB/T229-2007 Charpy pendulum impact test method for metal materials, measuring the impact toughness of the four room temperature impact test samples of the 1 st group, and obtaining the impact toughness average value alpha k1 of the four room temperature impact test samples of the 1 st group.
And so on;
the average value αki of the impact toughness of each group of the samples after isothermal gas quenching as shown in table 3 was obtained.
Table 3 impact toughness average units for each set of samples after isothermal gas quenching: j/cm 2
And 6, firstly, taking one sample from each group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into wear samples with phi of 6 multiplied by 20, and then performing room-temperature wear tests on a friction and wear tester according to ASTM standard D3702-94 (1999), wherein 400-mesh water-based abrasive paper is adopted as the abrasive, the external load of 20N is 20, and the test duration is 10min. The wear Mi was then measured by weighing to obtain the wear values for each set of wear samples shown in Table 4.
Table 4 the wear amount Mi unit for each wear sample: mg of (mg)
And 7, respectively performing wire cutting on the last sample in each group of isothermal gas quenched samples obtained in the step 4 according to the specification in GB 228-2002 'room temperature tensile test method for metal materials', processing the last sample into tensile samples with specified sizes, and sequentially performing tensile tests to obtain the tensile strength YSi of each group of tensile samples shown in Table 5.
Table 5 tensile strength YSi units for each set of tensile samples: mpa (Mpa)
Step 8, obtaining the comprehensive performance index delta i of the isothermal gas quenched sample according to the Rockwell hardness Hi, the impact toughness alpha ki, the abrasion loss Mi and the tensile strength YSi measured in the steps 4 to 7
In the formula (1):
hi represents the average hardness of any group of samples after isothermal gas quenching, and the unit is HRC;
αki represents the average value of the impact toughness of any group of samples after isothermal gas quenching, and the unit is J/cm 2 ；
Mi represents the abrasion loss of any group of samples after isothermal gas quenching, and the unit is mg;
YSi represents the tensile strength of any group of samples after isothermal gas quenching, and the unit is MPa;
δi represents the comprehensive performance index of any group of samples after isothermal gas quenching.
The hardness average value Hi, the impact toughness average value αki, the abrasion loss Mi and the tensile strength YSi obtained in the steps 4, 5, 6 and 7 are respectively carried into the formula (1), and the comprehensive performance index of each group of samples shown in table 6 is obtained.
Table 6 comprehensive Performance index of each group of samples
In steps 4 to 8, i represents the serial number of the sample group corresponding to any one of the 18 orthogonal test schemes, and i is a natural number of 1 to 18.
Step 9, selecting isothermal gas quenching process parameters corresponding to a group of test schemes with the largest δi value from the comprehensive performance indexes δi obtained in table 6 of step 8, namely, the best isothermal gas quenching process parameters of the SKD11 cold-working die material corresponding to the test scheme 15, wherein the technological parameters are as follows: the quenching temperature is 1000 ℃, the heat preservation time is 40min, the gas quenching pressure is 3bar, the isothermal temperature is 240 ℃, and the isothermal time is 3h, and the gas quenching method is used as the basis for determining the isothermal gas quenching process parameters of the cold working die material in industrial production.
Compared with the prior art, the specific embodiment has the following positive effects:
1. the specific embodiment determines the range of quenching temperature, heat preservation time, gas quenching pressure, isothermal temperature and isothermal time, carries out orthogonal test design according to the level of 5 factors 3, and establishes L 18 (3 5 ) The orthogonal test table is used for carrying out isothermal gas quenching according to a formulated test scheme, then carrying out hardness test, room temperature impact test, wear resistance test and tensile test on each group of samples subjected to isothermal gas quenching to obtain comprehensive performance index delta i of the samples subjected to isothermal gas quenching, and selecting one with the largest delta i value by comparing the delta i valuesThe isothermal gas quenching process parameters corresponding to the group test scheme are used as the basis for determining the isothermal gas quenching process parameters of the cold-working mold materials in industrial production, and the method is suitable for determining the isothermal gas quenching process parameters of various cold-working mold materials, and can improve the performance of the cold-working mold materials and prolong the service life of the cold-working mold.
2. The specific embodiment reasonably configures 5 technological parameters of isothermal gas quenching of the cold-working die material, and the isothermal gas quenching treatment is carried out on the cold-working die material under the technological parameters, and the test results show that: the hardness, impact toughness, wear resistance and tensile strength of the die material are all improved, the toughness nest density degree in the die material is improved after the fracture of steel is detected, and the die material is observed through a scanning electron microscope image: compared with the conventional heat treatment, after isothermal gas quenching is performed by adopting the process parameters determined by the specific embodiment, the obtained cold work die material is shown in the attached drawing, and fig. 1 is a scanning electron microscope image of cold work die steel after isothermal gas quenching by adopting the process parameters determined by example 1; fig. 2 is a scanning electron microscope image of a cold work die steel after conventional heat treatment. As can be seen from a comparison of fig. 1 and 2: the strip-shaped carbide of the cold-work die steel shown in fig. 1 disappears, the carbide is uniformly distributed, and the metal grains are finer. Therefore, the technological parameters determined by the specific embodiment can improve the performance of the cold-work die material after quenching, thereby prolonging the service life of the die.
Therefore, the specific embodiment is suitable for determining isothermal gas quenching process parameters of various cold-working die materials, and the determined process parameters can be used as the basis for determining the isothermal gas quenching process parameters of the cold-working die materials in industrial production, so that the performance and the service life of the cold-working die materials can be improved.
Claims (1)
1. A method for determining isothermal gas quenching process parameters for prolonging service life of cold working die materials is characterized by comprising the following steps:
step 1, selecting 5 factors of quenching temperature, heat preservation time, gas quenching pressure, isothermal temperature and isothermal time to perform 3-level orthogonal test design, and establishing L 18 (3 5 ) Orthogonal test table, obtaining 18 groups of orthogonal test schemes；
The 5 factors range: quenching temperature is 950-1050 ℃, heat preservation time is 10-40 min, gas quenching pressure is 3-9 bar, isothermal temperature is 200-280 ℃, isothermal time is 1-3 h;
five factors and three levels were valued: quenching temperature is 950 ℃, 1000 ℃ and 1050 ℃; the heat preservation time is 10min, 25min and 40min; the gas quenching pressure is 3bar, 6bar and 9bar; isothermal temperature is 200 ℃, 240 ℃ and 280 ℃; isothermal time is 1h, 2h and 3h;
step 2, selecting 18 multiplied by 3 cold-work die materials produced in the same batch as 18 groups of original samples, wherein each group of the cold-work die materials comprises 3 blocks;
step 3, selecting 3 original samples of the 1 st group, and carrying out isothermal gas quenching according to the 1 st orthogonal test scheme of the step 1 to obtain 3 isothermal gas quenched samples of the 1 st group;
selecting 3 original samples of the 2 nd group, and carrying out isothermal gas quenching according to the 2 nd orthogonal test scheme in the step 1 to obtain 3 isothermal gas quenched samples of the 2 nd group;
and so on;
selecting 3 original samples of the 18 th group, and carrying out isothermal gas quenching according to the 18 th orthogonal test scheme in the step 1 to obtain 3 isothermal gas quenched samples of the 18 th group;
step 4, according to the requirements of GB/T230.1-2004 Rockwell hardness test method, hardness measurement is carried out on 18 groups obtained in the step 3 and 3 isothermal gas-quenched samples thereof respectively:
firstly, 7 points are selected on the upper surface of a sample after isothermal gas quenching of the 1 st block of the first group to measure hardness, and the hardness value of the sample after isothermal gas quenching of the 1 st block is an average value of 5 hardness values after the maximum value and the minimum value are removed; obtaining the hardness values of the other 2 samples in the 1 st group according to the measurement; further, obtaining an average value H1 of the hardness of the samples subjected to isothermal gas quenching in the group 1 and 3;
and so on;
obtaining an average value Hi of the hardness of each group of 3 samples subjected to isothermal gas quenching;
step 5, taking one piece from the 1 st group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing the piece into four room temperature impact test samples with the thickness of 10mm multiplied by 55mm, respectively performing room temperature impact tests according to GB/T229-2007 Charpy pendulum impact test method for metal materials, measuring the impact toughness of the four room temperature impact test samples of the 1 st group, and obtaining an average value alpha k1 of the impact toughness of the four room temperature impact test samples of the 1 st group;
and so on;
obtaining the average value alpha ki of the impact toughness of each group of samples subjected to isothermal gas quenching;
step 6, firstly, taking one sample from each group of isothermal gas quenched samples obtained in the step 4, performing linear cutting, processing into wear samples, then performing room-temperature wear tests on a friction and wear tester according to ASTM standard D3702-94 (1999), and measuring by adopting a weighing method to obtain the wear quantity Mi of each group of wear samples;
step 7, according to the specification in GB 228-2002 'room temperature tensile test method for metallic materials', performing wire cutting on the last sample in each group of isothermal gas quenched samples obtained in the step 4 respectively, processing the last sample into tensile samples with specified dimensions, and then sequentially performing tensile tests to obtain the tensile strength YSi of each group of tensile samples;
step 8, obtaining the comprehensive performance index delta i of the isothermal gas quenched sample according to the Rockwell hardness Hi, the impact toughness alpha ki, the abrasion loss Mi and the tensile strength YSi measured in the steps 4 to 7
In the formula (1):
hi represents the average hardness of any group of samples after isothermal gas quenching, the unit is HRC,
αki represents the average value of the impact toughness of any group of samples after isothermal gas quenching, and the unit is J/cm 2 ，
Mi represents the abrasion loss of any group of samples after isothermal gas quenching, the unit is mg,
YSi represents the tensile strength of any group of samples after isothermal gas quenching, the unit is MPa,
δi represents the comprehensive performance index of any group of samples after isothermal gas quenching;
in the steps 4 to 8, i represents the serial number of the sample group corresponding to any one of the 18 orthogonal test schemes, and i is a natural number of 1 to 18;
and 9, selecting isothermal gas quenching process parameters corresponding to a group of test schemes with the maximum delta i value from the comprehensive performance index delta i obtained in the step 8, and taking the isothermal gas quenching process parameters as the basis for determining isothermal gas quenching process parameters of the cold working die material in industrial production.
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