CN110066909B - Heat treatment process for improving hardenability hardness of GCr15SiMn steel tail end - Google Patents
Heat treatment process for improving hardenability hardness of GCr15SiMn steel tail end Download PDFInfo
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- CN110066909B CN110066909B CN201910267092.2A CN201910267092A CN110066909B CN 110066909 B CN110066909 B CN 110066909B CN 201910267092 A CN201910267092 A CN 201910267092A CN 110066909 B CN110066909 B CN 110066909B
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/55—Hardenability tests, e.g. end-quench tests
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Abstract
The invention discloses a heat treatment process for improving the hardenability hardness of the tail end of GCr15SiMn steel, which comprises the following steps: machining an original steel into a heat treatment blank sample with the diameter of 30-35 mm, putting the heat treatment blank sample into a furnace, keeping the temperature for 50min after normalizing treatment at 930 ℃, keeping the temperature for 50min after the temperature reaches the temperature, blowing air to quickly cool to the room temperature after discharging, putting the sample after normalizing treatment into the furnace again, heating to 785 +/-10 ℃, keeping the temperature for 6h, then cooling to 700 +/-10 ℃ at the speed of not more than 20 ℃/h, keeping the temperature for 2h, then cooling to 650 ℃ along with the furnace, finally discharging and air cooling, machining the sample after isothermal annealing treatment into a tail end standard blank sample with the diameter of 25mm, and carrying out an end quenching test on the tail end standard blank sample with the diameter of 25 mm. The invention has the advantages that: the hardenability hardness of the tail end of the GCr15SiMn steel is improved under the condition of not adjusting the chemical components of the steel, the production cost of the GCr15SiMn steel is not increased, and the method has certain advantages in energy conservation and cost reduction.
Description
Technical Field
The invention relates to a heat treatment process for steel, in particular to a heat treatment process for improving the hardenability hardness of the tail end of GCr15SiMn steel, and belongs to the technical field of metal heat treatment.
Background
The GCr15SiMn steel is high-carbon and high-chromium bearing steel, has high compressive strength and fatigue limit, high hardness, good wear resistance and hardenability and certain toughness, and is commonly used for manufacturing bearing rings with the wall thickness of more than 12mm and the outer diameter of not less than 250 mm.
In order to evaluate whether the quality of the GCr15SiMn steel meets the standard requirements, the hardness of the end hardenability of the GCr15SiMn steel needs to be detected. Wherein the hardness value of the J15 point at the end hardenability is 58-64 HRC, and the hardness value of the J20 point at the end hardenability is 42-55 HRC.
At present, the heat treatment process commonly adopted by GCr15SiMn steel is as follows: original steel → normalizing → machining a standard blank sample with the end of phi 25mm → end quenching test.
Because of the great influence of the original steel specification, the uniformity of steel heating during normalizing treatment is poor, and the cooling speed after discharging is slow, so that the grain refining effect of the steel is not obvious, the uniformity of the internal structure is poor, and the network of carbide is serious. Therefore, after the GCr15SiMn steel is treated by the heat treatment process, the hardness value of the end hardenability is low, and the standard requirement cannot be met.
Generally, the commonly used method for improving the end hardenability of GCr15SiMn steel is as follows: the contents of elements such as Si, Mn, Cr and the like in GCr15SiMn steel are improved. This increases the production cost of GCr15SiMn steel to some extent.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide a heat treatment process capable of improving the hardenability hardness of the GCr15SiMn steel end under the condition of not adjusting the chemical composition of steel.
In order to achieve the above object, the present invention adopts the following technical solutions:
a heat treatment process for improving the hardenability hardness of the tail end of GCr15SiMn steel is characterized by comprising the following steps:
step 1: machining heat treatment blank sample
Machining an original steel into a heat treatment blank sample, wherein the diameter of the heat treatment blank sample is 30-35 mm;
step 2: normalizing
Putting the heat-treated blank sample into a furnace, keeping the temperature for 50min after the normalizing treatment temperature is 930 ℃, and blowing air to quickly cool to the room temperature after the sample is taken out of the furnace;
step 3: isothermal spheroidizing annealing
Putting the sample after normalizing into the furnace again, heating to 785 +/-10 ℃, preserving heat for 6h, then cooling to 700 +/-10 ℃ at the speed of not more than 20 ℃/h, preserving heat for 2h, then cooling to 650 ℃ along with the furnace, and finally discharging from the furnace for air cooling;
step 4: machining end standard blank sample
Machining the sample subjected to isothermal annealing treatment into a tail end standard blank sample with phi of 25 mm;
step 5: end quench test
And carrying out end quenching test on the tail end standard blank sample with the diameter of 25 mm.
The heat treatment process for improving the hardenability hardness of the GCr15SiMn steel end is characterized in that the diameter of a heat-treated blank sample is 32mm in Step 1.
The heat treatment process for improving the hardenability hardness of the GCr15SiMn steel end is characterized in that a box-type resistance furnace is adopted in Step2 and Step 3.
The heat treatment process for improving the hardenability hardness of the tail end of the GCr15SiMn steel is characterized in that the temperature rise speed of the box-type resistance furnace is less than or equal to 100 ℃/h.
The invention has the advantages that:
(1) because the original steel is machined into a heat treatment blank sample with the diameter of 32mm before normalizing, the heat treatment blank sample has smaller size, good heating uniformity and higher cooling speed after discharge, the tissue uniformity, the grain size and the carbide net shape of the sample are greatly improved, the hardenability hardness of the tail end of the GCr15SiMn steel is obviously improved, and the standard requirement is met;
(2) because the isothermal annealing treatment is added after the normalizing, the isothermal annealing can further improve the structural uniformity of the sample, and create a good preparation structure for an end quenching test, so the quenching performance of the GCr15SiMn steel is further improved;
(3) the hardenability hardness of the tail end of the GCr15SiMn steel is improved under the condition of not adjusting the chemical components of the steel, the production cost of the GCr15SiMn steel is not increased, and the method has certain advantages in energy conservation and cost reduction.
Drawings
FIG. 1 is a process curve for isothermal annealing treatment.
Detailed Description
The invention is described in detail below with reference to the figures and the embodiments.
The GCr15SiMn steel used in the invention comprises the following chemical components (by mass percent): 0.95-1.05% of C, Si: 0.45-0.75%, Mn: 0.95-1.25%, Cr: 1.40-1.65%, Mo is less than or equal to 0.10%, Ni: not more than 0.25%, Cu not more than 0.25%, P: less than or equal to 0.020%, S: less than or equal to 0.015 percent.
6 samples were taken of the raw steel, 3 samples were used in example 1 and 3 samples were used in example 2.
Example 1
Step 1: normalizing
Normalizing the original steel, specifically:
putting the original steel into a box-type resistance furnace, normalizing at 930 ℃, keeping the temperature for 50min after reaching the temperature, and blowing air to rapidly cool to room temperature after discharging.
Step 2: machining end standard blank sample
And machining the normalized steel into a tail end standard blank sample with the diameter of phi 25 mm.
Step 3: end quench test
And carrying out end quenching test on the tail end standard blank sample with the diameter of 25 mm.
Example 2
Under the condition of not adjusting the chemical components of GCr15SiMn steel, the heat treatment process for improving the hardenability hardness of the GCr15SiMn steel terminal provided by the invention specifically comprises the following steps:
step 1: machining heat treatment blank sample
And machining the original steel into a heat treatment blank sample with the diameter of 32 mm.
Considering the uniformity, grain size, decarburization, final end standard blank sample size and other factors of the sample during subsequent normalizing and isothermal annealing treatment, we finally determine to machine the original steel into a heat treatment blank sample with phi 32 mm.
Step 2: normalizing
Normalizing the heat-treated blank sample, specifically:
putting the heat-treated blank sample into a box type resistance furnace, keeping the temperature for 50min after the normalizing treatment temperature is 930 ℃, and blowing air to rapidly cool to the room temperature after the sample is taken out of the furnace.
Because the heat-treated blank sample phi is 32mm, the size is small, the heating uniformity is good, and the cooling speed after discharging is high, the texture uniformity, the grain size and the carbide net shape of the sample are greatly improved, and a prepared structure is prepared for isothermal annealing.
The normalizing treatment process is finally determined by considering factors such as the furnace type of the heat treatment furnace, the size of a sample, the characteristics of steel grades and the like.
Step 3: isothermal spheroidizing annealing
Carrying out isothermal spheroidizing annealing treatment on the normalized sample, wherein the isothermal spheroidizing annealing treatment process specifically comprises the following steps:
referring to FIG. 1, a sample is put into a box-type resistance furnace, heated to 785 +/-10 ℃ at a speed of less than or equal to 100 ℃/h (the heating speed is 90 ℃/h in the embodiment), kept for 6h, then cooled to 700 +/-10 ℃ at a speed of less than or equal to 20 ℃/h (the cooling speed is 18 ℃/h in the embodiment), kept for 2h, cooled to 650 ℃ along with the furnace, and finally taken out of the furnace for air cooling.
Isothermal spheroidizing annealing can not only obtain a spherical pearlite structure (which is a special spheroidizing annealing structure of high-carbon steel), but also further improve the uniformity of a sample structure, lighten the network of carbides, create a good preparation structure for an end quenching test, and avoid reducing the hardness of the tail end hardenability of steel due to the occurrence of soft spots after the end quenching test, namely improve the quenching performance.
Step 4: machining end standard blank sample
And machining the sample after isothermal annealing treatment into a tail end standard blank sample with the diameter of phi 25 mm.
Step 5: end quench test
And carrying out end quenching test on the tail end standard blank sample with the diameter of 25 mm.
After the heat treatment of the raw steel materials of examples 1 and 2, the hardness values of the end hardenability were compared as follows:
| —— | heat treatment process | J15/HRC | J20/HRC |
| Example 1 | Original process | 50.7、52.9、54 | 38.5、39.1、41.5 |
| Example 2 | New process | 59.5、60.5、61.4 | 42.7、52.2、52.5 |
| —— | Standard requirements | 58～64 | 42～55 |
Therefore, the heat treatment process provided by the invention obviously improves the end hardenability hardness of the GCr15SiMn steel, and enables the end hardenability hardness of the GCr15SiMn steel to reach the standard requirement.
It should be noted that the above-mentioned embodiments do not limit the present invention in any way, and all technical solutions obtained by using equivalent alternatives or equivalent variations fall within the protection scope of the present invention.
Claims (4)
1. A heat treatment process for improving the hardenability hardness of the tail end of GCr15SiMn steel is characterized by comprising the following steps:
step 1: machining heat treatment blank sample
Machining an original steel into a heat treatment blank sample, wherein the diameter of the heat treatment blank sample is 30-35 mm;
step 2: normalizing
Putting the heat-treated blank sample into a furnace, keeping the temperature for 50min after the normalizing treatment temperature is 930 ℃, and blowing air to quickly cool to the room temperature after the sample is taken out of the furnace;
step 3: isothermal spheroidizing annealing
Putting the sample after normalizing into the furnace again, heating to 785 +/-10 ℃, preserving heat for 6h, then cooling to 700 +/-10 ℃ at the speed of not more than 20 ℃/h, preserving heat for 2h, then cooling to 650 ℃ along with the furnace, and finally discharging from the furnace for air cooling;
step 4: machining end standard blank sample
Machining the sample subjected to isothermal annealing treatment into a tail end standard blank sample with phi of 25 mm;
step 5: end quench test
And carrying out end quenching test on the tail end standard blank sample with the diameter of 25 mm.
2. The heat treatment process for improving the hardenability of the GCr15SiMn steel terminal according to claim 1, wherein the diameter of the heat-treated blank sample is 32mm in Step 1.
3. The heat treatment process for improving the hardenability of the GCr15SiMn steel terminal according to claim 1, wherein a box-type resistance furnace is used in Step2 and Step 3.
4. The heat treatment process for improving the hardenability hardness of the GCr15SiMn steel terminal according to claim 3, wherein the temperature rise speed of the box-type resistance furnace is less than or equal to 100 ℃/h.
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| CN112941279A (en) * | 2021-01-26 | 2021-06-11 | 青海西钢特殊钢科技开发有限公司 | Heat treatment process for improving hardenability hardness of 20MnCr5+ HH steel tail end |
| CN115341076B (en) * | 2022-07-15 | 2023-08-18 | 大冶特殊钢有限公司 | Spring steel and spheroidizing annealing method thereof |
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