CN105548235A - Test method for accurate determination of optimal heat treatment process for pearlitic steel rail - Google Patents
Test method for accurate determination of optimal heat treatment process for pearlitic steel rail Download PDFInfo
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- CN105548235A CN105548235A CN201510914353.7A CN201510914353A CN105548235A CN 105548235 A CN105548235 A CN 105548235A CN 201510914353 A CN201510914353 A CN 201510914353A CN 105548235 A CN105548235 A CN 105548235A
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- steel rail
- cooling
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
Abstract
The invention relates to a test method for accurate determination of an optimal heat treatment process for a pearlitic steel rail. The test method is characterized by comprising the following steps: determining a static CCT curve of the pearlitic steel rail by utilizing a Formastor-F type thermal expansion instrument, and determining a critical cooling rate of the pearlite of the pearlitic steel rail and the phase-change range of supercooled austenite so as to provide a cooling rate range for subsequent designing of a test scheme; according to above-mentioned test results, simulating parameters of an on-line heat treatment process for the pearlitic steel rail on an MMS-200 thermal simulation testing machine; and through a continuous cooling process and a two-stage cooling process, determining the optimal austenitizing temperature, cooling rate range and final cooling temperature of the pearlitic steel rail. The test method provided by the invention has the following advantages: conventional heat treatment furnace testing and industrial on-line heat treatment testing means or devices are replaced with a fully-automatic phase-change instrument and a thermal simulation testing machine, so the optimal heat treatment process for the pearlitic steel rail is rapidly obtained, and process parameters are provided for industrial production of the pearlitic steel rail.
Description
Technical field
The present invention relates to a kind of test method of Accurate Determining pearlite steel rail optimum treatment process, belong to technical field of heat treatment technology.
background technology
Along with transportation by railroad is progressively to the development of high speed, heavy duty, the intensity of rail and the hardness of rail head are had higher requirement.The intensity of rail is improved and tread hardness is a kind of comparatively energy-conservation, economic method by heat-treatment of rail technology.Corresponding relation research between heat treated temperature, cooling rate, phase transition temperature, time and rail tissue, hardness obtains to meet railway heat-treated rail and to supply the key problem in technology required.The technical essential of pearlite steel rail Technology for Heating Processing mainly contains following two aspects: one is that cooling rate controls; Two is that temperature controls; As publication number be the patent 1 of CN101701284A, the patent 3 of publication number to be the patent 2 of CN1034583A and publication number be CN101016580A is all that rail head is heated to certain temperature range, utilize air cooling equipment that rail head is cooled to a certain wide temperature range, what have continues to be cooled to a certain temperature range with mist device for cooling again, indivedual last water-cooled.The shortcoming of this several patent is that the control temperature of the Technology for Heating Processing adopted is all comparatively wide in range, organizes wayward, adopts first air-cooled method length consuming time simultaneously, cannot adapt to on-the-spot actual production rhythm.
Summary of the invention
Pearlite steel rail is because of the difference of chemical composition, the process for cooling or variant of the best during thermal treatment, the formulation that the object of the invention is room equipment and reasonable experimental program by experiment provides a kind of test method of Accurate Determining pearlite steel rail optimum treatment process, for large commercial production provides rational process for cooling scope.
For achieving the above object, technical scheme provided by the invention is as follows:
1, Formastor-F type thermal dilatometer is utilized to measure the static CCT curve of pearlite steel rail, between the phase change zone determining its pearlitic Critical cooling speed and overcooling austenite, for plan design subsequently provides cooling rate scope;
2, thermal modeling test: according to the test findings of step 1, MMS-200 hot modeling test machine is simulated pearlite steel rail burning optimization on line technological parameter;
2.1 continuous coo1ing techniques
Pearlite steel rail is heated to different austenitizing temperatures, be incubated, room temperature is as cold as with several different cooling rate, carry out HRC hardness and metallographic structure to the sample under each technique to detect and analyze, obtain the corresponding relation of hardness from tissue and the cooling characteristics of different steel grade under each cooling rate condition;
2.2 two-stage chilling techniques
According to the test findings of 1,2.1, the time requirement allowed according to produced on-site rhythm, devises the process system of two-stage chilling.Pearlite steel rail is heated to different austenitizing temperatures, carry out the insulation of certain hour, the insulation that several different final cooling temperature carries out different time is as cold as with different cooling rates, rear air cooling, HRC hardness and metallographic structure detection analysis are carried out to the sample under each technique, determines the austenitizing temperature of the best of pearlite steel rail, cooling velocity scope and final cooling temperature.
One of difficult point that this test method solves finds out process for cooling best in pearlite steel rail heat treatment process by rational test method, i.e. rational process window, control the appearance of abnormal structure, can not occur bainite or martensitic stucture in tissue after the pearlite steel rail thermal treatment of i.e. correlation standard, and hardness meets relevant criterion.
The feature of this test method is the design by test technology, while realization accurately controls heat treatment temperature and cooling rate, realize hardness and tissue accurately test, technique can meet the time rhythm of produced on-site, avoid the blindness of debugging heat-treatment of rail technological parameter in large commercial production, can the test period be shortened, compression test cost, give full play to the control cold energy power of equipment.
Advantage of the present invention is: the technique adopting air-cooled insulation after the cold cooling of first mist, by method of the present invention, namely full-automatic phase transformation instrument and heat simulating tester is utilized to replace conventional heat-treatment furnace test and industrial burning optimization on line research technique or device, by autonomous Design test method, reach accurate, obtain the Technology for Heating Processing of pearlite steel rail the best fast, for the commercial production of this pearlite steel rail provides technological parameter.This test method workable, method is easy, is easy to realize heat treated temperature, cooling rate and rail hardness and corresponding relation between organizing is studied.
Embodiment
Below in conjunction with embodiment, the present invention is further detailed explanation:
Embodiment 1:U75V pearlite steel rail
(1) Formastor-F type thermal dilatometer is utilized to measure the static CCT curve of U75V, cooling velocity (DEG C/s): 20,18,12,10,8,7,6,5,4,3,2,1,0.5,0.25, its pearlitic Critical cooling speed is: 7 DEG C/s, by observing and micro-hardness testing the metallographic microstructure of sample under each cooling rate, tentatively determine the cooling rate scope tested: 4-18 DEG C/s.
(2) on MMS-200 hot modeling test machine, continuous coo1ing technique and two-stage chilling engineer testing is carried out, and the HRC hardness of sample and microstructure under measuring each concrete technology.
Continuous coo1ing technique: sample being heated to respectively temperature is 950 DEG C, 900 DEG C, 850 DEG C, is incubated after 10 minutes, respectively with 4-18 DEG C/s cool to room temperature; Measure HRC hardness and the microstructure of sample under each concrete technology, obtain the corresponding relation of hardness from tissue and the cooling characteristics of different steel grade under each cooling rate condition.
Two-stage chilling technique: the time requirement allowed according to upper two step test findings and produced on-site rhythm, devises the process system of two-stage chilling.The technique of test is: heating-up temperature is respectively 950 DEG C, 900 DEG C, 850 DEG C, be incubated 10 minutes, 450-620 DEG C of final cooling temperature is cooled to respectively using 4-18 DEG C/s cooling rate as the center line value of test, insulation 5-25 minute, air cooling again, by carrying out HRC hardness and metallographic structure detection analysis to sample, best Technology for Heating Processing can be obtained.Austenitizing temperature be 950 DEG C and 850 DEG C time, lower hardness.Cooling rate is greater than 15 DEG C/s and final cooling temperature lower than 570 DEG C, easily occurs abnormal structure's bainite and martensite in tissue, and cooling rate is less than 8 DEG C/s and final cooling temperature higher than 600 DEG C, and in tissue, ferrite content is more, and hardness does not conform to.
So U75V pearlite steel rail optimised process system is: 900 DEG C are incubated 10 minutes, and 8-15 DEG C/s cooling rate is cooled to 570-600 DEG C, air cooling.
Embodiment 2:U76CrRE pearlite steel rail
(1) Formastor-F type thermal dilatometer is utilized to measure the static CCT curve of U76CrRE, cooling velocity (DEG C/s): 20,10,8,7,6,4,3,2,1,0.5, its pearlitic critical transitions speed is: 2 DEG C/s, by observing and micro-hardness testing the metallographic microstructure of sample under each cooling rate, tentatively determine the cooling rate scope tested: 1-10 DEG C/s.
(2) on MMS-200 hot modeling test machine, continuous coo1ing technique and two-stage chilling engineer testing is carried out, and the HRC hardness of sample and microstructure under measuring each concrete technology.
Continuous coo1ing technique: sample is heated to 900 DEG C of insulations after 10 minutes, respectively with 2,4,6,8 DEG C/s cool to room temperature, is heated to 950 DEG C of insulations after 10 minutes, respectively with 1,2,3,4 DEG C/s cool to room temperature by sample; Measure HRC hardness and the microstructure of sample under each concrete technology, obtain the corresponding relation of hardness from tissue and the cooling characteristics of different steel grade under each cooling rate condition.
Two-stage chilling technique: the time requirement allowed according to upper two step test findings and produced on-site rhythm, devises the process system of two-stage chilling.The technique of test is: heating-up temperature is respectively 950 DEG C, 900 DEG C, be incubated 10 minutes, 550-630 DEG C of final cooling temperature is cooled to respectively using 2-10 DEG C/s cooling rate as the center line value of test, insulation 5-25 minute, air cooling again, by carrying out HRC hardness and metallographic structure detection analysis to sample, best Technology for Heating Processing can be obtained.When austenitizing temperature is 950 DEG C, lower hardness.When cooling rate is greater than 8 DEG C/s and final cooling temperature lower than 590 DEG C, easily occur abnormal structure's bainite and martensite in tissue, cooling rate is less than 4 DEG C/s and final cooling temperature higher than 610 DEG C, and in tissue, ferrite content is more, and hardness does not conform to.
So U76CrRE pearlite steel rail optimised process system is: 900 DEG C are incubated 10 minutes, and 6-10 DEG C/s cooling rate is cooled to 590-610 DEG C, air cooling.
Claims (1)
1. a test method for Accurate Determining pearlite steel rail optimum treatment process, is characterized in that:
1) Formastor-F type thermal dilatometer is utilized to measure the static CCT curve of pearlite steel rail, between the phase change zone determining its pearlitic Critical cooling speed and overcooling austenite, for plan design subsequently provides cooling rate scope;
2) thermal modeling test: according to the test findings of step 1, MMS-200 hot modeling test machine is simulated pearlite steel rail burning optimization on line technological parameter;
2.1) continuous coo1ing technique
Pearlite steel rail is heated to different austenitizing temperatures, be incubated, room temperature is as cold as with several different cooling rate, carry out HRC hardness and metallographic structure to the sample under each technique to detect and analyze, obtain the corresponding relation of hardness from tissue and the cooling characteristics of different steel grade under each cooling rate condition;
2) 2 two-stage chilling techniques
According to the test findings of 1,2.1, according to the time requirement that produced on-site rhythm allows, the process system of design two-stage chilling: pearlite steel rail is heated to different austenitizing temperatures, carry out the insulation of certain hour, the insulation that several different final cooling temperature carries out different time is as cold as with different cooling rates, rear air cooling, HRC hardness and metallographic structure detection analysis are carried out to the sample under each technique, determines the austenitizing temperature of the best of pearlite steel rail, cooling velocity scope and final cooling temperature.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107557557A (en) * | 2017-08-07 | 2018-01-09 | 包头钢铁（集团）有限责任公司 | A kind of burning optimization on line method for being used to eliminate rail abnormal structure |
| CN110592496A (en) * | 2019-10-29 | 2019-12-20 | 内蒙古科技大学 | Pearlite rail steel and preparation method thereof |
| CN110863169A (en) * | 2018-08-28 | 2020-03-06 | 河南科技大学 | Heat treatment optimization method for carburizing steel bearing ring |
| CN111189873A (en) * | 2020-01-14 | 2020-05-22 | 昆明理工大学 | Method for measuring CCT curve of low-carbon low-alloy steel |
| CN111638238A (en) * | 2020-05-15 | 2020-09-08 | 南京钢铁股份有限公司 | Method for measuring reverse transformation austenite by adopting expansion method |
| CN113403466A (en) * | 2021-05-20 | 2021-09-17 | 包头钢铁（集团）有限责任公司 | Production method for eliminating steel rail decarburized layer structure abnormality |
| CN113416822A (en) * | 2021-05-20 | 2021-09-21 | 包头钢铁（集团）有限责任公司 | Heat treatment method for improving hardness of U76CrRE heat treatment steel rail gas pressure welding joint |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107557557A (en) * | 2017-08-07 | 2018-01-09 | 包头钢铁（集团）有限责任公司 | A kind of burning optimization on line method for being used to eliminate rail abnormal structure |
| CN110863169A (en) * | 2018-08-28 | 2020-03-06 | 河南科技大学 | Heat treatment optimization method for carburizing steel bearing ring |
| CN110592496A (en) * | 2019-10-29 | 2019-12-20 | 内蒙古科技大学 | Pearlite rail steel and preparation method thereof |
| CN111189873A (en) * | 2020-01-14 | 2020-05-22 | 昆明理工大学 | Method for measuring CCT curve of low-carbon low-alloy steel |
| CN111638238A (en) * | 2020-05-15 | 2020-09-08 | 南京钢铁股份有限公司 | Method for measuring reverse transformation austenite by adopting expansion method |
| CN111638238B (en) * | 2020-05-15 | 2022-11-18 | 南京钢铁股份有限公司 | Method for measuring reverse transformation austenite by adopting expansion method |
| CN113403466A (en) * | 2021-05-20 | 2021-09-17 | 包头钢铁（集团）有限责任公司 | Production method for eliminating steel rail decarburized layer structure abnormality |
| CN113416822A (en) * | 2021-05-20 | 2021-09-21 | 包头钢铁（集团）有限责任公司 | Heat treatment method for improving hardness of U76CrRE heat treatment steel rail gas pressure welding joint |
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Application publication date: 20160504 |