CN1147019A - Bluing and low-carbon martensite heat treatment of high strength building steel bar - Google Patents
Bluing and low-carbon martensite heat treatment of high strength building steel bar Download PDFInfo
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- CN1147019A CN1147019A CN 96106625 CN96106625A CN1147019A CN 1147019 A CN1147019 A CN 1147019A CN 96106625 CN96106625 CN 96106625 CN 96106625 A CN96106625 A CN 96106625A CN 1147019 A CN1147019 A CN 1147019A
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Abstract
A blueing heat treatment of reinforcing bar used for building includes heating low-carbon or low-carbon alloy bar to 50-150 deg.C over Ac3, maintaining and quenching in liquid medium to control its surficial layer being lath martensite, and its core being the mixture of said martensite and ferrite. Treated reinforcing bar has self-tempering nature and high mechanical performance and can replace middle-carbon alloy bar. If said heat treatment is performed with the bar just after rolled, the afterheat can be used.
Description
The invention relates to a heat treatment method for steel, in particular to a bluing and low-carbon martensite heat treatment method for high-strength construction steel bars.
At present, according to the national and international standards, the mechanical properties of the steel bars (including steel wires) for high-strength construction are mainly classified into two types, one is the steel bar for prestressed concrete, and the other is the tensile strength (sigma)b) The minimumshould be 1470N/mm2Elongation (delta)10) 4-6%; the other is a steel bar for high-grade building components, the sigma of which isbThe lowest should be 1420N/mm2，δ10Is 5-8%. In order to ensure the engineering quality, the reinforcing steel bars have enough mechanical properties, so the material of the reinforcing steel bars is generally 40Si2Mn、48Si2Mn、45Si2Cr, 30CrMnSi, 30MnB and other medium carbon alloy steels and 27 SiMnB. The steel bar is rolled and then subjected to heat treatment, and the product is slender, so that the known heat treatment is carried out on an automatic production line, and the main processes sequentially comprise: straightening the steel bar by using a bidirectional straightening roller, heating the steel bar to 900-Heating the ribs to 400-450 ℃, tempering, cooling and coiling. The metallographic structure after heat treatment is troostite. Ordinary products are easy to rust in application, and in order to increase the rust-proof function, the bluing treatment which is extremely difficult to implement is separately carried out. The process method obviously requires good material quality, long working procedure, large energy consumption, time and labor consumption; the purchase of equipment is expensive, the occupied length of a workshop is long, and the cost is high.
In order to solve this technical problem, efforts are being made to develop new methods. Through patent search, U.S. patent application No. 184324 describes a "direct hot treatment method for hot rolled wire rod" which utilizes the residual heat of the wire rod itself from the roller press to pass through a controllable cooling device to reduce the temperature to a range of Ms-550 ℃, and then reheating the wire rod to a temperature corresponding to the nose of the isothermal cooling curve (T, T, T) and keeping the temperature for achieving the purpose of complete transformation to the sorbite structure. It may be advantageous in practice, but it seems that there still remains a deficiency in how to solve the problem of obtaining better technical and economic results in the most economical way.
The invention aims to provide a bluing and low-carbon martensite heat treatment for high-strength construction steel bars, which can effectively utilize low-carbon steel bars to form lath martensite structures after quenching, so that the lath martensite structures have self-tempering characteristics, eliminate a tempering procedure, improve mechanical properties and simultaneously complete bluing.
The purpose of the invention is realized as follows: the steel bar of low-carbon or low-carbon alloy steel is subjected to low-carbon martensite treatment, so that the steel bar has self-tempering property and high mechanical property. The process comprises the following steps: 1. the low carbon steel bar is heated to Ac3Above 50-150 ℃; 2. preserving the heat for 0-10 minutes; 3. in the quenching process, the quenching medium liquid with the temperature of 15-60 ℃ is directly used for intense cooling and quenching; 4. the steel bar is controlled to form a mixture of lath martensite on the surface layer and lath martensite and 0-10% of ferrite on the core part.
The quenching medium liquid can be selected from water, saline water, alkaline water or oilFirstly, performing primary filtration; or selecting bluing solution to form bluish black Fe on the surface of the steel bar during quenching3O4And (3) a layer. The bluing solution comprises 65-10 wt% of NaNo210-65% of NaNo310-20% KNO3And the balance H2O。
The intensive cooling quenching may be performed by spraying quenching over the entire length of the quenching ring. Or a quenching ring is used, one section is sprayed and quenched, and the other section is dipped and quenched. The whole process can also be dipping and quenching.
The invention has the advantages that: after the low-carbon or low-carbon alloy steel is used for replacing the reinforcing steel bar of the medium-carbon alloy steel for treatment, the mechanical property of the same high-strength reinforcing steel bar can be obtained and can reach the standard, and the bluing antirust function is realized; for the constructional engineering, the section of the steel bar can be relatively reduced, and the steel is saved; after quenching, a tempering process is cancelled, equipment, electric energy and plant length are saved, a production line is reformed, and cost can be saved; the steel bar hot rolling device is directly used with steel bar hot rolling, and the waste heat of the rolled steel bar is utilized for treatment, so that the economic benefit is more remarkable.
Description of the drawings:
FIG. 1 is a schematic illustration of the austenitic continuous cooling transformation curve of a carbon steel 20 according to the present invention;
FIG. 2 is a photograph of the lath-like martensite structure obtained from the test results.
Details of the proposed method according to the invention are described in detail below with reference to fig. 1-2.
The invention uses low carbon steel bar to make it have self-tempering property after low carbon martensite treatment, and cancels tempering procedure and has high mechanical property. The process comprises the following steps:
1. the low carbon steel bar is heated to Ac3Above50-150 ℃;
2. preserving the heat for 0-10 minutes;
3. in the quenching process, the quenching medium liquid strength at the temperature of 15-60 ℃ is directly used
Cooling and quenching;
4. controlling the steel bar to form a surface layer of lath martensite and a core of lath martensite,
0-10% of ferrite.
First, the low carbon steel means a low carbon steel and a low carbon alloy steel (the same applies hereinafter). The steel bar itself is heated to Ac3Above 50-150 ℃. The method comprises the following two aspects that the steel bar is heated to the temperature range by induction heating equipment at normal temperature; the other is that when the steel bar is hot rolled, after the hot rolling is finished, the waste heat of the steel bar is in the temperature range. It is important to the present invention that the heat treatment method, which is less involved in the heating method and apparatus, is based onThe method is the same. The temperature value of the temperature range is determined by the skilled person according to the material, application, heating conditions, etc.
The low-carbon steel bars at normal temperature are also straightened by a conventional bidirectional straightening roller, heated by induction heating equipment, and coiled after quenching operation is finished.
The quenching ring is formed by spirally winding a flat copper pipe, and a funnel for recovering quenching medium liquid is arranged below the quenching ring. The total length of the quenching ring needs to be determined by calculation according to factors such as the diameter of the steel bar, the speed and the like. There are three ways of intensive cooling quenching, which involve different quenching rings. The whole quenching process is spray quenching, and the quenching rings are arranged in the horizontal direction (the same direction as the steel bars). Spray holes pointing to the advancing track position of the steel bar are distributed on the whole inner circle (namely the inner wall of the flat copper pipe) of the quenching ring, and the spraying and quenching working pressure is 400-. The whole process of the two quenching processes is combined of spray quenching and immersion quenching, namely, one section is a quenching ring arranged in the horizontal direction, the other section is provided with a pipe slightly inclined downwards, water is continuously and sufficiently sprayed into the pipe from the end where the reinforcing steel bar enters, the other end of the pipe is discharged, spray quenching of one section (in the quenching ring) of the reinforcing steel bar is realized, and immersion quenching of the other section (in the pipe) is carried out in a flowing quenching medium. The whole quenching process is immersion quenching, a pipe slightly inclined downwards is arranged, the quenching medium liquid is fed into and discharged from the pipe, the whole process of immersion quenching in the flowing quenching medium liquid is realized when the reinforcing steel bar passes through the pipe, and the quenching ring is naturally cancelled.
The quenching medium liquid can be selected from one of water, saline water, alkaline water or oil, and can also be selected from a bluing solution. The former can only implement quenching, and the obtained low-carbon steel bar has a martensite structure effect but has no antirust protection; the latter uses bluing solution as quenching medium liquid, while the quenching effect is obtained, the steel bar surface will form bluish black Fe3O4And (4) obtaining double effects of quenching and bluing. The bluing solution consists of NaNo 65-10 wt%210-65% of NaNo310-20% KNO3The balance ofQuantity H2And O. If selected, NaNo2When the bluing solution mainly is quenched, the bluing chemical reaction equation is as follows:
due to the martensite start transformation point M of the low-carbon steelsAnd the martensite finish point MfAll above the greenhouse, self-tempering occurs in the quenching and cooling process, so the quenching and cooling device has self-tempering property and can cancel tempering. After quenching, the surface layer of the steel bar has compressive stress which is just favorable for meeting the requirement of bearing alternating load of the constructional engineering component. Even if the pressure stress is eliminated, the tempering treatment can be carried out only at the temperature of 220 ℃. After the low-carbon steel bar is quenched, the low-carbon steel bar is basically in a lath martensite structure, each lath is parallel to each other when being formed, so that impact cannot be generated, micro cracks cannot be generated, and the martensite laths have higher dislocation density; and because the supersaturated carbon content of the low-carbon martensite solid solution is low, the lattice distortion is small, and the self-tempering characteristic is realized, the low-carbon steel bar has medium hardness, high strength, good plasticity and toughness after the martensite treatmentGood weldability, and excellent welding performance. The mechanical properties of the treated steel bars of different low carbon steel grades are shown in the attached table 1.
It should also be noted that for those low carbon steel bars with too low a carbon content, the tensile strength after quenching is 1078N/mm2Above, even achieve the national standard requirement of high strength. The two meanings are provided, the first known hot-rolled steel bar is quenched by utilizing waste heat, and the technology is improved because the steel bar is too long and cannot be tempered, or the tempering is difficult to control, so that the invention aims to solve the problem. After the second low-carbon steel bar is quenched, the method has more practical significance for relatively reducing the diameter of the steel bar in application and saving steel.
Finally, the steel bar of carbon steel 20 is taken as an example for further explanation. The physical constant at normal temperature is blank diameter of 10mm, Ac3855℃，Ms425℃，Mf270℃。The processing procedure is that the reinforcing steel bars are straightened; heating the steel bar to 855 + 145-1000 deg.C by medium frequency inductor; keeping the temperature for zero minutes; adopting the whole spray quenching operation, wherein the quenching medium liquid adopts water with the temperature of 25 ℃ and the spray quenching working pressure is 400 kpa; and (4) directly coiling without tempering after quenching. It can be seen from fig. 1 that the cooling curve (indicated by the arrowed line in the figure) drops to MsAt this point, austenite begins to transform to martensite. The martensite produced first separates out carbide in the subsequent cooling process, self-tempering occurs, and cooling is carried out until MfAt this point, the austenite is completely transformed into martensite and self-tempering is completed. The lath-like martensite structure obtained after the treatment is shown in figure 2, and the mechanical properties are shown in the attached table 1. TABLE 1 attached table for mechanical properties of low carbon martensite treatment
Note: 1. according to different mechanical performance indexes, selecting proper steel grade.
| Thermal treatment Diameter of blank (mm) | Steel grade | Hardness of HRC | Tensile strength σb (N/mm2) | Yield limit σ0.2 (N/mm2) | Elongation percentage δ10 (％) | Reduction of area ψ (％) |
| Φ10 | 25MnSiB | 47.0 | 1637 | 1470 | 11.8 | 49.2 |
| Φ10 | 20Mnsi | 41.5 | 1425 | 1215 | 9.6 | 54.7 |
| Φ10 | 20MnV | 46.0 | 1499 | 1215 | 9.3 | 52.0 |
| Φ10 | 20 | 44.0 | 1440 | 1264 | 9.0 | 36.0 |
2. The hardness is HRC 40-47, the elasticity of the spring is in the range of positive value, so the reinforcing steel bar has better strength
Good elasticity.
Claims (7)
1. A high-strength construction steel bar bluing, low-carbon martensite heat treatment, its characteristic is to utilize the steel bar of the low-carbon or low-carbon alloy steel, after carrying on the low-carbon martensite treatment, make it have self-tempering characteristic, and high mechanical property, its process includes the following steps:
a. the low carbon steel bar is heated to Ac3Above 50-150 ℃;
b. preserving the heat for 0-10 minutes;
c. in the quenching process, the quenching medium liquid strength at the temperature of 15-60 ℃ is directly used
Cooling and quenching;
d. controlling the steel bar to form a surface layer of lath martensite and a core of lath martensite,
0-10% of ferrite.
2. The heat treatment according to claim 1, wherein the quenching medium liquid is selected from water, brine, alkaline water and oil.
3. The heat treatment according to claim 1, wherein the quenching medium liquid is a bluing solution, and the bluing solution is selected to form a bluish-black Fe on the surface of the steel bar during the quenching3O4And (3) a layer.
4. The heat treatment of claim 3It is characterized by that the bluing solution is made up by using 65-10% of NaNo210-65% of NaNo310-20% KNO3And the balance H2O。
5. The heat treatment according to claim 1, wherein the intensive quenching is carried out by spraying over the entire length of the quenching ring.
6. The heat treatment according to claim 1, characterized in that the intensive cooling quenching is carried out by means of a quenching ring, one section being subjected to spray quenching and the other section being subjected to dip quenching.
7. The heat treatment according to claim 1, characterized in that the intensive quenching is carried out by intensive cooling and optionally by immersion quenching.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN96106625A CN1045623C (en) | 1996-06-20 | 1996-06-20 | Bluing and low-carbon martensite heat treatment of high strength building steel bar |
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| CN96106625A CN1045623C (en) | 1996-06-20 | 1996-06-20 | Bluing and low-carbon martensite heat treatment of high strength building steel bar |
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| CN1147019A true CN1147019A (en) | 1997-04-09 |
| CN1045623C CN1045623C (en) | 1999-10-13 |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1327008C (en) * | 2005-07-07 | 2007-07-18 | 东北大学 | Post rolling fast cooling-production technology of high strength ribbed reinforced bar |
| CN1330785C (en) * | 2005-12-27 | 2007-08-08 | 东北大学 | Strength of extension 1000 MPa grade complex phase steel plate and mfg. method thereof |
| CN100348767C (en) * | 2005-12-27 | 2007-11-14 | 东北大学 | Strength of extension 750-795 MPa grade double-phase steel plate and mfg. method thereof |
| CN101974667A (en) * | 2010-11-16 | 2011-02-16 | 汤欣刚 | Manufacturing method of tube pile for underground foundations of high-rise buildings |
| CN101693941B (en) * | 2009-08-13 | 2011-06-08 | 巨力索具股份有限公司 | Method for quenching medium and low carbon alloy structural steel workpieces |
| CN103045816A (en) * | 2012-12-12 | 2013-04-17 | 张云江 | Quenching and bluing solution and using method thereof |
| CN109112260A (en) * | 2017-06-23 | 2019-01-01 | 江苏翔鹰五金弹簧有限公司 | A kind of heat treatment method of blue shift straight filament steel wire |
| CN110592357A (en) * | 2019-09-16 | 2019-12-20 | 中国科学院金属研究所 | Heat treatment method of iron-based wear-resistant coating plough shovel tip |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2064593B (en) * | 1979-09-06 | 1983-10-26 | Nippon Steel Corp | Direct sorbitic transformation of hotrolled steel rod |
| CN1023774C (en) * | 1991-01-24 | 1994-02-16 | 沈阳工业大学 | Process for improving the plasticity of cold deformation of low-carbon thread reinforcing steel |
-
1996
- 1996-06-20 CN CN96106625A patent/CN1045623C/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1327008C (en) * | 2005-07-07 | 2007-07-18 | 东北大学 | Post rolling fast cooling-production technology of high strength ribbed reinforced bar |
| CN1330785C (en) * | 2005-12-27 | 2007-08-08 | 东北大学 | Strength of extension 1000 MPa grade complex phase steel plate and mfg. method thereof |
| CN100348767C (en) * | 2005-12-27 | 2007-11-14 | 东北大学 | Strength of extension 750-795 MPa grade double-phase steel plate and mfg. method thereof |
| CN101693941B (en) * | 2009-08-13 | 2011-06-08 | 巨力索具股份有限公司 | Method for quenching medium and low carbon alloy structural steel workpieces |
| CN101974667A (en) * | 2010-11-16 | 2011-02-16 | 汤欣刚 | Manufacturing method of tube pile for underground foundations of high-rise buildings |
| CN103045816A (en) * | 2012-12-12 | 2013-04-17 | 张云江 | Quenching and bluing solution and using method thereof |
| CN109112260A (en) * | 2017-06-23 | 2019-01-01 | 江苏翔鹰五金弹簧有限公司 | A kind of heat treatment method of blue shift straight filament steel wire |
| CN109112260B (en) * | 2017-06-23 | 2023-04-11 | 江苏翔鹰五金弹簧有限公司 | Heat treatment method of bluing straight steel wire |
| CN110592357A (en) * | 2019-09-16 | 2019-12-20 | 中国科学院金属研究所 | Heat treatment method of iron-based wear-resistant coating plough shovel tip |
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| Publication number | Publication date |
|---|---|
| CN1045623C (en) | 1999-10-13 |
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