CN104388653A - Post-processing process of hot-rolled 12Cr1MoV seamless steel tube and processed steel tube - Google Patents
Post-processing process of hot-rolled 12Cr1MoV seamless steel tube and processed steel tube Download PDFInfo
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- CN104388653A CN104388653A CN201410660171.7A CN201410660171A CN104388653A CN 104388653 A CN104388653 A CN 104388653A CN 201410660171 A CN201410660171 A CN 201410660171A CN 104388653 A CN104388653 A CN 104388653A
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Abstract
The invention discloses a post-processing process of a hot-rolled 12Cr1MoV seamless steel tube and a processed steel tube, and belongs to the technical field of the post-processing process, including heat treatment and straightening procedures, of the seamless steel tubes. The post-processing process is capable of obtaining the 12Cr1MoV seamless steel tube, which is uniform in surface hardness and also conforms to relevant standard and agreement requirements in indexes such as tensile property and external dimension, by use of the steps and methods of performing sequential normalizing heat treatment, straightening treatment and tempering heat treatment on the hot-rolled 12Cr1MoV seamless steel tube, wherein the surface hardness is only 5%-12% higher than the matrix hardness.
Description
Technical field
The present invention relates to a kind of aftertreatment technology comprising thermal treatment and straightening process of weldless steel tube, particularly a kind of aftertreatment technology comprising thermal treatment and straightening process of hot rolling 12Cr1MoV weldless steel tube.
Background technology
12Cr1MoV weldless steel tube is usually used in manufacturing boiler superheater and main steam conduit, its main moulding process comprises hot rolling and cold-drawn, wherein hot rolling technology is little compared with cold-drawing technology difficulty of processing, high to the adjustment capability of steel microtexture, be more suitable for general industrial production, but in course of hot rolling there is obvious thermal distortion in steel, it is easily caused to occur the problems such as character is unstable, unrelieved stress is larger, for solving the problem, need through further aftertreatment, comprise the thermal treatment to the steel pipe after shaping and aligning.Be that normalizing combines with tempering to the heat treatment mode that the 12Cr1MoV weldless steel tube of hot-roll forming is common, as after 980 ~ 1020 DEG C of normalizings again with 720 ~ 760 DEG C of tempering, pass through thermal treatment, greatly solve the unrelieved stress of steel pipe and the problem of character instability, further, then by the straightening processing of straightener to steel pipe the deviation from circular from the axial bending produced in each process above and radial direction is corrected.The roller curve of straightener is envelope curve, its envelope align the four corner of caliber, in the process of aligning, steel pipe can produce elasticity and viscous deformation, and roller curve and outer diameter of steel pipes keep certain contact length, by external force, steel pipe is aligned, this Levelling principle easily causes outer surface of steel tube to form spiral contact surface simultaneously on the one hand,---namely rectify trace, on the other hand, the steel tube surface after aligning can be made to produce work hardening, and work hardening then causes steel tube surface hardness to improve.The deflection of steel pipe aligning is larger, the increase rate of steel tube surface hardness is larger, the detected result display of the surface hardness after the Hot rolling 12 Cr 1 MoV Steel pipe aligning of different size, after aligning, its surface hardness is generally than matrix hardness height about 12% ~ 20%, and rectifys the surface hardness height about 15% ~ 20% of surface hardness than other positions at trace place.
Summary of the invention
Based on the defect of above-mentioned prior art, one is the object of the present invention is to provide to obtain surface hardness even, the index such as tensile property and apparent size meets the aftertreatment technology of the hot rolling 12Cr1MoV weldless steel tube of relevant criterion and protocol requirement simultaneously, and another object of the present invention is to provides a kind of uniform 12Cr1MoV weldless steel tube of surface hardness utilizing this technique obtained simultaneously.
The present invention is achieved through the following technical solutions this technical purpose:
For the aftertreatment technology of hot rolling 12Cr1MoV weldless steel tube, it comprises the thermal treatment of weldless steel tube after hot-roll forming and straightening process, it is characterized in that: comprise the following steps:
1) normalizing thermal treatment is carried out to described hot rolled seamless steel tube, obtain steel pipe after normalizing;
2) straightening processing is carried out to steel pipe after described normalizing, obtain aligning rear steel pipe;
3) tempering heat treatment is carried out to steel pipe after described aligning.
Be that prior art passes through normalizing with the difference of prior art herein, align again after tempering heat treatment, there is defect as described in the background art thus, and the present invention changes the process of existing technique, the problem of stress remnants and the unstable properties produced in course of hot rolling is first tentatively eliminated through normalizing thermal treatment, again through aligning, revise the axial bending of hot rolling and normalizing heat-treated steel pipe and radial deviation from circular from, finally by tempering heat treatment, again eliminate the problem of stress remnants and the unstable properties occurred in preceding step on the one hand, on the other hand, consolidate the correction of straightening processing to steel pipe sizes and deformation.It will be appreciated by persons skilled in the art that this technologic improvement is not the adjustment of simple step, because in technique of the present invention, under different step, the thermodynamic state of steel pipe is not identical with the thermodynamic state of steel pipe under different step in prior art.
After above-mentioned aftertreatment technology, steel pipe can pack warehouse-in again after flaw detection, inspection.
For the aftertreatment technology of above-mentioned hot rolling 12Cr1MoV weldless steel tube, the present invention proposes a kind of preferred implementation, namely the type of cooling in described normalizing thermal treatment is the cold or Forced water cooling of air cooling, mist, the metallographic structure of normalizing heat-treated steel pipe is made up of ferrite, perlite and bainite, wherein, ferrite content is the highest, and is not less than 35%.
In the type of cooling, the hot rolling 12Cr1MoV weldless steel tube that general wall thickness is thinner can adopt air cooling, and the thicker hot rolling 12Cr1MoV weldless steel tube of wall thickness can adopt the cold or Forced water cooling of mist, the requirement of the metallurgical structure of the control demand fulfillment normalizing heat-treated steel pipe of speed of cooling, eliminates the uneven of the steel tube surface hardness caused because of normalizing thermal treatment and straightening processing relatively easily to enable follow-up tempering heat treatment process.If speed of cooling is too fast, the bainite in metallographic structure or content of pearlite in alloy is easily caused to increase substantially and make ferrite content be starkly lower than 35%, the intensity and hardness that cause steel pipe are significantly improved, when making straightening processing, required straightening deformation power and deflection also increase substantially, both be unfavorable for fully completing of straightening processing, and be also unfavorable for eliminating the uneven of the steel tube surface hardness caused because of normalizing thermal treatment and straightening processing in follow-up tempering heat treatment process.After meeting normalizing thermal treatment the metallurgical structure of hot rolling 12Cr1MoV weldless steel tube prerequisite under, speed of cooling can selectivity adjustment.
For the aftertreatment technology of above-mentioned hot rolling 12Cr1MoV weldless steel tube, the present invention proposes another kind of preferred implementation, and the Heating temperature namely in described normalizing thermal treatment is 980 ~ 1000 DEG C, and soaking time is 80 ~ 150min.
For the aftertreatment technology of above-mentioned hot rolling 12Cr1MoV weldless steel tube, the present invention proposes another kind of preferred implementation, namely straightening processing uses the mode of gag press straightening.Straightening parameters can meet selectivity adjustment under the prerequisite of fully aligning, and axial bending and the radial deviation from circular from of the rear steel pipe of abundant aligning i.e. aligning meet service requirements.
For the aftertreatment technology of above-mentioned hot rolling 12Cr1MoV weldless steel tube, the present invention proposes another kind of preferred implementation, namely in described tempering heat treatment charging temperature not higher than 250 DEG C, temperature rise rate is not more than 15 DEG C/min, rate of cooling in tempering stove is not more than 15 DEG C/min, furnace temperature is down to and is not come out of the stove after 250 DEG C, and continues cooling in atmosphere.
The selection of above parameter is in order to by the control of entering stove, tapping temperature and temperature rate, occurs new larger deformation to avoid steel pipe in tempering heat treatment.
For the above-mentioned aftertreatment technology of hot rolling 12Cr1MoV weldless steel tube and the preferred implementation in tempering heat treatment thereof, the present invention proposes further preferred implementation, namely select tempering Heating temperature in tempering heat treatment to be 740 ~ 760 DEG C, tempering insulation time is 120 ~ 210min.
The weldless steel tube that the preferred tempering heat treatment embodiment that present invention further proposes a kind of aftertreatment technology by this hot rolling 12Cr1MoV weldless steel tube prepares, according to test mode and the requirement of GB5310 " seamless steel tubes and pipes for high pressure boiler ", its mechanical property shows as:
Yield strength: be not less than 255MPa;
Tensile strength: 470 ~ 570MPa;
Unit elongation: be not less than 21%;
Surface hardness: 140 ~ 178HBW.
Simultaneously, the extreme difference of its surface hardness is 10 ~ 15HBW, the testing method used can reflect premised on the actual distribution situation of steel tube surface hardness to meet test result more all sidedly, as randomly by steel pipe circumferentially direction every 90 degree, length direction gets a test point every 500 millimeters, test its surface hardness, then a large amount of test results is carried out to the method for numerical statistic.
By above technical scheme, the present invention has following beneficial effect:
1) present, a lot of boiler for producing producer not only requires that 12Cr1MoV steel pipe must meet the regulation of GB5310 " seamless steel tubes and pipes for high pressure boiler ", and its surface hardness be also been proposed to the requirement exceeding GB5310 " seamless steel tubes and pipes for high pressure boiler " and specify, namely the span of control of surface hardness is 138 ~ 179HBW, and tensile strength is still by the regulation of GB5310 " seamless steel tubes and pipes for high pressure boiler ", its span of control is 470 ~ 640Mpa.According to the contrast relationship of tensile strength and hardness, when matrix hardness is 138 ~ 179HBW, the tensile strength of its correspondence is 470 ~ 591Mpa, after aligning by prior art, the surface hardness of 12Cr1MoV steel pipe is generally than matrix hardness height about 12% ~ 20%, rectify the surface hardness height about 15% ~ 20% of surface hardness than other positions at trace place, calculate accordingly, if the surface hardness of guarantee and tensile strength meet standard-required simultaneously, the tensile strength of finished product 12Cr1MoV steel pipe should control in the narrow range of 470 ~ 495Mpa, this just causes production difficulty large, conforming product rate is low.Technique of the present invention can make steel tube surface hardness only high by 5% ~ 12% relative to matrix hardness, and whole steel tube surface Hardness Distribution is comparatively even, and controlled tensile strength range is comparatively large, and production difficulty reduces.
2) in aftertreatment technology of the present invention, steel pipe first carries out tempering heat treatment again through aligning, it is remaining that tempering heat treatment can eliminate the stress produced in the surface hardening and aligning that in existing technique, after straightening processing, steel pipe occurs effectively, simultaneously because steel pipe have passed through normalizing treatment before aligning, remaining and the dimensional change of the stress that produces after hot rolling of major part is eliminated by normalizing treatment, so by suitable Selecting parameter in tempering heat treatment, steel pipe there will not be new unmanageable deformation, effective cooperation of each step in technique, can under the prerequisite ensureing steel pipe sizes and morphological requirements, farthest eliminate the unrelieved stress that steel pipe produces aborning, improve its use properties.
3) in the preferred embodiment of the present invention, further optimization has been carried out to tempering heat treatment, temperature rate and turnover furnace temperature etc. are set, can guarantee that steel pipe meets the requirement of GB5310 " seamless steel tubes and pipes for high pressure boiler " at the axial bending after tempering heat treatment and radial deviation from circular from, no longer need to carry out steel pipe aligning after this heat treatment step.
Accompanying drawing explanation
Fig. 1 is that lot number is its metallographic structure image that in the 12Cr1MoV weldless steel tube of H101, random sampling records from embodiment one;
Fig. 2 is that lot number is its metallographic structure image that in the 12Cr1MoV weldless steel tube of H102, random sampling records from embodiment one;
Fig. 3 is that lot number is its metallographic structure image that in the 12Cr1MoV weldless steel tube of H201, random sampling records from embodiment two;
Fig. 4 is that lot number is its metallographic structure image that in the 12Cr1MoV weldless steel tube of H202, random sampling records from embodiment two;
Fig. 1 ~ Fig. 4 is hot rolling 12Cr1MoV weldless steel tube after aftertreatment, the metallographic structure image of its proximity, and wherein, etchant solution is the nital of 4%, and metallographic structure image magnification is 100 times.
Embodiment
Below in conjunction with embodiments of the invention, the invention will be further elaborated.
Embodiment one:
Production specification is two batches, the hot rolling 12Cr1MoV weldless steel tube of 323.9 × 16mm:
Its technological process of production is: hot rolling 12Cr1MoV weldless steel tube → normalizing thermal treatment → pressure is rectified → tempering heat treatment → flaw detection, checked → packaging, warehouse-in.Concrete production process is:
1) two batches of 12Cr1MoV weldless steel tubes of H101 and H102 are respectively by hot-roll forming lot number;
2) carry out normalizing thermal treatment to these two batches of hot rolling 12Cr1MoV weldless steel tubes, its temperature rise rate is 3.5 DEG C/min, and Heating temperature is 1000 DEG C, and soaking time is 80min, is incubated laggard line space cold;
3) after these two batches of steel pipes are cooled to room temperature, gag press straightening to meet GB5310 " seamless steel tubes and pipes for high pressure boiler " requirement to the axial bending of steel pipe and radial deviation from circular from is carried out to it;
4) the hot rolling 12Cr1MoV weldless steel tube after aligning is carried out tempering in tempering stove, its charging temperature is 240 DEG C, temperature rise rate is 15 DEG C/min, Heating temperature is 750 DEG C, soaking time is 120 minutes, when cooling thereafter, first cools in tempering stove, rate of cooling is 15 DEG C/min, comes out of the stove and continue cooling after furnace temperature is down to 250 DEG C in static air;
5) two batches of hot rolling 12Cr1MoV weldless steel tubes of gained are detected a flaw, check after pack warehouse-in, in inspection, one group of sample is respectively got to these two batches of steel pipes.
Sample, after metallographic, mechanics inspection, visual inspection, can determine that the metallographic structure of two batches of 12Cr1MoV weldless steel tubes, mechanical property, longitudinal bending and deviation from circular from all meet the requirement of GB5310 " seamless steel tubes and pipes for high pressure boiler ".
Wherein, the mechanical experimental results of sample is as shown in the table:
Its surface hardness detect circumferentially direction every 90 degree, length direction samples every the mode of 500 millimeters of random sampling, test result is as shown in the table:
| Lot number | Hardness Surveillance result (HBW) |
| H101 | 152～163 |
| H102 | 157～167 |
Its microstructure examination result display lot number is that the metallographic structure of two batches of 12Cr1MoV weldless steel tubes of H101 and H102 forms by ferrite, perlite and bainite, and wherein ferrite content is maximum, and content of pearlite in alloy is taken second place, and bainite content is minimum.
Embodiment two:
Product batch number is respectively H201 and H202, and specification is two batches, the 12Cr1MoV weldless steel tube of 457.2 × 60mm, and its technical process is identical with embodiment one, and concrete technological process is as follows:
1) two batches of 12Cr1MoV weldless steel tubes of H201 and H202 are respectively by hot-roll forming lot number;
2) carry out normalizing thermal treatment to these two batches of hot rolling 12Cr1MoV weldless steel tubes, Heating temperature is 1000 DEG C, and soaking time is 150 minutes, and after insulation, mist is cold;
3) be cooled to after room temperature until steel pipe, gag press straightening is carried out to it, guarantee that steel pipe meets the requirement of GB5310 " seamless steel tubes and pipes for high pressure boiler " at the axial bending after normalizing thermal treatment and radial deviation from circular from;
4) the 12Cr1MoV steel pipe after aligning is carried out tempering heat treatment, its charging temperature is 230 DEG C, temperature rise rate is 15 DEG C/min, Heating temperature is 750 DEG C, soaking time is 210 minutes, when cooling thereafter, first cools in tempering stove, rate of cooling is 15 DEG C/min, comes out of the stove and continue cooling after furnace temperature is down to 250 DEG C in static air.
5) two batches of 12Cr1MoV steel pipes of gained are detected a flaw, check after pack warehouse-in, in inspection, one group of sample is respectively got to these two batches of steel pipes.
Sample, after metallographic, mechanics inspection, visual inspection, can determine that the metallographic structure of these two batches of 12Cr1MoV weldless steel tubes, mechanical property, longitudinal bending and deviation from circular from all meet the requirement of GB5310 " seamless steel tubes and pipes for high pressure boiler ".
Wherein, the mechanical experimental results of sample is as shown in the table:
Its surface hardness detect circumferentially direction every 90 degree, length direction samples every the mode of 500 millimeters of random sampling, test result is as shown in the table:
| Lot number | Hardness Surveillance result (HBW) |
| H201 | 163～173 |
| H202 | 159～170 |
Its microstructure examination result display lot number is that two batches of 12Cr1MoV weldless steel tubes metallographic structure of H201 and H202 forms by ferrite, bainite and perlite, and wherein ferrite content is maximum, and bainite content takes second place, and content of pearlite in alloy is minimum.
Although above in conjunction with the embodiments to invention has been detailed description, it will be appreciated by those skilled in the art that under the prerequisite not departing from present inventive concept, within the scope of the claims, can also to carry out above-described embodiment and more or change etc.
Claims (7)
1. an aftertreatment technology for hot rolling 12Cr1MoV weldless steel tube, it comprises the thermal treatment of weldless steel tube after hot-roll forming and straightening process, it is characterized in that: comprise the following steps:
1) normalizing thermal treatment is carried out to described hot rolled seamless steel tube, obtain steel pipe after normalizing;
2) straightening processing is carried out to steel pipe after described normalizing, obtain aligning rear steel pipe;
3) tempering heat treatment is carried out to steel pipe after described aligning.
2. the aftertreatment technology of hot rolling 12Cr1MoV weldless steel tube according to claim 1, it is characterized in that: the type of cooling in described normalizing thermal treatment is the cold or Forced water cooling of air cooling, mist, the metallographic structure of normalizing heat-treated steel pipe is made up of ferrite, perlite and bainite, wherein, ferrite content is the highest, and is not less than 35%.
3. the aftertreatment technology of hot rolling 12Cr1MoV weldless steel tube according to claim 1, it is characterized in that: the Heating temperature in described normalizing thermal treatment is 980 ~ 1000 DEG C, soaking time is 80 ~ 150min.
4. the aftertreatment technology of the hot rolling 12Cr1MoV weldless steel tube according to any one of claims 1 to 3, is characterized in that: described straightening processing uses the mode of gag press straightening.
5. the aftertreatment technology of hot rolling 12Cr1MoV weldless steel tube according to claim 1, it is characterized in that: in described tempering heat treatment, charging temperature is not higher than 250 DEG C, temperature rise rate is not more than 15 DEG C/min, rate of cooling in tempering stove is not more than 15 DEG C/min, furnace temperature is down to and is not come out of the stove after 250 DEG C, and continues cooling in atmosphere.
6. the aftertreatment technology of hot rolling 12Cr1MoV weldless steel tube according to claim 1 or 5, it is characterized in that: in described tempering heat treatment, tempering Heating temperature is 740 ~ 760 DEG C, tempering insulation time is 120 ~ 210min.
7. the weldless steel tube that obtains of the aftertreatment technology process of the hot rolling 12Cr1MoV weldless steel tube according to any one of claim 1 ~ 6, it is characterized in that: according to the test mode of GB5310 " seamless steel tubes and pipes for high pressure boiler ", the mechanical property of described weldless steel tube meets following index:
Yield strength: >=255MPa;
Tensile strength: 470 ~ 570MPa;
Unit elongation: >=21%;
Surface hardness: 140 ~ 178HBW.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108315532A (en) * | 2018-01-12 | 2018-07-24 | 湖北新冶钢特种钢管有限公司 | Steel pipe water fog cooling means |
| CN109540635A (en) * | 2018-11-22 | 2019-03-29 | 大唐东北电力试验研究院有限公司 | A kind of discrimination method of 12Cr1MoV steel serious nodularization and normal metallographic structure |
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| CN102953019A (en) * | 2012-09-25 | 2013-03-06 | 无锡润丰特种钢管有限公司 | Alloy steel seamless steel tube for geological drilling and machining method thereof |
| CN103276297A (en) * | 2013-06-09 | 2013-09-04 | 嘉兴市新纪元钢管制造有限公司 | Self-connecting type and high-strength seamless steel tube for rope coring drill rod, as well as manufacturing method thereof |
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2014
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Patent Citations (3)
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| CN102953019A (en) * | 2012-09-25 | 2013-03-06 | 无锡润丰特种钢管有限公司 | Alloy steel seamless steel tube for geological drilling and machining method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108315532A (en) * | 2018-01-12 | 2018-07-24 | 湖北新冶钢特种钢管有限公司 | Steel pipe water fog cooling means |
| CN109540635A (en) * | 2018-11-22 | 2019-03-29 | 大唐东北电力试验研究院有限公司 | A kind of discrimination method of 12Cr1MoV steel serious nodularization and normal metallographic structure |
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Application publication date: 20150304 |