CN104531965A - Method for heat treatment of high-plasticity low-yield-ratio concrete reinforcing bars - Google Patents
Method for heat treatment of high-plasticity low-yield-ratio concrete reinforcing bars Download PDFInfo
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- CN104531965A CN104531965A CN201410826750.4A CN201410826750A CN104531965A CN 104531965 A CN104531965 A CN 104531965A CN 201410826750 A CN201410826750 A CN 201410826750A CN 104531965 A CN104531965 A CN 104531965A
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Abstract
The invention discloses a method for heat treatment of high-plasticity low-yield-ratio concrete reinforcing bars. The heat treatment method comprises the following steps: heating a cold-deformed reinforcing bar to 740-850 DEG C for subcritical quenching so as to enable the metallographic structure of the reinforcing bar to be a ferrite and martensite dual-phase structure; heating the quenched reinforcing bar to be over 460 DEG C for tempering treatment, and applying a tensile force which is not more than 30 percent of the previous breaking force of the reinforcing bar to the reinforcing bar in the tempering treatment so as to change the metallographic structure of the reinforcing bar to a dual-phase structure of tempered troostite or tempered sorbite and ferrite which has the volume content less than 10 percent of total content of the metallographic structure, wherein the reinforcing bar is a medium-low-carbon reinforcing bar. According to the heat treatment method, the heating temperature of subcritical quenching is relatively low, and the ferrite which is not molten exists in the steel to stop increase of austenite grains, so that the actual grain of the reinforcing bar before quenching is relative fine, energy consumption can be reduced by 20-30 percent, and pollution can be reduced.
Description
Technical field
The present invention relates to the heat treating method of metallurgy industry steel, particularly a kind of heat treating method of middle low carbon steel.
Background technology
Reinforcing bar for prestressed concrete (or rod iron) has been widely used in the prestressed components such as the centrifugal pile tube of high-strength prestressed concrete, tall building foundation concrete tubular pile, overhead bridge pier concrete tubular pile, electric pole, railroad sleeper abroad.The Application Areas of domestic prestressing steel is extended to the engineering fields such as building, water conservancy, the energy and ground anchorage from railway, highway.Steel bar for prestressed concrete generally adopts heat treating method to obtain, and the high-strength prestress reinforcing bar being through heat treatment synthesizing carries out a kind of high-strength low-alloy structural steel that modifier treatment obtains after a little cold-drawn or cold rolling processing.This rod iron has the advantages such as intensity is high, relaxation rate is low.
Middle low carbon steel in pursuit high strength, while high tenacity, also using yield tensile ratio as an important indicator because the yield tensile ratio of steel is lower, then mean high work hardening exponent and high uniform elongation.If be applied in architectural by low yield strength ratio steel, the anti-seismic performance of buildings just can be improved; If use as auto sheet, then can significantly improve the cold forming capability of auto sheet.But, the yield tensile ratio of the steel that common quenching and tempering treatment technique obtains is higher (generally can reach 97%), cause the difference of the tensile strength of steel and yield strength less, safety margin is not enough, become the Hazard Factor of building materials, thus the yield tensile ratio problem of structural steel, has become the important topic of the safety margin meeting concrete structure steel.
Summary of the invention
One object of the present invention is the heat treating method providing a kind of high-strength plasticity low yield strength ratio concrete reinforcing bars, and these steel, while maintenance higher-strength, have low yield tensile ratio, high and uniform unit elongation, improves the security of building.
According to an aspect of the present invention, a kind of heat treating method of high-strength plasticity low yield strength ratio concrete reinforcing bars is provided, described method comprises the steps: that the reinforcing bar after by cold deformation is heated to 740 DEG C ~ 850 DEG C and carries out intercritical hardening process, makes the metallographic structure of reinforcing bar be ferrite and martensitic duplex structure; Reinforcing bar after quenching is heated to more than 460 DEG C and carries out temper, and in temper process, reinforcing bar is applied to be no more than the tension force of 30% of its original breaking force, the ferritic duplex structure becoming tempering troostite or tempered sorbite and volume content to make the metallographic structure of reinforcing bar and be less than 10% of metallographic structure total content; Wherein, reinforcing bar is middle low carbon steel muscle.
According to embodiments of the invention, in intercritical hardening treating processes, after the reinforcing bar after cold deformation being heated to 740 DEG C ~ 850 DEG C, immediately reinforcing bar is cooled to room temperature.
According to embodiments of the invention, the temperature of temper can be 460 DEG C ~ 560 DEG C.
According to embodiments of the invention, in temper process, the tension force being no more than 10% of its original breaking force is applied to reinforcing bar.
According to embodiments of the invention, in temper process, the tension force being no more than 3% ~ 8% of its original breaking force is applied to reinforcing bar.
According to embodiments of the invention, described middle low carbon steel muscle can comprise by weight percentage: the Mn of the C of 0.15% ~ 0.5%, the Si of 0.5% ~ 1.0% and 0.5% ~ 2.0%.
According to embodiments of the invention, quench treatment and the temper of reinforcing bar can be performed in Medium Frequency Induction Heating Furnace.
According to the heat treating method of high-strength plasticity low yield strength ratio concrete reinforcing bars of the present invention, from traditional to carry out quench hot to reinforcing bar different, the Heating temperature of intercritical hardening is lower, and in steel, there is not molten ferrite, the increase of austenite crystal can be stoped, therefore make the actual die of reinforcing bar before quenching comparatively thin, but also energy consumption 20% ~ 30% can be reduced, decreasing pollution.In addition, the not molten ferritic existence in the reinforcing bar before quenching can prevent the expansion of concentrating of stress and crackle, thus can improve the impelling strength of reinforcing bar.In addition, heat treating method of the present invention reduces the yield tensile ratio of reinforcing bar, improves the distribution of detrimental impurity, improves comprehensive mechanical performance.
Accompanying drawing explanation
By the description to embodiment carried out below in conjunction with accompanying drawing, above-mentioned and/or other object of the present invention and advantage will become apparent, wherein:
Fig. 1 is the schematic diagram of the thermal treatment process that traditional centering low carbon steel reinforced bar performs;
Fig. 2 is the schematic diagram of the exemplary embodiment of the heat treating method performed according to centering low carbon steel reinforced bar of the present invention;
Fig. 3 is the metallographic structure figure of the reinforcing bar after traditional thermal treatment;
Fig. 4 be according to the thermal treatment of exemplary embodiment of the present invention after the metallographic structure figure of reinforcing bar.
Embodiment
Describe the heat treating method of high-strength plasticity low yield strength ratio concrete reinforcing bars of the present invention below with reference to accompanying drawings in detail.But, the present invention can embody in many different forms, and should not be construed as limited to specific embodiment set forth herein, on the contrary, there is provided these embodiments to make the present invention to be thoroughly with complete, and scope of the present invention will be passed on fully to those skilled in the art.
Fig. 2 is the schematic diagram of the exemplary embodiment of the heat treating method performed according to centering low carbon steel reinforced bar of the present invention.Fig. 4 be according to the thermal treatment of exemplary embodiment of the present invention after the metallographic structure figure of reinforcing bar.
With reference to Fig. 2 and Fig. 4, comprise the following step of order execution according to the heat treating method of high-strength plasticity low yield strength ratio concrete reinforcing bars of the present invention: intercritical hardening process is carried out to the middle low carbon steel muscle after cold deformation; Temper is carried out to the reinforcing bar after quenching.
Method according to the present invention for be middle low carbon steel muscle, it can comprise by weight percentage: the Mn of the C of 0.15% ~ 0.5%, the Si of 0.5% ~ 1.0% and 0.5% ~ 2.0%.
According to the present invention, carrying out in the step of intercritical hardening process to the middle low carbon steel muscle after cold deformation, the middle low carbon steel muscle after cold deformation is being heated to 740 DEG C ~ 850 DEG C (that is, Ac
1+ 30 DEG C ~ 60 DEG C) carry out quench treatment.Specifically, by reinforcing bar being heated to 740 DEG C ~ 850 DEG C, the metallographic structure of reinforcing bar is made to be austenite and ferritic duplex structure; Afterwards, reinforcing bar is cooled fast (such as, water-cooled) to room temperature, make the metallographic structure of reinforcing bar be martensite and ferritic duplex structure.
Reinforcing bar after quenching is being carried out in the step of temper, reinforcing bar after quenching is heated to more than 460 DEG C (such as, 460 DEG C ~ 560 DEG C) carry out temper, and in temper process, certain tension force (applying to be no more than the tension force of 30% of its original breaking force to reinforcing bar) is applied to reinforcing bar, be less than the ferritic duplex structure of 10% of the total content of metallographic structure to make the metallographic structure of reinforcing bar for tempered sorbite or tempering troostite and volume content.Finally, water-spraying control is carried out to the reinforcing bar after temper, thus obtains the finished product.Here, the tension force applied reinforcing bar in temper process refers to that those skilled in the art can understand this point under the teachings of the present invention in an in-line process to the one external tension force that reinforcing bar applies.
In an embodiment of the present invention, in temper process, 10% of its original breaking force can not surmounted to the value of the tension force that reinforcing bar applies, such as, 3% ~ 8%.
In an embodiment of the present invention, above-mentioned quench treatment and temper can be performed in Medium Frequency Induction Heating Furnace.
According to heat treating method of the present invention, adopt intercritical hardening, the metallographic structure of reinforcing bar can be made to be martensite and ferritic duplex structure.From traditional to carry out quench hot to reinforcing bar different, the Heating temperature of intercritical hardening is lower, and there is not molten ferrite in steel, the increase of austenite crystal can be stoped, therefore make the actual die of reinforcing bar before quenching comparatively thin, but also energy consumption 20% ~ 30% can be reduced, decreasing pollution.In addition, the not molten ferritic existence in the reinforcing bar before quenching can prevent the expansion of concentrating of stress and crackle, thus can improve the impelling strength of reinforcing bar.According to the present invention, to the reinforcing bar after quenching through high tempering process, the last metallographic structure of reinforcing bar is made to be tempering troostite and a small amount of ferritic duplex structure (as shown in Figure 4) or tempered sorbite and a small amount of ferritic duplex structure, thus making the intensity of the reinforcing bar after thermal treatment higher, yield tensile ratio is lower.
In addition, heat treating method of the present invention has the advantages such as cost is low, energy saving standard.
In the prior art, there is through the reinforcing bar of traditional Q-tempering process the feature of underrelaxation, but yield tensile ratio is higher; And although there is through the reinforcing bar of stabilizing annealing process the feature of underrelaxation, often to carry out pickling and cause environmental pollution; And the intensity of the gren rod reinforcing bar generally used at present is lower, reinforcing bar common on market is HRB400 reinforcing bar, HRB500 reinforcing bar etc.In other words, up to this point, prior art does not also develop the concrete reinforcing bars for having underrelaxation, low yield strength ratio.But the reinforcing bar that heat treating method according to the present invention obtains has the over-all propertieies such as high strength, high-ductility, low yield strength ratio and underrelaxation rate, can be used for making up the defect of concrete reinforcing bars of existing domestic underrelaxation, low yield strength ratio.
Be described in more detail below in conjunction with the heat treating method of specific embodiment to high-strength plasticity low yield strength ratio concrete reinforcing bars according to the present invention.
Embodiment 1
By the steel bar continuous after cold deformation by the heating collar of Medium Frequency Induction Heating Furnace and cooling hydrosphere, to carry out quench treatment (quenching temperature is 740 DEG C), water-spraying control immediately afterwards.Carry out continuous print temper subsequently, tempering temperature controls at 460 DEG C, and reinforcing bar is applied to the tension force of 30% of its original breaking force.The performance of the reinforcing bar after thermal treatment is see table 1.
Embodiment 2 and embodiment 3
The technical process of embodiment 2 and embodiment 3 is with embodiment 1, and the performance of the reinforcing bar after processing parameter and thermal treatment is see table 1.
Comparative example 1 ~ 3
Comparative example 1 ~ 3 is that centering low carbon steel reinforced bar carries out traditional heat treated example.Fig. 1 is the schematic diagram of the thermal treatment process that traditional centering low carbon steel reinforced bar performs.With reference to Fig. 1, by the steel bar continuous after cold deformation by the heating collar of Medium Frequency Induction Heating Furnace and cooling hydrosphere, reinforcing bar is heated to Ac
3+ 30 DEG C ~ 70 DEG C (namely 870 DEG C ~ 950 DEG C), are heated to complete austenitizing single phase region by reinforcing bar, afterwards water-spraying control immediately, are quenched to whole martensitic stucture.Carry out continuous temper subsequently, tempering temperature controls, between 460 DEG C ~ 540 DEG C, to obtain tempered martensite's (as shown in Figure 3).The performance of the reinforcing bar after the processing parameter of comparative example 1 ~ 3 and thermal treatment is see table 1.
Table 1
As can be seen from Table 1, the yield tensile ratio of the reinforcing bar obtained by heat treating method of the present invention is all lower than the yield tensile ratio of the reinforcing bar obtained by traditional heat treating method, and the unit elongation of the reinforcing bar obtained by heat treating method of the present invention remains on higher level.The experimental result of table 1 shows, heat treating method of the present invention can obtain the concrete reinforcing bars of its underrelaxation rate of high-strength plasticity low yield strength ratio.
Through further researching and analysing discovery, the reason that thermal treatment process of the present invention obtains high-strength plasticity low yield strength ratio reinforcing bar is, the Quench heating of heat-treated steel bar heats in two-phase region, obtain austenite+ferritic structure, quench cooled obtains martensite+ferrite dual phase tissue subsequently, through high tempering process, end product be organized as tempering troostite (or tempered sorbite)+ferritic structure; And the finished product that common tempering process of quenching obtains be organized as tempered martensite, the intensity of material is higher, yield tensile ratio is higher, is unsuitable for the demand for development of modern architecture.
In sum, by heat treating method of the present invention, make containing ferritic structure in the metallographic structure of reinforcing bar, make the intensity of the reinforcing bar after by thermal treatment of the present invention higher, plasticity is higher, and yield tensile ratio is lower, and relaxation rate is lower.
By the reinforcing bar that heat treating method of the present invention obtains, there is the advantages such as intensity high-ductility is high, yield tensile ratio is low, relaxation rate is low, the safety savings ability of building can be improved.
In addition, heat treating method of the present invention has the advantages such as cost is low, energy saving standard.
More than describe the preferred embodiment of the present invention in detail; but; the present invention is not limited to the detail in above-mentioned embodiment; within the scope of technical conceive of the present invention; can carry out multiple simple variant and combination to technical scheme of the present invention, these simple variant all belong to protection scope of the present invention.
Claims (7)
1. a heat treating method for high-strength plasticity low yield strength ratio concrete reinforcing bars, is characterized in that described heat treating method comprises the steps:
Reinforcing bar after cold deformation is heated to 740 DEG C ~ 850 DEG C and carries out intercritical hardening process, make the metallographic structure of reinforcing bar be ferrite and martensitic duplex structure;
Reinforcing bar after quenching is heated to more than 460 DEG C and carries out temper, and in temper process, the tension force being no more than 30% of its original breaking force is applied to reinforcing bar, the ferritic duplex structure becoming tempering troostite or tempered sorbite and volume content to make the metallographic structure of reinforcing bar and be less than 10% of metallographic structure total content
Wherein, reinforcing bar is middle low carbon steel muscle.
2. heat treating method according to claim 1, is characterized in that, in intercritical hardening treating processes, immediately reinforcing bar is cooled to room temperature after the reinforcing bar after cold deformation being heated to 740 DEG C ~ 850 DEG C.
3. heat treating method according to claim 1, is characterized in that, the temperature of temper is 460 DEG C ~ 560 DEG C.
4. heat treating method according to claim 1, is characterized in that, in temper process, applies to reinforcing bar the tension force being no more than 10% of its original breaking force.
5. the heat treating method according to claim 1 or 4, is characterized in that, in temper process, applies to reinforcing bar the tension force being no more than 3% ~ 8% of its original breaking force.
6. heat treating method according to claim 1, is characterized in that, described middle low carbon steel muscle comprises by weight percentage: the Mn of the C of 0.15% ~ 0.5%, the Si of 0.5% ~ 1.0% and 0.5% ~ 2.0%.
7. heat treating method according to claim 1, is characterized in that, performs quench treatment and the temper of reinforcing bar in Medium Frequency Induction Heating Furnace.
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Application publication date: 20150422 |