CN102277476A - Cold-deformation and high-plasticity pretreatment process for high-carbon bearing steel - Google Patents
Cold-deformation and high-plasticity pretreatment process for high-carbon bearing steel Download PDFInfo
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Abstract
The invention relates to a cold-deformation and high-plasticity pretreatment process for high-carbon bearing steel, which is characterized by comprising the following steps: 1) heating, namely heating a high-carbon bearing steel workpiece blank to Ac1 to Accm; 2) heat preservation, wherein the heat preservation time is worked out according to the effective thickness of the high-carbon bearing steel workpiece blank, namely an expression: t=lDmin, wherein t is the heat preservation time, D is the effective thickness of the workpiece blank, the unit of the effective thickness is mm, and l is a heating factor and is equal to 1.5 to 2.0 min/mm; and 3) cooling, namely cooling to 500 DEG C at a cooling speed of 7.6DEG C/min, and then cooling in the air to room temperature. The process can effectively improve the cold-deformation plasticity of the heat-treated workpiece blank.
Description
Technical field
The present invention relates to a kind of high carbon bearing steel cold deformation high-ductility pretreatment technology.
Background technology
The carbon content of high carbon bearing steel is between 0.95wt%～1.05wt%, and hardness is big, the intensity height, and cold deformation plasticity is low, belongs to the difficult shaped material of room temperature.Such material parts adopts thermoforming usually, and spillage of material is big, and forming accuracy is low, and follow-up machining not only consumes a large amount of man-hours but also destroys the metal structure streamline, has reduced production efficiency and quality product.Compare thermoforming, cold shaping precision height, the material use efficiency height, internal soundness is good, the productivity height, technological and economical advantages is remarkable.But cold shaping requires material to have plasticity preferably, and the cold deformation plasticity ability that therefore improves high carbon bearing steel blank is most important.
The conditioning heat treatment of workpiece blank is an important process of improving the blank structure property before the cold shaping.Conditioning heat treatment is heated to suitable temperature by the initial workpiece blank that tissue is departed from equilibrium state, the insulation certain hour, and slowly cooling then, thus acquisition is near the cold shaping workpiece blank of equilibrium state tissue.By improving speed of cooling, can effectively reduce after the thermal treatment volume of cementite particle in the high-carbon bearing steel workpiece blank, improve the structure property and the plastic deformation ability of workpiece blank after the conditioning heat treatment.Yet traditional conditioning heat treatment technology adopts furnace cooling usually, not only loses time and the energy, and the cementite particle of workpiece blank pearlitic structure is bigger after the conditioning heat treatment, has influenced the performance of the cold deformation plasticity of workpiece blank and the back workpiece that is shaped.
Summary of the invention
At above present situation, the object of the present invention is to provide a kind of high carbon bearing steel cold deformation high-ductility pretreatment technology, this technology can improve the cold deformation plasticity of workpiece blank after the thermal treatment effectively.
To achieve these goals, the technical solution used in the present invention is: high carbon bearing steel cold deformation high-ductility pretreatment technology is characterized in that it may further comprise the steps:
1) heating: high-carbon bearing steel workpiece blank is heated to A
C1～A
CcmBetween;
2) insulation: soaking time is calculated with the net thickness of high-carbon bearing steel workpiece blank: t=lDmin, t is a soaking time in the formula, D is the net thickness of workpiece blank, the unit of net thickness is that mm (press diameter and calculate: for the hollow cylinder workpiece blank by the cylindrical work blank, (h)/wall thickness (d)≤1.5 o'clock highly, net thickness is in h; When h/d 〉=1.5, net thickness is in 1.5d; When h/d＞7, net thickness is in solid cylinder, and net thickness D is a diameter of phi; For hollow female cone body workpiece blank, net thickness is in external diameter Φ * 0.8), l is a heating coefficient, l=1.5～2.0min/mm;
3) cooling: the speed of cooling with 7.6 ℃/min is cooled to 500 ℃, and air cooling is to room temperature then.
The carbon content of described high carbon bearing steel is 0.95wt%～1.05wt%.
Described high carbon bearing steel is the most frequently used GCr15 bearing steel.
The invention has the beneficial effects as follows: (7.6 ℃/min), reduced the volume of cementite particle after the thermal treatment, this technology has improved the cold deformation plasticity of workpiece blank after the thermal treatment effectively by the appropriate design speed of cooling.
Description of drawings
Fig. 1 is conditioning heat treatment process curve figure of the present invention.
Fig. 2 is material microstructure figure after the conditioning heat treatment of the present invention (being microstructure contrast before and after the GCr15 thermal treatment among the embodiment 1); Among the figure: (a) original structure, (b) through annealing process A, (c) through annealing process B, (d) through annealing process C.
Fig. 3 is material extending experiment standard specimen figure (unit among the figure is mm) after the conditioning heat treatment of the present invention.
Fig. 4 be after the conditioning heat treatment of the present invention material list to tensile stress-strain curve figure (GCr15 bearing steel annealing after stress-strain curve).
Embodiment
In order to understand the present invention better, further illustrate content of the present invention below in conjunction with embodiment, but content of the present invention not only is confined to the following examples.
High carbon bearing steel cold deformation high-ductility pretreatment technology, realize as follows:
(1) base: it is that 52.5mm, internal diameter are that 32.5mm, height are the high carbon bearing steel ring of 20mm (being high-carbon bearing steel workpiece blank) that the upsetting of GCr15 bearing steel bar high temperature is become external diameter; The carbon content of GCr15 Steel Bar During is 0.95wt%～1.05wt%.
(2) heating: (this temperature is A to be heated to 790 ℃ with three groups high carbon bearing steel rings (high-carbon GCr15 bearing steel ring)
C1～A
Ccm), as shown in Figure 1, make its austenitizing.
(3) insulation: batch=16700g/m
3, three groups high carbon bearing steel rings are all at 790 ℃ of insulation 20min[t=lDmin, l=1.5, D=15], be as cold as 690 ℃ with stove then, insulation 180min makes its nodularization abundant, as shown in Figure 1.
(4) cooling: three groups high carbon bearing steel rings are cooled to 500 ℃ (corresponding to: annealing process A, annealing process B, annealing process C) with the speed of 7.6 ℃/min, 4.3 ℃/min and 2.1 ℃/min respectively, and air cooling is to room temperature, as shown in Figure 1 again.
The three groups high carbon bearing steel rings of handling are taken a sample respectively, with sample roughly grind, finish grind, after corrosion and the polished finish, nital with 4% corrodes, and observes the tissue topography of the inner different sites of each sample then under Philips Quanta200 type scanning electron microscope, as shown in Figure 2.The size of the cementite particle in the survey sheet 2, diameter are followed successively by 0.5 μ m, 1.0 μ m and 1.5 μ m, and conditioning heat treatment speed of cooling as can be seen is more fast, and cementite particle is more little.
With the microhardness of model for three samples of HXD1000 microhardness tester test.When testing the hardness in a zone, wantonly 3 hardness in this zone of test is obtained mean value then as end-result earlier, and is as shown in table 1.Can find out that from table 1 the conditioning heat treatment speed of cooling is slow more, the hardness of workpiece blank is high more after the conditioning heat treatment.
The three groups high carbon bearing steel bars that the present invention was handled are processed into the standard specimen of stretching experiment as shown in Figure 3, be placed on model and be on the mechanical property experimental installation of Zwick/Roell Z100 and carry out stretching experiment, obtain the mechanical property of material, result such as table 1 and shown in Figure 4.As can be seen, the conditioning heat treatment speed of cooling is in 2.1 ℃/min～7.6 ℃/min scope, and speed of cooling is fast more, and Tensile strength is high more, unit elongation is good more.
Mechanical property and microhardness after the different conditioning heat treatment technologies of table 1
Above-mentioned description of test: when speed of cooling is 7.6 ℃/min, reduced the volume of cementite particle after the thermal treatment, improved the cold deformation plasticity of thermal treatment blank effectively.
Embodiment 2:
Substantially the same manner as Example 1, difference is: be incubated be 30min[t=lDmin, l=2.0, D=15].
Experimental technique is identical with embodiment 1, and experimental result shows: when speed of cooling is 7.6 ℃/min, reduced the volume of cementite particle after the thermal treatment, improved the cold deformation plasticity of thermal treatment blank effectively.
Claims (2)
1. high carbon bearing steel cold deformation high-ductility pretreatment technology is characterized in that it may further comprise the steps:
1) heating: high-carbon bearing steel workpiece blank is heated to A
C1～A
CcmBetween;
2) insulation: soaking time is calculated with the net thickness of high-carbon bearing steel workpiece blank: t=lDmin, and t is a soaking time in the formula, and D is the net thickness of workpiece blank, and the unit of net thickness is mm, and l is a heating coefficient, l=1.5～2.0min/mm;
3) cooling: the speed of cooling with 7.6 ℃/min is cooled to 500 ℃, and air cooling is to room temperature then.
2. high carbon bearing steel cold deformation high-ductility pretreatment technology according to claim 1, it is characterized in that: the carbon content of described high carbon bearing steel is 0.95wt%～1.05wt%.
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Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101921901A (en) * | 2010-03-26 | 2010-12-22 | 瓦房店光阳轴承集团有限公司 | Heat processing method of high-carbon chromium bearing steel bearing part |
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2011
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101921901A (en) * | 2010-03-26 | 2010-12-22 | 瓦房店光阳轴承集团有限公司 | Heat processing method of high-carbon chromium bearing steel bearing part |
Non-Patent Citations (4)
| Title |
|---|
| 《Materials and Design》 20101203 M.Wu, et al "Influence of the annealing cooling rate on the microstructure evolution and deformation behaviours in the cold ring rolling of medium steel" 2292-2295，2299 1-2 第32卷, * |
| 《江南学院学报》 20010630 刘新佳，等 "GCr15轴承钢管冷拔横裂原因分析" 13-14 1-2 第16卷, 第2期 * |
| M.WU, ET AL: ""Influence of the annealing cooling rate on the microstructure evolution and deformation behaviours in the cold ring rolling of medium steel"", 《MATERIALS AND DESIGN》 * |
| 刘新佳，等: ""GCr15轴承钢管冷拔横裂原因分析"", 《江南学院学报》 * |
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Application publication date: 20111214 |