CN103388059A - Thermal treatment method for low alloy steel - Google Patents
Thermal treatment method for low alloy steel Download PDFInfo
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- CN103388059A CN103388059A CN2013103094472A CN201310309447A CN103388059A CN 103388059 A CN103388059 A CN 103388059A CN 2013103094472 A CN2013103094472 A CN 2013103094472A CN 201310309447 A CN201310309447 A CN 201310309447A CN 103388059 A CN103388059 A CN 103388059A
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Abstract
The invention relates to a thermal treatment method for low alloy steel. A material is heated to 1020-1080 DEG C and subjected to heat preservation for 10-30 min, thereby converting the material into an austenite completely and dissolving carbides into the austenite. Then, the austenite is subjected to isothermal treatment at 500-380 DEG C for 1-5 h to precipitate the carbides and convert the austenite into lower bainite. Then the lower bainite is subjected to low-temperature tempering at 160-180 DEG C for 0.8-1.5 h and is cooled in air. Compared to the prior art, the low alloy steel treated by the method has not only high hardness, but also good toughness, good wear resistance, small dynamic-load notch sensitivity, high fatigue strength, good casting performance and high rate of finished casting products.
Description
Technical field
The present invention relates to a kind of heat treating method of low alloy steel, specifically, relate to a kind of heat treating method of the low alloy steel as bucket tooth.
Background technology
Bucket tooth generally is fixed in the lower end of excavator-type shovel clamshell excavator, the material that directly contacts road surface and need to scoop up, and as hard things such as silt, stone, earth, thereby the protection bucket is not damaged.But due in use, bucket tooth needs constantly hard thing contact and the friction such as stone, earth, and therefore bucket tooth just easily is worn in use for some time.
In prior art, bucket tooth generally adopts the low-carbon alloy steel, and the comprehensive mechanical property of low-carbon alloy steel is better, is not prone to the situation of snapping, but hardness generally only has the HRC50 left and right, in use for some time, the wearing and tearing of low alloy steel material are more serious, when may wear to can not play a protective role the time, need to change processing, must change in general 2～3 months, and and change frequently bucket tooth, not only make Efficiency Decreasing, but also make use cost also greatly increase; And if while using the higher high-content alloy material of hardness to make bucket tooth, although the alloy material of this higher hardness has wear resisting property preferably, comprehensive mechanical property is poor, higher hardness causes its fragility also larger, as easy as rolling off a log snapping during use; And in order to obtain wear resistance relatively better comprehensive mechanical property alloy material relatively preferably, just need to be when the alloy material melting, add more alloy to carry out modified, but the use cost of alloying element is higher, thereupon the cost of alloy material is also corresponding significantly increases.
The purpose of this invention is to provide a kind of hardness high, good toughness, shock-resistant, the heat treating method of the low alloy steel material that can be used for bucket tooth that notch sensitivity is low.
Summary of the invention
The purpose of this invention is to provide a kind of hardness high, good toughness, the impact-resistant heat treating method that can be used for the low alloy steel material of bucket tooth.
The composition of low alloy steel of the present invention (% by weight) is: C:0.85～1.24%; Mn:1.35～1.85%; Cr:1.40～1.90%:V:0.1～0.6%; Mo:0.15～0.2%; All＜0.025%, all the other are Fe and inevitable impurity for RE0.1～0.3%, Si:0.2～0.35%, S, P.
In above-mentioned chemical composition, carbon is the most cheap strengthening element that adopts in common steel.Carbon main form with solid solution or Formed compound in steel exists.Carbide can be used as wild phase increases hardness and the intensity of steel, utilize heat treating method, first make at higher temperature during carbide all is melted in austenite, then utilize carbide miniaturization quenching mode to heat-treat, make carbide particle very tiny and be uniformly distributed, can further improve the obdurability of steel.
Chromium and iron can form continuous solid solution, and can form multiple carbide with carbon (iron).Add a certain amount of chromium in steel, can improve hardness and intensity, along with the increase of chromium content, the tensile strength of steel and hardness also significantly rise, and therefore, chromium is the normal chemical element that adopts in wear resisting steel.Vanadium and carbon have extremely strong avidity, and it mainly exists with carbide morphology in steel.The Main Function of vanadium in steel is thinning microstructure and crystal grain, improves intensity and the toughness of steel, and the carbide of vanadium has high hardness and wear resistance.In addition, silicon also mainly exists with the form of carbide in steel, and the extreme hardness of silicon carbide, and be distributed in crystal boundary can prevent that crystal grain from growing up fast.
The purpose that adds people's rare earth in the present invention: the one, improve the castability of steel, increase the mobility of steel stream, and improve the surface quality of steel ingot or foundry goods, improve casting yield; The 2nd, plasticity and the toughness of raising steel, because rare earth has deoxidation, desulfurization, degassed, reduce the effect of inclusion, therefore, can improve plasticity and the toughness of steel, on the other hand, the sulfide of rare earth element, oxide compound and other compound are in the solidification of molten steel process, all crystallization nuclei, thus effectively refinement crystal grain, this also is conducive to improve plasticity and the toughness of steel.
The present invention is after the molten refining of smelting furnace, and molten steel can be cast into steel ingot, then forges or rolling is become a useful person, making articles thermal treatment; Molten steel also can directly be washed and cast foundry goods and heat-treat use again in addition, preferably becomes foundry goods then to heat-treat use its direct pouring.
The heat treating method that adopts is as follows: be heated to 1020～1080 ℃ of insulation 10～30min, make material be converted into austenite fully, and carbide dissolve in austenite; Then at 500～380 ℃ of isothermal processes 1～5h, carbide is evenly separated out, and austenite is converted into lower bainite, 160～180 ℃ of low-temperaturetemperings insulation, 0.8～1.5h then, air cooling.
Metallographic structure this moment is: lower bainite+carbide+residual austenite.The hardness of lower bainite and intensity are a little less than tempered martensite, but plasticity is good, and notch sensitivity is low, and impelling strength is good, are suitable as very much the core material of bucket tooth.
In addition, for guaranteeing the bucket tooth of making, have better wear resistance and shock resistance, also foundry goods can be carried out carburizing and metallic cementation and process, namely carry out surface treatment.
Low alloy steel of the present invention before heat treating method, also comprises process of surface treatment:
Described process of surface treatment is as follows: 1) bucket tooth is put into ion implanting and processed stove, vacuumize, when vacuum tightness reaches 0.5～10Pa, pass into nitrogen to normal pressure, then be heated to 800 ℃～840 ℃, pulsed current impacts the target of being made by tungstenalloy, and pulsed electrical a fluid stream density is 0.3～6mA/cm
2, pulse-repetition is at 25～50HZ, and acceleration voltage is at 30～40KV, and the Implantation Energy of tungsten ion, at 50～300KeV, injects the concentration 20～50% of tungsten ion, processes 15～40h, then with the stove Slow cooling;
2) bucket tooth that will complete step 1) is put in cementing furnace, slowly is heated to 800～950 ℃, after insulation 2～10h, carries out 60～80 ℃ of isothermal oil quenching after being cooled to 800～900 ℃ with stove.
Method of the present invention also comprises: before carrying out above-mentioned surface treatment, first with the working face of bucket tooth polishing oxide film dissolving and cleaning (pickling and alkali cleaning).
According to above-mentioned process of surface treatment, the ion implanting carbide layers degree of depth is 1.0～2mm, more than its surface hardness can reach 60HRC, WC is arranged, Fe in pervious course simultaneously
2W, Fe
6W
6C, FeW
3The intermetallic compounds such as C, their existence have improved bulk strength and the wear resistance of bucket tooth greatly.
Compared with prior art, low alloy steel provided by the invention not only has higher hardness, but also has toughness preferably, and wear resisting property is good; The moving load notch sensitivity is little, also has higher fatigue strength; And good casting property, casting yield is high, is specially adapted to bucket tooth.
Embodiment
The present invention is described further below in conjunction with specific embodiment.Specialize as nothing, the present invention's raw material used is commercial.
Embodiment 1
Utilize vacuum induction furnace smelting low alloy steel of the present invention, its specific chemical composition is as shown in table 1.
Table 1 chemical component table
| ? | C | Si | Mn | Cr | V | Mo | RE | Fe | Remarks |
| 1 | 1.24 | 0．29 | 1．55 | 1．4l | 0.26 | 0.15 | 0.1 | Surplus | Foundry goods |
| 2 | 0.88 | 0.30 | 1.84 | 1.90 | 0.59 | 0.2 | 0.15 | Surplus | Foundry goods |
| 3 | 1.11 | 0.32 | 1.45 | 1.7l | 0.45 | 0.19 | 0.2 | Surplus | Forging |
| 4 | 0.92 | 0.28 | 1.60 | 1.81 | 0.50 | 0.18 | 0.18 | Surplus | Forging |
After smelting is completed, a part of molten steel casting is become strand, heat-treat respectively (sample 1) and surface treatment+thermal treatment (sample 2), another part is cast into ingot casting, steel ingot is forged into base subsequently, forging stock is heat-treated (sample 3) and surface treatment+thermal treatment (sample 4)
Described casting technique comprises the following steps:
(1) make apperance: make apperance with foam materials, the profile of tooth of apperance is consistent with profiled parts;
(2) coating and drying: be coated with tackiness agent on the apperance surface, sandblast and oven dry; Described sandblast is silicon carbide; The size of its particle is 5-10 μ m; Described tackiness agent is polyacrylamide;
(3) moulding: the apperance of drying is placed in sandbox, places running channel, carry out moulding toward back-up sand in sandbox, and rising head is set on apperance;
(4) cast, knockout and cleaning: toward pouring molten iron in sandbox, cooling rear unpacking knockout, clear up foundry goods, vacuumize in casting process, and vibration, vacuum tightness is less than 0.1Mpa.
Heat treating method and process of surface treatment are as follows:
The heat treating method that sample 1 adopts is as follows: be heated to 1020 ℃ of insulation 10min, make material be converted into austenite fully, and carbide dissolve in austenite; Then at 500 ℃ of isothermal processes 1h, carbide is evenly separated out, and austenite is converted into lower bainite, 160 ℃ of low-temperaturetemperings insulation 0.8h then, air cooling.
Sample 2 first carries out the ion implanting wolfram varbide to be processed, and concrete steps are: 1) ion implanting tungsten: process the vacuum tightness 5～10Pa of stove, pulsed electrical a fluid stream density is 2～2.5mA/cm
2, pulse-repetition is at 30HZ, and acceleration voltage is between 30KV, and the Implantation Energy of tungsten ion is at 100KeV, and the concentration of injecting tungsten ion is being 25～30%, the time of oozing tungsten ion is 20h.After handling, sample in stove with taking out sample after the stove Slow cooling.
2) carburizing and quenching is processed: will complete step 1) sample put in common cementing furnace, after slowly being heated to 900 ℃, take out fast after being cooled to 830 ℃ with stove after insulation 2h, the quenching oil of putting into 60 ℃ quenches.The surface hardness of treated sample is HRC56～58.Annotating carburized tungsten layer thickness M2 is 1.0～1.2mm, and wherein wolfram varbide enriched layer thickness Ml is 0.3mm.
Then heat-treat, the heat treating method of employing is as follows: be heated to 1080 ℃ of insulation 15min, make material be converted into austenite fully, and carbide dissolve in austenite; Then at 380 ℃ of isothermal processes 4h, carbide is evenly separated out, and austenite is converted into lower bainite, 180 ℃ of low-temperaturetemperings insulation 1.5h then, air cooling.
The heat treating method that sample 3 adopts is as follows: be heated to 1060 ℃ of insulation 20min, make material be converted into austenite fully, and carbide dissolve in austenite; Then at 400 ℃ of isothermal processes 2h, carbide is evenly separated out, and austenite is converted into lower bainite, 160 ℃ of low-temperaturetemperings insulation 1h then, air cooling.
Sample 4 first carries out the ion implanting wolfram varbide to be processed, and concrete steps are 1) ion implanting tungsten: process the vacuum tightness 20～30Pa of stove, pulsed electrical a fluid stream density is 0.5～2mA/cm
2, pulse-repetition is at 40～50HZ, and acceleration voltage is at 40KV, and the Implantation Energy of tungsten ion is at 300KeV simultaneously, and the concentration of injecting tungsten ion is being 40～50%, the time of oozing tungsten ion is 36h.Sample in stove with taking out sample after the stove Slow cooling.
2) carburizing and quenching is processed: will complete step 1) sample put in common cementing furnace, after slowly being heated to 950 ℃, take out fast after being cooled to 830 ℃ with stove after insulation 5h, the quenching oil of putting into 75 ℃ quenches.The surface hardness of treated sample is HRC60～62.Annotating carburized tungsten layer thickness is 1.5～1.8mm, and wherein wolfram varbide enriched layer thickness is 0.3mm.
Then heat-treat, the heat treating method of employing is as follows: be heated to 1020～1080 ℃ of insulation 10～30min, make material be converted into austenite fully, and carbide dissolve in austenite; Then at 500～380 ℃ of isothermal processes 1～5h, carbide is evenly separated out, and austenite is converted into lower bainite, 160～180 ℃ of low-temperaturetemperings insulation, 0.8～1.5h then, air cooling.
To through thermal treatment and the casting that grinds, forge sample and carry out the test of polishing scratch width and hardness test, test-results is as shown in table 2.In addition, also tested casting yield and casting crystalline grain degree, its result is as shown in table 3.Polishing scratch width experimental test on ring-block abrasion tester.
The test of polishing scratch width and the hardness test test result of table 2 sample
| Test result | Polishing scratch width (mm) | Hardness (HRC) |
| 1 | 4.2 | 69 |
| 2 | 4.1 | 62 |
| 3 | 4.7 | 58 |
| 4 | 4.2 | 65 |
The casting yield of table 3 sample and casting crystalline grain degree test result
| Test result | Yield rate (%) | Grain fineness number (level) |
| 1 | 97 | 10 |
| 2 | 94 | 9-10 |
| 3 | 90 | 10-11 |
| 4 | 92 | 9-10 |
Obviously, low alloy steel provided by the invention not only has higher hardness, but also has toughness preferably, and wear resisting property is good; The moving load notch sensitivity is little, also has higher fatigue strength; And good casting property, casting yield is high.
Claims (4)
1. the heat treating method of a low alloy steel, is characterized in that, described low alloy steel comprises the composition of following weight percentage: C:0.85～1.24%; Mn:1.35～1.85%; Cr:1.40～1.90%:V:0.1～0.6%; Mo:0.15～0.2%; All＜0.025%, all the other are Fe and inevitable impurity for RE0.1～0.3%, Si:0.2～0.35%, S, P;
The heat treating method that described low alloy steel adopts is as follows: be heated to 1020～1080 ℃ of insulation 10～30min, make material be converted into austenite fully, and carbide dissolve in austenite; Then at 500～380 ℃ of isothermal processes 1～5h, carbide is evenly separated out, and austenite is converted into lower bainite, 160～180 ℃ of low-temperaturetemperings insulation, 0.8～1.5h then, air cooling.
2. the heat treating method of low alloy steel according to claim 1, is characterized in that, described low alloy steel before heat treating method, also comprises process of surface treatment.
3. the heat treating method of low alloy steel according to claim 2, it is characterized in that, described process of surface treatment is as follows: 1) bucket tooth is put into ion implanting and processed stove, vacuumize, when vacuum tightness reaches 0.5～10Pa, pass into nitrogen to normal pressure, then be heated to 800 ℃～840 ℃, pulsed current impacts the target of being made by tungstenalloy, and pulsed electrical a fluid stream density is 0.3～6mA/cm
2, pulse-repetition is at 25～50HZ, and acceleration voltage is at 30～40KV, and the Implantation Energy of tungsten ion, at 50～300KeV, injects the concentration 20～50% of tungsten ion, processes 15～40h, then with the stove Slow cooling;
2) bucket tooth that will complete step 1) is put in cementing furnace, slowly is heated to 800～950 ℃, after insulation 2～10h, carries out 60～80 ℃ of isothermal oil quenching after being cooled to 800～900 ℃ with stove.
4. the heat treating method of low alloy steel according to claim 3, is characterized in that, before carrying out above-mentioned surface treatment, first with the working face of bucket tooth polishing oxide film dissolving and cleaning.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104988411A (en) * | 2015-06-03 | 2015-10-21 | 宁波吉威熔模铸造有限公司 | Excavator bucket tooth and manufacturing method thereof |
| CN105972114A (en) * | 2016-07-20 | 2016-09-28 | 西安理工大学 | Brake disc and manufacturing method thereof |
| CN105970149A (en) * | 2016-07-20 | 2016-09-28 | 西安理工大学 | Low-carbon high-tungsten alloy steel and preparation method of low-carbon high-tungsten alloy steel body |
| CN109023096A (en) * | 2018-09-17 | 2018-12-18 | 四川易亨机械制造有限公司 | A kind of high performance low-alloy steel and preparation method thereof for pitching the heart for manufacturing railway |
| CN110438487A (en) * | 2019-07-16 | 2019-11-12 | 华电电力科学研究院有限公司 | Wear-resistant corrosion-resistant laser cladding layer of a kind of micro-nano granules enhancing and preparation method thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102864383A (en) * | 2012-10-22 | 2013-01-09 | 宁波吉威熔模铸造有限公司 | Low alloy steel |
| CN102912242A (en) * | 2012-10-22 | 2013-02-06 | 宁波吉威熔模铸造有限公司 | Low alloy steel |
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2013
- 2013-07-19 CN CN2013103094472A patent/CN103388059A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102864383A (en) * | 2012-10-22 | 2013-01-09 | 宁波吉威熔模铸造有限公司 | Low alloy steel |
| CN102912242A (en) * | 2012-10-22 | 2013-02-06 | 宁波吉威熔模铸造有限公司 | Low alloy steel |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104988411A (en) * | 2015-06-03 | 2015-10-21 | 宁波吉威熔模铸造有限公司 | Excavator bucket tooth and manufacturing method thereof |
| CN105972114A (en) * | 2016-07-20 | 2016-09-28 | 西安理工大学 | Brake disc and manufacturing method thereof |
| CN105970149A (en) * | 2016-07-20 | 2016-09-28 | 西安理工大学 | Low-carbon high-tungsten alloy steel and preparation method of low-carbon high-tungsten alloy steel body |
| CN105972114B (en) * | 2016-07-20 | 2018-09-21 | 西安理工大学 | A kind of preparation method of brake disc |
| CN105970149B (en) * | 2016-07-20 | 2018-11-27 | 西安理工大学 | A kind of preparation method of low-carbon high-tungsten alloy steel and low-carbon high-tungsten alloy steel ontology |
| CN109023096A (en) * | 2018-09-17 | 2018-12-18 | 四川易亨机械制造有限公司 | A kind of high performance low-alloy steel and preparation method thereof for pitching the heart for manufacturing railway |
| CN110438487A (en) * | 2019-07-16 | 2019-11-12 | 华电电力科学研究院有限公司 | Wear-resistant corrosion-resistant laser cladding layer of a kind of micro-nano granules enhancing and preparation method thereof |
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Application publication date: 20131113 |