A method of producing a cold-formed steel for an engineering machine pick

Abstract

The application discloses a preparation method of cold forming engineering machinery pick steel, and belongs to the technical field of metallurgy. The chemical components of the pick steel are as follows in percentage by mass: C: 0.28-0.39%, Si: 0.15-0.45%, Mn: 0.80-1.50%, P: ≤0.020%, S: ≤0.020%, Cr: ≤0.30%, Ni: ≤0.030%, Mo: ≤0.06%, Cu: ≤0.030%, Al: 0.010-0.060%, Ti: 0.010-0.060%, B: 0.005-0.035%, [N]: ≤0.0100%, [O]: ≤0.0030%, [H]: ≤0.00050%, and the balance is Fe and inevitable impurities. The preparation steps are as follows: converter smelting, LF refining, RH refining, continuous casting, casting blank heating, rolling, rolled material cooling, ultrasonic flaw detection and magnetic flux leakage flaw detection, spheroidizing annealing and packaging and warehousing. The steel prepared by the method has a low cost advantage, the spheroidizing structure is uniform after spheroidizing annealing, and the use requirement of no cracking in large deformation cold forming processing is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metallurgy and relates to a preparation method of cold-formed engineering mechanical pick tooth steel. BACKGROUND

[0002] The pick tooth is a cutter assembled on a cutting wheel of a coal mining machine, a heading machine, a rotary excavator and the like, and is mainly used for cutting of coal rock, hard rock and the like or road construction. The pick tooth rotates at a high speed with the cutting wheel during operation of the equipment and is in contact with hard materials, and thus bears a strong stress load at all times. Therefore, the pick tooth must have high strength and high wear resistance to meet the high-efficiency cutting task in a short time.

[0003] In the pick tooth machining process, a cold forming machining technology is generally used. Compared with a hot forming product, the forged piece prepared by the method has higher surface quality, size precision and material yield, can reduce subsequent turning and grinding processing amount, and realizes low energy consumption, low emission and low cost production. In order to make the steel have plastic deformation ability under cold forming machining, an annealing heat treatment method is generally used to adjust the steel organization and hardness.

[0004] Chinese Patent Publication No. CN202210991314.7 relates to a production method of engineering mechanical pick tooth steel AISI8740H, which provides a CrNiMo steel, the components and wt% of which are as follows: C: 0.37-0.44%; Si: 0.20%-0.30%; Mn: 0.70%-1.05%, P: 0-0.025%, S: 0-0.025%, Cr: 0.35%-0.65%, Ni: 0.35-0.75%, Mo: 0.20%-0.30%, Al: 0.015%-0.065%, B: 0-0.0006%, N: 0.0040%-0.0090%, and the rest is iron. The possibility of stress cracking is reduced by controlling the finish rolling temperature and rolling speed, and the internal crack problem of the material is solved. The high alloy steel is designed by adding Ni and Mo alloy elements, which results in high cost. SUMMARY

[0005] In view of the above problems, the application aims to solve the defects in the prior art and provides an engineering mechanical pick tooth round steel and a spheroidizing annealing process thereof. The steel grade with low cost advantage is designed, and the pick tooth steel with uniform spheroidized structure can be obtained after spheroidizing annealing of the rolled material.

[0006] The technical scheme of the present application is: the cold forming engineering machinery pick tooth steel; the chemical components of the pick tooth steel contain, in percentage by mass, C: 0.28-0.39%, Si: 0.15-0.45%, Mn: 0.80-1.50%, P: ≤0.020%, S: ≤0.020%, Cr: ≤0.30%, Ni: ≤0.030%, Mo: ≤0.06%, Cu: ≤0.030%, Al: 0.010-0.060%, Ti: 0.010-0.060%, B: 0.005-0.035%, [N]: ≤0.0100%, [O]: ≤0.0030%, [H]: ≤0.00050%; the balance is Fe and inevitable impurities.

[0007] Further, the preparation method comprises the following steps: converter smelting, LF refining, RH refining, continuous casting, casting blank heating, rolling, rolled material cooling, ultrasonic flaw detection + magnetic flux leakage detection, spheroidizing annealing and packaging into the warehouse.

[0008] Further, the converter smelting is: adding molten iron and scrap steel into a converter according to a certain proportion to obtain primary smelting molten steel, and then hoisting the molten steel to an LF ladle refining furnace to adjust the content of each element to reach a target range.

[0009] Further, the RH refining is: adopting a vacuum degree ≤100 Pa and vacuum holding time ≥10 min to make the content of H in the dehydrogenated molten steel ≤0.00015%.

[0010] Further, the continuous casting is: adopting large-section casting blank production, full-protective casting during continuous casting, superheat 10-50℃, pulling speed 0.40-0.80 m / min, using crystallizer electromagnetic stirring, end stirring and light pressing down during casting.

[0011] Further, the casting blank heating is: cold charging the casting blank into a continuous heating furnace, total heating time ≥300 min, and ensuring that the blank is transparently burned.

[0012] ≥300 min, and ensuring that the blank is transparently burned.

[0013] Further, the rolling is: adopting high-pressure water to remove phosphorus, removing the surface iron oxide skin after the casting blank heating, water pressure ≥18 MPa, and using KOCKS rolling mill for temperature control rolling before entering the rolling mill, water cooling before entering the rolling mill, and controlling the rolling mill inlet temperature ≤900℃.

[0014] Further, the rolled material cooling is: collecting and stack cooling after rolling, stack cooling starting temperature ≥350℃, stack cooling ending temperature ≤100℃, and further removing the influence of H element.

[0015] Further, the ultrasonic flaw detection + magnetic flux leakage flaw detection is: ultrasonic flaw detection is carried out according to 2-grade precision in GB / T 37566, the maximum defect in the rolled material is guaranteed to be within phi 0.5*6.4mm, and the magnetic flux leakage flaw detection is carried out according to N-0.2mm precision, and the maximum defect depth on the surface of the rolled material is guaranteed to be within 0.2mm.

[0016] Further, the spheroidizing annealing is: the annealing holding temperature is controlled at 680-740 DEG C, after holding for 6-9 hours, the cooling speed is 20-50 DEG C / h, and the furnace is discharged and air-cooled after being cooled to below 600 DEG C.

[0017] Further, the electromagnetic stirring is 150-450A, the end stirring is 350-550A, and the light reduction is 8-12mm.

[0018] Further, the high-temperature section temperature of the heating furnace is 1150-1260 DEG C, which can effectively promote the homogenization of the blank composition.

[0019] Further, the KOCKS rolling mill inlet temperature is 810-880 DEG C, which can meet the requirement of refining grains.

[0020] Further, the annealing holding temperature is controlled at 700-730 DEG C, after holding for 7-9 hours, the cooling speed is 30-50 DEG C / h, and the furnace is discharged and air-cooled after being cooled to below 600 DEG C, which can meet the requirement of spheroidizing organization being greater than or equal to 4-grade.

[0021] The beneficial effect of the present application is: the steel prepared by the method has the advantages of low cost, the spheroidizing organization is uniform after spheroidizing annealing, and the use requirement of not cracking in cold forming processing of large deformation is met. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the operation flow chart of the present application;

[0023] Figure 2 is the spheroidizing organization metallographic chart of example 1 in the present application;

[0024] Figure 3 is the spheroidizing organization metallographic chart of example 2 in the present application;

[0025] Figure 4 is the spheroidizing organization metallographic chart of example 3 in the present application. DETAILED DESCRIPTION

[0026] The specific technical scheme of the present application will be further described in detail in combination with specific examples.

[0027] Example 1

[0028] The preparation method of the cold forming engineering machinery tooth pick steel comprises the following steps: converter smelting, LF refining, RH refining, continuous casting, casting blank heating, rolling, rolled material cooling, ultrasonic flaw detection + magnetic flux leakage detection, spheroidizing annealing and packaging into the warehouse.

[0029] The elements content of the molten steel reaches the target range through the converter and LF, and then the molten steel is vacuum degassed by RH, with a vacuum degree of 50 Pa and a vacuum holding time of 10 min; the obtained molten steel chemical composition is: C: 0.35%, Si: 0.25%, Mn: 1.32%, P: 0.015%, S: 0.005%, Cr: 0.22%, Ni: 0.007%, Mo: 0.005%, Cu: 0.04%, Al: 0.027%, Ti: 0.030%, B: 0.017%, [N]: 0.0031%, [O]: 0.0012%, [H]: 0.00018%; the balance is Fe and inevitable impurities;

[0030] The continuous casting process adopts full protection pouring, the long nozzle argon sealing protection is adopted from the ladle to the tundish, the submerged entry nozzle protection pouring is adopted from the tundish to the crystallizer, the covering agent is used for the molten steel in the ladle and the tundish, the protective slag is used for the crystallizer, and the electromagnetic stirring is used for the continuous casting: 350 A, end stirring: 500 A, light reduction amount: 10 mm, superheat: 23℃, and the pulling speed is 0.78 m / min; finally, the 250mm*300mm section casting blank is obtained.

[0031] The temperature of the high-temperature section of the heating furnace is 1220℃, the total heating time is 318 min, the high-pressure water is used to remove phosphorus after the blank is discharged, and the surface iron oxide skin after heating of the casting blank is removed. The KOCKS rolling mill is used for temperature control rolling, the rolling mill inlet temperature is 834℃, the post-rolling collection is stacked and cooled, the stacking cooling starting temperature is 383℃, the stacking cooling ending temperature is 37℃, and the influence of H element is further removed; the material is subjected to ultrasonic flaw detection + magnetic flux leakage detection, and the qualified rate of the surface and the interior is 100%.

[0032] Spheroidizing annealing: the annealing holding temperature is controlled at 720℃, after holding for 7 hours, the cooling speed is 40℃ / h, and the temperature is cooled to below 600℃ to be discharged and air cooled.

[0033] The diameter 28mm round steel prepared through the above manufacturing process has the hardenability J1.5: 54HRC, J9: 52HRC, the actual grain size of the metallographic examination is 8 levels, the spheroidizing organization is 4 levels, and the material hardness is 138HBW.

[0034] Example 2

[0035] The preparation method of the cold forming engineering machinery pick tooth steel comprises the following steps: converter smelting, LF refining, RH refining, continuous casting, casting blank heating, rolling, rolled material cooling, ultrasonic flaw detection + magnetic flux leakage detection, spheroidizing annealing and packaging into the warehouse.

[0036] The elements content of the molten steel reaches the target range through the converter and LF, and then the molten steel is vacuum degassed by RH, with a vacuum degree of 50 Pa and a vacuum holding time of 10 min; the obtained molten steel chemical composition is: C: 0.38%, Si: 0.23%, Mn: 1.08%, P: 0.013%, S: 0.003%, Cr: 0.11%, Ni: 0.005%, Mo: 0.004%, Cu: 0.08%, Al: 0.023%, Ti: 0.027%, B: 0.021%, [N]: 0.0028%, [O]: 0.0014%, [H]: 0.00015%; the balance is Fe and inevitable impurities;

[0037] The continuous casting process adopts full protection pouring, the long nozzle argon sealing protection is adopted from the ladle to the tundish, the submerged entry nozzle protection pouring is adopted from the tundish to the crystallizer, the covering agent is used for the molten steel in the ladle and tundish, the protective slag is used for the crystallizer, and the electromagnetic stirring is used for the continuous casting: 300 A, end stirring: 450 A, light reduction 10 mm, superheat 27℃, drawing speed 0.80 m / min, and the 250 mm*300 mm section casting blank is obtained.

[0038] The heating furnace high temperature section temperature is 1225℃, the total heating time is 334 min, the blank is discharged after the high pressure water phosphorus removal is carried out by using 20 MPa water pressure, and the surface iron oxide skin after heating of the casting blank is removed. The KOCKS rolling mill is used for temperature control rolling, the rolling mill inlet temperature is 828℃, the post-rolling collection is stacked and cooled, the stacking cooling starting temperature is 394℃, the stacking cooling ending temperature is 32℃, and the influence of H element is further removed; the material is subjected to ultrasonic flaw detection + magnetic flux leakage detection, and the surface and internal qualified rate is 100%.

[0039] Spheroidizing annealing: the annealing holding temperature is controlled at 710℃, after holding for 8 hours, the cooling speed is 30℃ / h, and the temperature is cooled to below 600℃ and discharged for air cooling.

[0040] The diameter 26 mm round steel prepared through the above manufacturing process has the hardenability J1.5: 56HRC, J9: 53HRC, the actual grain size of the metallographic examination is 9 levels, the spheroidizing organization is 5 levels, and the material hardness is 137HBW.

[0041] Example 3

[0042] The preparation method of the cold forming engineering machinery tooth pick steel comprises the following steps: converter smelting, LF refining, RH refining, continuous casting, casting blank heating, rolling, rolled material cooling, ultrasonic flaw detection + magnetic flux leakage detection, spheroidizing annealing and packaging into the warehouse.

[0043] In the method, the content of each element of the molten steel reaches the target range through the converter and the LF, and then the RH vacuum degassing is performed with a vacuum degree of 50 Pa and a vacuum holding time of 15 min; the obtained molten steel has the following chemical components: C: 0.32%, Si: 0.28%, Mn: 0.88%, P: 0.016%, S: 0.003%, Cr: 0.25%, Ni: 0.004%, Mo: 0.004%, Cu: 0.05%, Al: 0.031%, Ti: 0.024%, B: 0.019%, [N]: 0.0036%, [O]: 0.0016%, [H]: 0.00011%, and the balance is Fe and inevitable impurities.

[0044] In the continuous casting process, full protection pouring is adopted, argon sealing protection is adopted for the long nozzle from the ladle to the tundish, and submerged nozzle protection pouring is adopted for the tundish to the crystallizer; the molten steel in the ladle and the tundish uses a covering agent, the crystallizer uses a protective slag, and electromagnetic stirring is used in the continuous casting: 250 A, end stirring: 500 A, light reduction 8 mm, superheat 24 ℃, and the drawing speed is 0.70 m / min, so as to obtain a 250 mm*300 mm cross-section casting blank.

[0045] The high-temperature section of the heating furnace is at a temperature of 1218 ℃, and the total heating time is 343 min; after the blank is discharged, high-pressure water is used to remove phosphorus at a water pressure of 20 MPa to remove the surface iron oxide scale after heating of the casting blank; KOCKS rolling mill is used for temperature control rolling, the rolling mill inlet temperature is 828 ℃, and after rolling, the material is collected for stack cooling, the stack cooling starting temperature is 396 ℃, and the stack cooling ending temperature is 38 ℃, so as to further remove the influence of H element; the material is subjected to ultrasonic flaw detection + magnetic flux leakage detection, and the qualification rate of the surface and the interior is 100%.

[0046] Spheroidizing annealing: the annealing holding temperature is controlled at 725 ℃, after holding for 6.5 hours, the cooling speed is 30 ℃ / h, and the temperature is cooled to below 600 ℃ to be discharged for air cooling.

[0047] The diameter 26 mm round steel prepared through the above manufacturing process has a metallographic test actual grain size of 8 levels, a hardenability J1.5: 53HRC, J9: 50HRC, a spheroidizing structure of 4 levels, and a material hardness of 142HBW.

[0048] The tooth pick steel prepared by the method has a low cost advantage, the spheroidizing structure is uniform after spheroidizing annealing, and the use requirement of no cracking in large deformation cold forming processing is met.

Claims

1. A type of steel for cold-formed cutting teeth in engineering machinery, characterized in that: The chemical composition of the steel used for cutting teeth, by mass percentage, is as follows: C: 0.28~0.39%, Si: 0.15~0.45%, Mn: 0.80~1.50%, P: ≤0.020%, S: ≤0.020%, Cr: ≤0.30%, Ni: ≤0.030%, Mo: ≤0.06%, Cu: ≤0.030%, Al: 0.010~0.060%, Ti: 0.010~0.060%, B: 0.005~0.035%, [N]: ≤0.0100%, [O]: ≤0.0030%, [H]: ≤0.00050%; the balance is Fe and unavoidable impurities. The preparation steps are as follows: converter smelting → LF refining → RH refining → continuous casting → billet heating → rolling → rolled material cooling → ultrasonic flaw detection + magnetic flux leakage flaw detection → spheroidizing annealing → packaging and warehousing. The converter smelting process is as follows: molten iron and scrap steel are added to the converter in proportion to obtain primary molten steel, and then the molten steel is hoisted to the LF ladle refining furnace to adjust the content of each element to reach the target range. The RH refining process is as follows: using a vacuum degree ≤100Pa and a vacuum holding time ≥10min, so that the H content in the dehydrogenated molten steel is ≤0.00015%; The continuous casting process is as follows: large cross-section billets are used for production, the continuous casting process is fully protected during casting, the superheat is 10-50℃, the casting speed is 0.40-0.80m / min, and electromagnetic stirring, end stirring and light pressure are used in the crystallizer during casting. The electromagnetic stirring is 150~450A, the end stirring is 350~550A, and the light pressing amount is 8~12mm. The process for heating the billet is as follows: the billet is cold-charged into a continuous heating furnace, and the total heating time is ≥300 min to ensure thorough heating of the billet; The temperature of the high-temperature section of the heating furnace is 1150-1260℃. The rolling process is as follows: high-pressure water descaling is used to remove the iron oxide scale on the surface of the billet after heating, with a water pressure ≥18Mpa; The final rolling is carried out using a KOCKS rolling mill for temperature control. The mill is cooled by water before entering the mill, and the inlet temperature is controlled to be ≤900℃. The inlet temperature of the KOCKS rolling mill is 810-880℃. The cooling process for the rolled material is as follows: after rolling, the material is collected and cooled in a pile, with the initial temperature of the pile cooling being ≥350℃ and the final temperature of the pile cooling being ≤100℃. The ultrasonic testing + magnetic flux leakage testing process is as follows: ultrasonic testing is performed according to the second-level precision in GB / T 37566 to ensure that the maximum defect in the rolled material is φ0.5×6.4mm; magnetic flux leakage testing is performed according to the N-0.2mm precision to ensure that the maximum defect depth on the surface of the rolled material is 0.2mm. The spheroidizing annealing process is as follows: the annealing holding temperature is controlled at 680-740℃, and after holding for 6-9 hours, the temperature is cooled to below 600℃ at a cooling rate of 20-50℃ / h before being removed from the furnace and air-cooled. The annealing holding temperature is controlled at 700-730℃. After holding for 7-9 hours, the temperature is cooled to below 600℃ at a cooling rate of 30-50℃ / h before being removed from the furnace and air-cooled to meet the requirement of spheroidization structure ≥ 4.

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