CN114574768A - Niobium-vanadium composite microalloying and high contact fatigue performance gear steel for automobile and manufacturing method of gear - Google Patents

Abstract

The invention discloses niobium-vanadium composite microalloying steel for a gear with high contact fatigue performance for an automobile, which consists of C, Si, Mn, Cr, P, S, Nb, V, Al, Ti and Fe and is formed according to the processes of continuous casting and continuous rolling. Also disclosed is a method of manufacturing a gear, first blanking a steel blank to form a blank and forging the blank into a gear blank; turning a blank of the gear blank and then hobbing; sequentially carburizing, quenching at a strong carburizing temperature, and finally performing coarse grinding and fine grinding to obtain a finished product. The invention has the obvious effects of improving the contact fatigue and bending fatigue performance by adjusting the element composition, optimizing the smelting and manufacturing process so as to meet the performance requirement of products.

Description

Niobium-vanadium composite microalloying and high contact fatigue performance gear steel for automobile and manufacturing method of gear

Technical Field

The invention relates to a high-performance alloy steel material, in particular to a high-performance steel for a gear and a manufacturing method of the gear.

Background

In the carburizing process of the automobile gear steel, an oxidizing atmosphere is inevitably generated, oxygen adsorbed on the surface of a part at high temperature can diffuse along austenite grain boundaries, and is subjected to oxidation reaction with elements (such as Ti, Si, Mn, Al, Cr and the like) with higher affinity with the oxygen to generate metal oxides, so that the alloy elements in a matrix are reduced, the hardenability is reduced, a non-martensite structure tends to be generated in the subsequent quenching process, and finally the microhardness and the contact fatigue life in a carburized layer are reduced, which is called internal oxidation. Research shows that the effective control of element components and carburizing process can reduce the occurrence of internal oxidation.

The 20CrMo steel is used as a common steel grade of gear steel, and the performance of the steel can basically meet the application requirements. But when the researchers use the material to manufacture the gear of the gearbox, the bending fatigue performance of the gear is not as expected, and the new research point is formed.

Disclosure of Invention

The invention firstly provides niobium-vanadium composite microalloying steel for a gear with high contact fatigue performance for an automobile, which is characterized by comprising the following elements in percentage by weight: c: 0.16-0.21%; si: less than or equal to 0.10 percent; mn: 1.2-1.60%; cr: 1.4-1.8%; p is less than or equal to 0.03 percent; s is less than or equal to 0.003 percent; the combined element X is less than or equal to 0.12 percent; the balance of Fe; the combined element X is selected from any three elements of Nb, V, Al and Ti.

Furthermore, the invention also provides a method for manufacturing the niobium-vanadium composite microalloyed high-contact fatigue performance gear for the automobile, which is characterized by comprising the following steps:

step 2.1, blanking the steel billet to form a blank, and forging the blank into a gear blank;

step 2.2, heating the gear blank to 930-950 ℃, keeping the temperature for 10-15min, cooling to 600-615 ℃, keeping the temperature for 1-2h, and cooling to room temperature;

step 2.3, rolling teeth after turning a blank;

step 2.4, carburizing;

the strong cementation temperature is 930 ℃ and 950 ℃, the carbon potential CP is 0.8-1.2, and the time is 4-5 hours; the diffusion temperature is 910-;

step 2.5, raising the temperature to 880-900 ℃, keeping the carbon potential CP at 0.6-0.9 for 1-2 hours, and then putting quenching oil into the quenching oil to cool the quenching oil to room temperature;

step 2.6, heating to 160-;

step 2.7, obtaining a finished product through coarse grinding and fine grinding in sequence;

step 2.8, shot blasting;

and 2.9, cleaning, surface treatment and oiling.

Drawings

FIG. 1 is a P-S-N curve of contact fatigue of test steel grades at 50%, 95%, 99% survival rates;

FIG. 2 is a P-S-N curve of contact fatigue for comparative steel grades at 50%, 95%, 99% survival rates;

FIG. 3 is a view showing an appearance state of a test gear made of a test steel grade after a bending fatigue property test;

FIG. 4 is a view showing the appearance of a comparative gear made of a comparative steel grade after the bending fatigue property test.

Detailed Description

The present invention will be further described with reference to the following examples and the accompanying drawings.

First, an embodiment

Examples 1 to 6:

the niobium-vanadium composite microalloying and high contact fatigue property gear steel for the automobile comprises the following elements according to the following table 1:

table 1, elemental compositions (weight%/wt%) of examples 1 to 6

	C	Si	Mn	Cr	P	S	Nb	V	Al	Ti	Fe
												Example 1	0.18	0.10	1.2	1.4	0.02	0.003	0.04	0.03	0.02	--	Bal.
Example 2	0.18	0.10	1.2	1.4	0.02	0.003	--	0.03	0.02	0.02	Bal.
												Example 3	0.16	0.10	1.4	1.8	0.01	0.002	--	0.04	0.04	0.04	Bal.
Example 4	0.21	0.08	1.6	1.6	0.03	0.002	0.05	--	0.02	0.02	Bal.
												Example 5	0.21	0.10	1.6	1.5	0.01	0.001	0.05	0.05	--	0.02	Bal.
Example 6	0.16	0.10	1.2	1.4	0.03	0.003	0.04	0.04	0.01	--	Bal.

Example 7:

the niobium-vanadium composite microalloyed high-contact fatigue property steel for the gears for the automobiles is prepared by the following steps:

step 1.1, smelting molten steel having the corresponding element in any one of embodiments 1 to 6;

step 1.2, flowing molten steel into a continuous casting machine, controlling the casting temperature to be 1500 ℃, controlling the superheat degree to be 20 ℃, arranging a heating device in a tundish of a continuous casting blank, adding electromagnetic stirring and soft reduction in the casting process to ensure fine grains and narrow banded structures of the continuous casting blank, and naturally cooling to 150-;

step 1.3, heating the casting blank to 900-960 ℃, keeping for 20-30min, and then heating to 1100-1180 ℃ and keeping for 30-45 min;

and step 1.4, continuously rolling to form a steel billet, and controlling the cooling speed of the steel billet according to the size of the steel billet to prevent cracking.

Example 8:

a method for manufacturing a niobium-vanadium composite microalloyed high-contact fatigue performance gear for an automobile comprises the following steps:

step 2.1, blanking the steel billet obtained in example 7 to form a billet, and forging the billet into a gear blank;

step 2.2, heating the gear blank to 930-950 ℃, keeping the temperature for 10-15min, cooling to 600-615 ℃, keeping the temperature for 1-2h, and cooling to room temperature;

step 2.3, rolling teeth after turning a blank;

step 2.4, carburizing;

the strong cementation temperature is 930 ℃ and 950 ℃, the carbon potential CP is 0.8-1.2, and the time is 4-5 hours; the diffusion temperature is 910-;

step 2.5, raising the temperature to 880-900 ℃, keeping the carbon potential CP at 0.6-0.9 for 1-2 hours, and then putting quenching oil into the quenching oil to cool the quenching oil to room temperature;

step 2.6, heating to 160-;

step 2.7, obtaining a finished product through coarse grinding and fine grinding in sequence;

step 2.8, performing strong shot blasting treatment; the diameter of the pill is 0.4-0.6mm, and the shot blasting strength SAE standard sheet is 0.6A.

And 2.9, cleaning, surface treatment and oiling.

Example 9:

the niobium-vanadium composite microalloyed high-contact fatigue property steel for the gears for the automobiles is prepared by the following steps:

step 1.1, smelting molten steel with the corresponding elements in the embodiment 1;

step 1.2, flowing the molten steel into a continuous casting machine, controlling the casting temperature to be 1500 ℃, controlling the superheat degree to be 20 ℃, arranging a heating device in a tundish of a continuous casting billet, adding electromagnetic stirring and soft reduction in the casting process to ensure fine grains and narrow strip-shaped structures of the continuous casting billet, and naturally cooling to 150-200 ℃ to form the casting billet;

step 1.3, heating the casting blank to 950 +/-2 ℃, keeping for 25min, and then heating to 1150 +/-1 ℃ and keeping for 40 min;

and 1.4, forming a test steel grade by continuous rolling, and controlling the cooling speed of the steel billet according to the size of the test steel grade to prevent cracking.

Example 10:

a method for manufacturing a niobium-vanadium composite microalloyed high-contact fatigue performance gear for an automobile comprises the following steps:

step 2.1, blanking the test steel grade obtained in example 9 to form a blank, and heating and forging the blank to form a gear blank;

step 2.2, heating the gear blank to 945 +/-1 ℃, keeping the temperature for 15min, cooling to 610 +/-1 ℃, keeping the temperature for 1.5h, and cooling to room temperature in air;

step 2.3, hobbing the blank after turning;

step 2.4, carburizing;

the strong infiltration temperature is 940 +/-1 ℃, the carbon potential CP is 0.9, and the time is 4.5 hours; the diffusion temperature is 920 +/-1 ℃, the carbon potential CP is 0.8, and the time is 2 hours;

step 2.5, heating to 890 +/-1 ℃, keeping the carbon potential CP of 0.8 for 1 hour, and then putting into quenching oil until the temperature is cooled to room temperature;

step 2.6, heating to 180-;

step 2.7, obtaining a finished product through coarse grinding and fine grinding in sequence;

step 2.8, performing strong shot blasting treatment;

2.9, cleaning, surface treatment and oiling; obtaining a test gear;

the target parameters of the control test gear are as follows: modulus M ﹦ 1.75 mm; the number of teeth Z ﹦ 32; the tooth width b ﹦ 9 mm; helix angle β ﹦ 0 °; reference circle pressure angle α n ﹦ 20 °; the addendum height coefficient ha ﹦ 1.

Example 11:

a manufacturing method of a 20CrMo steel gear comprises the following steps:

3.1, adopting 20CrMo steel as a comparison steel grade, blanking the steel to form a blank, and heating and forging the blank to form a gear blank;

step 3.2, heating the gear blank to 950 +/-1 ℃, keeping the temperature for 18min, cooling to 620 +/-1 ℃, keeping the temperature for 1.8h, and cooling to room temperature in air;

3.3, rolling teeth after turning a blank;

step 3.4, carburizing;

the strong infiltration temperature is 940 +/-1 ℃, the carbon potential CP is 0.9, and the time is 4.5 hours; the diffusion temperature is 920 +/-1 ℃, the carbon potential CP is 0.8, and the time is 2 hours;

step 3.5, heating to 900 +/-1 ℃, keeping the carbon potential CP at 0.8, and then adding quenching oil to cool to room temperature after keeping for 1.2 hours;

step 3.6, heating to 190-;

step 3.7, obtaining a finished product through coarse grinding and fine grinding in sequence;

3.8, performing strong shot blasting treatment;

3.9, cleaning, surface treatment and oiling to obtain a comparison gear;

and controlling the specification and parameters of the gear to be consistent with those of the test gear.

Second, performance test

Test one: and (3) contact fatigue performance testing:

according to the national application research of heavy ZF gearbox gear steel, Chongqing automobile research institute, Qijiang gear factory, page 26, 4 month, 1991, 3.1-4 test methods and conditions, (1) the contact fatigue performance of the test steel grade and the comparison steel grade is tested by a deep spalling contact fatigue test. Specifically, the test is carried out on an IPM-1 type machine, a sample is cooled, No. 20 engine oil is used for lubrication, the oil temperature is not more than 60 degrees, the slip is-15.14 percent, after the sample is installed, the radial run-out is not more than 0.03mm, the load is selected from six grades, and the test result is used for processing data by a least square method or a quick fatigue test method.

The P-S-N curves of the tested steel grade and the comparative steel grade for the contact fatigue with the survival rates of 50%, 95% and 99% are respectively shown in the graph 1 and the graph 2; as can be seen from fig. 1 and 2: the contact fatigue properties of the test steel grades are slightly better than those of the comparative steel grade (20CrMo steel).

And (2) test II: and (3) testing the bending fatigue property:

according to the GB/T14230 standard, the bending fatigue properties of a gear made of test steel (test gear) and a gear made of comparative steel (20CrMo steel) (comparative gear) are respectively tested under the same conditions, the appearance state of the test gear after the bending fatigue test is shown in figure 3, and the appearance state of the comparative gear after the bending fatigue test is shown in figure 4.

As can be seen from FIG. 3, after the test gear was subjected to the bending fatigue test, a fracture (as indicated by an arrow) occurred only at the tooth root of one tooth; it can be seen from fig. 4 that 4 fractures (indicated by arrows) occurred in the comparative gears after the bending fatigue test, and the locations and extent of the fractures were also significantly inferior to those of the test gears made of the test steel grades. Thus, it can be known that: the bending fatigue performance of the gear made of the test steel grade is obviously superior to that of the comparative gear made of the comparative steel grade.

Has the advantages that: aiming at the problem of poor bending fatigue performance of the 20CrMo steel automobile gearbox gear, the invention adjusts the element composition, optimizes the smelting and manufacturing process, improves the bending fatigue performance and keeps the contact fatigue performance close to that of the 20CrMo steel.

Finally, it should be noted that the above-mentioned description is only a preferred embodiment of the present invention, and those skilled in the art can make various similar representations without departing from the spirit and scope of the present invention.

Claims (5)

1. The niobium-vanadium composite microalloyed steel for the gear with high contact fatigue performance for the automobile is characterized by comprising the following elements in percentage by weight:

c: 0.16-0.21%; si: less than or equal to 0.10 percent; mn: 1.2 to 1.60 percent; cr: 1.4-1.8%; p is less than or equal to 0.03 percent; s is less than or equal to 0.003 percent; the combined element X is less than or equal to 0.12 percent; the balance of Fe;

the combined element X is selected from any three elements of Nb, V, Al and Ti.

2. The niobium-vanadium composite microalloyed steel for gears with high contact fatigue performance for automobiles according to claim 1 is characterized by comprising the following elements in percentage by weight:

c: 0.18 percent; si: 0.10 percent; mn: 1.2 percent; cr: 1.4 percent; p: 0.02 percent; s: 0.003%; nb: 0.04 percent; v: 0.03 percent; al: 0.02 percent; and the balance of Fe.

3. The niobium-vanadium composite microalloyed steel for gears with high contact fatigue performance for automobiles according to claim 1 is characterized by comprising the following elements in percentage by weight:

c: 0.18 percent; si: 0.10 percent; mn: 1.2 percent; cr: 1.4 percent; p: 0.02 percent; s: 0.003%; v: 0.03 percent; al: 0.02 percent; ti: 0.02 percent; the balance of Fe.

4. The niobium-vanadium composite microalloyed steel for gears with high contact fatigue performance for automobiles according to claim 1, 2 or 3, is characterized by being prepared by the following steps:

step 1.1, smelting molten steel with corresponding elements;

step 1.2, flowing molten steel into a continuous casting machine, controlling the casting temperature to be 1500 ℃, controlling the superheat degree to be 20 ℃, arranging a heating device in a tundish of a continuous casting blank, adding electromagnetic stirring and soft reduction in the casting process to ensure fine grains and narrow banded structures of the continuous casting blank, and naturally cooling to 150-;

step 1.3, heating the casting blank to 900-960 ℃, keeping for 20-30min, and then heating to 1100-1180 ℃ and keeping for 30-45 min;

and step 1.4, continuously rolling to form a steel billet, and controlling the cooling speed of the steel billet according to the size of the steel billet to prevent cracking.

5. A method for manufacturing a niobium-vanadium composite microalloyed high-contact fatigue performance gear for an automobile is characterized by comprising the following steps of:

step 2.1, blanking the steel billet to form a blank, and forging the blank into a gear blank;

step 2.2, heating the gear blank to 930-950 ℃, keeping the temperature for 10-15min, cooling to 600-615 ℃, keeping the temperature for 1-2h, and cooling to room temperature;

step 2.3, hobbing the blank after turning;

step 2.4, carburizing;

the strong cementation temperature is 930 ℃ and 950 ℃, the carbon potential CP is 0.8-1.2, and the time is 4-5 hours; the diffusion temperature is 910-;

step 2.5, raising the temperature to 880-900 ℃, keeping the carbon potential CP at 0.6-0.9 for 1-2 hours, and then putting quenching oil into the quenching oil to cool the quenching oil to room temperature;

step 2.6, heating to 160-;

step 2.7, obtaining a finished product through coarse grinding and fine grinding in sequence;

step 2.8, shot blasting;

and 2.9, cleaning, surface treatment and oiling.

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