1. The aluminum profile die nitriding process is characterized by comprising the following steps of:

s1 cleaning the appearance and the internal structure of the mold;

s2 grinding and polishing the die;

s3, removing dust on the surface and inside of the die, and uniformly coating antirust oil;

s4 nitriding, namely, in the first stage of the nitriding process, a nitriding furnace nitriding mold is used, the temperature of the nitriding furnace is controlled to be T1, the flow of an ammonia gas flowmeter is controlled to be L1, the pressure is kept to be P1, and the heat preservation duration is T1; after the first stage of the nitriding process is finished, standing for t 2;

s5 in the second stage of the nitriding process, the temperature of the nitriding furnace is controlled to be T2, the flow of the ammonia gas flowmeter is controlled to be L2, the pressure is kept to be P2, and the heat preservation duration is T3; after the second stage of the nitriding process is finished, standing for t 4;

in the third stage of S6 nitriding process, the temperature of the nitriding furnace is controlled to be T3, the flow of the ammonia gas flowmeter is controlled to be L3, the pressure is kept to be P3, and the heat preservation duration is T5; after the first stage of the nitriding process is finished, opening a furnace cover for natural cooling time t 6;

wherein T2 is more than T1 and is more than or equal to T3; l1 is more than or equal to L3 and more than L2; p3 is more than P1 and is more than or equal to P2; t1 > t3 > t 5; t6 > t4 > t 2;

{T1，T2，T3}∈[450℃，550℃]；{L1，L2，L3}∈[0.4L/H，0.8L/H]；{P1，P2，P3}∈[30Kpa，50Kpa]；{t1，t3，t5}∈[2h，5h]；{t2，t4，t6}∈[10min，50min]。

2. the aluminum profile die nitriding process according to claim 1, characterized in that: the mold includes an upper mold and a lower mold, which are fixed using a detachable part after step S3.

3. The aluminum profile die nitriding process according to claim 1, characterized in that: in step S4, after the first stage of the nitridation process is completed, the ammonia valve is closed, and the mixture is allowed to stand for a time t 2.

4. The aluminum profile die nitriding process according to claim 1, characterized in that: in step S5, after the second stage of the nitridation process is finished, the ammonia valve is closed, and the ammonia valve is left for a standing time t 4.

5. The aluminum profile die nitriding process according to claim 1, characterized in that: in step S6, after the third stage of the nitridation process is completed, the ammonia valve is closed, and the furnace cover is opened for a natural cooling time t 6.

6. The aluminum profile die nitriding process according to claim 1, characterized in that: in step S4, T1 ═ 460 ℃ ± 5 ℃, 0.6L/H ≤ L1 ≤ 0.8L/H, 30Kpa ≤ P1 ≤ 40Kpa, T1 ═ 7H, and T2 ≤ 10 min.

7. The aluminum profile die nitriding process according to claim 1, characterized in that: in step S5, T2 ℃ ± 5 ℃, 0.4L/H ≤ L2 ≤ 0.6L/H, 30Kpa ≤ P2 ≤ 40Kpa, T3 ≤ 5H, and T4 ≤ 15 min.

8. The aluminum profile die nitriding process according to claim 1, characterized in that: in step S6, T3 ℃ ± 5 ℃, 0.6L/H ≤ L3 ≤ 0.8L/H, 40Kpa ≤ P3 ≤ 50Kpa, T5 ≤ 2H, and T6 ≥ 30 min.

9. The aluminum profile die nitriding process according to claim 1, characterized in that: and step S7, measuring the nitrided die by a Vickers hardness tester, wherein the hardness is more than or equal to 1000HV and is qualified.

Background

The nitriding process can be divided into the following steps: the method comprises the steps of gas nitriding, ion nitriding, liquid nitriding and the like, wherein in each nitriding mode, a plurality of nitriding technologies exist, and the method can adapt to the requirements of different workpieces with different steel grades and types. Because the nitriding technology is low in temperature, the nitriding process does not need to be cooled violently, and the deformation of the die is influenced a little, so that the surface strengthening of the die is realized by adopting the nitriding technology earlier and is also most widely applied.

In addition to the rational combination of the matrix itself with sufficiently high strength and toughness, the surface properties of the mold are critical to the working performance and the service life of the mold during operation. These surface properties refer to: wear resistance, corrosion resistance, friction coefficient, fatigue performance and the like. The improvement of these properties is very limited, necessarily depending on the matrix itself. This is also the reason why the surface treatment technology is rapidly developed.

The use of nitriding processes also typically has the property of increasing the overall toughness and strength of the die steel. The abrasion on the surface of the working belt of the die is serious due to excessive friction times during discharging through the die opening. Therefore, the main purpose of nitriding the aluminum profile die is to improve the continuous use frequency of the die and reduce the production cost.

In the existing technological process of nitriding die steel, a nitriding process using different substances exists, a nitrided layer of the nitrided die steel cannot effectively permeate and adhere to the nitrided die steel, and factors such as non-durability, non-wear-resistance and the like exist in a working zone of the die steel.

Disclosure of Invention

In view of the above, the present invention provides a nitridation process for an aluminum mold to improve the adhesion strength of a solidified nitrided layer of the aluminum mold.

In order to achieve the purpose, the invention provides the following technical scheme:

the aluminum profile die nitriding process comprises the following steps:

s1 cleaning the appearance and the internal structure of the mold;

s2 grinding and polishing the die;

s3, removing dust on the surface and inside of the die, and uniformly coating antirust oil;

s4 nitriding, namely, in the first stage of the nitriding process, a nitriding furnace nitriding mold is used, the temperature of the nitriding furnace is controlled to be T1, the flow of an ammonia gas flowmeter is controlled to be L1, the pressure is kept to be P1, and the heat preservation duration is T1; after the first stage of the nitriding process is finished, standing for t 2;

s5 in the second stage of the nitriding process, the temperature of the nitriding furnace is controlled to be T2, the flow of the ammonia gas flowmeter is controlled to be L2, the pressure is kept to be P2, and the heat preservation duration is T3; after the second stage of the nitriding process is finished, standing for t 4;

in the third stage of S6 nitriding process, the temperature of the nitriding furnace is controlled to be T3, the flow of the ammonia gas flowmeter is controlled to be L3, the pressure is kept to be P3, and the heat preservation duration is T5; after the first stage of the nitriding process is finished, opening a furnace cover for natural cooling time t 6;

wherein T2 is more than T1 and is more than or equal to T3; l1 is more than or equal to L3 and more than L2; p3 is more than P1 and is more than or equal to P2; t1 > t3 > t 5; t6 > t4 > t 2;

{T1，T2，T3}∈[450℃，550℃]；{L1，L2，L3}∈[0.4L/H，0.8L/H]；{P1，P2，P3}∈[30Kpa，50Kpa]；{t1，t3，t5}∈[2h，5h]；{t2，t4，t6}∈[10min，50min]。

alternatively, the mold includes an upper mold and a lower mold, and after step S3, the upper mold and the lower mold are fixed using a detachable part.

Optionally, in step S4, after the first stage of the nitridation process is finished, the ammonia valve is closed, and the ammonia valve is left standing for a time t 2.

Optionally, in step S5, after the second stage of the nitridation process is finished, the ammonia valve is closed, and the ammonia valve is left for a time t 4.

Optionally, in step S6, after the third stage of the nitridation process is finished, the ammonia valve is closed, and the furnace cover is opened for a natural cooling time t 6.

Optionally, in step S4, T1 ═ 460 ℃ ± 5 ℃, 0.6L/H ≤ L1 ≤ 0.8L/H, 30Kpa ≤ P1 ≤ 40Kpa, T1 ═ 7H, and T2 ≤ 10 min.

Optionally, in step S5, T2 ═ 540 ℃ ± 5 ℃, 0.4L/H ≤ L2 ≤ 0.6L/H, 30Kpa ≤ P2 ≤ 40Kpa, T3 ═ 5H, and T4 ≤ 15 min.

Optionally, in step S6, T3 ═ 440 ℃ ± 5 ℃, 0.6L/H ≤ L3 ≤ 0.8L/H, 40Kpa ≤ P3 ≤ 50Kpa, T5 ═ 2H, and T6 ≥ 30 min.

Optionally, step S7 is further included, the nitrided mold is measured by a vickers hardness tester, and the hardness is not less than 1000HV and is qualified.

The invention has the beneficial effects that:

the invention can effectively improve the adhesive strength of the solidified nitrided layer, consolidate the wear resistance and toughness strength of the whole nitrided layer attached to the die, avoid deformation factors after the die is nitrided, improve the continuous use efficiency of the die and save the maintenance cost.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram showing the total thickness of a nitride layer of sample No. 1;

FIG. 2 is a schematic diagram showing the total thickness of the nitride layer of sample No. 2;

FIG. 3 is a schematic diagram showing the total thickness of the nitride layer of sample No. 3;

fig. 4 is a schematic diagram showing the total thickness of the nitride layer of sample 4 #.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.

Referring to fig. 1 to 4, the aluminum profile mold nitridation process according to the present invention includes the following steps:

cleaning the working tape: the appearance and the internal structure of the die are cleaned, the cleaning is carried out without repeatedly contacting the working belt area by hard objects, and the cleaning and wiping of soft cotton cloth are mainly used.

Polishing the die: the manual hand-held polishing machine is used for grinding and polishing the inner wall of the upper die working belt, the material guiding hole, the lower blank cutter, the shunting hole wall and the inner wall of the lower die welding chamber, so that smoothness, no foreign body sensation, no scratch and aluminum residual impurity prevention are ensured.

Rust prevention of a mold: and wiping the surface of the die by using clean cotton cloth, removing dust, and uniformly coating antirust oil.

Installing a die: the upper and lower die fixing and positioning pins should be fastened by bolts to prevent falling off during transportation.

A first stage of the nitridation process: in order to further obtain the nitriding process, a mold is hoisted into a nitriding furnace by using a traveling crane, and a temperature control meter is used for setting the temperatureThe temperature is 460 +/-5 ℃, and the ammonia gas flow meter is adjusted to be 0.6-0.8L/H^{Note 1}The pressure is kept between 30 and 40Kpa^{Note 2}And keeping the temperature for 7 hours after the temperature reaches the set temperature, closing an ammonia valve of the nitriding furnace after the end of one stage of the process, stopping introducing ammonia into the furnace, and standing for less than or equal to 10 min. The low-temperature heat preservation time is long, and the adhesion function of a nitrided layer can be slowly softened.

Two stages of the nitridation process: in order to further obtain the nitriding process method, the set temperature of a temperature control meter is adjusted to be 540 +/-5 ℃, the ammonia gas flow meter is adjusted to be 0.4-0.6L/H, the pressure is kept at 30-40 Kpa, and the temperature is kept for 5 hours after the set temperature is reached. And closing an ammonia valve of the nitriding furnace after the second stage of the process is finished, stopping introducing ammonia into the furnace, standing for less than or equal to 15min, and consolidating the wear resistance of the working belt of the die.

Three stages of the nitridation process: in order to further obtain the nitriding process method, the set temperature of a temperature control meter is adjusted to be 440 +/-5 ℃, an ammonia gas flow meter is adjusted to be 0.6-0.8L/H, the pressure is kept at 40-50 Kpa, and the temperature is kept for 2 hours after the set temperature is reached. And after the three-stage time of the process is reached, when the temperature is reduced to be less than or equal to 180 ℃, closing the ammonia gas inlet valve, opening the furnace cover, standing for natural cooling for more than or equal to 30min, ensuring that nitrogen and carbon atoms in the working zone of the mold are completely absorbed by the surface of the mold, diffusing and permeating into the surface layer of the mold to obtain a nitrogen-carbon co-permeation layer mainly containing nitrogen, and then hanging out and placing at a safe region.

And (3) a step of delivering and inspecting the mold test block, which is to measure the test block by using a Vickers hardness tester and ensure that the hardness is not less than 1000HV in a qualified state.

This example provides the results of testing 4 mold samples prepared by the above process, and hardness tests were performed in the first stage of nitriding only and in all three nitriding stages, respectively, and the thickness of the nitrided compound layer and the total thickness of the nitrided layer were measured. The detection results are as follows:

hardness test, test equipment: FV-810 type Wechsler hardness tester, test environment: 23 ℃ 30% RH using standard: ISO6507-1-2018

Table one: experimental results of hardness testing

And (4) conclusion: the mean value of the hardness of the sample piece is above 1050HV, and the test result is obviously superior compared with the new method. Thickness test, test equipment: thickness gauge MikroTest/F6 special for nitriding layer, test environment: 22 ℃ using standard: GB/T11354-2005

And (4) conclusion: the thickness result of the nitriding layer shows that the method is superior obviously, and the wear resistance and the toughness of the die can be effectively improved. Metallographic structure test, experimental facilities: AXIO universal research grade inverted material microscope and test environment: 22 ℃ using standard: GB/T11354-2005, the test results are shown in the attached drawing. The total thickness of the nitriding layer is increased by at least 0.1mm, and the wear resistance and toughness of the die can be effectively improved.

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.