Method for improving hardness and wear resistance of photovoltaic aluminum frame extrusion die

Abstract

The invention relates to the technical field of extrusion dies, in particular to a method for improving hardness and wear resistance of a photovoltaic aluminum frame extrusion die. The method comprises the steps that firstly, a photovoltaic aluminum frame extrusion die made of steel is placed in a heating furnace, heating and austenitizing are conducted in a staged heating mode, and then quenching is conducted; tempering the quenched mold for 2-3 times, and air-cooling the mold to room temperature after tempering each time; then plasma nitriding is conducted on the working face of the photovoltaic aluminum frame extrusion die, and strengthening treatment is conducted on the surface of the working face; and after surface strengthening treatment, a ceramic oxide layer is formed on the surface by adopting a micro-arc oxidation process, or hard chromium plating treatment is carried out. After heat treatment and surface treatment, the surface hardness of the extrusion die can reach 1000 HV or above, the wear resistance can reach 4.0 mg / ten thousand times or below, and the extrusion die should adapt to the strict service working condition faced by the photovoltaic aluminum frame extrusion die.

Description

Technical Field

[0001] This invention relates to the field of extrusion die technology, and specifically to a method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies. Background Technology

[0002] As the photovoltaic industry moves towards larger, thinner aluminum frames, extrusion dies are facing more stringent service conditions: High-intensity wear: During high-temperature extrusion of aluminum alloys, the working zone of the die is subjected to high contact stress, leading to surface adhesive wear and oxidation wear failure; Dynamic impact: The periodic mechanical impact caused by high-speed extrusion requires the die to have both high hardness and fatigue resistance; Precision maintenance: Photovoltaic frame cross-sections require high precision, and the deformation after traditional heat treatment is difficult to meet the micron-level dimensional stability requirements.

[0003] In existing technologies, the performance of aluminum alloy extrusion dies is often improved through heat treatment or surface treatment. For example, Chinese patent CN109402332A discloses a heat treatment process for aluminum alloy extrusion dies, which includes machining, boronizing, quenching, tempering, cleaning, and soft nitriding steps. This process improves the heat resistance and anti-adhesion properties of aluminum alloy extrusion dies. However, the single-stage heating can easily lead to insufficient dissolution of carbides in H13 steel and large fluctuations in matrix hardness. Chinese patent CN105908119A discloses a surface oxidation treatment method for aluminum alloy extrusion dies. This method applies Ar to the pre-oxidation heating process of aluminum alloy extrusion dies. By controlling the air (O2) flow rate, furnace pressure, voltage, etc. during the oxidation process of aluminum alloy extrusion dies, an oxide film is obtained on the die surface, making the oxidation process controllable. The thickness and uniformity of the oxide film are good. However, the single surface treatment technology has a low upper limit for hardness improvement and cannot meet the high gloss (Ra≤0.2μm) extrusion requirements of photovoltaic aluminum materials.

[0004] Therefore, there is a need to develop a stable method that significantly improves the hardness and wear resistance of photovoltaic aluminum frame extrusion dies. Summary of the Invention

[0005] To address the problems in the prior art, this invention proposes a method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies, comprising the following steps:

[0006] Step 1: Place the extrusion die for the photovoltaic aluminum frame of the steel in a heating furnace, heat and austenitize it in stages, and then quench it; the final heating temperature is greater than 1000℃, and the temperature of each stage is at least 200℃ higher than the previous one, and the holding time is shorter than the previous one.

[0007] Step 2: Temper the quenched mold 2-3 times, air-cooling it to room temperature after each tempering; the temperature of the last tempering should be higher than the temperature of the first tempering, and the holding time of the last tempering should be shorter than the holding time of the first tempering. The holding time is calculated based on the maximum effective thickness of the mold: 0.6-1.5 min / mm.

[0008] Step 3: Perform plasma nitriding on the working surface of the photovoltaic aluminum frame extrusion die to strengthen the surface of the working surface;

[0009] Step 4: After the surface strengthening treatment in step 3, a ceramic oxide layer is formed on the surface using a micro-arc oxidation process, or a hard chromium plating treatment is performed.

[0010] Furthermore, the steel is H13 steel.

[0011] Furthermore, in step 1, a four-stage heating process is adopted. First, the temperature is raised to 400-450℃ and held for 30-40 minutes. Second, the temperature is raised to 650-700℃ and held for 25-35 minutes. Third, the temperature is raised to 850-900℃ and held for 15-25 minutes. Fourth, the temperature is raised to 1020-1050℃ and held for 10-20 minutes.

[0012] Furthermore, in step 2, two tempering processes are used. The first tempering temperature is 580-620℃, and the holding time is calculated based on the maximum effective thickness of the mold: 1.2-1.5 min / mm. The second tempering temperature is increased to 630-650℃, and the holding time is shortened to 0.8-1.0 min / mm.

[0013] Furthermore, the plasma nitriding treatment parameters in step 3 are: nitrogen partial pressure 0.3-0.5 kPa, glow discharge voltage 500-700 V, treatment temperature 480-520 °C, heat preservation time 8-12 h, and nitriding layer depth reaching 0.15-0.25 mm.

[0014] Furthermore, the hard chromium plating process described in step 4 employs a three-stage gradient current density process, with the initial stage current density being 30-35 A / dm³. 2 Mid-term upgrade to 45-50A / dm 2 Later, it dropped to 25-30 A / dm 2 The coating thickness is controlled between 15-25μm.

[0015] Furthermore, the micro-arc oxidation process described in step 4 specifically involves using a sodium silicate system as the electrolyte, a voltage of 300-400V, and a processing time of 20-60 minutes to form a ceramic oxide layer.

[0016] This invention achieves full dissolution and austenitization of carbides in steel through precise temperature control of the quenching process and continuous staged heating before reaching the quenching temperature. After cooling and quenching, the resulting martensite contains a high density of dislocations, while carbide-forming elements such as Cr, Mo, and V precipitate at grain boundaries, producing a precipitation strengthening effect and increasing the hardness of the matrix. Subsequently, multiple tempering processes promote the decomposition of residual austenite, eliminate quenching stress, and form small carbide particles, giving it high strength. Finally, carburizing and hardening layers are sequentially formed on the surface. This composite surface treatment allows for greater potential for increasing surface hardness, meeting the high gloss requirements of photovoltaic aluminum materials. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] Example 1

[0019] A method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies includes the following steps:

[0020] Step 1: Place the H13 steel photovoltaic aluminum frame extrusion die in a heating furnace and heat and austenitize it in stages, followed by quenching; specifically, four stages of heating are used: first, heat to 400℃ and hold for 30 minutes; second, heat to 650℃ and hold for 25 minutes; third, heat to 850℃ and hold for 15 minutes; fourth, heat to 1020℃ and hold for 15 minutes.

[0021] Step 2: Temper the quenched mold twice. The first tempering temperature is 580℃, and the holding time is calculated based on the maximum effective thickness of the mold: 1.2min / mm. The second tempering temperature is increased to 630℃, and the holding time is shortened to 0.8min / mm. After each tempering, air cool to room temperature.

[0022] Step 3: Plasma nitriding is performed on the working surface of the photovoltaic aluminum frame extrusion die to strengthen the surface of the working surface; the plasma nitriding parameters are: nitrogen partial pressure 0.3kPa, glow discharge voltage 500V, treatment temperature 480℃, heat preservation time 10h, and the nitriding layer depth reaches 0.15-0.25mm.

[0023] Step 4: After the surface strengthening treatment in Step 3, perform hard chrome plating. The hard chrome plating process uses a three-stage gradient current density process, with the initial stage current density being 30-35 A / dm². 2 Mid-term upgrade to 45-50A / dm 2 Later, it dropped to 25-30 A / dm2 The coating thickness is controlled between 15-25μm.

[0024] Example 2

[0025] A method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies includes the following steps:

[0026] Step 1: Place the H13 steel photovoltaic aluminum frame extrusion die in a heating furnace and heat and austenitize it in stages, followed by quenching; specifically, four stages of heating are used: first, heat to 450℃ and hold for 40 minutes; second, heat to 700℃ and hold for 35 minutes; third, heat to 900℃ and hold for 25 minutes; fourth, heat to 1050℃ and hold for 20 minutes.

[0027] Step 2: Temper the quenched mold twice. The first tempering temperature is 620℃, and the holding time is calculated based on the maximum effective thickness of the mold: 1.5min / mm. The second tempering temperature is increased to 650℃, and the holding time is shortened to 1.0min / mm. After each tempering, air cool to room temperature.

[0028] Step 3: Plasma nitriding is performed on the working surface of the photovoltaic aluminum frame extrusion die to strengthen the surface of the working surface; the plasma nitriding parameters are: nitrogen partial pressure 0.5kPa, glow discharge voltage 700V, treatment temperature 520℃, heat preservation time 10h, and the nitriding layer depth reaches 0.15-0.25mm.

[0029] Step 4: After the surface strengthening treatment in step 3, an oxide layer is formed on the surface using a micro-arc oxidation process. The specific process parameters are as follows: the electrolyte is a sodium silicate system with a concentration of 0.5 g / L, the voltage is 300 V, and the treatment time is 30 min to form a ceramic oxide layer.

[0030] Comparative Example 1

[0031] A method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies includes the following steps:

[0032] Step 1: Place the H13 steel photovoltaic aluminum frame extrusion die in a heating furnace and heat it to 1020℃ for heating and austenitization by direct heating. Hold it at that temperature for 60 minutes, and then quench it.

[0033] Step 2: Temper the quenched mold twice, with a tempering temperature of 600℃ and a holding time of 10min for each tempering.

[0034] Step 3: Plasma nitriding is performed on the working surface of the photovoltaic aluminum frame extrusion die to strengthen the surface of the working surface; the plasma nitriding parameters are: nitrogen partial pressure 0.3kPa, glow discharge voltage 500V, treatment temperature 480℃, heat preservation time 10h, and the nitriding layer depth reaches 0.15-0.25mm.

[0035] Step 4: After the surface strengthening treatment in Step 3, perform hard chrome plating. The current density for hard chrome plating is 30 A / dm². 2 The coating thickness is controlled between 15-25μm.

[0036] After treatment by the method in Example 1, the surface hardness of the extrusion die was 1200 HV and the wear resistance was 3.8 mg / 10,000 cycles. After treatment by the method in Example 2, the surface hardness of the extrusion die was 1100 HV and the wear resistance was 3.9 mg / 10,000 cycles. After treatment by the method in Comparative Example 1, the surface hardness of the extrusion die was 800 HV and the wear resistance was 9.8 mg / 10,000 cycles. It can be seen that the surface hardness and wear resistance of the extrusion die treated by this method are significantly improved. The gradient current process can further control the growth direction of chromium crystals. The high current density stage promotes the preferential growth of the (110) crystal plane, and the low current density stage induces the growth of the (200) crystal plane, thereby improving its hardness and wear resistance.

[0037] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in suitable ways, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies, characterized in that, Includes the following steps: Step 1: Place the extrusion die for the photovoltaic aluminum frame of the steel in a heating furnace, heat and austenitize it in stages, and then quench it; the final heating temperature is greater than 1000℃, and the temperature of each stage is at least 200℃ higher than the previous one, and the holding time is shorter than the previous one. Step 2: Temper the quenched mold 2-3 times, air-cooling to room temperature after each tempering; the temperature of the later tempering should be higher than the temperature of the previous tempering, and the holding time of the later tempering should be shorter than the holding time of the previous tempering. The holding time is calculated based on the maximum effective thickness of the mold. 0.6-1.5 min / mm; Step 3: Perform plasma nitriding on the working surface of the photovoltaic aluminum frame extrusion die to strengthen the surface of the working surface; Step 4: After the surface strengthening treatment in step 3, a ceramic oxide layer is formed on the surface using a micro-arc oxidation process, or a hard chromium plating treatment is performed.

2. The method for improving the hardness of a photovoltaic aluminum frame extrusion die according to claim 1, characterized in that, The steel is H13 steel.

3. The method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies according to claim 1, characterized in that, Step 1 uses a four-stage heating process. First, the temperature is raised to 400-450℃ and held for 30-40 minutes. Second, the temperature is raised to 650-700℃ and held for 25-35 minutes. Third, the temperature is raised to 850-900℃ and held for 15-25 minutes. Fourth, the temperature is raised to 1020-1050℃ and held for 10-20 minutes.

4. The method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion die according to claim 1, characterized in that, Step 2 involves two tempering processes. The first tempering temperature is 580-620℃, and the holding time is calculated based on the maximum effective thickness of the mold: 1.2-1.5 min / mm. The second tempering temperature is increased to 630-650℃, and the holding time is shortened to 0.8-1.0 min / mm.

5. The method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies according to claim 1, characterized in that, The parameters for plasma nitriding in step 3 are: nitrogen partial pressure 0.3-0.5 kPa, glow discharge voltage 500-700 V, treatment temperature 480-520 ℃, heat preservation time 8-12 h, and nitriding layer depth 0.15-0.25 mm.

6. The method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion dies according to claim 1, characterized in that, The hard chrome plating process described in step 4 employs a three-stage gradient current density process, with the initial stage current density being 30-35 A / dm². 2 Mid-term upgrade to 45-50A / dm 2 Later, it dropped to 25-30 A / dm 2 The coating thickness is controlled between 15-25μm.

7. The method for improving the hardness and wear resistance of photovoltaic aluminum frame extrusion die according to claim 1, characterized in that, The micro-arc oxidation process described in step 4 is as follows: the electrolyte is a sodium silicate system, the voltage is 300-400V, the processing time is 20-60min, and a ceramic oxide layer is formed.