Aluminum alloy bar and application thereof in field of rail transit

Abstract

The invention relates to an aluminum alloy bar and application thereof in the field of rail transit. The aluminum alloy bar is obtained through alloy smelting, refining, standing, casting and aging treatment. The mold for the aluminum alloy melt to enter through injection comprises a cast iron mold body, the front section of the cast iron mold body is provided with two functional areas, each functional area comprises a cooling unit and a heating unit, and an isolation unit is arranged between each cooling unit and the corresponding heating unit. By increasing the content of Si, the distribution of the Fe-rich phase can be further optimized under the condition that the content of Fe is not changed. During die casting, distribution of a Fe-rich phase is further controlled in a cold and hot alternating die, the thickness of a Fe-poor phase region is increased to the maximum extent on the premise that it is guaranteed that the mechanical strength is not reduced, meanwhile, the proportion of the Fe-rich phase is reduced, large-area agglomeration of the Fe-rich phase is avoided, and therefore the service life of the aluminum alloy bar under the extreme condition is remarkably prolonged.

Description

Technical Field

[0001] The invention relates to an aluminum alloy bar and application thereof in the field of rail transportation, belonging to the technical field of aluminum alloy bars. Background Art

[0002] In the field of rail transit, the key to the application of high-silicon aluminum alloys in rail transit and other aspects lies in the unique properties of the Si phase itself, such as high hardness, high modulus, low density and low thermal expansion coefficient, which is especially suitable for the wear-resistant field.

[0003] In aluminum alloys with high silicon content, heat-resistant elements (such as Fe, Ni, etc.) are introduced to achieve the purpose of improving both room / high temperature performance and structural stability. However, the metastable Fe-rich phase caused by rapid solidification will undergo phase transformation and growth and coarsening controlled by diffusion during subsequent processing or high temperature and long-term working conditions (LG Hou, et al. Int. J. Miner. Metall. Mater., 2010, 17: 297.), indicating that Fe element alloying is still insufficient in optimizing the thermal stability of alloy structure.

[0004] After analysis, it is found that if the harmful needle-shaped Fe-rich phase in the aluminum alloy is enriched in large quantities on the surface of the aluminum alloy rod, it will hinder the application of the aluminum alloy rod under extreme conditions. For example, in an environment of -10°C, it may cause large-scale cracking when working continuously at high intensity, and eventually lead to fracture at the cracks.

[0005] Therefore, the present invention is proposed. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides an aluminum alloy bar and its application in the field of rail transportation. The specific technical solution is as follows:

[0007] An aluminum alloy bar, composed of the following components in percentage by weight:

[0008] Si: 10~12%; Mg: 0.1~0.5%; Fe: 0.2~0.3%; Cu: 0.3~0.7%; Mn: ≤0.05%; Ti: 0.01~0.03%; Zn: ≤0.05%; Cr: ≤0.03%; the rest is Al.

[0009] As a further improvement, the method for preparing the aluminum alloy bar comprises the following steps:

[0010] Step 1: Alloy smelting

[0011] Mix and weigh the raw materials according to the proportion, and put the aluminum alloy into the melting furnace for melting;

[0012] Step 2: Refining

[0013] Adding a refining agent into the smelting furnace and blowing argon gas into the furnace for refining;

[0014] Step 2: Let stand

[0015] After refining, the aluminum alloy melt in the melting furnace is left to stand for at least 30 minutes;

[0016] Step 3: Casting

[0017] The aluminum alloy melt is die-casted by an aluminum alloy die-casting machine to obtain a die-casting rod;

[0018] Step 4: Aging treatment

[0019] The die-cast rods are subjected to aging treatment to obtain finished aluminum alloy rods.

[0020] As a further improvement, in step 1, the smelting temperature is 860°C to 930°C, and the smelting time is 10h to 12h.

[0021] As a further improvement, in step 2, the refining time is 30 to 40 minutes and the refining temperature is 720 to 740°C.

[0022] As a further improvement, in step 3, the initial temperature of the aluminum alloy melt when it is injected into the mold is 780-800°C, the casting speed is 11-13 mm / min, and the casting pressure is 70 MPa-95 MPa.

[0023] As a further improvement, in step 4, an aging treatment is performed at 190°C to 220°C for 2-3 hours.

[0024] A further improvement is that the mold includes a cast iron mold body, a die-casting rod cavity is arranged in the center of the cast iron mold body; the front section of the cast iron mold body is provided with two functional areas, the functional areas include a cooling unit and a heating unit, the cooling unit includes a coolant heat exchange channel arranged in the cast iron mold body, the coolant heat exchange channel is distributed on the outside of the die-casting rod cavity, and liquid carbon dioxide is introduced into the coolant heat exchange channel; an isolation unit is arranged between the cooling unit and the heating unit, the isolation unit includes a concrete casting block, an alumina ceramic ring is arranged in the center of the concrete casting block, and the inner cavity of the alumina ceramic ring constitutes a part of the die-casting rod cavity; the outer periphery of the heating unit is provided with an electromagnetic induction heating coil.

[0025] Further improvement, the functional area close to the input end of the die casting rod cavity is the first functional area, and the other functional area is the second functional area; the temperature of the cooling unit in the first functional area is -4 to 0°C, and the temperature of the heating unit in the first functional area is 510 to 525°C; the temperature of the cooling unit in the second functional area is 0 to 4°C, and the temperature of the heating unit in the second functional area is 390 to 410°C;

[0026] The length of the cooling unit in the first functional zone is equal to the length of the cooling unit in the second functional zone, and the ratio of the length of the heating unit in the second functional zone to the length of the heating unit in the first functional zone is 1.3:1.

[0027] As a further improvement, the inner wall of the alumina ceramic ring is coated with a release agent.

[0028] A further improvement is the application of the above-mentioned aluminum alloy bars in the field of rail transportation.

[0029] Beneficial effects of the present invention:

[0030] 1. The present invention improves the Si content by optimizing the design formula, and can further optimize the distribution of the Fe-rich phase while keeping the Fe content unchanged.

[0031] 2. By further controlling the distribution of the Fe-rich phase in the hot and cold alternating mold during die casting, the thickness of the Fe-poor phase area is maximized while ensuring that the mechanical strength does not decrease. At the same time, the proportion of the Fe-rich phase is reduced to avoid large-scale agglomeration of the Fe-rich phase, thereby significantly improving the service life of the aluminum alloy bar under extreme conditions and enabling it to meet the application needs in the field of rail transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure of the mold described in Example 3. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] The formula of aluminum alloy bar is composed of the following components by weight percentage:

[0036] Si: 10~12%; Mg: 0.1~0.5%; Fe: 0.2~0.3%; Cu: 0.3~0.7%; Mn: ≤0.05%; Ti: 0.01~0.03%; Zn: ≤0.05%; Cr: ≤0.03%; the rest is Al.

[0037] The method for preparing the aluminum alloy bar comprises the following steps:

[0038] Step 1: Alloy smelting

[0039] The aluminum alloy raw materials are put into a smelting furnace for smelting according to the proportion and weight; the smelting temperature is 860℃~870℃, and the smelting time is 12h.

[0040] Step 2: Refining

[0041] Add refining agent into the smelting furnace, and blow argon into the furnace for refining; the refining time is 40 minutes, and the refining temperature is 720-730°C. The hydrogen content after refining is ≤0.28ml / 100g.

[0042] Step 2: Let stand

[0043] After refining, the aluminum alloy melt in the melting furnace is left to stand for 30 minutes.

[0044] Step 3: Casting

[0045] The aluminum alloy melt is die-casted through an aluminum alloy die-casting machine to obtain a die-cast rod; the initial temperature of the aluminum alloy melt when it is injected into the mold is 780-790°C, the casting speed is 11mm / min, the casting pressure is 70MPaMPa, and the temperature of the mold itself is maintained at 350-360°C.

[0046] Step 4: Aging treatment

[0047] The die-cast rod is subjected to aging treatment at 190° C. for 3 hours to obtain a finished aluminum alloy rod.

[0048] Example 2

[0049] The formula of aluminum alloy bar is composed of the following components by weight percentage:

[0050] Si: 10~12%; Mg: 0.1~0.5%; Fe: 0.2~0.3%; Cu: 0.3~0.7%; Mn: ≤0.05%; Ti: 0.01~0.03%; Zn: ≤0.05%; Cr: ≤0.03%; the rest is Al.

[0051] The method for preparing the aluminum alloy bar comprises the following steps:

[0052] Step 1: Alloy smelting

[0053] The aluminum alloy raw materials are put into a smelting furnace for smelting according to the proportion and weight; the smelting temperature is 915°C ~ 930°C, and the smelting time is 10hh.

[0054] Step 2: Refining

[0055] Add refining agent into the smelting furnace, and blow argon into the furnace for refining; the refining time is 30 minutes, and the refining temperature is 730-740°C. The hydrogen content after refining is ≤0.28ml / 100g.

[0056] Step 2: Let stand

[0057] After refining, the aluminum alloy melt in the melting furnace is left to stand for 40 minutes.

[0058] Step 3: Casting

[0059] The aluminum alloy melt is die-casted through an aluminum alloy die-casting machine to obtain a die-cast rod; the initial temperature of the aluminum alloy melt when it is injected into the mold is 790-800°C, the casting speed is 12mm / min, the casting pressure is 80MPa, and the temperature of the mold itself is maintained at 510-525°C.

[0060] Step 4: Aging treatment

[0061] The die-cast rod is subjected to aging treatment at 220° C. for 2 hours to obtain a finished aluminum alloy rod.

[0062] Example 3

[0063] The formula of aluminum alloy bar is composed of the following components by weight percentage:

[0064] Si: 10~12%; Mg: 0.1~0.5%; Fe: 0.2~0.3%; Cu: 0.3~0.7%; Mn: ≤0.05%; Ti: 0.01~0.03%; Zn: ≤0.05%; Cr: ≤0.03%; the rest is Al.

[0065] The method for preparing the aluminum alloy bar comprises the following steps:

[0066] Step 1: Alloy smelting

[0067] The aluminum alloy raw materials are put into a smelting furnace for smelting according to the proportion and weight; the smelting temperature is 870℃~915℃, and the smelting time is 11h.

[0068] Step 2: Refining

[0069] Add refining agent into the smelting furnace, and blow argon into the furnace for refining; the refining time is 30-40 minutes, and the refining temperature is 730-740°C. The hydrogen content after refining is ≤0.28ml / 100g.

[0070] Step 2: Let stand

[0071] After refining, the aluminum alloy melt in the melting furnace is left to stand for 30 minutes.

[0072] Step 3: Casting

[0073] The aluminum alloy melt is die-casted through an aluminum alloy die-casting machine to obtain a die-cast rod; the initial temperature of the aluminum alloy melt when it is injected into the mold is 780-790° C., the casting speed is 13 mm / min, and the casting pressure is 95 MPa.

[0074] Step 4: Aging treatment

[0075] The die-cast rod is subjected to aging treatment at 210° C. for 2 hours to obtain a finished aluminum alloy rod.

[0076] Among them, in step 3, if Figure 1 As shown, the mold includes a cast iron mold body 30, and a die-casting rod cavity 31 is arranged in the center of the cast iron mold body 30; the front section of the cast iron mold body 30 is provided with two functional areas 10, and the functional areas 10 include a cooling unit 13 and a heating unit 11, and the cooling unit 13 includes a coolant heat exchange channel 131 arranged in the cast iron mold body 30, and the coolant heat exchange channel 131 is distributed on the outside of the die-casting rod cavity 31, and liquid carbon dioxide is introduced into the coolant heat exchange channel 131; an isolation unit 12 is arranged between the cooling unit 13 and the heating unit 11, and the isolation unit 12 includes a concrete casting block 121, and an alumina ceramic ring 122 is arranged in the center of the concrete casting block 121, and the inner cavity of the alumina ceramic ring 122 constitutes a part of the die-casting rod cavity 31; the outer periphery of the heating unit 11 is sleeved with an electromagnetic induction heating coil 20.

[0077] The hardness of alumina ceramics is very high, and its Rockwell hardness is second only to diamond, far exceeding the wear resistance of wear-resistant steel and stainless steel.

[0078] The functional area 10 near the input end of the die casting rod cavity 31 is the first functional area 10, and the other functional area 10 is the second functional area 10; the temperature of the cooling unit 13 in the first functional area 10 is -4 to 0°C, and the temperature of the heating unit 11 in the first functional area 10 is 510 to 525°C; the temperature of the cooling unit 13 in the second functional area 10 is 0 to 4°C, and the temperature of the heating unit 11 in the second functional area 10 is 390 to 410°C;

[0079] The length of the cooling unit 13 in the first functional zone 10 is equal to the length of the cooling unit 13 in the second functional zone 10, and the ratio of the length of the heating unit 11 in the second functional zone 10 to the length of the heating unit 11 in the first functional zone 10 is 1.3:1.

[0080] The inner wall of the alumina ceramic ring 122 is coated with a release agent, which is used to reduce the friction resistance between the die-cast rod and the alumina ceramic ring 122. The setting of the isolation unit 12 allows a large temperature difference between the heating unit 11 and the cooling unit 13. Liquid carbon dioxide allows the cooling unit 13 to cool down quickly and maintain a lower temperature range. After the electromagnetic induction heating coil 20 is powered on, electromagnetic induction heating is used to heat the area where the heating unit 11 is located.

[0081] Comparative Example 1

[0082] The only difference between this example and Example 3 is that, in this example, the temperature of the cooling unit 13 in the first functional zone 10 is -4 to 0°C, and the temperature of the heating unit 11 in the first functional zone 10 is 510 to 525°C; the temperature of the cooling unit 13 in the second functional zone 10 is -4 to 0°C, and the temperature of the heating unit 11 in the second functional zone 10 is 510 to 525°C; the rest remains unchanged.

[0083] Comparative Example 2

[0084] The only difference between this example and Example 3 is that in this example, the temperature at the heating unit 11 in the first functional zone 10 is 350-360° C.; the temperature at the heating unit 11 in the second functional zone 10 is 350-360° C.; and the rest remains unchanged.

[0085] Comparative Example 3

[0086] The only difference between this example and Example 3 is that in this example, the temperature at the cooling unit 13 in the first functional zone 10 is 20-25° C., the temperature at the cooling unit 13 in the second functional zone 10 is 20-25° C., and the rest remains unchanged.

[0087] The performance parameters of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1:

[0088] Table 1

[0089] Fatigue strength(MPa) Elastic modulus(GPa) h(mm) λ Example 1 119 7.1 0.8 11.5％ Example 2 128 6.8 0.5 13.6％ Example 3 141 7.6 9.7 7.9％ Comparative Example 1 133 7.1 2.2 7.4％ Comparative Example 2 139 7.5 1.3 10.1％ Comparative Example 3 138 7.2 1.1 9.2％

[0090] An electron microscope is used to observe the image of the radial cross section of an aluminum alloy rod sample (such as the aluminum alloy rod product in Example 1, the diameter of the aluminum alloy rod sample is 3 cm), and the area percentage of the Fe-rich phase in an arbitrary area extending from the surface of the aluminum alloy rod sample toward the center thereof is calculated. The maximum value of the thickness of the area between the surface of the aluminum alloy rod sample and the Fe-rich phase area (Fe-poor phase area) is calculated, and the value is the thickness of the Fe-poor phase area, which is denoted by h.

[0091] The area percentage of the Fe-rich phase refers to the ratio of the total area of ​​the Fe-rich phase within the field of view of the electron microscope to the field of view area of ​​the electron microscope, and the ratio is calculated by the point counting method / point calculation method.

[0092] In any region of the Fe-poor phase region, the area percentage of the Fe-rich phase is ≤5%.

[0093] The maximum area percentage of the Fe-rich phase is λ, which is the maximum area percentage of the Fe-rich phase obtained by analyzing and calculating all images in the radial cross section of the aluminum alloy bar sample.

[0094] In the present invention, the aluminum alloy melt in the die-casting process is treated by alternating between two huge temperature difference zones, extreme cold and high heat, and the external temperature distribution is controlled, which is beneficial to controlling the crystallization direction of the Fe-rich phase and further reducing diffusion and grain growth and coarsening.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An aluminum alloy bar, characterized in that: The following components are used in percentage by weight composition: Si: 10-12%; Mg: 0.1~0.5%; Fe: 0.2~0.3%; Cu: 0.3~0.7%; Mn: ≤0.05%; Ti: 0.01~0.03%; Zn: ≤0.05%; Cr: ≤0.03%; the rest is Al.

2. The aluminum alloy bar according to claim 1, characterized in that: The method for preparing the aluminum alloy bar comprises the following steps: Step 1: Alloy smelting Mix and weigh the raw materials according to the proportion, and put the aluminum alloy into the melting furnace for melting; Step 2: Refining Adding a refining agent into the smelting furnace and blowing argon gas into the furnace for refining; Step 2: Let stand After refining, the aluminum alloy melt in the melting furnace is left to stand for at least 30 minutes; Step 3: Casting The aluminum alloy melt is die-casted by an aluminum alloy die-casting machine to obtain a die-casting rod; Step 4: Aging treatment The die-cast rods are subjected to aging treatment to obtain finished aluminum alloy rods.

3. The aluminum alloy bar according to claim 2, characterized in that: In step 1, the smelting temperature is 860° C. to 930° C., and the smelting time is 10 h to 12 h.

4. The aluminum alloy bar according to claim 2, characterized in that: In step 2, the refining time is 30-40 minutes, and the refining temperature is 720-740°C.

5. The aluminum alloy bar according to claim 2, characterized in that: In step 3, the initial temperature of the aluminum alloy melt when it is injected into the mold is 780-800° C., the casting speed is 11-13 mm / min, and the casting pressure is 70 MPa-95 MPa.

6. The aluminum alloy bar according to claim 2, characterized in that: In step 4, an aging treatment is performed at 190° C. to 220° C. for 2 to 3 hours.

7. The aluminum alloy bar according to claim 5, characterized in that: The mold comprises a cast iron mold body (30), a die-casting rod cavity (31) is arranged at the center of the cast iron mold body (30); the front section of the cast iron mold body (30) is provided with two functional areas (10), the functional areas (10) include a cooling unit (13) and a heating unit (11), the cooling unit (13) includes a coolant heat exchange channel (131) arranged in the cast iron mold body (30), the coolant heat exchange channel (131) is distributed on the outside of the die-casting rod cavity (31), and the Liquid carbon dioxide is introduced into the interior of the cooling liquid heat exchange channel (131); an isolation unit (12) is provided between the cooling unit (13) and the heating unit (11), the isolation unit (12) comprising a concrete casting block (121), an alumina ceramic ring (122) is provided at the center of the concrete casting block (121), and the inner cavity of the alumina ceramic ring (122) constitutes a part of the die-casting rod cavity (31); and an electromagnetic induction heating coil (20) is provided on the outer periphery of the heating unit (11).

8. The aluminum alloy bar according to claim 7, characterized in that: The functional zone (10) close to the input end of the die casting rod cavity (31) is the first functional zone (10), and the other functional zone (10) is the second functional zone (10); the temperature of the cooling unit (13) in the first functional zone (10) is -4 to 0°C, and the temperature of the heating unit (11) in the first functional zone (10) is 510 to 525°C; the temperature of the cooling unit (13) in the second functional zone (10) is 0 to 4°C, and the temperature of the heating unit (11) in the second functional zone (10) is 390 to 410°C; The length of the cooling unit (13) in the first functional zone (10) is equal to the length of the cooling unit (13) in the second functional zone (10), and the ratio of the length of the heating unit (11) in the second functional zone (10) to the length of the heating unit (11) in the first functional zone (10) is 1.3:

1.

9. The aluminum alloy bar according to claim 7, characterized in that: The inner wall of the alumina ceramic ring (122) is coated with a release agent.

10. Use of the aluminum alloy bar according to any one of claims 1 to 9 in the field of rail transportation.

Images