Al-Si series aluminum alloy flat cast ingot and preparation method thereof

Abstract

The invention discloses an Al-Si series aluminum alloy flat cast ingot and a preparation method thereof, relates to the Al-Si series aluminum alloy flat cast ingot and the preparation method thereof, and aims to solve the problem of low flaw detection passing rate of the Al-Si series aluminum alloy flat cast ingot. The method comprises the following steps: weighing aluminum ingots, metal Zn and an aluminum-silicon intermediate alloy as smelting raw materials according to the following components in percentage by mass: 7.50% of Si, 1.05% of Zn, less than 0.80% of Fe, less than 0.25% of Cu, less than 0.10% of Mn, less than 0.05% of Mg, less than 0.05% of Cr, less than 0.05% of Ti and the balance of Al; and then smelting and casting. The yield of the Al-Si series aluminum alloy flat cast ingot reaches 80.6%. The method is applied to the field of aluminum alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to an Al-Si series aluminum alloy flat ingot and a preparation method thereof. BACKGROUND

[0002] Al-Si series aluminum alloy is a wrought aluminum alloy with silicon as the main alloying element. Due to the high silicon content, it has the characteristics of low melting point and good melt flowability, easy feeding, and will not cause the product to be brittle. At the same time, it also has good thermal conductivity and corrosion resistance, can resist the corrosion of most acids and alkalis, and is easy to react with oxygen to form an oxide film, further improving the corrosion resistance. These properties make it suitable for applications that require thermal conductivity and corrosion resistance, such as heat exchange component manufacturing. In addition, it has good welding performance and can be welded by TIG welding, MIG welding and other methods, with high strength of the welded joint.

[0003] Due to its good comprehensive performance, it is widely used in the automotive and refrigeration industries. However, the coarse and flaky primary silicon and β-Al5FeSi iron phase in Al-Si series aluminum alloy can split the matrix and cause stress concentration. For example, in the as-cast microstructure of 4343A aluminum alloy without modification treatment, the small face characteristics of β-Al5FeSi phase are easy to induce cracking under the action of cooling water. In addition, when the content of impurity element Fe in the alloy is too high, needle-shaped AlFeSi phase will be formed. This brittle phase is easily broken during pressure processing and is distributed in the form of strips or chains along the rolling direction of the metal, resulting in a decrease in intergranular bonding strength and the induction of cracks by local stress concentration. Moreover, the thermal expansion coefficient of Al-Si series aluminum alloy is relatively large, and the temperature change during rolling will produce a large thermal stress. The ingot is also subjected to restraint stress during rolling, which will cause cracks when the stress exceeds the strength limit of the alloy. Defects such as oxide inclusions, pores and shrinkage holes produced during casting can become crack sources. For example, the oxide inclusions produced during high-temperature melting and pouring of the aluminum liquid remain in the aluminum liquid and can cause cracks during subsequent rolling. High or low rolling temperature, excessive reduction, and uneven rolling speed can all cause uneven deformation of the alloy and generate a large internal stress, thereby causing cracks. Based on the above reasons, Al-Si series aluminum alloy is prone to cracks during subsequent rolling, resulting in a low yield of the ingot. SUMMARY

[0004] The purpose of the present application is to solve the problem of low yield of Al-Si series aluminum alloy flat ingot, and to provide an Al-Si series aluminum alloy flat ingot and a preparation method thereof.

[0005] The Al-Si system aluminum alloy flat ingot is composed of 6.80-8.20% of Si, 0.70-1.30% of Zn, Fe<0.80%, Cu<0.25%, Mn<0.10%, Mg<0.05%, Cr<0.05%, Ti<0.05% and the balance of Al.

[0006] The preparation method of the Al-Si system aluminum alloy flat ingot is carried out according to the following steps:

[0007] I. ingredient: according to the mass percentage, Si: 6.80-8.20%, Fe<0.80%, Cu<0.25%, Mn<0.10%, Mg<0.05%, Cr<0.05%, Zn: 0.70-1.30%, Ti<0.05% and the balance of Al, the aluminum ingot, metal Zn and aluminum silicon intermediate alloy are weighed as smelting raw materials;

[0008] II. smelting: the aluminum ingot and aluminum silicon intermediate alloy weighed in step I are added to the smelting furnace, the smelting temperature is 720-750 DEG C, the metal Zn is added when the melt temperature is 690-710 DEG C, and then the alloy melt is obtained after covering the flux under the condition of 720-750 DEG C stirring;

[0009] III. casting: the alloy melt obtained in step II is introduced into the natural gas holding furnace at the temperature of 730-750 DEG C, and after refining, it is placed in the degassing tank and the filter tank, then the melt is injected into the crystallizer, and then under the conditions of the casting speed of 45-55 mm / min, the casting temperature of 730-750 DEG C, the casting water flow of 80-100 m³ / h, the casting water temperature of 22-28 DEG C and the crystallizer metal liquid level of 90-100 mm, the Al-Ti-0.2B wire is seeded in line to carry out semi-continuous casting to obtain the Al-Si system aluminum alloy flat ingot.

[0010] The present application selects different adding time according to the characteristics of different alloys, solves the problem of full alloying of each element, and through the addition of Zn element as a trace additive element, a solid solution can be formed with aluminum, a small amount of addition can improve the strength and hardness of the alloy through solid solution strengthening effect, especially during heat treatment (such as aging treatment), it can form a strengthening phase with other elements, further improving the mechanical properties. Trace zinc helps to optimize the casting performance of the alloy and reduce the probability of defects such as cracks in the processing process. The melt flows into the online degassing device, which can effectively remove H2 in the melt; flows into the filtering device, which can effectively remove slag.

[0011] The present application has the following advantages:

[0012] I. The present application optimizes semi-continuous casting parameters (temperature control / speed / water + degassing and slag removal): melt 730-750℃ into crystallizer, control casting speed 45-55mm / min, cooling water flow 80-100m³ / h (water temperature 22-28℃), while removing H2 through the degassing box, removing slag through the filter box, and online broadcasting Al-Ti-0.2B wire. Degassing and slag removal directly remove gas (easy to form pores) and non-metallic inclusions (developed as defects during flaw detection) in the melt, which is the key to improving flaw detection pass rate; precise temperature, speed and cooling water parameters can control the uniformity of alloy solidification rate, avoid hot cracks due to rapid cooling, and form coarse grains and porosity due to slow cooling; Al-Ti-0.2B wire can refine the grain structure, reduce intergranular defects, and further reduce the risk of flaw detection failure.

[0013] II. Precise component regulation (Zn element + strict control of impurities): directional addition of 0.70%-1.30% Zn element, while strictly controlling the content of impurity elements such as Fe<0.80%, Cu<0.25%. Zn forms a solid solution with Al, which can improve the strength of the alloy through solid solution strengthening, and can also optimize the casting fluidity and reduce cracks caused by stress concentration during solidification; strict control of impurities can avoid

[0014] Fe, Cu and other elements to form brittle compounds (such as AlFeSi phase), which will become internal defect sources, leading to an increase in unqualified rate during flaw detection.

[0015] The present application improves the yield rate through precise component regulation and optimization of semi-continuous casting parameters, and the yield rate of the Al-Si series aluminum alloy flat cast ingot prepared by the present application reaches 80.6%. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The physical map of the Al-Si series aluminum alloy flat cast ingot prepared by the present application. DETAILED DESCRIPTION

[0017] The technical solution of the present application is not limited to the following specific embodiments, but also includes any combination of the specific embodiments.

[0018] Specific embodiment one: the Al-Si series aluminum alloy flat cast ingot of the present embodiment is composed of 6.80%-8.20% Si, 0.70%-1.30% Zn, Fe<0.80%, Cu<0.25%, Mn<0.10%, Mg<0.05%, Cr<0.05%, Ti<0.05% and the balance of Al.

[0019] Embodiment two: the difference between this embodiment and embodiment one is that the Al-Si aluminum alloy flat ingot is composed of 7.50% of Si, 1.05% of Zn, Fe <0.80%, Cu <0.25%, Mn <0.10%, Mg <0.05%, Cr <0.05%, Ti <0.05% and the balance of Al in terms of mass percentage. The others are the same as embodiment one.

[0020] Embodiment three: the preparation method of the Al-Si aluminum alloy flat ingot in this embodiment is carried out according to the following steps:

[0021] I. batching: taking aluminum ingot, metal Zn and aluminum-silicon intermediate alloy as smelting raw materials according to mass percentage of Si: 6.80%~8.20%, Fe <0.80%, Cu <0.25%, Mn <0.10%, Mg <0.05%, Cr <0.05%, Zn: 0.70%~1.30%, Ti <0.05% and the balance of Al;

[0022] II. smelting: adding the aluminum ingot and aluminum-silicon intermediate alloy in step I into a smelting furnace, the smelting temperature is 720~750℃, when the melt temperature is 690~710℃, add metal Zn, stir at 720~750℃, then cover the flux to obtain the alloy melt;

[0023] III. casting: introducing the alloy melt obtained in step II into a natural gas holding furnace at a temperature of 730~750℃, after refining, standing, passing through a degassing box and a filtering box, pouring the melt into a crystallizer, then under the conditions of casting speed of 45mm / min~55mm / min, casting temperature of 730~750℃, casting cooling water flow of 80-100m³ / h, casting water temperature of 22~28℃, crystallizer metal liquid level of 90~100mm and in-line seeding of Al-Ti-0.2B wire, carrying out semi-continuous casting to obtain the Al-Si aluminum alloy flat ingot.

[0024] Embodiment four: the difference between this embodiment and embodiment three is that the stirring time in step II is 10~20min. The others are the same as embodiment three.

[0025] Embodiment five: the difference between this embodiment and embodiment three or four is that the flux covered in step II is composed of 45% of KCl, 30% of NaCl and 25% of Na3AlF6 in terms of mass percentage. The others are the same as embodiment three or four.

[0026] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods Three to Five in that: Step Three, after refining, involves refining with argon gas for 30 minutes and then letting it stand for 30 to 60 minutes. Everything else is the same as in Specific Implementation Methods Three to Five.

[0027] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods Three to Six in that: in step three, the casting speed is 50 mm / min, the casting temperature is 740℃, the casting cooling water flow rate is 90 m³ / h, the metal liquid level in the crystallizer is 95 mm, and the online seeding speed of Al-Ti-0.2B wire is 500 mm / min per ingot for semi-continuous casting. Everything else is the same as in Specific Implementation Methods Three to Five.

[0028] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods Three to Seven in that: the casting speed is 45 mm / min, the casting temperature is 730~750℃, the casting cooling water flow rate is 80 m³ / h, the casting water temperature is 22~28℃, and the metal liquid level in the crystallizer is 90 mm. Everything else is the same as in Specific Implementation Methods Three to Seven.

[0029] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods Three to Eight in that: the casting speed is 55 mm / min, the casting temperature is 730~750℃, the casting cooling water flow rate is 100 m³ / h, the casting water temperature is 22~28℃, and the metal liquid level in the crystallizer is 100 mm. Everything else is the same as in Specific Implementation Methods Three to Eight.

[0030] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods Two to Nine in that the degassing box in step three uses a dual-rotor degassing system, with each rotor having a flow rate of 4 Nm³. 3 / h, pressure is 0.2 bar. Everything else is the same as in any of the specific embodiments two to nine.

[0031] Specific Implementation Method Eleven: This implementation method differs from Specific Implementation Methods Two to Nine in that the filter box in step three uses dual ceramic filter sheets with a mesh size of 30+50 ppi. Everything else is the same as in Specific Implementation Methods Two to Nine.

[0032] Specific Implementation Method Twelve: This implementation method differs from Specific Implementation Methods Two to Eleven in that the Al-Si aluminum alloy flat ingot obtained by semi-continuous casting in step three has a thickness of 520 mm, a width of 1320 mm, and a length of 5000 mm to 6000 mm. Everything else is the same as in Specific Implementation Methods Two to Eleven.

[0033] The beneficial effects of the present invention are verified using the following embodiments:

[0034] Embodiment one: the preparation method of the Al-Si aluminum alloy flat ingot is carried out according to the following steps:

[0035] I. Ingredients: according to the mass percentage of 7.50% of Si, 1.05% of Zn, Fe < 0.80%, Cu < 0.25%, Mn < 0.10%, Mg < 0.05%, Cr < 0.05%, Ti < 0.05% and the balance of Al, Al 99.70 ingot, metal Zn and aluminum silicon intermediate alloy are weighed as smelting raw materials;

[0036] II. Smelting: the aluminum ingot and aluminum silicon intermediate alloy weighed in step I are added to the smelting furnace, the smelting temperature is 720-750℃, when the melt temperature is 700℃, the metal Zn is added, and then the alloy melt is obtained after covering with flux under the condition of 720-730℃ stirring;

[0037] III. Casting: the alloy melt obtained in step II is introduced into the natural gas holding furnace at a temperature of 740-750℃, and after refining, it is placed in the degassing tank and the filter tank, then the melt is injected into the crystallizer, and then under the conditions of casting speed 55mm / min, casting temperature 740-750℃, casting cooling water flow 100m³ / h, casting water temperature 22-28℃, crystallizer metal liquid level 100mm, and on-line seeding of Al-Ti-0.2B wire, the semi-continuous casting of the Al-Si aluminum alloy flat ingot is carried out.

[0038] The Al-Si aluminum alloy flat ingot obtained in this embodiment is shown in Figure 1 The chemical composition is qualified, the surface is free of cracks, slag and other defects, and the yield reaches 80.6%.

Claims

1. An Al-Si based aluminum alloy flat casting ingot, characterized in that... The Al-Si aluminum alloy flat ingot is composed of 6.80%–8.20% Si, 0.70%–1.30% Zn, Fe < 0.80%, Cu < 0.25%, Mn < 0.10%, Mg < 0.05%, Cr < 0.05%, Ti < 0.05%, and the balance Al by mass percentage.

2. The Al-Si aluminum alloy flat casting ingot according to claim 1, characterized in that... The Al-Si aluminum alloy flat ingot is composed of 7.50% Si, 1.05% Zn, Fe < 0.80%, Cu < 0.25%, Mn < 0.10%, Mg < 0.05%, Cr < 0.05%, Ti < 0.05%, and the balance Al by mass percentage.

3. The method for preparing an Al-Si aluminum alloy flat ingot as described in claim 1, characterized in that... The preparation method is carried out according to the following steps: I. Batching: Weigh aluminum ingots, metallic Zn, and aluminum-silicon master alloy as smelting raw materials according to the following mass percentages: Si: 6.80%–8.20%, Fe < 0.80%, Cu < 0.25%, Mn < 0.10%, Mg < 0.05%, Cr < 0.05%, Zn: 0.70%–1.30%, Ti < 0.05%, and the balance Al.

2. Melting: Add the aluminum ingots and aluminum-silicon master alloy weighed in step 1 into the melting furnace. The melting temperature is 720-750℃. When the melt temperature is 690-710℃, add metallic Zn. Stir at 720-750℃ and then cover with flux to obtain the alloy melt. III. Casting: The alloy melt obtained in step II is introduced into a natural gas holding furnace at a temperature of 730~750℃. After refining and settling, the melt is injected into the crystallizer after passing through a degassing box and a filter box. Then, under the conditions of casting speed of 45mm / min~55mm / min, casting temperature of 730~750℃, casting cooling water flow rate of 80-100m³ / h, casting water temperature of 22~28℃, and metal liquid level in the crystallizer of 90~100mm, and Al-Ti-0.2B wire is seeded online, semi-continuous casting is carried out to obtain Al-Si aluminum alloy flat ingots.

4. The method for preparing an Al-Si aluminum alloy flat ingot according to claim 1, characterized in that, The stirring time mentioned in step two is 10-20 minutes.

5. The method for preparing an Al-Si aluminum alloy flat ingot according to claim 1, characterized in that, The flux used in step two consists of 45% KCl, 30% NaCl, and 25% Na3AlF6 by mass percentage.

6. The method for preparing an Al-Si aluminum alloy flat ingot according to claim 1, characterized in that, Step 3, refining followed by settling, refers to refining with argon gas for 30 minutes and then letting it stand for 30-60 minutes.

7. The method for preparing an Al-Si aluminum alloy flat ingot according to claim 1, characterized in that, The semi-continuous casting process in step three is carried out under the following conditions: casting speed of 50 mm / min, casting temperature of 740℃, casting cooling water flow rate of 90 m³ / h, metal liquid level in the crystallizer of 95 mm, and online seeding speed of Al-Ti-0.2B wire of 500 mm / min per ingot.

8. The method for preparing an Al-Si aluminum alloy flat ingot according to claim 1, characterized in that, Step three's degassing chamber uses a dual-rotor degassing system, with each rotor having a flow rate of 4 Nm³. 3 / h, pressure is 0.2 bar.

9. The method for preparing an Al-Si aluminum alloy flat ingot according to claim 1, characterized in that, The filter box in step three uses dual ceramic filter plates with a mesh size of 30+50ppi.

10. The method for preparing an Al-Si aluminum alloy flat ingot according to claim 1, characterized in that, The Al-Si aluminum alloy flat ingot obtained by semi-continuous casting in step three has a thickness of 520 mm, a width of 1320 mm, and a length of 5000 mm to 6000 mm.

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