阅读说明：本技术 一种防止铝合金铸棒产生应力表面裂纹的方法 (Method for preventing aluminum alloy cast rod from generating stress surface cracks ) 是由 廖健 于 2019-09-23 设计创作，主要内容包括：本发明公开了一种防止铝合金铸棒产生应力表面裂纹的方法,它包括以下步骤：S1、合金铝液的制备：将适量的铝合金铸锭投放到合金炉内熔化,升高合金炉内温度,合金炉将6061铝合金铸锭熔化,升温20~30min后,在合金炉内制得铝液；S2、改变合金成分中Fe/Si比值：先测定出铝液中Fe和过剩Si的百分含量比值,若检测出Fe的百分含量低于0.2%,则向合金炉内添加单质Fe,直至Fe的百分含量大于0.2%,随后计算出Fe和过剩Si的百分含量比值,若Fe/过剩Si比值大于1.417,则不再向合金炉内加入Fe,最终改变合金成分中Fe/Si比值；S3、铝合金铸棒的浇铸。本发明的有益效果是：有利于减少表面裂纹缺陷的产生、工艺步骤简单、特别适用于浇铸铝合金铸棒。(The invention discloses a method for preventing an aluminum alloy cast rod from generating stress surface cracks, which comprises the following steps of S1, preparing alloy aluminum liquid, putting a proper amount of aluminum alloy cast ingots into an alloy furnace for melting, raising the temperature in the alloy furnace, melting 6061 aluminum alloy cast ingots by the alloy furnace, heating for 20 ~ 30min, and then preparing the aluminum liquid in the alloy furnace, S2, changing the Fe/Si ratio in alloy components, firstly measuring the percentage content ratio of Fe and excessive Si in the aluminum liquid, if the percentage content of Fe is detected to be lower than 0.2%, adding simple substance Fe into the alloy furnace until the percentage content of Fe is higher than 0.2%, then calculating the percentage content ratio of Fe and excessive Si, if the Fe/excessive Si ratio is higher than 1.417, no more adding Fe into the alloy furnace, and finally changing the Fe/Si ratio in the alloy components, and S3, casting the aluminum alloy cast rod.)

1. A method for preventing an aluminum alloy cast rod from generating stress surface cracks is characterized by comprising the following steps: it comprises the following steps:

s1, preparing alloy molten aluminum, namely putting a proper amount of aluminum alloy cast ingot into an alloy furnace for melting, raising the temperature in the alloy furnace, melting 6061 aluminum alloy cast ingot by the alloy furnace, raising the temperature for 20 ~ 30min, and then preparing the molten aluminum in the alloy furnace;

s2, changing the Fe/Si ratio in the alloy components:

firstly, measuring the percentage content ratio of Fe and excessive Si in the aluminum liquid, if the percentage content of Fe is detected to be lower than 0.2%, adding simple substance Fe into the alloy furnace until the percentage content of Fe is higher than 0.2%, then calculating the percentage content ratio of Fe and excessive Si, if the percentage content of Fe/excessive Si is higher than 1.417, not adding Fe into the alloy furnace, and finally changing the percentage value of Fe/Si in the alloy components;

s3, casting the aluminum alloy cast rod, which comprises the following steps:

s31, blocking the runner in front of a casting die of the casting machine by a plurality of baffle plates in sections, and filling the molten aluminum in the alloy furnace into each section of runner;

s32, heating the temperatures of the die plate and the launder until the temperatures of the die plate and the launder reach 150 ~ 160 ℃;

s33, setting the parameters of the casting machine as a casting speed of 63 ~ 127mm/min, a casting stream outlet temperature of 704 ~ 714 ℃, a casting front end temperature of 689 ~ 698 ℃, a casting rear end temperature of 686 ~ 695 ℃, a casting water temperature of 27.5 ~ 29 ℃ and a cooling water flow rate of 250 ~ 470m³/h；

And S34, filling the molten aluminum in the launder into the casting cavity of the casting machine within 12 ~ 15S, and opening the casting machine after 15 ~ 25min to take the cast and formed product out of the casting cavity.

2. The method of preventing stress surface cracking in an aluminum alloy cast bar according to claim 1, wherein: and in the step S34, the product is cooled in air.

3. The method of preventing stress surface cracking in an aluminum alloy cast bar according to claim 1, wherein: the casting cavity in the step S34 is hollow cylindrical.

Technical Field

The invention relates to a method for preventing an aluminum alloy cast rod from generating stress surface cracks.

Background

6061 aluminum alloy is a high-quality aluminum alloy product produced by a heat treatment pre-stretching process, has the excellent characteristics of excellent processing performance, excellent weldability, electroplating property, excellent corrosion resistance, high toughness, no deformation after processing, compact and defect-free material, easiness in polishing, colored film, excellent oxidation effect and the like, and is widely applied to the fields of aerospace, rail transit, communication equipment, ships and the like. In order to pursue higher mechanical property requirements of products, various manufacturers actively explore the more appropriate alloy composition design of 6061 aluminum alloy cast rods. Practice has shown that cast rods cast from 6061 aluminum alloy exhibit a higher tendency to crack during casting than similar 6063, 6060 alloys. Unlike the common central cracks, the cracks are mainly stress surface cracks generated in the solidification and cooling process of the cast rod. For the surface cracks, if the surface cracks are not controlled and cut off in time in the casting process, the surface cracks can be further deepened and prolonged in the subsequent heat treatment process, so that products are scrapped, and great loss is brought.

Analysis of the chemical composition and related properties of 6061 shows that the 6061 alloy has a high surface crack tendency mainly due to the following three points:

1. high content of Mg2Si strengthening phase: mg (magnesium)₂Si is the main strengthening phase of AI-Mg-Si series alloy, the ingredients are calculated according to the alloy, and the Mg in 6061 alloy₂The Si content is higher than that of 6063 alloy by about 50%, the strengthening phase content in the alloy is high, the strength of the cast state is increased, and meanwhile, under the unbalanced cooling condition, the strengthening phase on the grain boundary is increased, the plasticity is naturally reduced, and the crack tendency of the alloy is increased. The increase of the Mg2Si content in the alloy widens the crystallization temperature range, which increases the stress applied when crystal cracks are formed, and deteriorates the shrinkage at the end of solidification and the welding conditions, thereby increasing the crack tendency. Further, the thermal conductivity of the alloy is lowered, the liquid pocket is deepened during casting, the wall thickness of the liquid pocket is thinned, and the unit tensile stress is increased, thereby further improving the crack tendency.

2. The design of the Fe/Si ratio is not reasonable: after Si in 6061 alloy and Mg form Mg2Si phase, excessive Si forms compound with Fe and Al, and microscopic structure analysis shows that when Si is larger than Fe, the Si is mainly beta phase which is acicular and has higher brittleness, thus causing increased crack tendency.

3. Cold ingot separation with too long filling time: the surface cracks usually occur at the beginning of casting, and as is clear from observation of aluminum bars with surface cracks on site, most of the aluminum bars with surface cracks exist along with separation of cold ingots at the bar heads, and extend along with cold cracks in the radial direction, the surface of the aluminum bar at the crack extension part presents a bright line, and no cracks starting from the middle part or the tail part of the aluminum bar are found through ultrasonic flaw detection.

It was initially thought that plugging of the crystallizer water passages could cause surface crack defects due to surface stress concentrations during casting, which still occurred after all the crystallizer had been cleaned. Then, the generation of surface cracks cannot be avoided by searching and reducing the casting speed, the temperature of the molten aluminum, the speed of the titanium boron wire and the like. Therefore, a method for preventing the generation of stress surface cracks during casting is needed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for preventing an aluminum alloy cast rod from generating stress surface cracks, which is beneficial to reducing the generation of surface crack defects, has simple process steps and is particularly suitable for casting the aluminum alloy cast rod.

The purpose of the invention is realized by the following technical scheme: a method for preventing stress surface cracks from being generated on an aluminum alloy cast rod comprises the following steps:

s1, preparing alloy molten aluminum, namely putting a proper amount of aluminum alloy cast ingot into an alloy furnace for melting, raising the temperature in the alloy furnace, melting 6061 aluminum alloy cast ingot by the alloy furnace, raising the temperature for 20 ~ 30min, and then preparing the molten aluminum in the alloy furnace;

s2, changing the Fe/Si ratio in the alloy components:

firstly, measuring the percentage content ratio of Fe and excessive Si in the aluminum liquid, if the percentage content of Fe is detected to be lower than 0.2%, adding simple substance Fe into the alloy furnace until the percentage content of Fe is higher than 0.2%, then calculating the percentage content ratio of Fe and excessive Si, if the percentage content of Fe/excessive Si is higher than 1.417, not adding Fe into the alloy furnace, and finally changing the percentage value of Fe/Si in the alloy components;

s3, casting the aluminum alloy cast rod, which comprises the following steps:

s31, blocking the runner in front of a casting die of the casting machine by a plurality of baffle plates in sections, and filling the molten aluminum in the alloy furnace into each section of runner;

s32, heating the temperatures of the die plate and the launder until the temperatures of the die plate and the launder reach 150 ~ 160 ℃;

s33, setting the parameters of the casting machine as a casting speed of 63 ~ 127mm/min, a casting stream outlet temperature of 704 ~ 714 ℃, a casting front end temperature of 689 ~ 698 ℃, a casting rear end temperature of 686 ~ 695 ℃, a casting water temperature of 27.5 ~ 29 ℃ and a cooling water flow rate of 250 ~ 470m³/h；

And S34, filling the molten aluminum in the launder into the casting cavity of the casting machine within 12 ~ 15S, and opening the casting machine after 15 ~ 25min to take the cast and formed product out of the casting cavity.

And in the step S34, the product is cooled in air.

The casting cavity in the step S34 is hollow cylindrical.

The invention has the following advantages: (1) the invention changes the Fe/Si ratio in the alloy components, and reduces the crack tendency of the cast rod when Fe is larger than Si, thereby ensuring that no crack is generated on the cast rod. (2) The invention achieves the purposes of reducing the temperature drop of the filled aluminum liquid as much as possible and slowing down the separation of cold ingots by shortening the filling time, fully preheating the flow groove and improving the liquid level of the flow groove in the filling process, thereby greatly facilitating the reduction of the generation of surface crack defects and further ensuring that no cracks are generated on the cast rod.

Drawings

FIG. 1 is a graph showing the number of cracks in a cast rod cast with molten aluminum having different Fe/excess Si ratios.

Detailed Description

The invention will be further described with reference to the accompanying drawings, without limiting the scope of the invention to the following: