Brass casting is a process of making brass products from molten brass.
It entails having the mold in the shape of the product you want to make. Once molten brass cools, it takes the shape of the cavity.
In this guide, you will find all information you are looking for about casting brass.
Whether you want to choose the best alloys, know the benefits, limitations, possible defects or surface finishes – all information you are looking for is right here.
Keep reading to learn more.
Brass Grades/Alloys for Casting Process
These alloys include the following:
C84400 Leaded Semi-Red Brass
This is an alloy that contains copper, zinc, tin, lead and a small amount of aluminum. It is known for its good corrosion resistance and machinability. C84400 is a leaded alloy that contains about 4% lead which provides good machinability and reduces the tendency for the formation of hot tears during casting and machining.
C83600 Leaded Red Brass
This alloy contains copper, zinc and lead, with a higher lead content than C84400 alloy.
It refers to brass alloys that do not contain lead as one of their main alloying elements. Lead is often added to brass alloys to improve their machinability, as it acts as a lubricant during the machining process.
However, lead can also have negative effects on the environment and human health, so non-leaded alloys are becoming more popular in certain applications.
- C82400: This alloy contains copper, zinc and aluminum.
- C87850: This alloy contains copper, zinc, and tin.
- C87600: This alloy contains copper, zinc, and iron.
This is a leaded alloy that contains copper, zinc, tin, lead and a small amount of nickel.
It is a leaded alloy that contains copper, zinc, tin, lead, and a small amount of nickel, iron, and manganese.
Advantages Of Casting Brass
Over the years, casting brass parts has been due to the numerous benefits the alloy offers. In fact, it is for this reason that the material is popular in many domestic and industrial applications.
Let’s look at some common benefits:
Brass is naturally resistant to corrosion compared to aluminum. This makes it a suitable choice for applications that will be exposed to the elements. These elements include marine, water distribution, and architectural applications.
This material has a warm, golden color that can be polished to a high shine. For this reason, it makes it a popular choice for decorative and architectural applications compared to the silver grey of steel.
It is also relatively easy to machine. This makes it easy to produce precise and accurate parts with a good surface finish. This is an advantage that it has over other metal casting methods such as zinc casting. Zinc casting is more brittle and harder to machine.
Good Electrical Conductivity
Its good electrical conductivity makes it a suitable choice for electrical usages. This is an advantage that this casting has over other casting methods such as plastic casting which has poor thermal conductivity.
Brass is relatively light in weight than cast iron which is comparatively heavy. This makes it easy to transport and handle castings of brass.
It is affordable to perform casting of brass for large scale purposes than when using god or platinum casting which are costly.
Limitations of Brass Casting
Casting brass, like any other casting method, has its own set of limitations. Some of the most notable disadvantages include:
Lead is often added to brass alloys to improve their machinability. Also, lead can have negative effects on the environment and human health. This could be a limitation for projects that are required to meet strict environmental regulations.
You will experience limitations if you want to attain specific surface finishes with cast brass. For example, achieving a mirror-like finish is more difficult to achieve compared to other metal casting methods such as chrome plating.
Cast brass may not be able to produce complex shapes as easily as other casting methods such as investment casting which can produce intricate geometries.
This casting may not be as strong as castings made from other metals such as steel. It can limit the use of brass in high-stress applications or in applications where high strength is required.
Brass Casting History
The history of brass casting can be traced back to ancient times, with evidence of brass casting found in Egyptian and Roman artifacts. Early brass casting methods included the lost wax method. Here, a wax model was coated in clay and then heated to melt out the wax. It left behind a mold for the brass to be poured into.
During the Middle Ages, the sand-casting method was developed. Here, a mold was made from sand and the brass was poured into it. This method was:
- More cost-effective
- Allowed for larger parts to be cast
- The could cast complex shapes and parts
Development of Brass Casting in 19th Century
In the 19th century, the invention of the steam engine led to an increase in demand for brass parts and improvements in casting techniques. It led to the development of the centrifugal casting method. Here, the mold is spun to distribute the molten metal evenly. This method was mainly used to cast cylindrical shapes such as pipes and tubes.
Casting Brass Parts in 20th Century and Beyond
In the 20th century, new casting methods were developed. This include pressure casting, die casting and investment casting. These methods allowed for improved brass cast precision and surface finish. Besides, they are widely used today in various industries such as automotive, electrical, and household items.
In recent years, advances in technology have allowed for even more specialized casting methods like micro investment cast and vacuum-assisted investment cast brass.
Common Brass Casting Methods
Over the years, foundry shops have adopted affective and reliable ways to cast brass parts. Each process has unique advantages and disadvantages.
Additionally, you can also make many simple to complex parts, depending on the casting specific requirements.
Let’s look at some common brass casting techniques:
Brass Investment Casting
It is a method where a wax or plastic pattern of the desired shape is coated with a refractory material to form a mold, into which molten brass is poured.
Ideally, you will replicate patterns using special wax.
Advantages of Brass Investment Casting
- High precision and accuracy
- Good surface finish
- Ability to cast complex shapes
- It leaves no parting lines
Disadvantages of Brass Investment Casting
- High cost due to the use of expensive refractory materials
- Long lead times due to the multi-step process
How Brass Investment Casting Process Works
Like any other casting process, investment casting is a systematic process which involves the following key processes:
- A wax or plastic pattern of the desired shape is created
- The pattern is coated in a refractory material to form a mold
- The mold is heated to melt out the wax or plastic
- Molten brass is poured into the mold
- The brass solidifies inside the mold
- Thereafter, you will remove the casting from the mold
Again, it worth noting that over the years, there have been significant improvements in brass investment casting process.
As a result, brass casting companies have adopted specialized process to improve part quality and complexity.
Some subcategories of brass investment casting process are:
Lost Wax Investment Casting brass: A traditional method where wax patterns are coated in refractory material to form a mold. Allows for high precision and accuracy, but can be costly and time-consuming.
Colloidal Silica Investment Cast Brass: A modern method that uses colloidal silica solution to create the mold. Faster production times and lower costs compared to lost wax investment casting, but precision and accuracy may not be as high.
Micro Investment Casting brass: Specialized method used to produce small, precise parts. Similar process to traditional investment casting but with smaller, more intricate wax patterns and molds.
Vacuum Assisted Investment Cast Brass: A method that applies a vacuum to the mold during the casting process to remove air bubbles and improve quality and reduce defects.
- All About Investment Casting – Source: Thomasnet
- Lost Wax Casting – Source: Wikipedia
- Lost Wax Casting Guide – Source: The Crucible
Brass Die Casting Process
This is a method where molten brass is injected into a steel mold under high pressure. Although the process may involves many detailed processes, you can summarize it as:
- Make a mold – this is basically a replica of the final die cast brass part you need
- First, you will preheat the mold to reduce thermal shock
- Molten brass is injected into the mold under high pressure
- The brass solidifies inside the mold
- Finally, you will remove the cast brass from the mold
Ideally, brass die casting is a popular technique in many brass foundry shops.
Advantages of Brass Die Casting
- High production rate
- Good dimensional accuracy and surface finish
- Low labor cost
Disadvantages of Brass Die Casting
- High initial mold cost
- Limited to simple geometries
Over the years, foundry shops have adopted other brass die casting techniques to meet the dynamic production needs. The most common brass die casting techniques include:
Hot Chamber Brass Die Casting Technique
This is a method where the molten metal is injected into the die (mold) by a piston that is heated by an external source. The main advantage of this method is its fast cycle time.
It makes it suitable for high production runs. However, it is limited to low-melting point alloys.
Cold Chamber Brass Die Casting Technique
This is a method where the molten metal is poured into a chamber separate from the die. It happens before being injected into the die. The main advantage of this method is that it can be used with high-melting point alloys.
However, it has a longer cycle time than hot chamber die casting. For this reason, it is less suitable for high production runs.
- Hot Chamber Die Casting – Source: Die Casting
- Cold Chamber Die Casting – Source: Dynacast
- Die Casting Brass – Source: Pacific Die Casting
Sand Casting Brass
This is a method where a sand mold is created, into which molten brass is poured. It is a process that is widely used to make many cast brass parts.
Among the key stages in sand casting brass are:
- A sand mold is created using a pattern
- The pattern is removed from the mold
- Molten brass is poured into the mold
- The brass solidifies inside the mold
- Finally, the casting is removed from the mold
Depending on the specific cast brass parts you wish to make, you can choose:
- Permanent mold – In this process, you will utilize recyclable metal dies.
- Green sand cast brass – Here, the mold comprises of flour, clay, sand, and water. It is suitable for small or even medium cast brass.
- No-bake sand – In this technique, you will mix catalysts that are hardened with resins and sand. Besides, the final cast brass has better finish.
- Sand cast brass precision shell – This process involves blowing non-reusable sand in iron patterns that are heated. The process will form molds that you will use to cast brass.
Advantages of Sand Casting Brass
- Low cost
- Ability to cast large and complex shapes
Disadvantages of Sand Casting Brass
- Poor dimensional accuracy and surface finish
- High labor cost
- Brass Casting with Sand Cores – Source: Instructables
- What is Sand Casting Brass – Source: Investment Casting
Top Brass Casting Applications
Casting brass is a versatile manufacturing process you can use to make many parts and components. In fact, virtually industries depend on cast brass accessories.
Here are some common examples:
- Automotive industry: gears, bearings, bushings, fittings.
- Plumbing and HVAC: valves, fittings, pipes, tubing.
- Electrical industry: switchgear, electrical connectors, terminals, circuit breaker parts.
- Marine industry: propellers, pumps, valves, marine hardware.
- Hardware and tools: locks, hinges, handles, knobs.
- Furniture industry: decorative elements, cabinet hardware.
- Home appliances: heating elements, cookware, and door knobs.
- Art and Decoration: sculpture, candlesticks, figurines, candle holders.
- Building and construction: door knobs, window hardware, plumbing fixtures.
- Musical instruments: trumpet and trombone parts, cymbals.
Design Considerations for Casting Brass
Design is critical aspects when casting brass. With a proper brass part design, you will get high quality and accurate part.
Whether you want to design the mold or brass parts, there are variable that will guarantee successful casting process. Let’s look at the critical aspects:
Compressing Stressed Regions
By keeping the stressed areas of the part in compression, it will be less likely to fail due to tensile stress. This is particularly important for parts that will be subject to loads and stresses.
Rounding the Exterior Corners
External corners are more likely to be subject to stress concentration and can be a potential failure point. Rounding the corners can help to distribute the stress more evenly and reduce the risk of failure.
Uniform Section Thickness
To avoid more stress on the cast, avoid abruptly altering the cross-section. However, gradually change the cross-section if it is mandatory.
Not Cramming Metal where they Join
Concentration of metal at the junction can cause uneven cooling and lead to defects in the casting. It’s important to design the part in a way that distributes the metal evenly throughout the mold.
Use Thick Sections
Very thin sections can be more prone to warping and cracking during casting. It’s important to avoid designing parts with very thin sections, or to take extra care to ensure that they are cast properly.
Conduct Shot Blasting
This process is usually done after casting and it helps to improve the overall endurance and appearance of the casting brass.
Common Defects & Solutions During Brass Casting Process
Here are some common issues that can occur during the process of casting brass and how to address them:
This refers to small voids or bubbles that can appear in the finished cast brass. It can be caused by:
- Poor pouring technique
- Improper mold design
- Insufficient venting and gating system.
To address this issue, conduct the following:
- Redesign the mold
- Rectify the pouring process
- Improve venting and gating units
It occurs when the mold parts are not properly aligned. This results in a distorted or incorrectly shaped cast brass parts. Check for proper alignment of the mold before casting brass to solve this issue.
The issue occurs when the object is not allowed to cool uniformly, resulting in a distorted shape. To solve this issue, allow the cast brass to cool slowly and uniformly. Use either natural or controlled cooling techniques to accomplish this.
It occurs when you fail to properly design the mold to account for the contraction that occurs as the brass cools and solidifies. To address this issue, modify the design to account for shrinkage, or a suitable allowance should be made in the mold.
Incomplete filling: Incomplete filling occurs when the molten brass does not completely fill the mold, resulting in an incomplete or under-filled object. To address this issue, the pouring technique should be corrected, and the mold should be redesigned to ensure proper filling.
This refers to the formation of dross or slag on the surface of the casting brass. Main causes include presence of impurities in the brass alloy or by poor pouring technique. To address this issue, check the alloy for impurities and rectify the pouring method.
Recommended Tolerance for Casting Brass
The typical tolerances for cast brass will depend on a number of factors, including:
- Size and complexity of the part
- Method of casting
- Desired level of precision and accuracy.
However, in general, cast brass can have dimensional tolerances of +/- 0.005 inches (0.13 mm) to +/- 0.015 inches (0.38 mm). Also, the surface finish tolerances can be between 32 and 63 micro inches (0.8 to 1.6 micrometers) RMS.
It’s also worth noting that, as the size of the casting increases, the tolerances might become wider.
Surface Finishes Available For Brass Casting
Some of the most common surface finishes for castings brass include:
This is the surface finish that is produced by the casting process itself. It has no further finishing or polishing. As-cast finishes typically have a rough and uneven surface with visible mold marks and other imperfections.
It entails blasting the surface of the casting brass with abrasive materials such as sand or glass beads. Sandblasting can produce a uniform, matte finish with a slight texture.
This involves polishing the surface of the casting with a polishing wheel and a polishing compound. It can produce a smooth, shiny finish with a high degree of reflectivity.
Here, you will electrodeposit a metal onto the surface of the casting brass. This can include chrome, nickel, gold and other metal plating.
It entails anodizing the surface of the casting. The process involves submerging the casting in an electrolytic bath and passing an electric current through it. This process creates a hard, protective oxide layer on the surface of the casting.
Paint and Powder Coating
This is a surface finish that is achieved by applying paint or powder coating on the surface of the casting.
Before casting brass parts, you should choose a suitable alloy then decide on the best production technique. You can choose investment casting, sand casting or die casting technique.
However, you must evaluate all the casting constrains to get quality and durable cast brass parts without any defects.
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Bronze Casting – Source: The Crucible
Casting Brass Process – Source: Junior
Casting Molten Brass in Sand – Source: Big Stack
How to Cast Brass – Source: Wiki How