There are several ways to determine the material of a screw or bolt:

1. Look for markings: Many screws and bolts will have markings on the head that indicate the material they are made of.

For example, a stainless steel bolt may be marked with "SS" or "316" to indicate its composition.

2. Check the color: Different materials will have different colors. For example, a steel bolt will typically be silver or gray in color, while a brass bolt will be a yellowish-gold color.

3. Use a magnet: Steel is magnetic, so if a magnet sticks to the screw or bolt, it is likely made of steel. Non-magnetic materials, such as aluminum or brass, will not attract a magnet.

4. Conduct a spark test: If you have the necessary equipment and expertise, you can perform a spark test to determine the material of a screw or bolt. Different materials will produce different sparks when exposed to a grinder or other high-speed tool. It's important to note that some screws and bolts may be plated or coated, which can make it difficult to determine the underlying material. In these cases, the plating or coating may need to be removed to determine the material underneath.

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In making the "screws" , commonly used materials are: 

Low Carbon Steel, Mild Steel, Alloy Steel, Stainless Steel and Brass.

Main materials for making "screws": low carbon steel, medium carbon steel, alloy steel, stainless steel, brass.

1. Carbon steel: We distinguish low carbon steel, medium carbon steel and high carbon steel and alloy steel by the carbon content in the carbon steel material.

Low carbon steel: C% ≤ 0.25%, basically called 1008, 1015, 1018, 1022 etc. abroad.

SAE/AISI bar steel, wire rod, semi-finished carbon steel for forging (C1005 ~ C1095)

Mainly used for grade 4.8 bolts and grade 4 nuts.

Very low carbon steel and medium carbon for cold forming or cold forging: 1035ACR , 1040ACR

2. Medium carbon steel: C% = 0.25%; heat treatment is usually done!

3. High carbon steel: C% > 0.45%. Not commonly used in the market.

4. Alloy steel: Add alloy elements to carbon steel to increase some special properties of steel:

Such as 35, 40 chromium molybdenum, SCM435, 10B38 (carbon boron steel and chromium vanadium boron alloy boron steel) . For alloy steel, heat treatment is definitely required!

Stainless steel: 

Stainless steel is a popular material used in screws due to its corrosion-resistant properties, durability, and strength. There are several different types of stainless steel, and the specific type used in a screw can depend on its intended application and the desired properties.

1.  Austenitic stainless steel: This type of stainless steel is the most commonly used in screws. It is highly corrosion-resistant and has good strength and toughness. Austenitic stainless steel screws are commonly made from grades such as SUS 304 or SUS 316, which contain varying amounts of chromium and nickel.

2. Martensitic stainless steel: This type of stainless steel is harder and more brittle than austenitic stainless steel. It has good wear resistance and can be heat-treated to increase its strength. Martensitic stainless steel screws are commonly made from grades such as SUS 410 or SUS 416.

3. Ferritic stainless steel: This type of stainless steel is less commonly used in screws. It has good corrosion resistance and is less brittle than martensitic stainless steel, but it is not as strong as austenitic stainless steel. Ferritic stainless steel screws are commonly made from grades such as SUS 430.

4. Duplex stainless steel: This type of stainless steel is a combination of austenitic and ferritic stainless steel. It has high strength and good corrosion resistance, making it well-suited for use in screws that will be subjected to high stresses. Duplex stainless steel screws are commonly made from grades such as 2205 or 2507.

In addition to these four main types, there are also several specialty grades of stainless steel that may be used in screws for specific applications. Some examples include precipitation-hardening stainless steel, which can be heat-treated to increase its strength, and superaustenitic stainless steel, which has even higher corrosion resistance than standard austenitic stainless steel.

Copper:

Copper and brass are often used in screws due to their excellent thermal and electrical conductivity, as well as their corrosion resistance. Here are some of the different types of copper and brass that may be used in screws:

1. Pure copper: This is a soft and ductile metal that has excellent thermal and electrical conductivity. It is not as strong as some other metals, so it may not be suitable for use in high-stress applications.

2. Brass: Brass is an alloy of copper and zinc. It is stronger and more corrosion-resistant than pure copper, and it can be easily machined and formed. The amount of zinc in the alloy can be varied to achieve different properties, such as increased strength or improved corrosion resistance.

3. Naval brass: This is a type of brass that contains about 60% copper, 39% zinc, and a small amount of tin. It is known for its excellent corrosion resistance, particularly in marine environments. Naval brass is often used in screws and other fasteners for ships and boats.

4. Phosphor bronze: This is an alloy of copper, tin, and phosphorus. It has good strength, wear resistance, and corrosion resistance, making it well-suited for use in screws and other fasteners. Phosphor bronze is often used in applications where high-stress and wear resistance are required, such as in machinery and equipment.

5. Beryllium copper: This is an alloy of copper and beryllium. It has excellent strength and wear resistance, as well as good thermal and electrical conductivity. Beryllium copper is often used in screws and other fasteners for aerospace and other high-performance applications where strength and durability are critical. It's important to note that some types of copper and brass may not be suitable for use in certain environments or applications. For example, brass may not be suitable for use in seawater or other corrosive environments, and beryllium copper can be hazardous if ingested or inhaled. It's important to carefully consider the specific properties and requirements of a screw before selecting the type of copper or brass to use.

Brass (C2600, C2680, C2801, C2801S)

C2600: Beautiful color, processability, ductility, suitable for stretching, easy for electroplating or painting, more suitable for art materials.

C2680: It has beautiful color, processability, ductility, good stretchability, easy electroplating or painting, and good weldability.

C2801/C2801S: Good intermediate processability, high strength and corrosion resistance, better sound quality with tin added, suitable for cymbals.

Uses: Used for its malleability and processing, connectors, terminals, arts and crafts, buttons, horn locks, consumer electronics materials.