People often ask about the material of screws. In fact, sometimes you can make a preliminary judgment by simple observation and touch. For example, if you gently suck with a magnet, the iron screw has strong magnetic force, the stainless steel has weak magnetic force or is almost non-magnetic, and the light one may be aluminum or titanium. These are some experiences accumulated in daily life.
At present, standard parts such as screws in the market are mainly made of carbon steel, stainless steel and copper.
Next, we will explore the characteristics of these common screw materials in depth.
1. Carbon steel
With its excellent strength, economical and wide applicability, it has become a common material in screw manufacturing. Specifically, it can be divided into the following three categories:
- Low carbon steel: This type of steel has a carbon content of no more than 0.25%, covering steel grades such as 1008, 1015, 1018, 1022, SAE1215, etc. They are mainly used to manufacture products such as 4.8-grade bolts, 4-grade nuts and small screws that have no special requirements for hardness.
- Medium carbon steel: Its carbon content ranges from 0.25% to 0.6%, including 1035, CH38F, 1039, 40ACR and other steel grades. This type of steel is often used to manufacture grade 8 nuts, grade 8.8 bolts and grade 8.8 hexagonal products.
- High carbon steel: Although its carbon content exceeds 0.6%, it is less common in the market due to its characteristics that are not suitable for all applications.
By understanding the characteristics of these different types of carbon steel and their application range, we can better select and utilize these materials to meet the needs of various screw manufacturing.
2. Stainless steel
This alloy composed of iron, chromium and other elements such as nickel or molybdenum is widely used in screw manufacturing due to its unique properties. The protective oxide layer formed by chromium on the surface of the screw - chromium oxide, gives it excellent corrosion resistance. Because of this, stainless steel screws are ideal for indoor and outdoor applications exposed to corrosive environments, and their strength and durability are excellent. Among them, stainless steel grades such as SUS302, SUS304 and SUS316 are particularly popular.
3. Copper
This metal element plays an important role in the production of standard components. Copper alloys such as H62, H65 and H68 are often used to make copper screws. They play an advantage in the electrical, electronic and plumbing industries due to their excellent electrical and thermal conductivity and corrosion resistance. However, it is worth noting that copper has a lower hardness than stainless steel, which may weaken its load-bearing and durability characteristics in some occasions to a certain extent.
4. The influence of various elements in the material on the properties of steel:
- Carbon (C): The carbon content has a significant effect on the hardness, strength and machinability of steel. As the carbon content increases, the hardness and strength of steel will also increase accordingly, but its ductility and toughness will decrease accordingly. Conversely, a lower carbon content helps to improve the ductility of steel, but reduces its hardness and strength.
- Iron (Fe): As the main component of steel, iron provides the structural basis for steel and gives it magnetism.
- Chromium (Cr): Chromium can enhance the corrosion resistance, hardenability and wear resistance of steel. It forms a protective chromium oxide layer on the surface of the steel, which effectively prevents oxidation and corrosion.
- Nickel (Ni): Nickel enhances the corrosion resistance, strength and toughness of steel. It also improves the material's resistance to high temperatures and gives steel resistance to acidic and alkaline environments.
- Manganese (Mn): Manganese helps increase the strength and hardness of steel while increasing its hardenability. It also facilitates deoxidation during steel production.
- Silicon (Si): Silicon increases the strength and hardness of steel and reduces its brittleness. It also promotes the formation of a protective oxide layer, which enhances the steel's resistance to oxidation and scaling.
- Vanadium (V): Vanadium refines the grain structure of steel, which increases its strength, toughness and heat resistance. It also helps form carbides, which improves the steel's wear resistance.
- Molybdenum (Mo): Molybdenum significantly increases the strength, hardness and corrosion resistance of steel, especially at high temperatures. It also improves the steel's resistance to corrosive chemical environments.
- Titanium (Ti): Titanium also refines the grain structure of steel, enhances its strength, and provides corrosion and pitting resistance. In addition, it forms carbides to further improve the wear resistance of steel.
In addition, phosphorus (P) and sulfur (S) are two types of impurities that need to be strictly controlled in steel production. Their excessive presence in steel can have an adverse effect on the mechanical properties of steel, such as impairing ductility and toughness.