Hardware is divided into "big hardware" and "small hardware." Big hardware usually refers to steel plates, rebar, flat iron, angle iron, channel iron, I-beams, and various types of steel materials.

Traditional hardware, also known as "small hardware," refers to the five metals: gold, silver, copper, iron, and tin. These can be crafted into art pieces like knives and swords or metal devices. Nowadays, hardware is a broader term, encompassing tools, parts, everyday hardware, construction hardware, and security products.

Small hardware products are generally not final consumer goods but are used as complementary products, semi-finished goods, and tools in the manufacturing process, like connectors, handles, springs, sofa legs, and coffee table legs in the furniture industry. 

The term "hardware" is a common saying, and small hardware is typically categorized into two main types: ferrous metals and non-ferrous metals. It's used in furniture in various forms like tubes, rods, plates, wires, and angles.

Ferrous Metal Parts
Mainly refers to iron products. The pros are: resistance to deformation, high strength, good wear resistance, high hardness, low cost, and long life. They are carbon iron alloys, which can be divided into high carbon steel, low carbon steel, and medium carbon steel based on carbon content. The uses of iron products are generally divided into round tubes, square tubes, angle iron, and steel plates based on shape.

Round tubes are mainly used for chair and sofa legs; square tubes for beams and brackets; steel plates for tabletop panels, screens, hanging pieces, arms, metal cabinets, and doors.

The cons of iron products are obvious: they rust easily, are heavy, and fear moisture, but these can be avoided through methods like electroplating, spraying, and blackening. There are many ways to process and shape iron products: bending, cutting, drilling, welding, cutting, and stamping. Iron products are easy to process, iron ore is abundant, and it's one of the most common and widely used materials in life.

Non-Ferrous Metal Parts
Refers to all metal parts except iron products, such as aluminum, copper, zinc, stainless steel, etc. They have one characteristic: they don't rust easily. Commonly used in furniture are aluminum plates, aluminum rods, stainless steel tubes, stainless steel plates, copper plates, zinc plates, and aluminum alloy sofa legs.

Stainless Steel Products
Stainless steel products are divided into two main categories: stainless iron and stainless steel. The "430" is often called stainless iron, and "304" is pure stainless steel. One way to tell them apart is with a magnet; "430" can be attracted by a magnet, while "304" cannot.

Stainless steel products are slightly heavier than iron products, but their price is more than four times that of iron products, so they are only used in high-end products.

Copper Products
Copper products are divided into pure copper and copper alloys. Pure copper, also known as red copper, has poor strength and hardness but good toughness. Among copper alloys, brass, which is mainly a zinc alloy of copper, is commonly used in furniture.

The price of pure copper is 30-40% higher than that of stainless steel, while brass is 20% lower than pure copper. Copper alloys have slightly higher hardness and strength than stainless steel but are prone to breaking and are more brittle. Copper parts in furniture are mainly used for handles and embedded screws. To prevent "rust," pure copper generally needs to be plated before use, while brass does not, and it is rarely used in large areas of furniture products.
 

Zinc Products
Pure zinc products are rarely used, mainly combined with zinc alloys or steel, such as galvanized plates and electrolytic plates. They are rarely used in furniture because zinc products have poor strength. Zinc alloy accessories, such as eccentric buckles and structural joint points (parts), are used. The density of zinc alloy is slightly lower than that of iron, about 6.8, and the price is between steel and aluminum alloy. Most zinc alloys are produced in the form of die-casting furniture accessories, and zinc alloy sofa legs are also one of the few types.

Titanium and Zirconium Alloys
These are relatively expensive metals, mostly used in furniture in the form of electroplating, for high-end handles, hinges, and high-end exposed connectors or in hotel furniture. Their electroplating cost is about 40% higher than chrome plating, but the appearance is high-end, similar to gold and silver products, with very good wear resistance and no rust.
 

Cast Metal
Many furniture hardware products use castings, such as handles and door hinges. There are many popular casting production processes in the market, such as precision casting, die casting, and sand casting. In addition to the aluminum alloys mentioned earlier, the materials for castings also include brass, stainless steel, and zinc-tin alloys. It's worth mentioning that cast sofa legs are extremely rare and basically not used in this process for sofa legs.

The characteristics of casting products are exquisite and unique in shape. The disadvantages are high single-piece costs, and the costs of different casting processes vary, roughly from high to low: precision casting > die casting > sand casting.

The cost of molds from high to low is: die casting > precision casting > sand casting. The disadvantage of casting products is that the production cycle is slightly long, and the products need to go through 2-3 processes to make qualified accessories, and the accessories also need to be decorated according to different requirements, such as electroplating, polishing, brushing, sandblasting, and painting.