Blog

What are the types of lubricants used in the process of wire drawing?

The types of lubricants used in the steel wire drawing process are mainly divided into two categories: solid lubricants and liquid lubricants. Their function is to form a lubricating film between the steel wire and the mold, reduce friction, lower energy consumption and temperature rise, thereby extending the mold life and improving product quality. The following are specific classifications and their functions and principles:

1. Solid lubricant

1. 1 Metal soaps

Ingredients: Sodium stearate, calcium stearate, barium stearate and other fatty acid metal salts.

Function and principle:

Sodium soap (such as sodium stearate): water-soluble, suitable for medium speed drying or when needed

The steel wire with subsequent coating is easy to clean.

Calcium soap (such as calcium stearate): forms a thick lubricating film, resistant to high temperature and high pressure, but difficult to dissolve in water, suitable for high-strength drawing.

Applicable scenarios: Low to medium speed dry drawing, such as coarse steel wire or situations where surface cleanliness is not required.

1.2. Additives

Extreme pressure additive:

Materials such as graphite:  molybdenum disulfide (MoS ₂), and polytetrafluoroethylene react with metal surfaces to form high melting point compounds, enhancing lubrication performance under high temperature and pressure.

Thickening agents: such as calcium carbonate and barium sulfate, increase the viscosity of lubricants and enhance the load-bearing capacity of lubricating films.

Preservatives: such as sodium nitrite, prevent lubricants from corroding steel wires.

2. Liquid lubricant

2.1. Soap solution

Ingredients: An aqueous solution of sodium soap or potassium soap, with a concentration of 0.5% to 3%.

Function and principle:

Lubrication and cooling: reduces friction and takes away heat, suitable for wet drawing of fine wires.   

Clean the surface: Remove impurities from the surface of the steel wire to improve the quality of subsequent processing.

Applicable scenarios: Wet drawing processes that require high surface smoothness, such as fine steel wire and copper wire.

2.2. Emulsion

Ingredients: Mineral oil, water, and emulsifier (such as methanol), with a concentration of 2% to 6%.

Function and principle:

Defoaming and antirust: silicone defoamer reduces foam, and mineral oil forms antirust film.  

Excellent cooling performance: suitable for high-speed drawing, such as stainless steel wire or high carbon steel wire.

Additives: Extreme pressure additives: Chlorinated paraffin and sulfurized oil enhance lubricity under extreme conditions.

Fungicide: Phenolic compounds prevent microbial growth.

3. Special lubricant

3.1. Paste like lubricating grease

Ingredients: A mixture of high viscosity lubricating oil and extreme pressure additives (such as vulcanized lard).

Function: Used for drawing coarse steel wire, providing high adhesion and wear resistance, but needs to be used in conjunction with circulating oil.

3.2. Paraffin based lubricant

Ingredients: Paraffin solution or emulsion.

Applicable scenarios: aluminum tube drawing,

It can be continuously pulled multiple times without the need for repeated coating, and the surface is clean.

4. Principles for lubricant selection

4.1. Steel wire material:

Low carbon steel: commonly treated with lime or borax, and lubricated with dry soap.   

Stainless steel: requires high extreme pressure emulsion or solid lubricant containing molybdenum disulfide.

4.2. Pulling speed:

High speed drawing (>20m/s): prioritize the use of emulsion or liquid lubricants containing extreme pressure additives.  

Low speed drawing: Dry soap or paste lubricating grease is more economical.

4.3. Subsequent process:

Steel wire to be coated: Use water-soluble sodium soap to avoid residue affecting the adhesion of the coating.   

Annealing treatment: A lubricant that is easy to remove is required to prevent residual carbonization from affecting surface quality.

5. Lubricant performance requirements

5.1. High pressure and high temperature resistance: The lubricating film remains stable under high pressure (>500MPa) and high temperature (200~300 ℃).

5.2. Elongability: The lubricating film does not break when the steel wire deforms, and the layered structure design is key.

5.3. Environmental friendliness: Does not contain heavy metals or harmful substances such as lead salts, and complies with RoHS standards. By selecting the appropriate lubricant type and formula, the drawing efficiency can be significantly improved (such as reducing energy consumption by 20%~30% in high-speed drawing) and the mold life can be extended (by 40%~50%). Specific applications need to be optimized based on process parameters and steel wire materials.