2. Applications
  3. Black scale removal and part lubrication for cold forging

Black scale removal and part lubrication for cold forging

Processing Details

  • Removal
  • Roughening
  • Scraping

What is WLS(Wet Blast Lubricant System)?

WLS (wet blasting / water based lubricant application) is treatment equipment for the lubrication process of cold forging lines. By integrating the substrate treatment (oxidation scale removal, degreasing washing, fine irregularity formation) and lubricant application, the installation area is 1/10, the water consumption is 1/30, and the industrial waste is less than 1/20 compared to conventional lubricant system.

Features of WLS processing

  • Significantly shortens lead times - Supports up to 30 SPM while integrating scale removal and lubricant application.
  • Streamlining / Cost reductionStreamlining through process shortening.
  • High lubrication performance - Maximizes the performance of the lubricant.

Illustrations of WLS treatment




Comparison of processes for WLS and zinc-phosphating + soap


3 Benefits of Inline Processing

Inline Processing in WLS

Sequential processing of wet blast pretreatment (descaling and base treatment) and single liquid lubricant application in one system produces various benefits compared with conventional zinc-phosphate treatment.

  • Easy installation and relocation - The system is smaller than chemical treatment systems requiring multiple processes, facilitating the installation or set-up when launching or relocating overseas.
  • No in-process inventory to reduce costs - Integration of processes in one system eliminates in-process (WIP) inventories, resulting in cost reductions.
  • Free from scratches and dents, ideal for net shape processing - The one-by-one feeding system causes no damage to workpieces.

Substrate treatment suitable for water-based lubricant application "wet blasting"

Wet blasting is a technique of spraying a mixture of water and abrasives at high speed with compressed air, then cleaning, processing and modifying the surface. Fine abrasives can be used for the wet blasting treatment, and it excels at forming fine irregularities while scraping off the part’s surface and removing dirt and foreign matter.


Surface after wet blast treatment


"Special stainless steel abrasive" for WLS

Performs oxidation scale removal / degreasing and fine irregularity formation using special sharp stainless steel abrasives. The highly tough abrasives contribute to reducing industrial waste.

Surface properties that improve trackability of the lubricant

The surface after wet blasting treatment has high wetness and can enhance the retention of the lubricant layer. As the lubricant tracks without layer breakage at the time of pressing, forging performance comparable to zinc-phosphate + soap can be obtained even with thin coatings.


Comparison of forging loads for WLS and zinc-phosphate + soap

wls_06※The basic surface of the workpiece is turned (Ra 0.8).

  Setting area enlargement ratio
651% 1004% 1358% 1712% 2065%
WLS(Adhesion amount: 5g/m2) Load[KN] 418 420 428 433 441
Seizure ×
Zinc-phosphate + Soap Load[KN] 422 426 431 445 Not-tested
Seizure ×
☑:No seizure  ×:Seizure occurs

Test Conditions

  • Test method: Rear extrusion test
  • Test speed: 35 spm
  • Punch: HAP72
  • Workpiece: S10C spheroid annealed material
  • Workpiece temperature: room temperature

Illustration of Test


Thin and uniform lubricant application

A "spray coating method," which is less prone to unevenness or lumps in water-based lubricant application, is used to form a thin, uniform water-based lubricating film. It is unnecessary to carry out a time-consuming initial make-up of electrolytic bath as the film is applied without elevating the liquid temperature or circulating it. Adjusting the injection volume gives the optimum adhesion weight for the workpiece and processing. Moreover, liquid exchange is simple, only requiring bottle replacement, eliminating the need for troublesome management unlike conventional chemical treatments.

Comparison of application methods

Dip Method

Application unevenness occurs
-> Cause of scum clogging in the mold

Spray Method

Thin and uniformly coated surface
-> Hard for lubricant scum to occur

Application Example

wls_sprayPin point
-> Reduce wasteful consumption of lubricant through accurate application

Coating System

wls_spray-systemBottle supply
-> Easy initial make-up of electrolytic bath for single liquid and easy management of liquid


We would like to introduce testimonials of customers who have employed MACOHO’s WLS (wet blasting + water-based lubricant application) equipment.

“Inline processing has doubled the service life of the dies.”

We originally introduced WLS to replace bonderizing and reduce work-in-progress (WIP) inventory. We knew that WLS creates optimal base surfaces for lubrication, but the significantly extended dielife also significantly reduced the die costs.

〈Key points〉

  • Improved lubricant film surface conformance by fine irregular texture of lubricant base.
  • Reduced forging pressure by feeding workpieces into the press machine while the workpiece temperature is kept at 50 to 60°C.

“WLS realized single liquid lubricant application, which we had given up on.”

We were looking for an alternative to bonderizing for in-house production of our products. We tested various white-colored lubricants on the surface after shot blasting for scale removal, but galling occurred. When we had no choice other than black-colored lubricants, we came across WLS and tried it. The first try was very successful. The difference in base treatment was astounding.

〈Key points〉

  • Improved lubricant film surface conformance by fine irregular texture of lubricant base.
  •  Process shortened by simultaneously performing scale removal after annealing.

“Defects due to clogging of the die are reduced.”

WLS was introduced to us when we were in trouble because we couldn’t find any bonderizing treatment provider that could deal with various materials. In addition to lubrication pretreatment by wet blasting compatible with a variety of materials, another reason for introduction of WLS is the spray coating method, where control of single liquid lubricant application is very easy. Since a thin and uniform film can be formed, the frequency of mold cleaning can be greatly reduced, resulting in molded products with fine finish.

〈Key points〉

  • Thin and uniform liquid lubricant film formed by spray coating.
  • Pretreatment by wet blasting regardless of workpiece materials.