Cold Blackening of pinion assembly in automotive industries

Cold blackening

1. SUZUKI SLEEVE REDDISH ISSUE & ACTIONS 20.06.2024

2. SUZUKI SLEEVE REDDISH ISSUE Problem Statement: Formation of reddish colour at forging area after hot blackening process of Sleeve. Around 50-60% components only found ok remaining having reddish issues. Blackening - Good Blackening - NG Reddish formation at forged area

3. SUZUKI SLEEVE REDDISH ISSUE Analysis details: 1. Audit done at Hot Blackening supplier M/s . Balambiga Industries, Bangalore and process parameters found OK Hot blackening trials with various process parameters carried out at M/s . Balambiga Industries. Still reddish issue not resolved. Hot blackening process tried at various sources like Delphi TVS, Export Blackening & VS Industries, Chennai. Still reddish issue not resolved. Root cause: 1. The reddish colour in the forged area is mainly due to the presence of MolyLube formed during the forging process. 2. In the forging process, the MolyLube embedded with the metal surface and this cannot be removed during the Hot Blackening process. 3. Even though it is not a rust, this seems to be reddish appearance only after Hot Blackening.

4. SUZUKI SLEEVE REDDISH ISSUE Actions & Results: 1. To overcome the reddish issue, Cold Blackening process tried . Hot phosphating introduced over cold blackening for better adhesion. Results found satisfactory. During Cold Blackening, the oxide coating covers over the Molylube coating thereby covering the reddish colour. Trial done for 500Nos and results found satisfactory. Zero rejection due to reddish colour formation in Cold Blackening process.

5. SUZUKI SLEEVE REDDISH ISSUE Alkaline degreasing Hot Blackening 1 DM Water washing DM Water washing Hot Blackening 2 Dewatering RP Oiling Alkaline degreasing Cold Blackening DM Water washing DM Water washing DM Water rinsing Hot Phosphating Water washing DM Water washing and RP Oiling BEFORE AFTER

6. REJECTION

7. 7 THANKS