THE STRENGTH OF HOT-DIP GALVANIZED HIGH STRENGTH SCREWS

ZUM FESTIGKEITSVERHALTEN FEUERVERZINKTER HV-SCHRAUBEN

HV SCREWS OF STRENGTH CLASS 10.9 (41 CR 4) ACCORDING TO DIN 6914 TOGETHER WITH NUTS OF STRENGTH CLASS 10 ACCORDING TO DIN 6915 AND WASHERS ACCORDING TO DIN 6916 WERE EXAMINED. THE CLEARANCE BETWEEN SCREW AND NUT THREADS NECESSARY FOR APPLYING THE ZINC LAYER WAS ATTAINED BY MEANS OF TWO DIFFERENT THREAD COMBINATIONS: DUE TO THE INCREASED TOLERANCE FOR THE SCREW THREAD (ACCORDING TO DRAFT DIN 267 SHEET 10) AND A CORRESPONDING TOLERANCE FOR THE NUT THREAD (SIMILAR OE STANDARD E 4015). THE NOTCH IMPACT STRENGTH WAS NOT REDUCED BY HOT GALVANIZING. THE MAX, LOADING CAPACITY OF HOT GALVANIZED HV JOINTS IS REDUCED ONLY BY ABOUT 2 % DUE TO THE INCREASED CLEARANCE NECESSARY FOR HOT GALVANIZING, COMPARED WITH THE SAME TYPE OF SCREWED JOINTS WITH NORMAL THREAD CLEARANCE. THE DIFFERENCES IN THE LOADING CAPACITY OF SCREWED JOINTS WITH THREAD CLEARANCE ACCORDING TO DRAFT DIN 267 SHEET 10 AND ACCORDING TO THE OE STANDARD ARE INSIGNIFICANT. A SUITABLE LUBRICATION OF HOT GALVANIZED HB BOLTS IS NECESSARY FOR ASSEMBLY (EG USING MOS2. THE FATIGUE STRENGTH OF HOT GALVANIZED HV SCREWS 10.9 IS ABOUT 16 % LOWER THAN UNGALVANIZED HV SCREWS. WITH VIBRATIONAL STRESSING THE DROP IN INITIAL STRESSING FORCE FOR HOT GALVANIZED HV JOINTS IS NOT SIGNIFICANTLY GREATER THAN FOR UNGALVANIZED JOINTS.