Ach, nureineschraube! NureineSchraube?

Transcription

1 Ach, nureineschraube! NureineSchraube? Qualitätsanforderungen an kritische Verbindungselemente einer WEA Meinert Hansen, 21. WINDENERGIETAGE

2 Wind Turbine Fasteners

3 Nacelle fasteners Hexagon bolts(m8-m64) according to standards including ISO 4014/17 and DIN 931/33 or customer specification Studs: M16-52 Rods: M16-52 DIN912: M16-M48 Quality 8.8, 10.9, 12.9 Surface treatment: HDG, Zinc flake

4 Blade bolt kits Wide range of studding (M16-64) according to standards or customer specification Quality: 10.9 Surface treatment: HDG, Zinc Flake

5 Tower flange bolts TÜV approved construction bolts for the tower: EN (DIN 6914/15/16) range from M12-M64 Quality 10.9 Surface treatment: HDG

6 Foundation kits Treaded rods for foundation in range from M Quality 8.8 Length: Up to 6000 mm Surface treatment: Black or with HDG Delivered with plastic shrink tube on part of rod that goes into concrete we even supply complete kits including anchor rings, all packed in containers ready for site-delivery

7 What is good quality? Why is consumers willing to pay 25% more for an Audi than they will pay for a Skoda with similar specifications? The difference is INSIDE! 12/11/2012 7

8 Quality = Full control in every step Raw material & supplier control Hot forging & robot handling Machining & Threading Quenching & Tempering Cleaning & Surface treatment Final quality verification Packaging & Distribution 12/11/2012 8

9 Raw material inspection Own material standards is always used Material certificate from steel mill Alloy composition verified with spectrograph Dimensional inspection Identification tag verification against documentation from supplier After approval is the material registered in ERP-system and released for production 12/11/2012 9

10 Robot assisted hot forging Product drawings on every item Repeatability 100 % reliability Temperature control Over temperature is scrapped Low temperature may be reheated once Dimension control by operator Calibrated tools Documented process data 12/11/

11 SPC and MPC control Automatic SPC control in new machines data storage Machining and threading In line dimension control by operator Calibrated inspection tools Only use of upper 75% of thread tolerance to ensure tight connections 12/11/

12 Quenching and tempering Quenching and temperingtemperature is 100% registered and documented for each steel batch Data kept for minimum 20 years Temperatures are set according to type of bolt, dimension and property class A hardening test from every steel batch is made prior to heat treatment of whole steel batch Vertical quenching to ensure straightness on long bolts More than 30 years of historical data 12/11/

13 Cleaning and surfacetreatment Mechanical cleaning introduced for all 10.9 products above M27 No pickling means no adding of hydrogen during the process Temperature controlled Hot Dip Galvanizing process Process is semi automatic and controlled by operator Zinc layer verified by operator New line fully PLC-controlled including optical inspection 12/11/

14 The final test is a verification of the process stability All process data stored Every batch has 100% traceability and are marked with a unique batch no. All batches are inspected according to product specifications and customer requirements Issue of 3.1 or 3.2 certificates acc. to EN Final quality verification 12/11/

15 Lowtemperatureductility According to ISO 898-1:2009: Additional material requirement for bolts with d 16mm: Impact strength test at -20 C, min. 27 Joule. Typical DF-values for 8.8 exceeds 80 Joule at -20 C Typical DF-values for 10.9 exceeds 30 Joule at -20 C 12/11/

16 Hardening capability exceeds 6 sigma! Ultimate tensile strenght Hardness CTQ 2: Tensile Strength Rm [N/mm²] Brinell Hardness [HB] 370, , , , , , , ,000 Dat a 4 Sigma LCL 4 Sigma UCL Target LSL USL 330, , , ,000 Dat a 4 Sigma LCL 4 Sigma UCL Target LSL USL 1000, , , , , # of pa r t s # of pa r t s Yield strength CTQ 1: proof stress Rp 0.2 [N/mm²] 1400, ,000 data points 1000, , , ,000 Data 4 Sigma LCL 4 Sigma UCL Target LSL USL 200,000 0, # of parts

17 Packagingand distribution Manual packing of large bolts 100 % visual inspection Control of straightness and surface quality Bolts packed according to customer requirements: O-rings Nuts and washers Protection sleeves Zero-failure products! 12/11/

18 Dokka Fasteners When safety matters! Thank you for your attention

19 What is hydrogen embrittlement? Hydrogen may lead to brittle fracture in high strength bolts Hexagon head screws and bolts in 10.9 or 12.9 qualities above 320 HV Case hardened thread forming screws and chipboard screws are also sensible Caused by absorption of atomic hydrogen in the steel Hydrogen is highly mobile and travels toward areas with the highest stress concentration The fracture occurs where the deformation is high The hydrogen enters at minor cracks and surface discontinuities In the transition zone between head and shaft In the transition from the thread run-out to the shaft Most commonly seen on dimensions smaller than 5 mm or larger than 30 mm. Characteristically indications of hydrogen embrittlement There is usually no elongation of the bolt material after fracture The fracture occurs during mounting or within 24 hours The failure load level is usually lower than the yield strength It happens suddenly without any advance warning The dark areas are brittle areas where the fracture has initiated

20 Where does the hydrogen come from? Raw material Through the hot rolling of bars folds and inclusions in the material must be avoided Temperature control during rolling Homogeneous structure in the raw materials ensures consistent quality of the final products. Impurities in the raw material especially sulphides, Processing Temperature control during hot forging Pressure and lubricant control Controlled temperature and time during hardening and tempering The pickling process is typically made in 8-16% hydrochloric acid Inhibitors are used to minimise the formation of hydrogen. Post baking at C for min. 4 hours to reduce the hydrogen level The amount of hydrogen from the process is cumulative!

21 What actions are taken at Dokka Fasteners? External processes Investigations made with Det Norske Veritas in Høvik in 2004 showed that the concentration of hydrogen was higher in the centre of broken bolts larger than M30 than the material close to the surface even though the bolts where hot dip galvanised. De-gassing is performed in the furnace at the steel mill prior to the hot rolling of bar or Baking is done at the steel mill after hot rolling of the bars at 650 C in 32 hours prior to processing at Dokka Fasteners Internal processes Equipment for structural analysis of steel bars has recently been installed in our laboratory Batch level inspection to validate grain size, homogeneity and impurities. The forging temperature is verified individually prior to forging The entire heat treatment process is computer controlled and all data is collected as documentation Mechanical cleaning prior to hot dip galvanizing eliminates the largest contributor of hydrogen Pre-loading test randomly performed on finished products according to ISO 15330