qualitätsanforderungen an kritische verbindungselemente einer...

21
Ach, nureineSchraube! NureineSchraube? Qualitätsanforderungen an kritische Qualitätsanforderungen an kritische Verbindungselemente einer WEA Meinert Hansen, 21. WINDENERGIETAGE 13.-15.11.2012

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Ach, nur eine Schraube!

Nur eine Schraube?Qualitätsanforderungen an kritische Qualitätsanforderungen an kritische

Verbindungselemente einer WEA

Meinert Hansen, 21. WINDENERGIETAGE 13.-15.11.2012

Wind Turbine 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

Nacelle fasteners

DIN912: M16-M48

Quality 8.8, 10.9, 12.9

Surface treatment: HDG, Zinc flake

Wide range of studding (M16-64) according to standards or customer specification

Quality: 10.9

Surface treatment: HDG, Zinc Flake

Blade bolt kits

TÜV approved construction bolts for the tower: EN 14399 (DIN 6914/15/16) range from M12-M64

Quality 10.9

Surface treatment: HDG

Tower flange bolts

Treaded rods for foundation in range from M16-52.

Quality 8.8

Length: Up to 6000 mm

Surface treatment: Black or with HDG

Foundation kits

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

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

Quality = Full control in every step

Hot forging & robot handling

Machining&

Threading

Quenching &

Tempering

Raw material & supplier

control

Cleaning &Surface

treatment

Packaging &

Distribution

Final quality verification

12/11/2012 8

Raw material inspection

• Own material standards is always used

• Material certificate from steel mill

• Alloy composition verified with spectrograph

• Dimensional inspection• 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

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

12/11/2012 10

Machining and threading

• SPC and MPC control

• Automatic SPC control in

new machines – data

storage

• In line dimension control by • In line dimension control by

operator

• Calibrated inspection tools

• Only use of upper 75% of

thread tolerance to ensure

tight connections

12/11/2012 11

Quenching and tempering

• Quenching and tempering-temperature 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 classtype 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

12/11/2012 12

Cleaning and surface treatment

• Mechanical cleaning introduced for all 10.9 products above M27

• No pickling means no adding of hydrogen during the process

• Temperature controlled Hot • 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

12/11/2012 13

Final quality verification• 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.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 10204

12/11/2012 14

According to ISO 898-1:2009:Additional material requirement for bolts with d≥16mm:Impact strength test at -20°C, min. 27 Joule.

Low temperature ductility

12/11/2012 15

Typical DF-values for 8.8 exceeds 80 Joule at -20°C

Typical DF-values for 10.9 exceeds 30 Joule at -20°C

Hardening capability exceeds 6 sigma!

CTQ 2: Tensile Strength

Rm [N/mm²]

1000,000

1050,000

1100,000

1150,000

1200,000

Dat a

4 Sigma LCL

4 Sigma UCL

Target

LSL

USL

Brinell Hardness [HB]

280,000

290,000

300,000

310,000

320,000

330,000

340,000

350,000

360,000

370,000

Dat a

4 Sigma LCL

4 Sigma UCL

Target

LSL

USL

Ultimate tensile

strenghtHardness

12.11.2012

950,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

# of pa r t s

270,000

280,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

# of pa r t s

CTQ 1: proof stress

Rp 0.2 [N/mm²]

0,000

200,000

400,000

600,000

800,000

1000,000

1200,000

1400,000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49

# of parts

data

poin

ts

Data

4 Sigma LCL

4 Sigma UCL

Target

LSL

USL

Yield

strength

Packaging and distribution

• Manual packing of large bolts

• 100 % visual inspection

• Control of straightness and surface quality

• Bolts packed according to customer requirements:customer requirements:– O-rings

– Nuts and washers

– Protection sleeves

• Zero-failure products!

12/11/2012 17

Dokka Fasteners

When safety matters!

Thank you for your attentionThank you for your attention

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 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

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,

ProcessingProcessing

– 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 200-230°C for min. 4 hours to reduce the hydrogen level

The amount of hydrogen from the process is cumulative!

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 processesInternal 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