History, background. l May. Peter Robertson shipwrecked outside Gothenburg, starts a forge, later the city forge.

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2 History, background l May. Peter Robertson shipwrecked outside Gothenburg, starts a forge, later the city forge. l 1851 David Robertson (grandson) starts D Robertson Mek. Verkstad (e.g. agricultural and steam engines). l 1900 Three years after the introduction of the diesel engine D. Robertson patents a hammering machine for piston rings. The first specialist company for piston rings. l 1948 Daros moved to new premises in Partille,

3 1999 Daros moves to new high tech facilities in Mölnlycke, Gothenburg.

4 Product Development l An area of priority l 4 % of the total turnover l Development work in close co-operation with the customers

5 Piston Ring Development 2-Stroke Engines Gas-Tight Top Ring Wear Resistant Coatings Compact Graphite Irons Running in Coatings Running in Profiles Alloyed Materials Traditional Cast Iron

6 Piston Ring Dynamics 7 times Ring lifetime today: rh = km DAROS Goal: rh

7 Manufacturing of Piston Rings. What to think about! l Pressure on liner-wall. Ring tension. ( 0,4-0,6 bar ~ f = 7,5-12 %) l Mounting and fitting on the piston. l Formability in the liner. l Wear resistance l Fatigue limit l Heat conductivity l Corrosive protection l Running in l Gas distribution in ring-pack. (9 x Radial thickness [a]) (E-module) (Hardness + geometry) (Material structure) (Graphite shape and size) (Material inhibitors) (Coating material and thickness) (Lock type)

8 Piston Ring production Negative Ovality Negative Ovality without end pressure Zero Ovality

9 Ring Gap / Ovality. Change of wall pressure distribution due to Diameter reduction Warm (and worn) Liner, warm ring = Large Ring Gap Cold Liner, warm ring = Small Ring Gap

10 Changes due to wear Zero Ovality Negative Ovality Negative Ovality without end pressure New ring Time Used ring

11 Pressure in ringpack... P1 - P2 (bar) P2 P1 / 2 P P2 Wear (mm) 3 2 1

12 Running in Taper faced rings in different positions during the stroke. Normal rings in different positions during the stroke. Liner wall

13 Taper Running in l Taper clearly visible on ring 1 & 2 l Rings 3-5 are without taper.

14 Wear and Ring-gap! Linerwear (mm) Increased ring gap (S01 - mm) s Ringwear (mm) The ring gap is increasing 6,2 mm with every mm of wear on the liner or the piston ring. The increased blowby in the gap causes a different pressure and heat distribution over the ring pack. It is advisable to measure the ring gap during a scavenge port inspection to get an idé of the wear intensity. S01

15 Cast iron l Has been used for piston ring material in more than 100 years l Excellent wear resistance combined with sufficient strength l Cost effective Pot-casting

16 The structure of cast iron for piston rings l Graphite - Size, distribution and geometry l Matrix - Pearlitic 1X100 l Hardface - Steadite, cementite & carbide distribution in matrix. 1X500 1X25

17 Improving the properties Alloying elements Piston Ring material Molybdenum Copper Chromium Manganese Vanadium Etc etc. Metallurgical treatment materials

18 Graphite l Without the graphite, the grey iron is actually a Steel-like material. l The shape and size of the graphite gives the Iron it s properties. Lamellar graphite Blunt edged graphite Vermicular graphite Nodular graphite

19 Different graphite types Lamellar graphite Compact graphite Nodular graphite

20 Bending Strength N/mm RAK RS C8 RM3 RM4 RM5 RVK DARCAST RSG Ordinary lamellar graphite Blunt edged lamellar graphite Compact graphite Nodular graphite

21 Impact / Fatigue resistance Impacts RAK RS C8 RM3 RM4 RM5 RVK DARCAST Ordinary lamellar graphite Blunt edged lamellar graphite Compact graphite

22 Soft Coatings Radial ring wear Wear pattern for soft coatings. Maximum wear Coating thickness Running hours Coating thickness

23 Hard Coatings Radial ring wear Prolonged interval Maximum wear Uncoated castiron ring Cast iron after coating is worn off Wear pattern for hard coatings. Coating thickness Coating Running hours Coating thickness

24 Different types of Coating Soft Coatings. (For running in purposes normally thin, soft coatings are used. Copper 0,15-0,25 mm Soft running-in coating Graphite 0,05-0,1 mm Soft abradable running-in coating Alu-Coat 0,2-0,3 mm Semi-soft running-in coating Hard Coatings. (Coatings used to reduce wear are normally made thicker.) Plasma 0,1-0,6 mm Anti-scuffing wear resistant coating Hard Chrome 0,2-0,3 mm Wear resistant coating Ceramic Chrome 0,2-0,3 mm Wear resistant coating with improved thermal stability.

25 Ceramic chromium 1:100 1:100 Ceramic Chromium. Etched photo showing primary cracks and ceramic layers. Ordinary hardcrome without multilayers.

26 Normal Wear l Piston rings: 0,1-0,35 mm/1000h l Cylinder liner: 0,05-0,10 mm/1000h

27 Traditional measuring limits Liner S - P F-A S - P F-A 2 mm 1,5 mm 1mm 0,5 mm Piston ring 0,25 mm 2 1 mm Light between wall and ring due to ovality or deep spots. Deep spots in liner due to temperature differences or from poor distribution of cylinder -oil. Normal wear in upper part

28 Wear types l Mechanical wear l Corrosive wear l Abrasive wear

29 Mechanical wear Severe mechanical wear. High temperature and friction causes a welding effect on the surface material.

30 Corrosive wear 1:50 Severe pitting caused by corrosion. Small particles are eroded out from the base matrix. 1:3000

31 Abrasive wear 1X100 Severe abrasive wear. Small particles scratch the surface. To the right, a hard pareticle in the base material have stopped the abrasive wear. 1X1000