I'd tested it before welding and it was nicely above 65 Brinell, which is what the car world generally regard as the limit for reconditioned car heads to be serviceable. I had previously checked this and several other heads and all the good ones were over that figure...but two were under that figure significantly...and both these had stripped holding down stud inserts ...just like this welded head. I've read so much about silicon aluminium alloys I now know more than any heat treater! The nearest alloy seems to be an old British type, LM9. These are high silicon, low (or no) copper alloys with significant additions of small amounts of magnesium and manganese to harden the alloy. They are certainly heat treatable, contrary to what some advised. It seems that they are probably strong enough in the as-cast condition for most purposes but can go soft with use and age...especially if they get 'cooked' in service, it seems. Two of mine are soft, as I previously said...and it was not welding that did it to them...they were considerably softer around the exhaust ports, indicating it was use that did it, not 'as made'. I managed to find an old reference book that lists the treatment procedure for LM9...it also says that if you stuff up the treatment times and temps (bar one) you can redo the treatment and recover it...and muck around till you find the correct one. That's nice, but at a quoted $200 per treatment...and with the race only a few weeks away I don't have that option available, I have to get it right first time. Treatment consists of "solution heat treatment of 520-535C for 2-4 hours, warm water quenching, then artificial aging, or precipitation, of 16 hours at 150-170C" ..and this will cost me $200!...wish I had an oven that would do the job. ************** It's been a while since this thread was active, but I've made some progress. The head ally has been analysed and it does not correspond directly with any current or older alloy types generally used for motorcycle heads. However, it is close to a couple of alloys for which I have found plenty of info so analysis was a worthwhile exercise. The welding industry recommendation/information on welding this type of alloy says it should not go soft, if it is not overheated during welding. I am told that weld preheat should be 150-190C then rested after several passes to bring the temp back under 200C. From comparison with alloys of similar composition (high silicon, low copper) it should be heat treatable, which is good. Why? Because being somewhat careful (anal?).... I tested several heads after selecting one to weld up I did this so that I could assess any softening that (mis)welding might produce, especially if the welder hurries the process, overheating the head. I discovered that 2 of the 6 heads in my possession are below the automotive repair industry's general recommendation that heads should have a minimum hardness of 65 Brinell. This is the only guideline I have been able to find, but it would appear to be appropriate enough for my purposes. It was interesting to note that the heads that had a roughly equal Brinell hardness of over 65 were the same no matter which part of the head was tested. The soft heads were noticeably softer near the exhaust ports. This type of head has 4 threaded inserts into which the holding down studs screw. Both the soft heads were old ones I picked up in boxes of parts and had the inserts pulled out of the alloy. Now I know why. It was not just that some ham-fisted 'mechanic' had overtightened the holding down studs, the bloody alloy was so soft the threads pulled out! The softest head also had loose valve guides, but none of the valve seats appeared to have hammered into the head, which is mazing because these motors have high valve seating pressure. ************** http://scholar.google.com/scholar?q=motorcycle +engine&hl=en&lr=&start=10&sa=N ******* No doubt there have been heads made from LM25 / 6060 ( or similar ) and HT'd - but this is the wrong material to use in the first place. The difference in the machining and mechanical properties of 6060 in it's various tempers is marked - whereas the more common head alloys are not so affected by temper. I suppose a vintage engine will be a bit of a lottery, certainly modern Japanese heads require no special weld procedures other than a bit of a warm up. I have seen many casting plants in China ( including Japanese parent companies ) and they certainly don't HT their heads. I have modified several of these and they machine beautifully before and after welding. ********************** Optimization of Al-Si cast alloys for cylinder head applications Feikus, F J One Hundred Second Annual Meeting of the American Foundrymen's Society; Atlanta, GA; USA; 10-13 May 1998. pp. 225-231. 1998 The development of novel diesel cylinder heads leads to a higher complexity of shape and occurring stresses during lifetime. This significantly increases the demands on strength, elongation and creep properties at elevated temperatures, for Al-Si cast alloys. Due to these requirements, an optimization and further development of existing cast alloys was motivated. Mechanical properties and physical data were investigated for various cylinder head alloys. These were the primary alloys Al-Si7-Mg and Al-Si9-Mg; furthermore, two new versions with 0.5 and 1.0% Cu, based on the primary alloy Al-Si7-Mg and, finally, two secondary alloys, Al-Si10-Mg and Al-Si9-Cu3. ****************** "The cylinder head is made of an aluminium alloy (in this case an A356 alloy) and locally experiences temperature cycles ranging from 20 to 300 °C. The ... " ********* The Al-Si alloy is a well-known casting alloy with high wear resistance, low thermal-expansion coefficient, good corrosion resistance, and improved mechanical properties at a wide range of temperatures. (356 was mentioned) These properties led to the application of Al-Si alloys in the automotive industry, especially for cylinder blocks, cylinder heads, pistons, and valve lifters. In the Al-Si equilibrium diagram, the binary eutectic or hypoeutectic alloys are characterized by good castability and corrosion resistance, while the hypereutectic alloys, such as 390 and 393, containing 15-25% silicon exhibit excellent wear resistance and low thermal-expansion coefficients (CTE); their machinability is improved as the silicon particles become finer and more evenly distributed. Strengthening these monolithic alloys is achieved by small additions of elements such as magnesium, copper, and nickel, which also bring about changes in other properties. For example, in hypoeutectic alloys, silicon provides good casting properties, and copper improves tensile strength, machinability, and thermal conductivity at the expense of a reduction in ductility and corrosion resistance. The 332 alloy, which contains higher silicon (approximately 9.5 wt.% silicon) and copper levels, is used in internal-combustion engines because of its thermal stability and lower CTE. These alloys selectively lend themselves to various foundry-casting methods and heat treatments, according to compositions and applications. While 319 can be used extensively for sand and permanent mold casting and 380 can be used for high-pressure die casting, both are supplied in as-cast temper. However, the strength and machinability of 319 can be improved by T6 or T5 heat treatments. Also, the age-hardenable Al-Si alloys containing magnesium (which produces the hardening Mg2Si precipitates) are cast in sand and permanent molds with excellent castability, pressure tightness, and corrosion resistance *********************** Liquid-Cooled Light Metal Cylinder Head Ruf, M A liquid-cooled light metal cylinder head for a reciprocating piston engine, having a combustion chamber wall separating the combustion chamber from a cooling liquid chamber, is made of a cast Al--B alloy of composition 2.5-4% boron, < 0.25% Si, maximum 0.5% other components and balance Al. The alloy has about double the thermal conductivity of conventional cylinder head alloys (i.e. 200 W/m deg C) so that a combustion chamber-side wall temperature of e.g. 180 deg C can be maintained (to avoid self-ignition of the fuel mixture) using the usual coolant temperature of e.g. 85 deg C without use of a special cooling circuit for the cylinder head. If a special cooling circuit is provided to give a coolant temperature of approx 45 deg C, then a combustion chamber-side wall temperature of approx 140 deg C can be maintained, thus reducing the knocking tendency so that higher compression and advanced ignition can be employed.--DCPI. ************************* Optimization of Alloys for Air-Cooled Aluminum Cylinder Heads by Means of Quality Control Testing Techniques Gobrecht, J; Babes, F Seventh International Light Metals Congress, Leoben/Vienna; Leoben/Vienna; 22-26 June 1981. pp. 208-209. 1981 Air-cooled cylinder heads are subjected to very high temperatures, in contrast to water-cooled cylinder heads. The demands made of the casting material are correspondingly high and special quality control techniques are required, to determine the optimal alloy and to monitor the commercial production. Primary criteria for determination of the suitability of a material for air-cooled, high-temperature cylinder heads are thermal resistance and creep strength. These two properties cannot be determined by standardized measuring techniques (hardness determination, tensile testing). A suitable and quick test for the determination of the pressure-creep strength is provided by the screw (bolt) test. The thermal resistance is examined on the basis of small test bodies and the complete cylinder head. The three methods are described. The extensive test results and alloys of the type G-AlMg4SiMn(Cu) are discussed. 6 ref.--Y.G.K.*. ************************** Development of Aluminum-Based Alloy Cylinder Head Strengthened Between Valve Ports by TIG Remelt Treatment Kanazawa, T; Miyake, J; Koyama, M; Oishi, S pp. 8, 1987 Surface remelt treatment by TIG arc was investigated for the partial strengthening of Al-based alloys. The mechanical properties, such as strength and toughness, and the thermal crack resistance of the treated area can be significantly improved by this treatment due to the structural refinement and the decrease in defects by the rapid solidification. Surface remelt treatment has been applied to the high power engine cylinder head of Al-based alloy for the strengthening of a portion between valve ports.--GRAI. **************************** Influence of Cu and Mg Addition on Mechanical Properties and Thermal Fatigue Life of Al-Si-Mg Cast Alloys for Cylinder Head. Moizumi, K; Tezuka, H; Sato, T Journal of Japan Foundry Engineering. 2003 As an attempt to optimize materials for diesel engine cylinder heads, the chemical composition and heat treatment procedure of Al-Si-Mg alloy were studied. The relation between additional elements and mechanical properties (tensile strength and elongation) was investigated on AC4C aluminum alloys containing additional Cu or Mg, and the optimum chemical composition was determined. In composition ranges within 0.6 mass%Mg or 1.0 mass%Cu, it was found that Cu or Mg addition increased tensile strength without deterioration of elongation, and also increased high cycle fatigue strength. However, thermal fatigue tests indicated that Cu addition affected thermal fatigue life. Especially thermal fatigue life markedly decreased with increasing plastic strain. In addition, excessive aging of Cu addition alloys resulted in increased thermal fatigue life. This is because the thermal fatigue life corresponding to plastic strain increases in excessively aged alloy. ********************** Microstructure changes of partial re-melting reinforced A319 alloy for diesel cylinder heads Kitamura, M; Liu, W-S; Tohriyama, S; Sato, T; Kamio, A ICAA-6: 6th International Conference on Aluminium Alloys, Toyohashi,Japan, 5-10 Japan 1998; pp. 309-314. 1998 Microstructures of A319 aluminum diesel cylinder head, which was reinforced by TIG re-melting method around the inter valve area, are investigated after actual engine durability test. Its microstructure changes are compared with separate soaking samples > 523K and also discussed in correlation with the result of thermo-mechanical fatigue test between 373K-523K. *************************** http://cdm.unipr.it/das2005/papers/111.pdf *********************** Optimization of the Aluminum Casting Alloy G-AlMg5Si1Cu in Regard to High-Temperature Creep Resistance Dichtl, H Air-Cooled Aluminum Cylinder Heads , pp. 1-12. 1982 Test results show that the high-temperature tensile creep resistance of the alloy Hy 511 can be decisively improved by both Cu and Mn. If the other properties are taken into account, then alloys with a high Cu content have the disadvantage that their ductility is very low and also that their corrosion resistance is likely to be poor. The electrical conductivity, and thus also the thermal conductivity, are somewhat increased, and this is advantageous for cylinder head alloys. Additions of Mn have almost no effect upon the ductility up to approx 1.3% Mn. This is an advantage compared to the Cu-rich variant. However, a disadvantage of the Mn-rich alloy for cylinder heads is that the electrical conductivity is very markedly reduced. The Mn-bearing alloys developed are also interesting from a different point of view. In the electrical industry there is often a need for castings with a low electrical conductivity. Up to now, such components have been produced using the alloy G-AlMg10, which is difficult to cast. A G-AlMg5CuSiMn alloy can be made which possesses a very low conductivity, approx 10S, and such alloys have considerably better casting properties. 9 ref.--AA. ********************* Trends for the cylinder heads Meyer, P H Alluminio e Leghe (Italy). Vol. 8, no. 83, pp. 49-59. Nov. 1996 The increased use and ongoing development of the aluminum cylinder head is prompted by increasing competition and tougher regulations about emissions and fuel economy that have challenged the automotive industry to develop more compact and efficient engines. The author discusses the importance of the metallurgical microstructure and the alloying elements, including the effect of Si, Cu, Mg, Sb, P, Ti, B, Zn, Fe, Mn and Ni on properties and microstructure during controlled cooling and annealing. Two main base alloy families compete for the cylinder head market: A356 type (Al-Si-Mg) and A319 type (Al-Si-Cu-Mg) alloys. The properties of the two alloys are compared. The High Performance Low Pressure (HPLP) of Montupet is described. The process uses a portfolio machine, low pressure metallic dies and a computer controlled process for cost and weight savings, reliability, high metallurgical quality, high output, quick mold exchange and easy mold accessibility. ********************** Application of Evaporative Pattern Casting Process to Sophisticated Aluminum Alloy Casting Lin, L C; Pan, G T; Huang, Y F Chukung (J. Chin. Foundrymen's Assoc.) , no. 37, pp. 1-14. June 1983 An evaporative pattern casting process is developed for trial manufacture of complex, close-tolerance C355 Al alloy cylinder heads of particular design using an expendable polystyrene pattern and dry unbonded zircon sand with vacuum assistance. Extensive studies on the application of the evaporative pattern casting process in making the cylinder head have shown tremendous advantages and application potential, including: no cores are required; coating is preferable but not essential for Al alloy casting with zircon sand mold; casting can be made to closer tolerances and deep fins as thin as 4 mm have been cast with satisfactory results; freedom to design the most effective layout for gating system. As a result of these advantages the evaporative pattern casting process offers a promising possibility to produce a casting of complex shape which is regarded as impossible by conventional bonded-sand casting techniques with reduced operative costs, reduced capital equipment costs, improved casting quality and cleaner, quieter working conditions. 15 ref.--AA **************************** Corrosion behavior of Al4 aluminum alloy hardened by CO2 laser radiation [Abstract Only] OPARA, B K; ANDRIYAKHIN, V M; VOLGIN, V I; BANDURKIN, V V Zashchita Metal , (MOscow). Vol. 21, no. 1, pp. 87-89. Jan.-Feb. 1985 The Al4 alloy, with a composition by weight of 9.5% Si, 0.30% Cu, 0.30% Mg, 0.20% Mn, 0.64% Fe and traces of zinc, is used frequently for complex and important parts that work under great loads, high temperatures and strong gas flows. Ways to increase normal operating life in V-block engines, where practice has shown regular failure of cylinder heads at the intake valves were studied. The cause of failure is traced to electronic effects which break down aluminum more rapidly than adjacent silicon. Test samples were given CO2 laser treatment at 7.5 to 8 MWT/sqm, causing melting to a depth of 1 mm. Other features of the laser process, as well as anode and cathode factors, are discussed. Results showed that as surface movement rate increased (and thus energy input declined), the rate of crystallization, homogeneity of the alloy and Si distribution all grew. A good correlation was noted between anode current flow density and cylinder head durability under test-stand conditions. ******************** Analysis of the Controlled Solidification Process of 1.6 L Cylinder Head Castings. (Retroactive Coverage) Sokolowski, J; Mazurek, J Transactions of the American Foundrymen's Society. Vol. 95; St. Louis, Missouri; USA; 5-10 Apr. 1987. pp. 373-376. 1987 The research and plant implementation program to improve the quality of cylinder head castings (319.2 alloy) made by semipermanent mold technology is presented. The role of the die bottom temperature on the cylinder head heavy bolt-boss porosity was determined. Calculations of the heat distribution during the solidification and cooling processes and the practical utilization of the technique used are given. Graphs. 2 ref.--AA(US). ****************************** Use of Aluminum in Cylinder Heads Bruni, L; Revello, P L Alluminio , no. 10, pp. 22-23. Oct. 1982 Silfer and Silgraf alloys, designed by AE Borgo of Alpignano (Turin), allow direct piston-head contact without additional surface treatment, thus having both economical and technical advantages. The new alloy Silfer contains 16-18% Si, 4-5% Cu, 4-5% Fe, 2-3% Mn, 1-1.3% Mg and 0.8-1.2% Ni. Results of recent experimental tests are given.--AA*. ******************** Portliner Cylinder Heads for Formula 1 Engine Wypior, R Aluminium. Vol. 65, no. 3, pp. 254. Mar. 1989 A 12-cylinder, 3.5 l vacuum engine is Lamborghini's latest contribution to Formula 1. The 80 deg angle engine weighs 162 kg and is extremely reliable even at > 12 000 rpm. Lamborghini allows for the extreme thermal load by the use of cylinder heads and whose outlet ports are lined with ceramic portliners made from aluminum titanite. The blanks for the cylinder head are sand cast from a special Al alloy (Nural G-AlSiCu) and weigh only 21 kg.--NFA. ************************ Michael, Sorry for confusion over my typo, the figure should have been Brinell 65, not 26. Things have been moving quite quickly here lately. My cylinder head chamber rework has stalled due to heavy work commitments (good news, .... I guess!) and our recent racing excursion resulted in more work due to the crankcase failure at the Easter meet. I also have orders for some replica 1962 Manx 4ls brakes and have been checking out the alloys used by my mate (who owns the patterns) and has built several sets of hubs/brakes over recent years. However, I recently found that locally, a few guys who have been casting heads, cases, hubs & wheels etc have been using AA601 (a form of LM25 or A356) with good success. This is a 6.5-7.5% Si, 0.3-0.4% Mg, Aluminium alloy....which is very similar to the ESO head composition, which has a higher Si and Mn content. According to "The Racing Motorcycle" by John Bradley "This material is known as a good all-round alloy commonly used for stronger engine castings.....with a Tensile strength of 230 N/square mm in the sand cast TF condition..........." Experience of several local guys shows it works okay for heads in race bikes. Depending on the success of the welded heads I might consider making a pattern so new ones can be cast rather than weld up the chambers, especially if I find such further experiments such as re-angling valves etc result in too extensive re-working of the old heads. Sure enough the ESO heads do go soft in service, it seems. As I might have mentioned before, I have several on the self with stripped threads and inserts that were found to be below the 'magic' 65 Brinell. The question is: were they ever heat treated correctly and were they ever hard? Or were they factory mistakes? The time/temperature criticality that causes over-aging has somehow been reached on these heads. (Maybe this is what happened in the factory?...the head would test ok but would go softer sooner in service?) So when I eventually get around to doing my own heat treatment (when the oven is finally re-furbished!) I will do the precipitation (age) hardening in stages as it is cumulative (I believe) I will heat, cool, test adn reheat as required until the 65 Brinell hardness is reached, I do not want to shorten the service life by getting close to over-aging the head before I get it on the machine! However, it was Ian D who wrote at some stage (if my memory serves me correctly) that: "No doubt there have been heads made from LM25 / 6060 ( or similar )and HT'd - but this is the wrong material to use in the first place. The difference in the machining and mechanical properties of 6060 in it's various tempers is marked - whereas the more common head alloys are not so affected by temper. LM25 is the wrong material to use for air cooled heads." I'm not sure what the '6060' material he mentioned is, but I certainly would not instantly disagree, as I know squat compared to him, of that I am certain.... but I would like to ask him what available (in Australia) alloys he would consider more suitable? Sure enough, AA601/LM25 can be as 'weak' as 130N/ squ mm in the as cast condition, 160 in the TB7 condition and up to 230 in the TF condition so one has to be careful of the treatment (and potentially short service life as an air-cooled head?) I need to learn more as regards what modern alloys are available locally for any new casting work I have done. I read what you passed on to me and it sparked memory of my question as to the significance of Mn in the mix. My head has 0.2% which is not insignificant, according to one tantalising snippet in one of your 'finds'. Evidently it can improve the high temp tensile creep resistance, but possibly at the expense of thermal conductivity. I would hazard a guess that this is important in an air cooled cylinder head. I need to find out more on this point as none of the other alloys that I have found that are close to the ESO composition have any Mn. For your interest, further info found on Al/Si/Mg alloys: http://www.tech.plym.ac.uk/sme/mech330/alcast1.htm I also found this, it 3explains the mechanism by which the Mg addition functions: "Heat Treatment of Aluminium-Silicon-Magnesium Alloys 356-360-355-LM9 The hardening agent is magnesium silicide, which contains about 63 parts of magnesium with 37 parts of silicon. However, the presence of this compound alone would give a composition with poor casting properties. For this reason, the magnesium silicide compound is used in an alloy with a rather large excess of silicon in order to obtain the casting advantages of the aluminum-silicon type of alloy. In 356-type alloy, the nominal silicon content is 7% and the magnesium approximately 0.35%. Thus, the actual magnesium silicide content is in the range of 0.5-0.6%. This type of alloy is the very best with respect to casting properties in either sand or permanent mold. In addition, in spite of the rather small content of magnesium silicide it develops very high tensile properties when properly heat treated and has excellent resistance to corrosion. A similar type of alloy sometimes used for die casting work is 360, containing approx 9.5% silicon and 0.5% magnesium. This alloy and an A360 modification of lower impurity content, have excellent die cast, test bar mechanical properties. However, they are handicapped by a rather pronounced tendency to stick in the die, thus causing some operational difficulties. For this reason, this alloy has not found as wide application in die casting as higher the 12% silicon or the 3.5% copper, 9% silicon type." It is a bit misleading sometimes when looking at 'equivalent' alloys around the world. This link shows the overlaps that occur when talking about 'equivalent' alloys as specified in different (country's) standards: http://www.zedlina.com.au/alum%20specifications1.htm You'll note that there are a heap of alloys that are 'equivalent' to LM25. Thanks Michael (and others) I appreciate the help and links that have been passed on to me....and I hope they continue. Regards, Greg ********* LM25-T6 is common for low volume heads, mass produced stuff is most likely one of these "self aging" alloys that the japs have made an art form. This self aging stuff is nice to machine, a little softer than LM25-T6, but still better than stuff older car heads were made out of. ( Often LM4 or similar - non heat treatable) Cheers, Ian ******************************** >So, This is the best alloy that you know of that is available for low volume >castings here in Oz Ian? I use LM25-T6 for everything I get done - it's a very good material, strong, good to machine and good to weld. You should really get it retempered if you weld it in T6 state, but a small weld only affects a small area, I usualy don't bother. BTW - make sure you use the right filler rod, the most commonly used GP filler rod won't temper up with the rest of the part. Cheers IAN ***************************** 90% of TIG & MIG wire sold is "5356" ( 5% Mg ), it is "general purpose", good for castings and wrought welding, but it will not temper up if you are getting castings HT'd after welding. It will also come out a slightly different color than the parent when anodised. If a foundary needs to weld up a blow hole or other void in LM25 / 6061, they will use a "4043" ( 5 % Si ) filler rod - it tempers up almost as well as the parent metal. >The castings I weld are have 9.55%Si and 0.31% Mg so maybe 4643 might be >better.... The closer you can get to the parent metal the better. Cheers IAN **********************