forgemaster Posted June 13, 2012 Share Posted June 13, 2012 I just went and ran 4140 in Matweb and looked at 4140 100 dia oil quenched as per the book, and 4140 normalised in still air. Oil quenched and tempered to 580 deg C came out at 235Hb normalised came out to 241Hb, so giveing a higher hardness as normalised then as HT. How does the cake recipe hold for that one. Phil Quote Link to comment Share on other sites More sharing options...
ciladog Posted June 13, 2012 Share Posted June 13, 2012 "But but but isnt 4140 an oil hardening steel" says I. "Yes essentially but in larger sizes etc etc you will not get a quick enough quench to get the required hardness using oil". "Hence we quench in water, in fact our water has a small amount of polymer in it so it probably quenches a little bit quicker than straight water". I suspected your success had something to do with the size and mass of the piece and getting the core temp down quickly. I don't think I will ever have to HT something out of 4140 where the size would require a water quench but I will keep it in mind. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 13, 2012 Share Posted June 13, 2012 The Books generally cite the exact size their charts were based on, The Experience helps modify the givens for your specific case. We often have this issue in knifemaking, only in reverse! The process cited for a 1" cube may be way too harsh for a 1/8" blade and it's well known that for such blades you usually slip one or even two suggested quenchants towards gentler so a water hardening steel may harden quite well in oil and an oil hardening steel in air. Quote Link to comment Share on other sites More sharing options...
MOblacksmith0530 Posted June 20, 2012 Author Share Posted June 20, 2012 I don’t know how many times I read heat treat posts and responses and say to myself “what the hell could these people be doing to achieve or not to achieve these results they talk about?”.Heat treatment is a process. 1) get it hot. 2) quench it. 3) temper it.Times, temperatures, quench media, checking methods, etc etc etc depending on what kind of resources you have available will produce results directly coinciding certain parameters getting met.In other words, if you didn’t get results, some parameters didn’t get met.4140 will harden in oil. Maybe not with the way some of you perform the process, but rather with a process where certain parameters are “met”.Down on the farm, in the garage, and in an industrially equipped heat treating facility can all have shortcomings as far as results go. But to outright say “that doesn’t work” or “regardless of what written specifications say” is a belittlement to some people who have spent large percentages of their lifespan in the specific industry. Your results in heat treatment are a reflection of “your” process, not “THE” process. Use what works for “YOU” because your shortcomings reflect on how “YOU” do your heat treatment, not how the world should do theirs. Spears. I realize that there are experts out there in the world that know more than I. I don't begrudge them their knowledge or their facilities and equipment. I know what processes I have used in the past and how to duplicate those processes. about 60 or 70 hand hammers made of 4140 will attest that my process worked around 60 or 70 times. I have not had one come back for a failure with one exception and that was my own hammer. I have also heat treated 4140 in oil and tempered to 450 f just like the books said (I use an IR non contact thermometer) and it did not stand up it did not get hard enough for even a light file test and under use room temp mild steel would easily mark it. I then redid the heat treat using my methods with water and again tempered it to 450 and it has held up amazingly well without chipping or cracking. I posted this to see if anyone else has had a similar experience that might have pointed out something that had not occurred to me, that might have been at fault. I guess that the consensus seems to be from some here that there are too many variables to be able to heat treat 4140 in the home shop. Restating the difficulties in heat treating doesn't really help everyone here rather it may discourage some from trying things because it sounds too difficult. I will continue to heat treat thing to the tested methods I have done in the past (there were definitely failures before success). I Will get out my ASTM steel guide to check on known steels and their heat treat methods and go on my merry way. Quote Link to comment Share on other sites More sharing options...
Quenchcrack Posted August 11, 2012 Share Posted August 11, 2012 The variability within a 4140 steel from one heat to the next is sufficient to cause variations in hardness if the same procedure is used every time. Variations from the top of the ingot to the bottom can do the same. This is due to the natural segregation of the alloys during solidification. Heat treaters usually demand the mill test reports on steel when large tonnages are involved. They generally make subtle adjustments to their process based on the actual chemistry. Even then, not every piece will be the exact same hardness. When I hear that someone has a process that works, I say stick with it. You have the major variables under control and small variations, while having a predictable effect, are not affecting the performance of the product. That's what good engineering, and smithing is all about. Quote Link to comment Share on other sites More sharing options...
Patrick Nowak Posted August 13, 2012 Share Posted August 13, 2012 Heat treating would be a science and would be very predictable if we knew all the variables and controlled them, but in actual practice this doesn't happen much. As Quenchcrack noted, there are variations from heat to and and within a heat compositionally. In addion, there can be variatoins in surface finish-as, forged vs machined prior to quenching. Then there are the subtle things like quenching multiple pieces at one time and a single piece the next time you get the job. How does having multiple pieces in the quench tank change the fluid flow and heat transfer characteristics during the quench? What happens if you have a big furnace load and the quench operator is using a fork lift to transfer parts from the furnace to the quench tank? Does he always take only a single load on the truck to the tank and then start is his quench or does he grab a load, put it on the quench tank elevator and get a second batch of parts before quenching? (Note that I deal with 2 tanks at work both with 50,000 gallons of quench media and a capacity and 50,000 lbs each). Additional consderations are things like parts with multiple cross secotions of significantly different size. I could go on, but the point is that though heat treatment is in simple terms the change of phase by thermal processing, the variables that affect the basics are so widely varying that it is not nearly as simple as baking a cake. You usually can tell by the hardness or tensile results if you somehow mix metals, and cracking could also be a give away for this. Patrick Quote Link to comment Share on other sites More sharing options...
forgemaster Posted August 14, 2012 Share Posted August 14, 2012 Thankyou for giving us your word of experience Patrick I was hoping you would contribute, thankyou. Phil Quote Link to comment Share on other sites More sharing options...
Stormcrow Posted November 22, 2014 Share Posted November 22, 2014 My buddy Tobin Nieto and I heat treated a 4140 block anvil for him yesterday. 56 pounds of steel at over 1500 degrees. Much fun. :) Quote Link to comment Share on other sites More sharing options...
Stormcrow Posted November 23, 2014 Share Posted November 23, 2014 Tobin just added a quick rebound test video. He's going to build a "west Texas tree stump" for it, at which point it should be a real dandy. :) Quote Link to comment Share on other sites More sharing options...
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