Heat Treating 1022 for Impact Resistance

If it's a brittle failure, anneal the part after heating in a water bath instead of annnealing in air to improve ductility.

That's interesting. I would not have thought 100 degrees C hot enough to anneal steel. What kind of annealing time do you expect would be required at this temperature, Wrench?

Have you tried cooling first, omitting the water spray
& asociated surface quench?
Maybe sandblast the scale after cooling?

Good suggestion, Pragmatist, but it is desirable to have a moderate coating of mill scale to provide weather resistance. Also the cost of an additional labor-intensive operation like sandblasting is not acceptable. But thanks for your input! -Bill Morrow

What is the heat treatment? What is it really doing for you in this low carbon steel? What is the section thickness? Are you starting from cold drawn or hot rolled steel? 1)There is such low hardenability in this steel, that I suspect all you are doing is refining the grain with your undescribed heat treatment. It is possible that you might be getting a slightly harder case hardness on the surface, but that doesn't help your impact issues- especially on small diameters/sections. 2)Impact property wants toughness not hardness. Mock carburized 1/2 inch section I have 14 ft lbs izod data at room temperature. 3)Annealled (Softened) 1022 should be in the 89 ft lb range at room temp for izod test, I expect it would pass Charpy at 15 at zero degrees. 4)My guess is heat treat is making your project worse, not better. What is the designer trying to accomplish with the heat treat? 5)Boiling will not anneal the parts, it will however "age" them, altering slightly %EL and % RA. This is often done to "assist" borderline samples for tensile testing where minimum ductility is specified. 6)After "hardening" by heat treatment, 400 degrees is the minimum effective tempering temperature. to temper back the martensite created by the quench. Milo

Hi Milo. Thanks for answering my post. You asked: "What is the heat treatment? What is it really doing for you in this low carbon steel?" The heat treatment described in my post helps the part pass the bending test but admittedly does little to improve fracture toughness. You asked: "What is the section thickness?" These are 3/4" dia. heavy duty fasteners. You asked: "Are you starting from cold drawn or hot rolled steel?" hot rolled You asked: "What is the designer trying to accomplish with the heat treat?" Our contract specifies the product pass the two tests described plus a tensile test (70,000 psi). Our market is highly competitive. Any significant cost increase in material or processing will take us out of competition. The heat treatment is intended to bring each item to the same normallized state (having undergone deformation in manufacture), clean off the excess scale (which cools the part to around 800-900F), and cool it down before any grain growth develops.

Here are the issues that I see: 70,000 psi tensile is not routinely acheivable in hot roll 1022. SAE J 1397 shows tensile of 62000 psi for 1022 hot roll; 69,000 for cold drawn. If you use these as an "average" for each condition, then you might get to 70,000 with cold drawn sometimes, but not as a routine realisable process. Normalizing might give you a boost of 1 or 2 ksi, but you're on thin ice here. (there is enough section thickness to prevent the section from 'air quenching' in addition to insufficient carbon.) Normalizing will not substantially boost ductility, though, annealling will; but annealling will certainly lower tensile strength. The 70,000 tensile callout is unusual, Take a look at SAE J429 look at Grade 2- That anticipates up to .55 carbon to get similar properties- without heat treating. For bending, such as U bolts, 1522 or 15B22 or 1541 are often used for ubolt applications- these typically do not need 'thermal treat' in order to accomplish bend. The issue in many bend failures is the radius of the bend as a multiple of section thickness. I can bend a 2 X 4 to a 100 foot radius, I can't bend it to a 2 foot radius without adding steam etc. Radius as function of thickness is issue. You might want to look in machinerys hand book for a discussion of bending allowances. How a heat treat cleans off scale is beyond me- the danger that I see is that you would develop an complex onion skin three phase scale by heat treating hot roll with Scale already on it. Milo

Dear Sir,

wht i feel is that you should do nitriding process .

slow heating of the part with nitrogen .

Rgds

Sandeep Bhanushali

omegates@yahoo.com