Transporting Steel Bars VS Magnetic Pickup

[met1]

Has anyone delt with, or heard of, 10 to 15ft long high speed steel bars picking up or becoming magnetic during transport from one facility to another? I'm being told that when a truck load of these bars leaves the distribution center they are checked for magnatism, on the truck, and it is not present. When they arrive at our facility they are checked again and some bars are magnatized. Sometimes the whole bar and other times just one end.

Is this possible and what is the mechanism?

 

[hacksaw]

the phenomena has been observed for over 400 years.

it is partly a shape effect, partly due to the presence of a geomagnetic foield and partly due to magnetostriction

there are commercial demag. units available.

 

[met1]

Hacksaw,

I appreciate your response but I'm not sure what is actually happening here.

I'm assuming you are saying there are geomagnetic fields, that if a truck load of steel bars passes through them, they can induce a magnetic field in the bars? Long round bars would probably more susceptible? How would magenetostrictive properties relate to the problem?

I'm familiar demaging. Any suggestions on prevention?

Thanks in advance!
met1

 

[hacksaw]

when you flex a ferromagnetic rod in the presence of an external field, it will magnetize. heat and mechanical
handling will accomplish same. magneto-striction, or more correctly its inverse form is measure of the coupling between the mechanical deformation and the magnetic properties.

whether the rod or bar remains magnetized depends on your carbon content (plus many other factors) and degree of work hardening.

you mentioned high-speed steel rods. they are very susceptible to retaining their magnetism. you can plan on about six man months of work to sort out the details, good luck in advance...