steels are quenched and tempered to match tool steel properties, the
selection and heat treatment recommendations critical.
What is hardness? The
resistance of the metal or the weld to penetration. Hardness is related to the
strength of the metal. A good way to test the effectiveness of the weld procedure
after the weld and heat treatment is complete, test the hardness of weld and
the base metal surrounding the weld.
all tool steels the first weld consideration should be does the weld require the
same hardness as the base.
Is the metal to be welded in the annealed or hardened condition.
lowest possible weld current, (smallest electrode diamaeter)
weaves use stringer beads.
each weld after completion,
parts are clean.
excess joint restraints.
What is Ductility? The
amount that a metal or weld will deform without breaking. Measured
on welds by the % of elongation in a 2 inch 51 mm test piece. An E71T-1 flux cored
electrode should result in a minimum of 20% elongation. An E70S--6 MIG weld should
produce approx 22%.
STEELS AND SMAW ELECTRODE DATA.
Electrodes most versatile weld process for tool steels.
3/32 2.5mm amperage 50 to 80 amps DCSP
1/8 3.2.5mm amperage 70 to 115 amps DCSP
5/32 4mm amperage 100 to 150 amps DCSP
tool and die SMAW electrodes use AC-DC Positive.
cored good for welds which benefit from high weld depositions.
TIG good for small precise welds.
What is Toughness? The ability of the metal or weld sample at a predetermined temperature to withstand
a shock.The test for toughness measures the impact of a pendulum on a notched
specimen. You may see that the required impact properties for the metal or
weld are 20ft-lbf @ -20 F (27 j @ -29C) reheat
at maximum pre-heat recommendation.
STEELS, PRE HEAT BASICS
Pre heat 900F (482C)
What is yield and tensile strength?. The
stress that can be applied to a base metal or weld without "permanent deformation"
of the metal. The "tensile strength". The ultimate tensile strength,
the maximum tensile strength that the metal or weld can with stand before "failure
steels preheat, for the weld stress relieve, machine harden temper.
STEELS AND PRACTICES TO AVOID CRACKING.