Zinc-coated steel for press hardening applications and method of production
AssigneeAK Steel Properties, Inc.
InventorsRalph Mutschler, Grant Thomas, Paul V. Janavicius, Luis G. Garza-Martinez
Life of this patent
Estimating the term…
Abstract
A zinc-coated steel may be produced by performing a pre-alloying heat treatment after galvannealing the steel and prior to the hot stamping the steel. The pre-alloying heat treatment is conducted at a temperature between about 850° F. and about 950° F. in an open coil annealing process. The pre-alloying heat treatment allows for shorter time at the austenitization temperature to form a desired α-Fe phase in the coating by increasing the concentration of iron. This also decreases the loss of zinc, and a more adherent oxide exists after hot stamping.
Claims12
A method of producing steel, the method comprising the steps of:
- galvannealing the steel to form a coating comprising Zn—Fe—Al on the steel, wherein the step of galvannealing includes heating in a galvannealing furnace at a temperature of 900 to 1200° F.;
- pre-alloying said galvannealed coating to increase the Fe content in the coating, without any additional coating step, using a pre-alloying heat treatment, the pre-alloying heat treatment is conducted at a temperature between about 850° F. and about 950° F. prior to hot stamping, wherein the steel is subject to the pre-alloying heat treatment for a treatment time, wherein the pre-alloying heat treatment is performed using an open coil annealing process with a dwell time of about 2 hours or more while the galvannealed coating is in an as-coated condition;
- and
- determining the treatment time of the pre-alloying heat treatment such that the Fe content in the coating is between 15 wt % and 25 wt % after the pre-alloying heat treatment.
Dependencies are inferred from the claim text.