Surface Quality of Heat-Treated Steel Rebar
Heat-treated steel rebar is widely used in the construction industry for its strength and durability. Rebars are made from reinforcing steel that is heat-treated in order to give the metal greater strength and ductility. Heat-treated rebar is known for its long-term durability and is often used in buildings and infrastructure in order to ensure that it can withstand the rigors of its intended use.
The quality of the surface of heat-treated steel rebar can affect its strength, fatigue resistance, and overall durability. The surface quality of heat-treated steel rebar is governed by GB 13014-1991, which describes the acceptance criteria for heat-treated steel rebar.
The first criterion addressed in GB 13014-1991 is the porosity of the steel rebar. The criteria state that there should not be any more than 10 pores per 10 cm2 of surface area. In addition, the pores that are present should be favorably distributed; meaning that there should not be any clusters of pores in any single area. The next criterion addressed in the standard is surface defects. The criteria for surface defects are fairly straightforward and state that no major mechanical defects or annealing or hardening cracks should be present on the surface of the rebar.
The third criteria addressed in GB 13014-1991 is that of surface roughness. In these standards, the roughness of the surface of the steel rebar is measured using a profilometer. The standard states that no more than 3% of the total surface area should have a surface peak-to-valley (P-V) distance of 0.4 μm or higher, and there should be no peaks with a P-V distance of 1.6 μm or higher.
The fourth criterion addressed in the standard is the hardness of the surface of the steel rebar. This is measured using a Shore Hardness durometer, and the criteria state that no more than 3% of the total surface area should have a hardness greater than HRC 70HV. The last criterion addressed in the standard is the bending of the rebar. The criteria state that the rebar should not have any major bends and the bends should not exceed 5 millimeters in any direction.
In conclusion, GB 13014-1991 defines the acceptance criteria for heat-treated steel rebar. The surface quality of the steel rebar should be such that the steel has no more than 10 pores per 10 cm2 of surface area, no major mechanical defects or annealing or hardening cracks, a P-V surface roughness of no more than 3% of the total surface area being 0.4 μm or higher, a hardness of no more than 3% of the total surface area greater than HRC 70HV, and no bends exceeding 5 millimeters in any direction.
