A device and a method for continuous temperature gradient heat treatment of a rod-shaped material are disclosed. The furnace body of the device includes an upper heating zone and a lower heating zone inside, which are independently controlled in temperature by means of an upper heating power supply and a lower heating power supply. Moreover, both the upper heating zone and the lower heating zone are closed heating zones. The closed heat insulation plates could prevent heat loss and ensure precise temperature control of the upper heating zone and the lower heating zone. In the device, a vacuum pumping equipment is included; an annular radiation screen is configured between the upper heating zone and the lower heating zone, and the rod-shaped material is not in contact with the annular radiation screen The rod-shaped material conducts one-dimensional heat transfer along the axial direction.

A stud-weldable rebar and a method for making the rebar are disclosed. The rebar has a steel body with a weld end and a diameter that is substantially uniform along a length of the body. A tip portion at the weld end includes a hardened zone and a base portion is formed of the remaining steel body. The hardened zone has a hardness that is about 1.5-3.0 times greater than a hardness of the base portion. Induction hardening is used to form the hardened zone.

In some embodiments, a coating applied to steel reinforcement bar (e.g., steel rebar) that could considerably extend the lifetime of concrete structures by reducing steel rebar corrosion is disclosed. The coating includes a thin, passivating steel (e.g., stainless steel) layer that is applied to the outside of conventional steel rebar. The coating can be applied in-line through metal cold spray manufacturing, which is a high throughput coating technique that can be integrated into existing steel manufacturing plants. Furthermore, a novel, high performance ferritic steel with tailored resistance to corrosion from chlorides is described. The new ferritic steel is distinct from other commercial and experimental steels, and is better suited for coating low-cost steel structures like rebar. Multiple alloying elements including Cr, Al, and Si will each form protective oxides independently, increasing the total amount of protection and extending it over much wider ranges of pH and electrical potential.

In some embodiments, a coating applied to steel reinforcement bar (e.g., steel rebar) that could considerably extend the lifetime of concrete structures by reducing steel rebar corrosion is disclosed. The coating includes a thin, passivating steel (e.g., stainless steel) layer that is applied to the outside of conventional steel rebar. The coating can be applied in-line through metal cold spray manufacturing, which is a high throughput coating technique that can be integrated into existing steel manufacturing plants. Furthermore, a novel, high performance ferritic steel with tailored resistance to corrosion from chlorides is described. The new ferritic steel is distinct from other commercial and experimental steels, and is better suited for coating low-cost steel structures like rebar. Multiple alloying elements including Cr, Al, and Si will each form protective oxides independently, increasing the total amount of protection and extending it over much wider ranges of pH and electrical potential.

A sucker rod steel, a heat treatment process therefor, and a manufacturing method comprising the heat treatment process are provided. The sucker rod steel comprises, in mass percent, the following chemical elements: C: 0.10˜0.20%, Si: 0.40˜0.80%, Mn: 0.20˜0.60%, Mo: 0.36˜0.46%, Cr: 6.15˜7.10%, Al: 0.015˜0.035%, Nb: 0.02˜0.06%, and N: 0.008˜0.015%, with the balance being Fe and other inevitable impurities. The microstructure of the sucker rod steel is tempered martensite and nanoscale precipitates. The grain size is higher than grade 10, the tensile strength is 920˜1320 Mpa, and the AKU2 impact energy is greater than or equal to 180 J.

An NPR non-magnetic steel material for rock bolt and a production method thereof are disclosed. The NPR non-magnetic steel material for rock bolt has a composition, in weight percent, consisting of: C: 0.4-0.7%, MN: 15-20%, Cr: 1-18%, Si: 0.3-3%, Ca: 0.05-0.15%, Cu: ≤0.03%, Ni: ≤0.02%, S: ≤0.001%, P: ≤0.001%, and the rest being Fe and unavoidable impurity elements. The NPR non-magnetic steel material for rock bolt and the production method thereof effectively solve the problems of steel materials for rock bolt in the prior art such as strong magnetism, low tensile strength and low effective elongation. The NPR non-magnetic steel material for rock bolt has a fully-austenitized structure and is non-magnetic, its yield strength is adjustable in the range of 600-1000 MPa, and its elongation is adjustable in the range of 20-60%.

Disclosed are a high-strength steel bar and a production method therefor. The high-strength steel bar comprises, by mass percentage, the following chemical components: C: 0.15-0.32%, Si+Mn: 0.5-1.9%, Mn+Cr+Mo+Ni: 1.1-2.1%, V: 0.02-0.8%, at least one of Nb, Ti and Al: 0.01-0.3%, and the balance of Fe and inevitable impurities; wherein Mn=(2.5-3.5)Si, and a carbon equivalent satisfies Ceq=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15≤0.56%.

Provided in the present disclosure is a method of heat treating a high-strength steel, wherein the high-strength steel comprises, by weight: 0.30-0.45% C, 1.0% or less Si, 0.20-2.5% Mn, 0.20-2.0% Cr, 0.15-0.50% Mo, 0.10-0.40% V, 0.2% or less Ti, 0.2% or less Nb, and a balance of Fe and other alloy elements and impurities, wherein the above alloy elements make Eq(Mn) according to the following formula (1) no less than 1.82, which method comprises the steps of 1) austenitizing; 2) carbide precipitation; and 3) tempering. The heat-treated steel in accordance with the present invention has high strength, high ductility and high toughness at the same time, especially improved reduction in area of tensile sample, so that it is particularly suitable for preparing spring members for vehicle suspension.

Eq(Mn)=Mn+0.26Si+3.50P+1.30Cr+2.67Mo  (1)

Provided is a heat treatment apparatus (1), including: a conveying device (10), which is configured to convey a rod-shaped workpiece (W) at a predetermined velocity along an axial direction of the workpiece (W); and a heating device (2) including a heating coil (3) configured to inductively heat the workpiece (W) being conveyed to a quenching temperature, wherein the heating coil (3) includes a first heating section (3A) and a second heating section (3B), which are coupled to each other in series along the axial direction of the workpiece (W), and is electrically connected to a single high-frequency power supply (4), and wherein a coil pitch (D2) of the second heating section (3B) arranged relatively on a front side in a conveying direction for the workpiece (W) is larger than a coil pitch (D1) of the first heating section (3A) arranged relatively on a rear side in the conveying direction.

A billet pushout system is provided for an electric induction billet heating line with long length revolute jointed pushout rods forming a non-jamming pushout rod assembly that is stored in a linear enclosure connected to an arcuate enclosure that deploys and retracts the pushout rod assembly to and from the electric induction billet heating line.