Nutec Bickley, Mexico, has been awarded a contract to manufacture and install five new lift-up furnaces, along with a fully modernized combustion system, for a leading U.S. manufacturer of high-quality alloy steel and carbon steel closed-die forgings. The project will take place between May and December 2023, with onsite work completed one furnace at a time to ensure the customer’s production schedules are not impacted. Two of the new furnaces will be used for tempering, while the remaining three will be used for austenitizing. Each furnace will be fitted with the latest control systems, complete fiber flues, and new exhaust and pressure control systems, along with insulation.
Nutec Bickley’s state-of-the-art combustion packages will be fully compliant with NFPA 86 standards, incorporating a fuel-only control system to allow maximum temperature uniformity potential for all cycles. The retrofitted furnaces will benefit from high-velocity nozzle mixing burners fitted with high-temperature burner blocks. The combustion systems will also feature automatic air control valves to adjust the maximum air volume used and to ensure proper burner ignition conditions.
The project will involve careful teamwork between the customer and Nutec Bickley to ensure successful delivery and highest quality outcomes. Rodrigo González, VP Metals at Nutec Bickley, emphasized the importance of constant communication and status updates with customers for a dynamic and mutually beneficial project result.
In crevice corrosion testing, treated 316 stainless steel compares favorably with alloy 625, as shown in the figure with three images. This figure shows three specimens at the end of a weeklong crevice corrosion test in natural seawater, at room temperature, under an applied potential of 300 mV.
Electrochemical polarization curves show a 600 to 800 mV increase in pitting potential in treated (900 to 1000 mV) versus nontreated (200 to 300 mV) type 316 in chloride solutions.
The combination of hardness and ductility achieved by low-temperature carburization also enhances resistance to erosion. The graph shows the results of cavitation testing of treated and nontreated 316 stainless steel specimens.
The images show wear maps for (a) treated and (b) nontreated 316 stainless steel. The T316 stainless steel was treated by low-temperature carburization.
The graph shows the results of fatigue testing of standard round bar 316 stainless steel specimens, in tension-compression cycling (R = –1) The symbols represent different sets of specimens, with nontreated specimens identified by triangles, treated specimens by squares.
One Minute Mentor: Residual Stress Profiles as Determined by X-Ray Diffraction
August 18, 2017
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For nitrocarburizing or consecutive carburizing and nitriding, the typical stress profile is smoother than for nitriding only. The graph shows residual stress profiles determined with destructive X-ray diffraction methods in carburized/nitrided AISI 316. Carburizing/nitriding: 2 hours at 970°F in an atmosphere consisting of 30% CO-70% hydrogen, followed by nitriding (23 hours at 820°F, at KN = 1.14.
For comparison a profile for a carburized (2.5 hours at 970°F, in 90% CO/10% H2) sample and for a nitrided (22 hours at 830°F, in 100% ammonia) sample are given. Residual stress values were calculated assuming that the same elastic constants apply for expanded austenite and austenite. The presented values are therefore only an indication that very high compressive stresses are present.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Low-Temperature Surface Hardening of Stainless Steel ⇒ Gaseous Low-Temperature Surface Hardening of Austenitic Stainless Steel
One MInute Mentor: X-Ray Diffraction Patterns in AISI 316
July 20, 2017
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The graph shows X-ray diffraction patterns of nitrided (and carburized) stainless steel AISI 316. Carburizing was carried out in 20% CO-80% H2 gas atmosphere at 515°C (788 K) for five hours. X-ray diffraction analysis corroborates that the nitrogen content is significantly higher in the sample nitrided at the highest nitriding potential. The 111 Bragg reflections (peaks) are shifted to lower scattering angles, where the largest shift is observed for the highest nitriding potential.
The peak shift is caused primarily by dissolution of nitrogen, leading to a dilation of the fcc lattice; residual stress and stacking faults also contribute. Peaks originating from the unexpanded austenite are visible in the sample nitrided at KN = 0.293, indicating that the γN zone is not as thick as for the samples nitrided at high potentials.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Low-Temperature Surface Hardening of Stainless Steel ⇒ Gaseous Low-Temperature Surface Hardening of Austenitic Stainless Steel
Despite the growth of alloy steels and special means of surface hardening, the ancient art of carburizing steel remains one of the fundamental operations in the manufacture of machine parts. It retains its popularity because it enables the workman to start with a material that can be easily machined, and end with an excessively hard and desirable surface for resisting wear, retaining ductile metal underneath with sufficient strength and shock-resisting properties to stand up to severe duty.
As is well known, most carburizing is done by the time-honored method of packing the steel with carbonaceous materials in suitable containers, covering it in such a way as to prevent infiltration of furnace gases, then raising the temperature to a suitably high point, and holding it there for some hours, depending upon the depth and character of case desired. Carburizing by this means is dependent on a number of factors, many of which arise from the character and uniformity of the compound; great care must therefore be vised in handling the compound to obtain satisfactory results. At best, there are still many variables that are hard to control and results that are difficult to explain. It has been felt for many years that this metallurgical process is too cumbersome and dirty to fit in well with modern manufacturing practice. To those who have studied the matter, it seemed that the desired improvement could be had in a process for carburizing with an externally prepared gaseous atmosphere. Such an atmosphere could be clean, of uniform composition, easily controlled, always fresh and theoretically desirable.
Despite the growth of alloy steels and special means of surface hardening, the ancient art of carburizing steel remains one of the fundamental operations in the manufacture of machine parts.
