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Title: Heat Treatment Procedure Qualification for Steel Castings

Abstract

Heat treatment practices used by steel foundries have been carefully studied as part of comprehensive heat treatment procedure qualification development trials. These studies highlight the relationships between critical heat treatment process control parameters and heat treatment success. Foundry heat treatment trials to develop heat treatment procedure qualifications have shed light on the relationship between heat treatment theory and current practices. Furnace load time-temperature profiles in steel foundries exhibit significant differences depending on heat treatment equipment, furnace loading practice, and furnace maintenance. Time-temperature profiles of furnace control thermocouples can be very different from the time-temperature profiles observed at the center of casting loads in the furnace. Typical austenitization temperatures and holding times used by steel foundries far exceed what is required for transformation to austenite. Quenching and hardenability concepts were also investigated. Heat treatment procedure qualification (HTPQ) schema to demonstrate heat treatment success and to pre-qualify other alloys and section sizes requiring lesser hardenability have been developed. Tempering success is dependent on both tempering time and temperature. As such, furnace temperature uniformity and control of furnace loading during tempering is critical to obtain the desired mechanical properties. The ramp-up time in the furnace prior to the establishment of steady state heatmore » treatment conditions contributes to the extent of heat treatment performed. This influence of ramp-up to temperature during tempering has been quantified.« less

Authors:
 [1];  [1];  [1];  [1];  [1]
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  1. Pennsylvania State Univ., University Park, PA (United States)
Publication Date:
Research Org.:
Pennsylvania State Univ., University Park, PA (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
836878
Report Number(s):
DE-FC07-99ID13841
TRN: US200706%%815
DOE Contract Number:
FC07-99ID13841
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; ALLOYS; AUSTENITE; CASTING; FOUNDRIES; FURNACES; HEAT TREATMENTS; MAINTENANCE; MECHANICAL PROPERTIES; PROCESS CONTROL; QUENCHING; STEELS; TEMPERING; THERMOCOUPLES; TRANSFORMATIONS; heat treatment; steel castings; procedure qualification

Citation Formats

Voigt, Robert C., Charles, Mariol, Deskevich, Nicholas, Varkey, Vipin, and Wollenburg, Angela. Heat Treatment Procedure Qualification for Steel Castings. United States: N. p., 2004. Web. doi:10.2172/836878.
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Voigt, Robert C., Charles, Mariol, Deskevich, Nicholas, Varkey, Vipin, & Wollenburg, Angela. Heat Treatment Procedure Qualification for Steel Castings. United States. doi:10.2172/836878.
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Voigt, Robert C., Charles, Mariol, Deskevich, Nicholas, Varkey, Vipin, and Wollenburg, Angela. 2004. "Heat Treatment Procedure Qualification for Steel Castings". United States. doi:10.2172/836878. https://www.osti.gov/servlets/purl/836878.
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@article{osti_836878,
title = {Heat Treatment Procedure Qualification for Steel Castings},
author = {Voigt, Robert C. and Charles, Mariol and Deskevich, Nicholas and Varkey, Vipin and Wollenburg, Angela},
abstractNote = {Heat treatment practices used by steel foundries have been carefully studied as part of comprehensive heat treatment procedure qualification development trials. These studies highlight the relationships between critical heat treatment process control parameters and heat treatment success. Foundry heat treatment trials to develop heat treatment procedure qualifications have shed light on the relationship between heat treatment theory and current practices. Furnace load time-temperature profiles in steel foundries exhibit significant differences depending on heat treatment equipment, furnace loading practice, and furnace maintenance. Time-temperature profiles of furnace control thermocouples can be very different from the time-temperature profiles observed at the center of casting loads in the furnace. Typical austenitization temperatures and holding times used by steel foundries far exceed what is required for transformation to austenite. Quenching and hardenability concepts were also investigated. Heat treatment procedure qualification (HTPQ) schema to demonstrate heat treatment success and to pre-qualify other alloys and section sizes requiring lesser hardenability have been developed. Tempering success is dependent on both tempering time and temperature. As such, furnace temperature uniformity and control of furnace loading during tempering is critical to obtain the desired mechanical properties. The ramp-up time in the furnace prior to the establishment of steady state heat treatment conditions contributes to the extent of heat treatment performed. This influence of ramp-up to temperature during tempering has been quantified.},
doi = {10.2172/836878},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2004,
month =
}
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DOI:  10.2172/836878
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  • The science of heat treatment has been well studied and is the basis from which existing specifications and practices for the heat treatment of steel castings have been developed. Although these existing specifications address the general needs of steel castings to be heat-treated, they do not take into account the variability in the parameters that govern the processes. The need for a heat treatment qualification procedure that accounts for this variability during heat treatment is an important step toward heat treatment quality assurance. The variability in temperatures within a heat treatment furnace is one such variable that a foundry hasmore » to contend with in its day-to-day activity. Though specifications indicate the temperatures at which a particular heat treatment has to be conducted, heat treatment specifications do not adequately account for all aspects of heat treatment quality assurance. The heat treatment qualification procedure will comprise of a robust set of rules and guidelines that ensure that foundries will still be able to operate within the set of constraints imposed on them by non-deterministic elements within the processes.« less

  • ; ; ; ...
    Heat treatment practices used by steel foundries have been carefully studied as part of comprehensive heat treatment procedure qualification development trials. These studies highlight the relationships between critical heat treatment process control parameters and heat treatment success. Foundry heat treatment trials to develop heat treatment procedure qualifications have shed light on the relationship between heat treatment theory and current practices. Furnace load time-temperature profiles in steel foundries exhibit significant differences depending on heat treatment equipment, furnace loading practice, and furnace maintenance. Time-temperature profiles of furnace control thermocouples can be very different from the time-temperature profiles observed at the center ofmore » casting loads in the furnace. Typical austenitization temperatures and holding times used by steel foundries far exceed what is required for transformation to austenite. Quenching and hardenability concepts were also investigated. Heat treatment procedure qualification (HTPQ) schema to demonstrate heat treatment success and to pre-qualify other alloys and section sizes requiring lesser hardenability have been developed. Tempering success is dependent on both tempering time and temperature. As such, furnace temperature uniformity and control of furnace loading during tempering is critical to obtain the desired mechanical properties. The ramp-up time in the furnace prior to the establishment of steady state heat treatment conditions contributes to the extent of heat treatment performed. This influence of ramp-up to temperature during tempering has been quantified.« less

  • ;
    Heat treatment and associated processing, such as quenching, are critical during high strength steel casting production. These processes must be managed closely to prevent thermal and residual stresses that may result in distortion, cracking (particularly after machining), re-work, and weld repair. The risk of casting distortion limits aggressive quenching that can be beneficial to the process and yield an improved outcome. As a result of these distortions, adjustments must be made to the casting or pattern design, or tie bars must be added. Straightening castings after heat treatments can be both time-consuming and expensive. Residual stresses may reduce a casting'smore » overall service performance, possibly resulting in catastrophic failure. Stress relieving may help, but expends additional energy in the process. Casting software is very limited in predicting distortions during heat treatment, so corrective measures most often involve a tedious trial-and-error procedure. An extensive review of existing heat treatment residual stress and distortion modeling revealed that it is vital to predict the phase transformations and microstructure of the steel along with the thermal stress development during heat treatment. After reviewing the state-of-the-art in heat treatment residual stress and distortion modeling, an existing commercial code was selected because of its advanced capabilities in predicting phase transformations, the evolving microstructure and related properties along with thermal stress development during heat treatment. However, this software was developed for small parts created from forgings or machined stock, and not for steel castings. Therefore, its predictive capabilities for heat treatment of steel castings were investigated. Available experimental steel casting heat treatment data was determined to be of insufficient detail and breadth, and so new heat treatment experiments were designed and performed, casting and heat treating modified versions of the Navy-C ring (a classical test shape for heat treatment experiments) for several carbon and low alloy steels in order to generate data necessary to validate the code. The predicted distortions were in reasonable agreement with the experimentally measured values. However, the final distortions in the castings were small, making it difficult to determine how accurate the predictions truly are. It is recommended that further validation of the software be performed with the aid of additional experiments with large production steel castings that experience significant heat treatment distortions. It is apparent from this research that the mechanical properties of the bonded sand used for cores and sand molds are key in producing accurate stress simulation results. Because of this, experiments were performed to determine the temperature-dependent elastic modulus of a resin-bonded sand commonly utilized in the steel casting industry. The elastic modulus was seen to vary significantly with heating and cooling rates. Also, the retained room temperature elastic modulus after heating was seen to degrade significantly when the sand was heated above 125°C. The elastic modulus curves developed in this work can readily be utilized in casting simulation software. Additional experiments with higher heating rates are recommended to determine the behavior of the elastic modulus in the sand close to the mold-metal interface. The commercial heat treatment residual stress and distortion code, once fully validated, is expected to result in an estimated energy savings of 2.15 trillion BTU's/year. Along with these energy savings, reduction of scrap and improvement in casting yield will result in a reduction of the environmental emissions associated with the melting and pouring of the metal which will be saved as a result of this technology.« less

  • ; ;
    Procedure WPS--2104-ASME-1 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc welding of 300 series Cr-Ni steels (P-8-1) to 2 1/4-1Mo steels (P-5-1), in thickness range 0.187 to 1.0 inch; filler metal is ERNiCr-3 (F-43); shielding gas is argon.

  • ; ;
    Procedure WPS-2102-ASME-2 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc welding of carbon steel (P-1-1) to 300 series Cr-Ni steels (P-8-1), in thickness range 0.035 to 1.0 inch; filler metal is ERNiCr-3 (F-43); shielding gas is argon.