Intensive Quenching Research Articles

High Ductile Medium Mn Lightweight Alloy: The Role of Intensive Quenching and Deep Cryogenic Treatment

Medium Mn lightweight steels with a relatively higher Mn content of 9–12 wt% have been actively developed recently to meet the demands of crashworthiness and lightweight vehicles. In this study, a combined intensive quenching (IQ) and deep cryogenic treatment (DCT) was first proposed to achieve the microstructural homogeneity as well as the final strength–ductility synergy of medium Mn lightweight steels with Mn segregation bands, together with a comparison with the conventional intercritical annealing. The proposed IQ and DCT process induced the formation of finer large fractioned plate-like martensite in the austenite matrix and thereby contributed to finer and uniform austenite grains after subsequent intercritical annealing. The martensitic transformation rate (dVγ/dε) and transformation kinetics (k value) were used to evaluate the mechanical stability of retained austenite, showing that the D700&750 sample exhibited a similar dVγ/dε value and extremely low k value when compared to the conventional IA650–850 samples, implying that the former had the higher mechanical stability of austenite. The higher mechanical stability of austenite enabled the TRIP effect to occur in a larger strain range, leading to continuous strain hardening behavior. Thus, the highest yield strength (728 MPa) and the largest total elongation of 61.6% were achieved in the D700&750 sample, where the ductility was more than three times higher than that of the conventional IA samples. The grain size and morphologies of retained austenite were believed to be the main factors influencing the strain-hardening behavior of this type of ultrafine lamellar and equiaxed ferrite and austenite duplex structure.

Optimal Hardenability Steel and Its Future Worldwide Application

In the paper the problem of intensive quenching (IQ) of optimal hardenability (OH) steel in low concentration of water solutions that eliminates film boiling is widely discussed. Currently, for performing IQ processes complicated quench systems and highly costly technological processes are used resulting in the slow application of IQ technologies in the heat-treating industry. Also, there is no complete understanding of what makes OH steel unique, especially after quenching in low concentrations of water polymer solutions. The paper states that OH steel should be quenched in water polymer solutions of low concentration (1%–3%) agitated by hydrodynamic emitters to guarantee the absence of the film boiling process. Optimal results one can obtain if OH steel is composed according to patented methodology and is quenched in condition 0.8≤Kn≤1. All of this simplifies the quenching process resulting in acceleration and wide use of IQ technologies in the heat-treating industry.

Intense Quench Process in Slow Agitated Water Salt and Polymer Solutions

In the paper it is shown that quenching in slow agitated water salt solution of optimal concentration and in low concentration of inverse solubility polymers is intensive quenching creating maximal temperature gradients at the beginning of cooling. The evidence to support such idea were collected by analyzing quenching process in liquid media where any film boiling process was completely absent. In this case, surface temperature at the beginning of cooling drops closely to saturations temperature of a liquid within the interval 1–2 seconds, independently on nature of water solution, and then during transient nucleate boiling process maintains at the level of boiling point of a liquid which is often called self–regulated thermal process. The computer modeling of such cooling processes provided Kondrat’ev numbered Kn which are strongly linear function of time. At the beginning of cooling Kondrat’ev number is almost equal to 1 while average Kondrat’ev number Kn≥0.8. According to US Patent, intensive quenching starts when Kn=0.8. Based on achieved results, it is possible to perform intensive quenching in slow agitated of low concentration water salt and polymer solutions, usually initiated by hydrodynamic emitters. Along with liquid agitation, emitters generate resonance wave effect which destroys film boiling processes making cooling very uniform and intensive. The proposed IQ process works perfectly when martensite starts temperature Ms>Ts. If saturation temperature Ts≥Ms, intensive austempering process via cold liquids can be successfully performed to replace slow cooling of molten salts and alkalis by intensive quenching in liquid media.

Quench Process and Steel Chemistry Optimization to Prevent Quench Cracking during Hardening of Splined Semi – Axles

In the paper the hardening process of splined semi-axles is discussed and physics of preventing the quench crack formation during intensive quenching (IQ) is explained. It is shown that during IQ process at the splined cylindrical surface very high compressive current band residual stresses are formed which prevent the possibility of quench crack formation on splines. It is enough to optimize the stress distribution through the section of semi-axle and perform IQ process in order to prevent quench cracks formation in splines. It is achieved via optimizing depth of surface hardened layer. In this case the depth of surface hardened layer for cylinders and for cylinders with splines are the same. There is no need to create a special thin shell on splines or perform carburization to create such shell. Due to larger martensite specific volume, it results in surface compressive residual stress formation. Absence of martensite phase at the core eliminates core swelling that could be a reason in tensile surface stresses. The idea is supported by FEM calculations and testing of real semi-axles in industrial condition. The new idea simplifies cardinally technological process and makes it less costly.

Mechanism of Film Boiling Elimination and IQ Process Design for Hardening Steel in Low Concentration of Water Polymer Solutions

The paper considers a mechanism of the elimination of the film boiling process during intensive quenching (IQ) of steel parts in water polymer solutions of low concentration. The use of the IQ process results in improvement of material mechanical properties and steel part performance characteristics. Evaluation of ways of eliminating of the film boiling process using a modern physics point of view allows significant improvement of the IQ equipment making it less costly and more efficient. All of this cardinally simplifies the implementation of the IQ technology in heat treat practice. The paper shows how creation of a thin insulating surface layer during quenching of steel parts in low concentration of inverse solubility polymers results in eliminating of film boiling processes that makes the quench process intensive. Historically in heat treating industry, an effective heat transfer coefficient was widely used for evaluating of the nucleate boiling process. And quenching during the nucleate boiling mode of heat transfer was considered as slow cooling.

Control of inter/intra-granular κ-carbides and its influence on overall mechanical properties of a Fe-11Mn-10Al-1.25C low density steel

In this study, a novel ultra-high yield strength Fe-11Mn-10Al-1.25C low density steel was developed with aiming to fundamentally understand the formation of inter/intra-granular κ-carbides and its influence on the overall mechanical properties by varying cooling patterns, e.g. air cooling (AC), water quenching (WQ) and intensive quenching (IQ). The results show that the IQ microstructure is almost fully austenitic with very fine intra-granular κ-carbides of less than 13nm, which is totally different from the chain-like ferrite and coarse inter-granular κ-carbides of 0.6–2.6µm in both cases of AC and WQ. In contrast, the IQ sample exhibits similar high YS and UTS values (~ 1.1GPa) to the others but significantly an enhanced ductility of ~ 29.3%, revealing an excellent balance of strength and ductility, i.e. the product of strength and ductility (PSE) can reach as high as 32.1GPa%. The improved overall performance and continuously increasing strain hardening are dominated by planar glide, which is mainly attributed to the uniform distribution of nano-sized and shearable κ-carbides in the austenitic matrix. These results may provide theoretical supports for the κ-carbides-related alloy design and microstructural modification of ultra-high-strength medium Mn low density steels.

Intensive Quenching for Lean Manufacturing of Steel Parts

Abstract Intensive quenching enables manufacturers to improve part performance at a lower cost than other available methods. This article describes how using direct-from-forge intensive quenching can significantly reduce the cost of manufacturing steel products when engineered into the lean part-making process.

Development and Use of a Small Laboratory Intensive Quenching (IQ) System

Abstract Intensive quenching (IQ) has been defined as “those quenching conditions that lead to uniform maximum surface compressive stresses,” which provide maximum surface compressive stresses with correspondingly optimized distortion control. An earlier paper described the design and construction of a laboratory system that provides sufficient heat transfer rates to be classified as an IQ system. This paper describes the experimental work conducted with this laboratory IQ system. Particular focus will be on construction and use of this laboratory device to quench SAE 5160 spring steel under IQ conditions and the corresponding cooling curves, heat transfer rates, and compressive stresses obtained.

INVESTIGATION OF BATCH INTENSIVE QUENCHING PROCESSES WHEN USING HYDRODYNAMIC EMITTERS IN QUENCH TANKS

The paper discusses patented in Ukraine a new intensive quenching IQ–2 technology based on film boiling resonance effect [1]. Namely, the paper discusses improving of the batch intensive quenching (IQ) process known as IQ-2 method by the use of hydrodynamic emitters installed in quench tanks. The hydrodynamic emitters produce oscillating waves in the quench media with the frequency of the film boiling process creating a resonance effect. Two- and three-step IQ-2 processes are considered. Specifics of the heat transfer during the IQ-2 process are presented with focusing on the first stage of quenching where film and nucleate boiling processes are taking place. Examples of production IQ-2 equipment and loads processed are also presented. Application of hydrodynamic emitters in the IQ water tanks in addition to currently used propellers is considered in details. It is shown that the proposed new method can fully eliminate the film boiling process resulting in significant reduction of part distortion during quenching. Further evaluation of the proposed method is needed for its implementation in heat treating practice.

Overview on Super Strengthening Phenomenon Taking Place During Intensive Quenching of Steels

Abstract This paper presents an overview on the super strengthening phenomenon that takes place during intensive quenching (IQ) of steels. It is shown that for obtaining an additional strengthening of material, one should pay special attention to whether the part cooling rate within the martensite range is high enough and whether compressive stresses are formed at the surface of steel parts. For hardening high carbon alloy steels with a low martensite start temperature, a two-step quenching procedure is recommended. At the first step of quenching, the martensite transformation is delayed, and, at the second step of quenching, the part cooling rate is accelerated within the martensite range. For hardening low and medium carbon steels, an IQ-3 quench method is recommended when a so-called direct convection cooling is applied for providing a maximal cooling rate within the martensite range and maximal compressive stresses at the surface of steel parts. To calculate a part cooling rate within the martensite range, a generalized equation is provided. Data on mechanical properties for different steels proving a presence of the super strengthening effect are provided also. A practical use of the super strengthening phenomenon is discussed in the paper.

Batch Intensive Quenching Processes for Minimizing Steel Part Distortion and Improving Part Performance Characteristics

Abstract This paper discusses an intensive quenching method known as the IQ-2 process. The IQ-2 method is a two- or three-step quenching process for steel parts conducted in highly agitated water. The method is based on the use of a self-regulated thermal process that takes place during the quenching of steel parts in cold liquids such as water or water–salt solution. This quenching method eliminates the film boiling process and provides better control of the martensitic transformation during quenching, resulting in a significant reduction of part distortion after quenching. It also improves material mechanical properties and the performance characteristics of steel parts. It is underlined that proper software and equipment should be used when applying the IQ-2 quenching method for steel parts. Several practical examples of the application of the IQ-2 process are provided.

Partial Decarburization and Intensive Quenching to Increase Fatigue Limit of Quenched Small Parts

Abstract The 5160 spring steel is mainly used to endure fatigue and since its Mf is below room temperature, retained austenite is usually present after conventional quenching, which is detrimental from a fatigue point of view. To reduce the amount of retained austenite, a partial decarburization was promoted (to increase the Ms and Mf, respectively) by austenitizing the steel at different temperatures and times in air, prior to performing an interrupted quenching in an accelerated media (brine) instead of the conventional oil quenching. The same quenching conditions with partial decarburization and without decarburization are compared. In addition, conventional oil quenching was performed as reference. Results showed that with a controlled partial decarburization, it is possible to increase the fatigue limit compared to the conditions without decarburization (both interrupted quenching and oil quenching). Fatigue experiments were carried out in a rotating bending fatigue type tester. Cooling curves, decarburization profiles, fraction of martensite plots, and fatigue data are discussed.

Shell hardening of unalloyed steel cylinders by high speed quenching

AbstractKobasko et al. have primarily shown that rapid water quenching can create compressive residual stresses near the surface and thereby a significant increase in the fatigue-limit (Intensive Quenching). Such processes result in an increase in hardness. Depending on steel grade, dimensions of the component and quenching intensity through hardening or only shell hardening will result. In this work, shell hardening processes were investigated in a more detailed manner for cylinders made of two different unalloyed steels. The goal of the work was discovering the general requirements to reach, on the one hand, a sufficient surface hardness paired with a non-through hardened hardening profile. On the other hand, compressive residual stresses in the near surface area should be as high as possible to achieve huge lifetime cycles for the heat treated work pieces. The experiments were carried out with a device that was especially developed for high speed quenching. As a quenching medium only tap water or water...

Intensive Quenching of Steel Parts and Tools in Water Salt Solutions of Optimal Concentration

Abstract In this paper, a method of intensive quenching in water salt solutions, known as the IQ-2 process, is considered. To realize the IQ-2 process, water salt solutions were used, including with NaNO3, Na2CO3, NaCl, CaCl2, MgCl2, Ca(OH)2, and others salts. It is shown that the effectiveness of intensive quenching can be improved via the use of water salt solutions of optimal concentration. In order to prevent the corrosion of steel parts, a small amount of Ca(OH)2 was added to water salt solutions of sodium and calcium chloride to create a pH of 8 to 12. The proposed technology is less expensive compared to conventional quenching methods while providing the same or better end results in terms of increasing the service life of steel parts and tools and components made of powder metal materials. It is shown that the intensive quenching of tools by water salt solutions of optimal concentration increases the service life of tools by 1.5 to 2 times as compared with the oil quenching process.

Duration of the Transient Nucleate Boiling Process and Its Use for the Development of New Technologies

Abstract In the paper a review of the transient nucleate boiling process duration is widely discussed. It has been established that duration of transient nucleate boiling process is directly proportional to square of the thickness of steel parts and inversely proportional to thermal diffusivity of a material, depends on the configuration of steel parts, liquid properties, and its velocity. The transient nucleate boiling (self-regulated thermal process) is followed by amazing regularities: The surface temperature during nucleate boiling is maintained at the level of the boiling point of the liquid, which is used as a quenchant. During this period, average effective heat transfer coefficients and average generalized Biot numbers and Kondratjev numbers can be found which significantly simplify core cooling time and cooling rate calculations. Using established characteristics of the transient nucleate boiling process, the new intensive quenching (IQ) technologies were developed: IQ-1; IQ-2: IQ-3. In the paper the steel super-strengthening phenomenon and optimal quenched layer, which provides maximal residual compressive stresses at the surface of steel parts, are discussed, which increase service life of products. Instead of oils, plain water is used as a quenchant, environmental conditions are significantly improved.

One More Discussion “What is Intensive Quenching Process?”

Abstract Three intensive quenching processes known as IQ-1, IQ-2, and IQ-3 are considered. In contrast to IQ-2 and IQ-3, processes that use water as a quenchant, the two-step IQ-1 technique is actually a combination of a conventional quench (in oil or polymer/water solution) as the first step, followed by intensive quenching in water (the second step). Similar to the IQ-2 and IQ-3 methods, the IQ-1 process provides residual surface compressive stresses, optimum hardened depth, and additional strengthening (superstrengthening) of the material. A database and a method of calculating the IQ-1 process parameters are considered. The authors underlined that IQ processes are green environmentally friendly methods that significantly reduce CO2 emissions and energy consumption. Also examples of the use of IQ-2 and IQ-3 methods for quenching different kinds of steel parts (such as shafts, pinions, crosses, etc.) are provided. It is shown that the IQ technology’s rapid and uniform cooling rates increase service life of steel parts due to the creation of high residual compressive stresses at the surface of steel parts and due to additional strengthening (superstrengthening) of the material.

Intensive Quenching Theory and Application for Imparting High Residual Surface Compressive Stresses in Pressure Vessel Components

An alternative method for the hardening of steel parts has been developed as a means of providing steel products with superior mechanical properties through development of high residual compressive stresses on the part surface, and involves the application of intensive quenching during heat treatment. This processing method, termed “Intensive Quenching,” imparts high residual compressive stresses on the steel surface, thus allowing for the use of lower alloy steels, reduction or elimination of the need for carburization and shot peening, and providing for more cost-effective heat treating. Intensive quenching also provides additional environmental benefits, as the process uses plain water as the quenching media in contrast to traditional heat treatment practices which typically employ hazardous and environmentally unfriendly quenching oil. This paper presents an overview of the theory and application of intensive quenching, as well as provides experimental and computational data obtained for a variety of steel products. Also presented will be results of computer simulations of temperature, structural and stress/strain conditions for a typical pressure vessel during intensive quenching.