Claims:WE CLAIM:
1. A method (100) for reducing amplitude of bounce of a ferrous material, said method comprising quenching austenitized steel from a temperature in the range of 850°C to 800°C, after a delay of 90 seconds to 120 seconds, in a polymer at a temperature in the range of 60°C to 70°C, followed by tempering at a temperature in the range of 640°C to 670°C.
2. The method (100) as claimed in claim 1 comprises the following steps until austenitized steel is obtained:
i. heating (102) the raw ferrous material at a first predetermined temperature in a heater;
ii. forging (104) the heated raw ferrous material in a die to obtain a forged ferrous material;
iii. cooling (106) said forging in ambient air; and
iv. austenitizing (108) said cooled forging at a second predetermined temperature for a time period in the range of 3 hours to 4 hours to obtain the austenitized ferrous material.
3. The method (100) as claimed in claim 1, wherein said ferrous material is steel that is a mixture of ferrite, unresolved pearlite and tempered martensite and the morphology of the ferrite is non-uniformly at the grain boundaries covering the colonies of pearlite and non-uniform patches of tempered martensite.
4. The method (100) as claimed in claim 1, wherein said ferrous material is medium carbon steel with 0.35 wt% to 0.5 wt% carbon.
5. The method (100) as claimed in claim 1, wherein the concentration of said polymer solution is in the range of 14 wt% to 20 wt%.
6. The method (100) as claimed in claim 2, wherein said first predetermined temperature in the range of 1100 °C to 200 °C.
7. The method (100) as claimed in claim 2, wherein said heater is selected from a group consisting of induction billet heater, or an oil, gas or electric furnace.
8. The method (100) as claimed in claim 2, wherein said die is selected from a group consisting of closed die and open die.
9. The method (100) as claimed in claim 2, wherein said second predetermined temperature is in the range of 850°C to 880°C.
, Description:FIELD
Embodiments disclosed herein a heat treatment method for producing steel with enhanced damping characteristic.
DEFINITION
As used in the present disclosure, the following term is generally intended to have the meaning as set forth below, except to the extent that the context in which it is used indicates otherwise.
Austenitizing: Austenitizing heat treatment is heating steel above the critical temperature, holding for a period of time long enough for transformation to occur. Critical temperature: For steel and steel alloys, the temperature above which austenite is the stable phase.
Quenching: Quenching is the soaking of a metal at a high temperature, below the melting point, followed by a rapid cooling process to obtain certain desirable material properties.
Tempering: Tempering is a process of improving the characteristics of a metal, especially steel, by heating it to a high temperature, though below the melting point, then cooling it, usually in air.
Forging: An object obtained as a result of a typical process of forging of a metal.
BACKGROUND
Heat treated medium carbon steels are widely used in the engineering industry for its combined benefits of strength and manufacturability. Such parts are used for manufacturing of moving applications in machineries which involve significant noise/ vibration. High magnitude of noise results in customer/operator inconvenience and reduction in fatigue life. Thus, parts responsible for creation and transfer of noise need to have better vibration damping characteristics.
It is highly desirable to have steel which continues to exhibit the good physical characteristics of elastic modulus, density, strength and hardness similar to that of known steel while at the same time has highly improved vibration damping characteristics.
Therefore, there is felt a need for a heat treatment method for producing steel with enhanced reduction in amplitude of bounce.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a heat treatment method for producing steel.
Another object of the present disclosure is to provide a heat treatment method for producing steel with enhanced reduction in amplitude of bounce.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a method for reducing amplitude of bounce of a ferrous material. The method comprises quenching austenitized steel from a temperature in the range of 850°C to 800°C, after a delay of 90 seconds to 120 seconds, in a polymer at a temperature in the range of 60-70°C, followed by tempering at a temperature in the range of 640°C to 670°C.
The method comprises the following steps for obtaining the austenitized steel. The method comprises the following steps until austenitized steel is obtained. Firstly, the raw ferrous material is heated at a first predetermined temperature in a heater. Secondly, the heated ferrous material is forged in a die to obtain a forging. Thirdly, the forging is cooled in ambient air until room temperature is reached to obtain a cooled ferrous material. Fourthly, the cooled ferrous material is austenitized at a second predetermined temperature for a time period in the range of 3 hours to 4 hours to obtain the austenitized ferrous material.
The ferrous material is steel that is a mixture of ferrite, unresolved pearlite and tempered martensite and the morphology of the ferrite is non-uniformly at the grain boundaries covering the colonies of pearlite and non-uniform patches of tempered martensite.
Preferably, the raw ferrous material is selected from medium carbon steel with 0.35 wt% to 0.5 wt% carbon.
Preferably, the first predetermined temperature in the range of 1100°C to 1200°C.
Preferably, the concentration of said polymer solution is in the range of 14-20 wt%.
Preferably, the first predetermined temperature in the range of 1100-200 °C.
The heater is selected from a group consisting of induction billet heater, or an oil, gas or electric furnace.
The die is selected from a group consisting of closed die and open die.
Preferably, the second predetermined temperature is in the range of 850-880°C.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 schematically illustrates the heat treatment method for steel in accordance with the prior art.
Figure 2 schematically illustrates the heat treatment method for steel in accordance with the present disclosure.
Figure 3a shows steel microstructure at 100x magnification, wherein the steel is manufactured in accordance with the heat treatment method of the prior art;
Figure 3b shows steel microstructure at 100x magnification, wherein the steel is manufactured in accordance with the heat treatment method of the present disclosure;
Figure 4 is a graphical illustration of damping characteristics of a reference steel prepared in accordance with the conventional process and steel-1 prepared in accordance with the heat treatment process of the present disclosure.
LIST OF REFERENCE NUMERALS
10 - Schematically illustration of the heat treatment method in accordance with the prior art
11 - Heating
12 - Forging
13 - Cooling
14 - Austenitizing
15 - Quenching delay
16 - Quenching
17 - Tempering
18 - Cooling
100 - Schematically illustration of the method in accordance with the present disclosure
102 - Heating
104 - Forging
106 - Cooling
108 - Austenitizing
110 - Quenching delay
112 - Quenching
114 - Tempering
116 - Cooling
DETAILED DESCRIPTION
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms ”comprises“, ”comprising”, “including”, and “having” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
When an element is referred to as being ”mounted on”, “engaged to”, ”connected to”, or ”coupled to“ another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Terms such as “inner”, “outer”, ”beneath”, ”below”, ”lower”, ”above”, ”upper”, and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.
Heat treated ferrous materials such as medium carbon steels are widely used in the engineering industry for its combined benefits of strength and manufacturability. Such parts are used for manufacturing of moving applications in machineries which involve significant noise/vibration. High magnitude of this noise results in customer/operator inconvenience and reduction in fatigue life. Thus, parts responsible for creation and transfer of this noise need to have better damping characteristics.
Figure 1 illustrates a conventional heat treatment method (10), comprising the following steps. Raw steel is heated at a temperature at a temperature in the range of 1100 °C-1200 °C in a heater. The heated steel is forged in a die to obtain a steel forging. The steel forging is cooled in ambient air. The cooled forged steel is austenitized at a temperature 845 °C for a time period of 0.5 hours to obtained an austenitized steel. The quenching of the austenitized steel is delayed for a time period of maximum 45 seconds. The austenitized steel is then quenched in water or polymer at ambient temperature to obtain quenched steel. The quenched steel is further tempered at a temperature in the range of 370 °C to 565 °C for a time period of 1 hour to obtain tempered steel. The tempered steel is cooled in ambient air to obtain the steel.
It would be extremely desirable if steel could be formulated which continued to exhibit the good physical characteristics of, elastic modulus, density, strength and hardness similar to that of known steel while at the same time have highly improved damping characteristics.
The present disclosure envisages a method for reducing amplitude of bounce of a ferrous material, particularly suitable for parts manufacturing of moving applications in machineries which involve significant vibration. The method is a heat treatment method that involves a medium carbon steel bar (% carbon in the range of 0.30 to 0.60) through ingot-cast or continuous-cast route subjected to hot forging process at 1100-1200°C (closed-die) and cooled under ambient air condition. The air-cooled forgings undergo heating to austenitizing temperature (850-880°C) in a conveyor type (mesh-belt) furnace. The parts are soaked at the temperature for 3-4 hours. The austenitized parts are further quenched in polymer with concentration in water maintained at 12-20% and at a temperature of 30-60 °C. The parts are cooled to 40-70 °C at the end of the quenching process. The quenched parts further undergo tempering process at 640-670 °C. The parts are soaked at the temperature for 4 to 5 hours in a conveyor type (mesh-belt) furnace. These parts are then cooled in ambient air.
The disclosure will now be described with reference to the accompanying drawing which will not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
Figure 2 illustrates a method (100) of the present disclosure, comprising the following steps. In this method, the raw ferrous material is heated at a first predetermined temperature in a heater. The heated ferrous material is forged in a die to obtain a forging. The forging is then cooled in ambient air. According to an aspect of the present disclosure, the cooled steel forging is austenitized at a second predetermined temperature for a time period of 3 hours to 4 hours to obtain an austenitized ferrous material. According to another aspect of the present disclosure, the quenching of the austenitized ferrous material is delayed for a time period of 90 seconds to 120 seconds. According to yet another aspect of the present disclosure, the austenitized ferrous material is quenched in a hot polymer solution at a temperature in the range of 50-70 °C to obtain a quenched ferrous material. According to still another aspect of the present disclosure, the quenched steel is tempered at a third predetermined temperature for a time period of 4 hours to 5 hours to obtain tempered ferrous material. Lastly, the tempered ferrous material is cooled in ambient air to obtain the ferrous material with enhanced damping characteristics
The ferrous material is steel with reduced amplitude of bounce, for the natural frequency of vibration of the particular component manufactured therefrom. The steel has a higher damping ratio. The steel obtained after the heat treatment of the present disclosure is a mixture of ferrite, unresolved pearlite and tempered martensite. The morphology of the ferrite is non-uniform at the grain boundaries covering the colonies of pearlite and non-uniform patches of tempered martensite.
Preferably the raw ferrous material is selected from medium carbon steel with 0.35 wt% to 0.5 wt% carbon.
Preferably the first predetermined temperature in the range of 1100 °C to 1200 °C.
Preferably the heater is selected from induction billet heater, or an oil, gas or electric furnace. Preferably, the second predetermined temperature is in the range of 850-880°C. Preferably, the third predetermined temperature is in the range of 640-670°C.
Preferably the die is selected from a closed die and an open die.
Figure 3a shows a reference steel microstructure at 100x magnification. The reference steel is prepared in accordance with the conventional heat treatment method (10). The figure 3a shows uniform presence of tempered martensite with negligible ferrite.
Figure 3b shows a steel-1 microstructure at 100x magnification. The steel-1 with enhanced damping characteristics is prepared in accordance with the heat treatment method (100) of the present application. The figure 3b shows non-uniform presence of ferrite (white) at the grain boundaries.
The microstructure of the parts as an outcome of the above process of the present disclosure is a mixture of ferrite, unresolved pearlite and tempered martensite. The morphology of the ferrite is such that it is formed non-uniformly at the grain boundaries covering the colonies of pearlite (mostly unresolved). Also, present are non-uniform patches of tempered martensite.
The specific microstructure, as shown in figure 3b, that is formed as a result of the heat treatment method disclosed in the present disclosure, offers enhanced damping characteristics in a part which is excited mechanically by an external vibration source. This is due to the presence of non-uniform ferrite phase with irregular shapes and sharp edges that create stress concentration at the grain boundaries. The remaining phases of unresolved pearlite and patches of tempered martensite offer good mechanical properties required for most applications.
The polymer used for quenching is selected from the group consisting of water-based organic polymers.
The present disclosure is further described in light of the following experiment which is set forth for illustration purpose only and is not to be construed for limiting the scope of the disclosure.
Experiment 1: Frequency response function (comparison of output acceleration/ input force versus frequency of vibration of reference steel and steel-1:
The reference steel is prepared in accordance with the conventional heat treatment method (10). The steel-1 with enhanced damping ratio is prepared in accordance with the heat treatment method (100) of the present application. Respective plots showing response (amplitude of the ratio of output acceleration/ input force) measured at the driving point of vibration itself, vs. frequency of vibration of external input are presented in Figure 4, which is a graphical illustration of damping characteristics of a reference steel prepared in accordance with the conventional process and steel-1 prepared in accordance with the heat treatment process of the present disclosure. The results of damping characteristics of the reference steel and steel-1 are summarized in table 1.
Table-1
Peak vibration frequency
(Hz) Response amplitude
(m/s2)/N
Reference steel 2732 228
Steel-1 2725 103
Inference: Due to uniform presence of tempered martensite with negligible ferrite in the reference steel, high stress is developed in the steel manufactured with the method of the present disclosure. In steel-1 (i.e., steel manufactured with the method of the present disclosure), ferrite (white) is present at the grain boundaries in non-uniform pattern, which leads to higher damping of vibration at a given peak vibration frequency.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a heat treatment process for steel. The technical advantages are as stated below:
• provide steel with enhanced reduction in amplitude of bounce; and
• provide steel with less stressed microstructure by controlling mixture of phases and their distribution as grains.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.