CN110453050B - Experimental method for determining free ferrite cause in salt furnace heat treatment - Google Patents
Experimental method for determining free ferrite cause in salt furnace heat treatment Download PDFInfo
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- CN110453050B CN110453050B CN201910807679.8A CN201910807679A CN110453050B CN 110453050 B CN110453050 B CN 110453050B CN 201910807679 A CN201910807679 A CN 201910807679A CN 110453050 B CN110453050 B CN 110453050B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
- C21D1/58—Oils
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
- C21D1/60—Aqueous agents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
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- Oil, Petroleum & Natural Gas (AREA)
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- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
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Abstract
An experimental method for determining the reason for free ferrite in salt furnace heat treatment relates to the technical field of heat treatment process, and specifically comprises the following steps: placing quenching oil on the upper part of a quenching rack, and setting the distance between a product to be tested at the discharge door of the rear air lock chamber and the quenching oil to be 300 mm; quenching salt is stored in a quenching tank at the upper part of the quenching rack; will wait that the experiment product is from the ejection of compact of back air-lock chamber manual work immediately respectively shift into in quenching oil, quenching salt, set for the temperature and the heat preservation time in quenching heat preservation district, protective atmosphere is: nitrogen, propane and methanol, wherein the carbon potential is controlled to be 0.75 +/-0.5 percent c; the quenching oil is special bright isothermal grading quenching oil for the bearing; the quenching salt is salt (1:1 sodium nitrite and potassium nitrate) +0.5% of water; after the experimental product is quenched according to a normal quenching procedure, detecting whether free ferrite exists or not through a microscope; the invention determines that the root cause of the generation of free ferrite structure of the salt furnace product is water contained in quenching salt.
Description
Technical Field
The invention relates to the technical field of heat treatment processes, in particular to an experimental method for determining the reason for free ferrite in salt furnace heat treatment.
Background
As is known, free ferrite refers to ferrite that is free from other structures and exists independently; the proeutectoid ferrite has different forms such as equiaxial form, crystal form, spindle form, zigzag form, acicular form, etc. depending on the formation conditions. Ferrite is also the matrix of the pearlite structure. In hot rolled (normalized) and annealed structures of carbon steel and low alloy steel, ferrite is the main constituent phase; the ferrite components and structures have important influence on the technological properties of the steel, and have influence on the service performance of the steel in certain occasions; the product processed on the salt quenching production line of the rod furnace is easy to generate free ferrite, the depth is usually about 0.005mm, the adjustment of process parameters cannot be well improved, and the basic appeal of technical personnel in the field is found in order to meet the requirements of customers and find out the root cause of the free ferrite.
Disclosure of Invention
In order to overcome the defects in the background art, the invention discloses an experimental method for determining the reason of free ferrite in the heat treatment of a salt furnace.
In order to realize the purpose, the invention adopts the following technical scheme:
an experimental method for determining the cause of free ferrite in salt furnace heat treatment specifically comprises the following steps:
(1) preparing quenching medium quenching oil and quenching salt;
placing quenching oil on the upper part of a quenching rack, and setting the distance between a product to be tested at the discharge door of the rear air lock chamber and the quenching oil to be 300 mm; quenching salt is stored in a quenching tank at the upper part of the quenching rack;
(2) the product to be tested is manually transferred into quenching oil and quenching salt respectively immediately after being discharged from the rear air lock chamber, the temperature of the set quenching heat preservation area is 845 +/-5 ℃, the heat preservation time is 65 +/-5 minutes, and the protective atmosphere is: nitrogen, propane and methanol, wherein the carbon potential is controlled to be 0.75 +/-0.5 percent c;
the quenching oil is special bright isothermal grading quenching oil for the bearing; the quenching salt is salt (1:1 sodium nitrite and potassium nitrate) +0.5% of water;
(3) and quenching the product to be tested according to a normal quenching procedure and detecting whether free ferrite exists or not through a microscope.
In the experimental method for determining the reason of free ferrite in the heat treatment of the salt furnace, the introduction amount of nitrogen is 20 cubic meters per hour; the introduction amount of methanol was: 2 liters per hour; the propane is controlled by an electromagnetic valve and is automatically switched on and off, and the introduction amount is less than or equal to 600 liters per hour.
According to the experimental method for determining the reason of the free ferrite in the salt furnace heat treatment, the to-be-tested products are a plurality of bearing products with the same model.
Due to the adoption of the technical scheme, the invention has the following beneficial effects:
according to the experimental method for determining the reason for the free ferrite in the salt furnace heat treatment, different quenching media are adopted, quenching oil and quenching salt are used for quenching respectively, and the result of a comparative test shows that the product adopting the quenching oil has no free ferrite and the product using the quenching salt has free ferrite.
Detailed Description
The present invention will be explained in detail by the following examples, which are disclosed for the purpose of protecting all technical improvements within the scope of the present invention.
The experimental method for determining the reason for the free ferrite in the heat treatment of the salt furnace specifically comprises the following steps:
(1) preparing quenching medium quenching oil and quenching salt;
placing quenching oil on the upper part of a quenching rack, and setting the distance between a product to be tested at the discharge door of the rear air lock chamber and the quenching oil to be 300 mm; quenching salt is stored in a quenching tank at the upper part of the quenching rack;
(2) the product to be tested is manually transferred into quenching oil and quenching salt respectively immediately after being discharged from the rear air lock chamber, the temperature of the set quenching heat preservation area is 845 +/-5 ℃, the heat preservation time is 65 +/-5 minutes, and the protective atmosphere is: nitrogen, propane and methanol, wherein the carbon potential is controlled to be 0.75 +/-0.5 percent c;
the quenching oil is special bright isothermal grading quenching oil for the bearing; the quenching salt is salt (1:1 of sodium nitrite and potassium nitrate) and water, and the proportion of the water is 0.5 percent of the total weight of the salt;
(3) and quenching the product to be tested according to a normal quenching procedure and detecting whether free ferrite exists or not through a microscope.
In the experimental method for determining the reason of free ferrite in the heat treatment of the salt furnace, the introduction amount of nitrogen is 20 cubic meters per hour; the introduction amount of methanol was: 2 liters per hour; the propane is controlled by an electromagnetic valve and is automatically switched on and off, and the introduction amount is less than or equal to 600 liters per hour.
According to the experimental method for determining the reason of the free ferrite in the salt furnace heat treatment, the to-be-tested products are a plurality of bearing products with the same model.
Examples
Comparative experiments were carried out using experimental protocol a and experimental protocol B:
after the experimental scheme is implemented, the detection result is as follows: quenching by adopting a quenching oil medium, wherein no free ferrite exists in the four same bearings with the model of 6226-2RS/01 and the four same bearings with the model of NU314/01 which are detected under a microscope; the quenching salt with the components of (1:1 sodium nitrite and potassium nitrate) +0.5% of water is not quenched in a medium, and the generation of free ferrite is detected under a microscope, the ferrite is caused by the oxidation of the product in the quenching process, and the oxygen required by the oxidation is caused by the water in the quenching salt, so that the root cause of the generation of the free ferrite structure of the salt furnace product is determined to be the water in the quenching salt.
The present invention is not described in detail in the prior art.
The embodiments selected for the purpose of disclosing the invention, are presently considered to be suitable, it being understood, however, that the invention is intended to cover all variations and modifications of the embodiments which fall within the spirit and scope of the invention.
Claims (2)
1. An experimental method for determining the cause of free ferrite in salt furnace heat treatment is characterized in that: the method specifically comprises the following steps:
(1) preparing quenching medium quenching oil and quenching salt;
placing quenching oil on the upper part of a quenching rack, and setting the distance between a product to be tested at the discharge door of the rear air lock chamber and the quenching oil to be 300 mm; quenching salt is stored in a quenching tank at the upper part of the quenching rack;
(2) the product to be tested is manually transferred into quenching oil and quenching salt respectively immediately after being discharged from the rear air lock chamber, the temperature of the set quenching heat preservation area is 845 +/-5 ℃, the heat preservation time is 65 +/-5 minutes, and the protective atmosphere is: nitrogen, propane and methanol, wherein the carbon potential is controlled to be 0.75 +/-0.5 percent c; the introduction amount of nitrogen is 20 cubic meters per hour; the introduction amount of methanol was: 2 liters per hour; the propane is controlled by an electromagnetic valve and is automatically switched on and off, and the introduction amount is less than or equal to 600 liters per hour;
the quenching oil is special bright isothermal grading quenching oil for the bearing; the quenching salt is salt (1:1 of sodium nitrite and potassium nitrate) and water, and the weight of the water is 0.5 percent of the weight of the salt;
(3) and quenching the product to be tested according to a normal quenching procedure and detecting whether free ferrite exists or not through a microscope.
2. The experimental method for determining the cause of free ferrite in the heat treatment of a salt furnace as claimed in claim 1, wherein: the products to be tested are a plurality of bearing products with the same model.
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| CN101760602A (en) * | 2009-12-25 | 2010-06-30 | 重庆齿轮箱有限责任公司 | Large-scale thin wall gear ring quenching deformation control method |
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| CN103111472A (en) * | 2013-01-24 | 2013-05-22 | 首钢总公司 | Method for controlling free ferrite content of tire cord steel |
| CN104762449A (en) * | 2015-03-25 | 2015-07-08 | 湖北三环离合器有限公司 | Thermal treatment technology for clutch disc hub |
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| JPS5333937A (en) * | 1976-09-10 | 1978-03-30 | Hitachi Ltd | Surface hardened stainless steel and production method thereof |
| JPH0674458B2 (en) * | 1986-02-07 | 1994-09-21 | 株式会社神戸製鋼所 | Method for producing high strength steel sheet excellent in hydrogen sulfide resistance and toughness |
| JP3387149B2 (en) * | 1993-05-13 | 2003-03-17 | 住友金属工業株式会社 | Wire for reinforced high-strength steel wire and method of manufacturing the same |
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| CN101760602A (en) * | 2009-12-25 | 2010-06-30 | 重庆齿轮箱有限责任公司 | Large-scale thin wall gear ring quenching deformation control method |
| CN102181614A (en) * | 2011-04-08 | 2011-09-14 | 常州克劳诺斯特种轴承制造有限公司 | Quenching process for heat treatment color finished products |
| CN103111472A (en) * | 2013-01-24 | 2013-05-22 | 首钢总公司 | Method for controlling free ferrite content of tire cord steel |
| CN104762449A (en) * | 2015-03-25 | 2015-07-08 | 湖北三环离合器有限公司 | Thermal treatment technology for clutch disc hub |
| CN109722505A (en) * | 2018-12-27 | 2019-05-07 | 浙江辛子精工机械股份有限公司 | Middle low carbon steel automobile clutch parts machining method and its equipment |
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