WO2019223491A1

WO2019223491A1 - Method for manufacturing high-strength crankshaft

Info

Publication number: WO2019223491A1
Application number: PCT/CN2019/084409
Authority: WO
Inventors: 殷文元; 钱祥鑫
Original assignee: 江苏万力机械股份有限公司
Priority date: 2018-05-21
Filing date: 2019-04-25
Publication date: 2019-11-28
Also published as: CN108588386A

Abstract

The present invention provides a method for manufacturing a high-strength crankshaft, the method comprising feeding a molded crankshaft into a fluidized bed particle furnace and raising the temperature to 900ºC for austenitization, wherein the temperature deviation is ± 5ºC, and the austenitization time is 30-180 min; introducing ammonia gas into the furnace, and subjecting an austenitic stainless steel workpiece to a nitrocarburization treatment under the protection of ammonia gas to form a diffusion layer; and then austempering same in the fluidized bed particle furnace at 250ºC-360ºC. The method of the present invention introduces argon to carry out high-temperature gas nitrocarburization while carrying out nitrocarburization with austenite. The continuous introduction of argon reduces the oxidizing atmosphere, can eliminate the source of hydrocyanic acid generation to replace ferrite nitrocarburizing, which not only eliminates hydrocyanic acid pollutants, but also improves the depth of an effective hardened layer. The introduction of argon improves the hardness and corrosion resistance of a workpiece at the same time, and the process of the present invention has the characteristics of a high processing speed and a simple process, and is suitable for large-scale popularization and use.

Description

Manufacturing method of high-strength crankshaft

Technical field

The invention relates to the technical field of metal surface treatment, in particular to an austenitic nodular cast iron crankshaft and a treatment method for improving hardness and corrosion resistance.

Background technique

Austempered Ductile Iron (Austempered Ductile Iron), also referred to as Austempered Ductile Iron (ADI), also known as Austempered Ductile Iron, has better comprehensive mechanical properties than ordinary ductile iron, especially outstanding bending fatigue performance and high The abrasion resistance has attracted widespread attention from materials scientists and engineering technicians. Using austenite isothermal quenching technology, a high-strength, high-toughness isothermally quenched ductile iron with a tensile strength greater than 1000 MPa and an elongation greater than 15% was developed. Isothermally quenched ductile iron also has the characteristics of high strength and high toughness. Its comprehensive mechanical properties are significantly better than ferritic ductile iron and pearlite ductile iron. Its casting properties, heat resistance, corrosion resistance, wear resistance, vibration reduction Its properties such as flexibility, machinability and economy are superior to those of cast steel, and are considered to be "really cheap new materials." Isothermally quenched ductile iron is an important progress in strengthening and toughening ductile iron. It is hailed as one of the major achievements in the metallurgy of cast iron in the past 30 years and is expected to replace expensive cast steel and forged workpieces.

Isothermal quenching is a process method in quenching heat treatment. It mainly includes two processes of austenitizing and isothermal treatment: first, the casting is heated to a temperature above the A3 line, and is held for a period of time (called austenitizing treatment); and then cooled at a rate greater than that of pearlite formation. The cooling medium is rapidly cooled to the bainite transformation region for isothermal. Different from ordinary quenching and heat treatment, the temperature of the cooling medium (isothermal medium) is higher in the isothermal quenching and heat treatment. In the temperature range above the martensitic transformation point Ms of the casting and below the pearlite transformation temperature (that is, the intermediate temperature zone), After being kept in an isothermal medium for a period of time (also known as isothermal treatment), a bainite transformation occurs, and a mixture of acicular ferrite (or bainite-type ferrite) and high-carbon austenite without carbides is obtained. The salt bath isothermal quenching process has always been the main method for producing isothermally quenched ductile iron. In addition, it also includes staged cooling, continuous cooling and as-cast, quasi-cast and other production processes.

At present, nodular cast iron crankshafts produced at home and abroad are generally heated by a well-type resistance furnace after forming. The disadvantage is that the crankshaft is deformed and the oxide scale is thick, forming a protective layer, so that the temperature difference between the inside and outside of the crankshaft is large during the next quenching. Isothermal quenching of the bath is harmful to the human body, pollutes the environment, consumes more energy, and has poor safety.

Summary of the invention:

Technical problem: The object of the present invention is to provide a method for producing a crankshaft with high strength, abrasion resistance, oxidation resistance, environmental pollution, and safety, in view of the shortcomings of the prior art.

Technical solution: In order to achieve the above-mentioned object, the present invention is achieved by the following technical solutions:

The invention relates to a method for producing a high-strength crankshaft. The formed crankshaft is put into a fluidized bed particle furnace and heated to 900 ° C to perform austenitization, the temperature deviation is ± 5 ° C, and the austenitization time is 30 to 180min; Ammonia gas is introduced into the furnace, and under the protection of ammonia gas, the austenitic stainless steel workpiece is subjected to nitrocarburizing treatment to form an infiltrated layer; and then quenched at 250-360 ° C in a fluidized bed particle furnace.

Preferably, the nitrocarburizing treatment is gas infiltration; the thickness of the infiltration layer is greater than or equal to 10 microns.

Preferably, the high-temperature gas nitrocarburizing time is 2 to 6 hours.

Preferably, the surface hardness of the infiltration layer is greater than 1200 HV.

Beneficial effects: Compared with the prior art, the beneficial effects of the present invention are:

(1) In the method of the present invention, argon gas is introduced to perform nitrocarburizing at the same time as nitrocarburizing with austenite. The continuous argon gas reduces the oxidative atmosphere and can eliminate the source of hydrocyanic acid. It can be used instead of ferrite nitrocarburization, which not only eliminates the pollution of hydrocyanic acid, but also increases the depth of the effective hardened layer. The introduction of argon gas simultaneously improves the hardness and corrosion resistance of the workpiece, and the process of the invention has the characteristics of fast processing speed and simple process, and is suitable for large-scale popularization.

(2) In the method of the present invention, after the austenite gas nitriding is completed, the fluidized bed particle furnace is subjected to isothermal quenching at 250-360 ° C. The waste heat is used to immediately cool and then the insulation is performed to achieve isothermal quenching, which can save the conventional heating equipment and media isothermal quenching equipment. The cleaning equipment and its production process not only save money, labor and energy, but also save raw materials, no pollution, and achieve safe production. Because the fluidized bed particle furnace has the advantages of rapid contact heat and mass transfer, energy saving, and uniform furnace temperature, the crankshaft does not deform, is not easy to be oxidized and decarburized, has a smooth surface, uniform performance after heat treatment, good comprehensive mechanical properties, non-toxic, and no pollution. Environment and production safety.

Detailed ways

Examples of the present invention will be described below. Elements and features described in one embodiment of the present invention may be combined with elements and features shown in one or more other embodiments. It should be noted that, for the sake of clarity, representations and descriptions of components and processes not related to the present invention and known to those of ordinary skill in the art are omitted in the description.

Example 1

The formed crankshaft was heated to 900 ° C by a fluidized bed particle furnace heating device for austenitizing, and ammonia gas was introduced into the furnace. The flow rate of argon gas was 12 L / min. Under the protection of ammonia gas, the austenite was The stainless steel workpiece is subjected to nitrocarburizing treatment to form an infiltrated layer. The thickness of the infiltrated layer is 10 micrometers and the surface hardness of the infiltrated layer is 1200 HV. After one hour, it is released from the furnace and then quenched at 250 ° C in a fluidized bed particle furnace.

Example 2

The formed crankshaft was heated to 900 ° C by a fluidized bed particle furnace heating device for austenitizing, and ammonia gas was introduced into the furnace. The flow rate of argon gas was 16L / min. Under the protection of ammonia gas, the austenite was The stainless steel workpiece was subjected to nitrocarburizing treatment to form an infiltration layer. The thickness of the infiltration layer was 15 micrometers, and the surface hardness of the infiltration layer was 1300 HV. After 330 minutes, it was released from the furnace and then quenched at 360 ° C in a fluidized bed particle furnace.

Example 3

The formed crankshaft was heated to 900 ° C by a fluidized bed particle furnace heating device for austenitizing, and ammonia gas was introduced into the furnace. The flow rate of argon gas was 14 L / min. Under the protection of ammonia gas, the austenite was The stainless steel workpiece is subjected to nitrocarburizing treatment to form an infiltrated layer. The thickness of the infiltrated layer is 20 micrometers, the surface hardness of the infiltrated layer is 1300 HV, the furnace is discharged after 300 minutes, and then quenched isothermally in a fluidized bed particle furnace at 360 ° C.

In the method of the present invention, argon gas is introduced to perform nitrocarburizing at the same time as nitrocarburizing with austenite. The continuous argon gas reduces the oxidative atmosphere and can eliminate the source of hydrocyanic acid. It can be used instead of ferrite nitrocarburization, which not only eliminates the pollution of hydrocyanic acid, but also increases the depth of the effective hardened layer. The introduction of argon gas simultaneously improves the hardness and corrosion resistance of the workpiece, and the process of the invention has the characteristics of fast processing speed and simple process, and is suitable for large-scale popularization.

Finally, it should be explained that, obviously, the above-mentioned embodiments are merely examples for clearly explaining the present invention, and are not intended to limit the embodiments. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. There is no need and cannot be exhaustive for all implementations. The obvious changes or variations derived from this are still within the protection scope of the present invention.

Claims

A method for producing a high-strength crankshaft, characterized in that the formed crankshaft is put into a fluidized bed particle furnace and heated to 900 ° C to perform austenitization with a temperature deviation of ± 5 ° C and an austenitization time of 60 ～ 360min; pass argon into the furnace, and under the protection of argon, perform nitrocarburizing treatment on austenitic stainless steel workpieces to form an infiltration layer; then quench at 250-360 ℃ isothermally in a fluidized bed particle furnace.
The method for producing a high-strength crankshaft according to claim 1, wherein the nitrocarburizing treatment is gas infiltration; and the thickness of the infiltration layer is greater than or equal to 10 microns.
The method for producing a high-strength crankshaft according to claim 1, wherein the nitrocarburizing time of the high-temperature gas is 120 to 330 minutes.
The method for producing a high-strength crankshaft according to claim 1, wherein a surface hardness of the infiltration layer is greater than 1200 HV.
The method for producing a high-strength crankshaft according to claim 1, wherein the flow rate of argon gas is 12 to 16 L / min.