CN111390165A

CN111390165A - Sintering and hardening process for blank of built-in flywheel of automobile clutch

Info

Publication number: CN111390165A
Application number: CN202010320447.2A
Authority: CN
Inventors: 施昌旭; 夏敏; 石小荣; 戴定中; 黄亿奇; 张艳伟
Original assignee: Jiangsu Zhizao New Material Co ltd
Current assignee: Jiangsu Zhizao New Material Co ltd
Priority date: 2020-01-16
Filing date: 2020-04-22
Publication date: 2020-07-10

Abstract

The invention discloses a blank sintering and hardening process of an automobile clutch built-in flywheel, which comprises the working procedures of sintering, rapid quenching and tempering. The sintering process is carried out in a mesh belt type sintering hardening furnace, the sintering temperature of a hearth is 1160-1180 ℃, and the sintering is carried out for 30-45 min in an oxidation-free environment. In the rapid quenching process, firstly, a sintered blank is taken, a quenching medium is used as nitrogen, and rapid quenching is carried out at a cooling rate of 2.5-5.0 ℃/S. In the tempering procedure, the blank which is quenched and is at room temperature is placed in a tempering furnace at the temperature of 180 +/-5 ℃, the tempering time is 60 +/-5 min, and the surface hardness of the tempered blank is 300-312 HV 5. The invention implements rapid quenching after the blank is sintered, which not only makes full use of the heat energy of sintering, but also saves a conventional heat treatment heating procedure, and most importantly, achieves the purpose of improving the strength of the blank.

Description

Sintering and hardening process for blank of built-in flywheel of automobile clutch

Technical Field

The invention belongs to a technology in the technical field of heat treatment processes, and particularly relates to a heat treatment process of automobile parts, in particular to a blank sintering and hardening process of an automobile clutch built-in flywheel.

Background

The clutch is a component directly connected with an engine in an automobile transmission system, is used for cutting off and combining power and the transmission system, and also requires stable automobile starting, smooth gear shifting and prevention of overload of the transmission system in the using process. The main parts of the automobile clutch comprise a flywheel, a clutch cover and a pressure plate, wherein the flywheel is arranged at the rear end of a crankshaft of an engine. The flywheel is a disc-shaped component which utilizes the mass of the outer contour to form inertia, and stores part of energy generated by the engine acting stroke during rotation so as to overcome the resistance of other auxiliary strokes and enable the crankshaft to rotate uniformly, thereby improving the short-term overload capacity of the engine and enabling the automobile to start more easily. In view of the requirements of energy conservation and emission reduction, modern automobile parts generally require lightweight design, and are preferably produced by adopting a near-net forming technology. The prior art generally adopts a powder metallurgy process to realize the integrated manufacture of the clutch flywheel, and the process sequentially implements conventional sintering and heat treatment procedures after a blank is pressed and formed, although the prior art can produce qualified products. However, in the high-temperature quenching process, due to the fact that the physical size or the section of each part of the clutch flywheel is greatly different, quenching thermal shock and quenching degree are inconsistent, stress and deformation generated along with the inconsistent quenching thermal shock and quenching degree are different, the hidden danger of cracks exists at the stress concentration position, and the adverse factors seriously restrict the manufacturing quality of the clutch flywheel.

Disclosure of Invention

The invention mainly aims at the defects of the prior art and provides a blank sintering and hardening process of an automobile clutch flywheel, which has a reasonable scheme, a simple path and easy implementation, and the process implements quick quenching after the blank is sintered, i.e. the heat energy of sintering is fully utilized, a heating procedure of conventional heat treatment can be omitted, and the pearlite structure formed by sintering the blank is directly converted into a martensite structure, so that the aim of improving the strength of the blank is fulfilled.

The invention achieves the technical aim through the following technical scheme.

A process for sintering and hardening the blank of built-in flywheel of clutch for car includes such steps as sintering, quick quenching and tempering. The improvement is that: the sintering process is carried out in a mesh belt type sintering hardening furnace, the sintering temperature of a hearth is 1160-1180 ℃, and the sintering is carried out for 30-45 min in an oxidation-free environment. In the rapid quenching process, firstly, a sintered blank is taken, a quenching medium is used as nitrogen, and rapid quenching is carried out at a cooling rate of 2.5-5.0 ℃/S. In the tempering procedure, the blank which is quenched and is at room temperature is placed in a tempering furnace at the temperature of 180 +/-5 ℃, the tempering time is 60 +/-5 min, and the surface hardness of the tempered blank is 300-312 HV 5.

As a further improvement scheme, the mesh-belt type sintering hardening furnace matched with the sintering process is a high-temperature continuous sintering furnace.

As a further improvement, the oxygen-free environment in the sintering process refers to that the hearth is filled with 90% of nitrogen and 10% of hydrogen.

Compared with the prior art, the invention has the following positive effects:

1. the blank is sintered at high temperature, so that the iron powder and other alloy elements are fused to form an alloy body with stable and strong metallographic structure;

2. the quenching adopts a rapid cooling method, so that a pearlite structure formed by sintering a blank is directly converted into a martensite structure, and because the martensite structure has high hardness, the subsequent finishing process and related heat treatment process are directly omitted, thereby greatly saving the production cost;

3. the blank can obviously reduce thermal shock and avoid generating overlarge internal stress after being rapidly quenched, thereby reducing the generation of cracks and achieving the aim of improving the product quality.

Detailed Description

A process for sintering and hardening the blank of built-in flywheel of clutch for car includes such steps as sintering, quick quenching and tempering. The sintering process belongs to the core process of the process and is a process implemented in a mesh belt type sintering hardening furnace, and the heating temperature in a hearth is required to be higher than the conventional sintering temperature during sintering. The mesh-belt type sintering hardening furnace applied in the embodiment is a high-temperature continuous sintering type furnace, the furnace is suitable for batch sintering operation, the heating temperature in a hearth is required to be 1160-1180 ℃ during sintering, 90% of nitrogen and 10% of hydrogen are required to be injected into the hearth, and a blank is sintered for 30-45 min in the oxygen-free environment, so that the iron powder and other alloy elements can be fused, and an alloy body with stable metallographic structure and high strength can be formed. The quick quenching process is established on the basis of the sintering process, firstly, a blank which is just sintered is taken, the blank is quickly put into a quenching medium, and the used medium is nitrogen, so that the quick quenching is carried out at the cooling rate of 2.5-5.0 ℃. The blank is quenched by adopting a rapid cooling method, so that a sintered pearlite structure is directly transformed into a martensite structure. Due to the fact that the martensite structure is high in hardness, a subsequent finishing process and a related heat treatment process are directly omitted, and therefore production cost is greatly saved. In addition, the blank can obviously reduce thermal shock, namely reduce the generation of internal stress and avoid the generation of cracks after being rapidly quenched. The tempering process is the first process of the process, and when the tempering process is implemented, a blank which is quenched and is cooled to room temperature is put into a tempering furnace, the temperature of the tempering furnace is 180 +/-5 ℃, and the tempering time is 60 +/-5 min. After the blank is tempered, the surface hardness is stabilized between 300-312 hv5, and most importantly, the internal stress of the blank can be further eliminated, so that the quality of the blank is improved.

The invention is further illustrated by the following examples, the specific effects of which are summarized in the examples:

summary of the examples

From the information reported in the above table, each example achieved the desired quality index, with the best overall performance being example 3.

Claims

1. A blank sintering and hardening process for a built-in flywheel of an automobile clutch comprises the working procedures of sintering, rapid quenching and tempering; the method is characterized in that: the sintering process is carried out in a mesh belt type sintering hardening furnace, the sintering temperature of a hearth is 1160-1180 ℃, and the sintering is carried out for 30-45 min in an oxidation-free environment; the rapid quenching process comprises the steps of firstly, taking a sintered blank, using a quenching medium as nitrogen, and performing rapid quenching at a cooling rate of 2.5-5.0 ℃/S; in the tempering procedure, the blank which is quenched and is at room temperature is placed in a tempering furnace at the temperature of 180 +/-5 ℃, the tempering time is 60 +/-5 min, and the surface hardness of the tempered blank is 300-312 HV 5.

2. The sintering and hardening process for the blank of the flywheel embedded in the automobile clutch according to claim 1, characterized in that: the mesh belt type sintering hardening furnace matched with the sintering procedure is a high-temperature continuous sintering furnace.

3. The sintering and hardening process for the blank of the flywheel embedded in the automobile clutch according to claim 1, characterized in that: the oxygen-free environment in the sintering process refers to that the hearth is filled with 90% of nitrogen and 10% of hydrogen.