CN102021305A - Super-conventional performance heat treatment process for large axial forgings of carbon steel - Google Patents

Abstract

The invention discloses a super-conventional heat treatment process for axial forgings of carbon steel in large forgings, comprising the steps of conventional quenching treatment, sub-temperature quenching and tempering. Incomplete austenitizing is adopted in the step of sub-temperature quenching, aiming to reduce intercrystalline precipitates and refined grains. The practical effect shows the aim is achieved. A detail must be paid attention to: the upper limit sub-temperature can not exceed Ac3. The process has the following advantages: obtaining the needed structure preparation through conventional quenching treatment, reducing the intercrystalline precipitates and refined grains through the incomplete austenitizing characteristic of sub-temperature quenching treatment under the premise of ensuring the strength, and improving the structure and the mechanical performance. The process ensures the common carbon steel to break through the bottleneck and obtain higher impact toughness.

Description

The unconventional property heat treatment technology of large-scale carbon steel forged shaft

Technical field

The present invention relates to a kind of thermal treatment process, the unconventional thermal treatment process of specifically a kind of large-scale carbon steel forged shaft belongs to field of machining.

Background technology

Metal heat treatmet is metal works to be placed on be heated to suitable temperature in certain medium, and keep certain hour in this temperature after, again with the friction-motion speed cooling, controls a kind of technology of its performance by changing metal material surface or inner weave construction.

Metal heat treatmet is one of important process in the machinofacture, compare with other complete processings, thermal treatment does not generally change the shape and the whole chemical ingredients of workpiece, but by changing the microstructure of workpiece inside, or change the chemical ingredients of workpiece surface, give or improve the use properties of workpiece.Be characterized in improving the inner quality of workpiece, and this generally not to be naked eyes can see.

For making metal works have needed mechanical property, physicals and chemical property, except that reasonable select materials and various forming technology, thermal treatment process is requisite often.Iron and steel is a material most widely used in the mechanical industry, and the microstructure of iron and steel complexity can be controlled by thermal treatment, so the thermal treatment of iron and steel is the main contents of metal heat treatmet.In addition, aluminium, copper, magnesium, titanium etc. and alloy thereof also can change its mechanics, physics and chemical property by thermal treatment, to obtain different use propertieies.

As the normal steels of mechanical forging, carbon steel has its advantage clearly, and the prices of raw and semifnished materials are cheap, and intensity and hardness reach design requirements easily.But along with improving constantly of service requirements and design requirements, impelling strength to carbon steel tugboat forging shaft has also had higher requirement, even greater than the requirement among the mechanical industry standard JB/T9178.1-1999 of country " open die forgings general technical specifications on the water pressure engine ", conventional modifier treatment can be satisfied the design requirements of intensity and hardness, but to some difficulty of higher impelling strength (heavy froging of general carbon steel, impelling strength are bottlenecks).Conventional modified (quenching+high tempering) technology, be organized as ferritic structure and pearlitic structure, based on pearlitic structure, organize comparatively inhomogeneous, and existing technology can't be controlled intergranular in the quench cooled process preferably and separate out refinement with grain fineness number, impelling strength can't higherly be promoted, cause the material can't breakthrough bottleneck.

Summary of the invention

In order to address the above problem, the present invention has designed a kind of unconventional thermal treatment process at the carbon steel forged shaft, obtaining required tissue by the conventional quenching processing prepares, under the prerequisite of proof strength, the incomplete austenitizing characteristic of handling by intercritical hardening again, reduce intergranular precipitate and crystal grain thinning, improve tissue, improve mechanical property.Make the general carbon steel breakthrough bottleneck, obtain higher impelling strength.

Technical scheme of the present invention is: the unconventional thermal treatment process of carbon steel forged shaft, and concrete steps are as follows:

(1) quench treatment: be warming up to 650 ℃ by power, be incubated after 3 hours, be warming up to 860 ± 10 ℃ by≤80 ℃/hour speed, samming, the insulation 6 hours after, water-cooled 20 minutes, oil cooling 30 minutes;

(2) intercritical hardening: be warming up to 650 ℃ by power, be incubated after 3 hours, be warming up to 780 ± 10 ℃ by≤80 ℃/hour speed, samming, the insulation 6 hours after, water-cooled 20 minutes, oil cooling 30 minutes;

(3) tempering: be warming up to 350 ℃ by power, be incubated after 3 hours, be warming up to 570 ± 10 ℃ by≤60 ℃/hour speed, samming, insulation are after 12 hours, and stove is cold.

The invention has the advantages that: handle obtaining required tissue preparation by conventional quenching, under the prerequisite of proof strength, the incomplete austenitizing characteristic of handling by intercritical hardening reduces intergranular precipitate and crystal grain thinning again, improves tissue, raising mechanical property.Make the general carbon steel breakthrough bottleneck, obtain higher impelling strength.

Description of drawings

Fig. 1 is the process flow sheet of the embodiment of the invention.

Embodiment

Below the preferred embodiments of the present invention are described, should be appreciated that preferred embodiment described herein only is used for description and interpretation the present invention, and be not used in qualification the present invention.

Use the equipment situation as follows in this technological process:

(1) forging heat tracing: 800KW bench vehicle type electrical resistance furnace;

(2) forging lifting: main driving of colluding carrying 32T;

(3) forging cooling: volume be 132 tons tank, synthetic quenching liquid bath each one.

As shown in Figure 1, steel forged shaft thermal treatment process, concrete steps are as follows:

(1) quench treatment: be warming up to 650 ℃ by power, be incubated after 3 hours, be warming up to 860 ± 10 ℃ by≤80 ℃/hour speed, samming, the insulation 6 hours after, water-cooled 20 minutes, oil cooling 30 minutes;

(2) intercritical hardening: be warming up to 650 ℃ by power, be incubated after 3 hours, be warming up to 780 ± 10 ℃ by≤80 ℃/hour speed, samming, the insulation 6 hours after, water-cooled 20 minutes, oil cooling 30 minutes;

(3) tempering: be warming up to 350 ℃ by power, be incubated after 3 hours, be warming up to 570 ± 10 ℃ by≤60 ℃/hour speed, samming, insulation are after 12 hours, and stove is cold.

Product that technology of the present invention is produced is: 45# steel tugboat forging shaft, by the design of Chengdu building material industry design and research institute, use on φ 4.8 * 72M rotary kiln.The tugboat shaft size is totally 30 of φ 750*3180 and φ 680*2850 etc., blank weight 11880KG and 8710KG.Impelling strength is greater than the requirement among the mechanical industry standard JB/T9178.1-1999 of country " open die forgings general technical specifications on the water pressure engine " in its design.

It should be noted that at last: the above only is the preferred embodiments of the present invention, be not limited to the present invention, although the present invention is had been described in detail with reference to previous embodiment, for a person skilled in the art, it still can be made amendment to the technical scheme that aforementioned each embodiment put down in writing, and perhaps part technical characterictic wherein is equal to replacement.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (1)

1. the unconventional property heat treatment technology of large-scale carbon steel forged shaft is characterized in that comprising the steps:

(1) quench treatment: be warming up to 650 ℃ by power, be incubated after 3 hours, be warming up to 860 ± 10 ℃ by≤80 ℃/hour speed, samming, the insulation 6 hours after, water-cooled 20 minutes, oil cooling 30 minutes;

(2) intercritical hardening: be warming up to 650 ℃ by power, be incubated after 3 hours, be warming up to 780 ± 10 ℃ by≤80 ℃/hour speed, samming, the insulation 6 hours after, water-cooled 20 minutes, oil cooling 30 minutes;

(3) tempering: be warming up to 350 ℃ by power, be incubated after 3 hours, be warming up to 570 ± 10 ℃ by≤60 ℃/hour speed, samming, insulation are after 12 hours, and stove is cold.

Images