Practice of using heat treatment process materials

Practice of using heat treatment process materials to realize less and no oxidation heating

Abstract: the quality of heat treatment products is controlled by process, and the accurate implementation of process is guaranteed by process equipment and process materials. When the process equipment can not meet the process implementation, we can choose heat treatment process materials to achieve less oxidation heating, obtain good heat treatment products, and realize heat treatment quality control, which is worthy of the attention and practice of heat treatment production managers

key words: heat treatment process materials; Less and no oxidation, protective heating technology

I. Preface:

less and no oxidation heat treatment is the pursuit of heat treatment workers and the development trend of modern production of heat treatment

nowadays, the technology of less heat treatment and no oxidation has developed rapidly. Vacuum heating equipment and controllable atmosphere protection heating technology combined with computer control have been used in mass and assembly line production in the heat treatment industry. Achieve stable product quality and good economic benefits

to realize the modernization of process equipment, a lot of funds must be invested in infrastructure construction, equipment purchase, installation, commissioning, personnel training, etc. Many small and medium-sized enterprises cannot afford it. Many products will be encountered in the production process of heat treatment, some of which are large-scale structures or large tools and moulds, and the heating chambers of vacuum heating furnaces and controllable atmosphere furnaces are difficult to accommodate, while others are processed parts with certain batches and strict technical requirements. How to ensure that the above-mentioned parts can realize less and no oxidation heating, and how to select less and no oxidation protection heating process materials to meet the technical requirements is the only technical measure, Less oxidation process materials have also developed rapidly in recent decades, with many kinds. It is necessary to combine the process and reasonably select materials with less heat treatment and no oxidation process according to the technical requirements of the workpiece

II. "Steel heating protective agent"

the "steel heating protective agent" introduced in this paper is a process material suitable for preventing and controlling workpiece oxidation and decarburization in the process of heat treatment. It is easy to apply and has obvious anti-oxidation effect

after being used in production in 1967, it was not popularized and applied due to many factors, and it was gradually spread and applied in Beijing and its surrounding areas until 1990

"steel heating protective agent" is named for its anti oxidation and anti decarburization effect in the heating process of steel products. It is a water-based material, and the application process is suitable for the process mechanism of heat treatment. Generally, as long as the operator has the basic knowledge of heat treatment, he can master it smoothly. It is said that it is applicable to the heat treatment process mechanism, that is, when the furnace temperature reaches the moving temperature, the workpiece can be injected into the furnace by spraying, splashing, soaking and throwing immediately after entering the furnace, and dripping and brushing can also be applied, which is convenient and optional

"steel heating protectant" is a non-toxic, odorless, long-term storage, low consumption, cost-effective heat treatment process material. RX box type resistance furnace only needs to input about 50ml with the workpiece once, while RX box type resistance furnace or RT trolley type resistance furnace only needs to input about ml once. When it is put into operation, the light smoke overflowing from the furnace seam indicates that the heating chamber is full of protective substances, and the workpiece can form a layer of a scrapped car in a few minutes. A scrapped car can provide more than 30 kinds of useful material protective cover film. As long as the cover film is not damaged, the workpiece can achieve the effect of less oxidation protection and heating. After quenching or discharging, if the film is not damaged, it still has a protective effect. If it needs to be removed, the tooling will fall off with a slight touch, or the film will be removed easily with air blowing, blowing and brushing. Because its film is extremely thin, it will not affect the cooling effect and the cooling intensity during quenching, and a higher hardened surface can be obtained. When normalizing, the ideal grain structure can be obtained under different air cooling conditions. Its membrane does not pollute the quenching medium, and can be cleared by precipitation or filtration

1. 40Cr steel connecting rod normalizing + quenching and tempering process:

heating process: 840 ℃ × 4h

heating equipment: RX box type and RT trolley type resistance furnaces realize less and no oxidation heating

technical requirements: 40C "R steel connecting rod hot forging has caused surface decarburization of 0.30mm, and the collaborator requires that the decarburization layer after heat treatment be ≯ 0.30mm.

heat treatment has two processes, normalizing + quenching and tempering. It is found that the decarburization after normalizing is 0.35mm in production, and then the decarburization layer reaches 0.40mm through the quenching and tempering process, which is beyond the requirements of the collaborator.

the heat treatment equipment of this factory only has RX box resistance furnace and RT trolley resistance furnace, which is not qualified for the technical requirements of the collaborator.

"Steel heating protective agent" stacks the workpiece in the packing box 700 × four hundred × 300mm on average, each box can be packed, each furnace can be packed, and the dosage is ml each time. Finally, the technical conditions of the cooperative party are met, and the decarburization layer is controlled within 0.30mm

2. Normalizing process of cross support composition:

material: qczc

single weight: 50.76

technical requirements: normalize the weld between the rod body and the positioning seat ring, the grain size of the heat affected zone is ≤ 6.5, and the depth of the decarburization layer of the rod body is ≯ 0.2mm

heating equipment: RT trolley resistance furnace (four)

tooling: 100 pieces of cross bars for each tooling, two tooling for each furnace (a total of 200)

process:

in order to prevent oxidation and decarburization on the inner and outer surfaces of the workpiece pipe wall, the workpiece is impregnated and clamped on the tooling. When the furnace temperature reaches the temperature, the tooling is hoisted into the trolley, and two tooling for each furnace (200 cross bars) are put 250ml of protective agent before closing the furnace door, After being discharged from the furnace, an axial flow fan is used for forced cooling to control the quality to meet the technical conditions and realize mass production. The project has selected the process materials in the book, After process test, the "steel heating protective agent" is finally selected ", analyze the reason: it can ensure the grain size and anti decarburization conditions after normalizing and air cooling. Because the protective cover film is extremely thin, it does not hinder the air cooling effect, and then impregnation can achieve the protection of the inner and outer surfaces of the pipe. At the same time, the operation is simple and easy for workers to master.

3. Heat treatment of the bearing container

material: 34CrMo4

process temperature: 870 ℃

holding time: 2 hours

quenching medium: water

tempering temperature: 640 ℃ × Technical requirements: HB

tensile strength: ≥ 850mpa

yield strength: ≥ 735mpa

elongation: ≥ 20%

the original heat treatment process cannot solve the decarburization and oxide produced on the inner wall of the container. A special cleaning process is set to remove the oxidation on the inner surface, but the effect is not ideal. By spraying "steel heating protective agent" into the inner wall of the container with a spray gun, the oxidation and decarburization of the surface of the container are effectively prevented, and the heavy labor of cleaning the inner wall is omitted. The jar shaped container has a large bore and a small mouth. Sand blasting is used, and the shot blasting process is not easy to implement. Manual cleaning of the inner cavity oxide is heavy physical labor, and the efficiency is extremely low. The use of "steel heating protective agent" to protect the heating from oxidation also omits the inner cavity cleaning process, which improves the product quality and work efficiency

4. Application of large GCr15 steel roll quenching to prevent oxidation and decarburization:

workpiece: GCr15 steel roll diameter 500 × 400mm (maximum diameter 900, weight 2 tons). Processing equipment: RT trolley resistance furnace (the furnace is 4m long, 1.2m wide and 0.8m high)

process temperature: 840 ℃ × 6 hours

select "steel heating protective agent" and put it into 500ml at one time. After protective heating, the hardness can be controlled HRC after quenching, and the product quality is stable after several years of production practice

5, 60si2mu spring sheet

workpiece Name:

spring sheet thickness 0.8 × sixty-eight × 20mm

heating temperature: 840 ℃

heat preservation time: 5min

because the use of salt furnace and vacuum heating do not meet the technical conditions, RX box resistance furnace is used, and several small shovel type tooling are self-made. The workpiece is soaked in "steel heating protective agent" for heating, or sprayed with protective agent after entering the furnace for heating, which can obtain ideal hardening effect

6. Different types of tools and dies, structural parts and small parts made of different materials are heated in the same furnace and quenched respectively. The following three parts

5crmnmo hot film diameter 240 × 300mm holding time: 6 hours scroll spring fatigue testing machine maintenance

45 steel mold sleeve 400 × two hundred × 100mm insulation time: 2 hours

40cr pin diameter 28 × 150mm holding time: 50 minutes

heating temperature: 840 ℃

three types of workpieces are put into the furnace at the same time, and the "steel heating protective agent" is sprayed into the furnace for quenching three times according to different times to achieve heating protection. The overlapping of heating time can improve work efficiency, and the quality can be controlled

III: Summary:

1, "steel heating protective agent" has been applied by different types of manufacturers for many years. The stabilizer meets the global ultraviolet aging standard for automobiles. Practice has proved that it is suitable for heat treatment process materials with less or no oxidation protection heating in air heating medium furnaces

2. It is widely applicable to different materials and different types of workpieces, and can be widely used through technical measures

3. Using steel heating protective agent can improve product quality, reduce labor intensity and improve work efficiency

4. The steel heating protective agent is non-toxic, pollution-free, convenient for storage, transportation, management and use, and improves work efficiency

5. After years of production verification, steel processing protective agent is a kind of process material with high cost performance, economic and practical, energy saving and high efficiency, which ensures the quality control of heat treatment. (end)