Japanese pure water quenching technology - heat treatment can also be environmentally friendly

1. Salt bath heat treatment

Company A is located in Sendai City, Miyagi Prefecture, Japan, about 300km from Tokyo. The company mainly produces a wide variety of mechanical blades, the longest of which is more than 5m. The blades are mainly made of high speed steel, hard alloy and alloy tool steel. The heat treatment heating furnace includes a salt bath furnace, a vacuum furnace, a box type multi-purpose furnace, a large protective atmosphere furnace, a large gas carburizing furnace, and the like.

There are two sets of salt bath furnaces being produced at the site: one set for Cr12MoV steel tool quenching line and the other set for high speed steel or base steel quenching line.

(1) There are 3 equipments on the production line of Cr12MoV steel cutters (large and thin circular saw blades, etc.): 1 The preheating furnace salt bath composition is BaC12+NaC1, and the indicated temperature is 810 °C. 2 The heating furnace is 100% BaC12, and the heating temperature is 1020 to 1030 °C. 3 The cooling furnace is KNO3+NaNO2, indicating a temperature of 220 °C.

The salt bath furnace is semi-buried and semi-inserted, all of which are three-phase; the thermocouple is directly inserted into the furnace for temperature measurement, and the temperature control is a digital display recorder.

The Cr12MoV steel circular saw blade is flattened immediately after quenching at 220 °C, and the fixture is placed in the basket for tempering. The tempering is carried out in the nitrate salt, and the tempering temperature is 180-200 °C.

(2) High-speed steel and base steel tool salt bath production line has 6 sets of equipment: 1 drying resistance furnace, its drying temperature is 500-600 °C, double when heating. 2 preheating furnace, salt bath composition is BaC12+NaC1, indicating temperature 850 °C; single furnace double board preheating, there is a crane, but the site operation is manual. 3 heating furnace, salt bath composition is 100% BaC12, M2 steel quenching heating temperature is 1215 ~ 1220 ° C, do not look at the metallographic phase, there is no metallographic chamber in the workshop, only Rockwell hardness tester. 4 Cooling furnace, salt bath components are BaC12, CaC12, SrC12, it is said that the melting point is 430 ° C, the use temperature is 480 ~ 550 ° C. The classification time is the same as the high temperature heating time. 5 isothermal furnace, mixed salt of KNO3, NaNO2, isothermal temperature 240 ~ 280 ° C, isothermal time 0.5 ~ 2h. Immediately after isothermal, remove the residue and wash it at room temperature. The straightforward product is immediately clamped and tempered on the fixture. The 6-return furnace is a 100% nitrate bath with a tempering temperature of 550-580 °C. Since the mechanical blade does not require too high a hardness, the tempering temperature is relatively high.

The salt bath electrode is also semi-buried and semi-inserted, with only one side of the electrode in the salt bath. The transformer is a dry salt furnace transformer, air cooled. The temperature of the salt bath is not measured by the radiant pyrometer, nor by the radiant temperature sensor. Instead, it is directly measured by a thermocouple, and the digital display is automatically recorded. The thermocouple is inserted into the furnace to directly measure the temperature with high accuracy, and the product has high heat treatment quality stability.

It is said that some high-speed steel tool tempering formulas in Japan have SrC12+K2CO3, plus KOH deoxidizer.

Japan's heat treatment furnace front boring tool inspection quenching hardness and decarburization method can be borrowed. The first piece of quenching can be judged by the hardness of the file. If the hardness is too high, the quenching temperature is low, and the temperature is high. If the hardness is suitable (such as 62 ~ 63HRC), then the quenching is correct. Use a triangular boring tool to quench the surface of the fire, and depending on the depth of the raft, estimate whether the salt bath is decarburized. The above must be completed by an operator with rich experience on the spot, which is difficult for ordinary people to implement.

2. Large controllable atmosphere heat treatment furnace

This furnace is a special furnace designed by the company. It is mainly used for brazing long blades: brazing, heating and quenching compound heat treatment. The total length of the roller transmission is 18m, the total power of the equipment is 460kW, and the maximum heating temperature is 1300°C. The furnace volume is about 1.6t. It is a rapid heating process when it is kept at quenching temperature for 15-20 min. Microcomputer temperature control, automatic printing. The furnace is filled with nitrogen for protection. The quenching and cooling also fills the liquid nitrogen, such as a high-speed steel blade, and is cooled to 600 ° C to be air-cooled.

The tempering furnace is also a special furnace designed by itself. The tempering temperature depends on the material of the cutting edge and the required hardness, and generally fluctuates between 460 and 600 °C.

3. Box type multi-purpose furnace

The box type multi-purpose furnace is working during the visit. The product in the furnace is a Cr12MoV steel circular saw blade or cutter. The size is about φ100～φ120mm, the thickness is 3~5mm, the heating temperature is 1020°C, and the quenching cooling medium is about 150°C.

The tempering is carried out in the nitrate tank. From the scene, it can be found that the Japanese tool industry, nitrate salt application is very common.

4. Large well type carburizing furnace

The company has several large well carburizing furnaces with a depth of 6.5m and the infiltration agent is methanol + acetone. This type of furnace is mainly used for carburizing the machine guide rails. The cross-sectional dimensions of the guide rail are 60 to 80 mm × 80 to 100 mm, and the length of the guide rail is 4 to 6 m. The carburizing thickness is about 2mm. After carburization, the temperature is reduced and quenched, and the temperature is required to be 56 to 62 HRC.

The company has a strong machine tool manufacturing capacity, most of the self-made, according to the characteristics of the blade processing, the special machine is refined, perhaps one of the factors that they are prosperous and maintain strong competitiveness.

5. High temperature rolling and setting quenching furnace

Some rotary cutters and planers are formed by inserting. That is, the blade steel and the Q235 steel body are heated to the forging temperature, then rolled to a prescribed size, air cooled to room temperature, and then boxed and annealed. Such blade steel is basically low- and medium-alloy steel, the annealing temperature is 810-830 ° C, the heat preservation is about 3 h, and the furnace is cooled to 550 ° C to be air-cooled.

The quenching furnace does not have a protective atmosphere. The ordinary sealed box furnace is directly quenched after heating and holding, and the water temperature is strictly controlled. It is not known whether there is additive in the water. Due to the "3.11" earthquake and tsunami that caused fatal trauma to the company in 2011, it was heartbreaking. When asked about this, the Japanese side is not happy. The author estimates that there will be no other chemicals in the water, that is, a large flowing tank. Controlling the temperature of the effluent is the core technology, energy saving and environmental protection, see if you have the guts and technology.

6. Blade quenching technology

The measures to reduce and avoid heat treatment for environmental pollution have both prevention and treatment, and the Japanese have done it. Cr12MoV steel large blade quenching site is the first fire, after the smoke, after a few seconds, there is no fireworks, there is no oil in the workshop; low and medium alloy steel blade quenching (pressing blade production line) of course no pollution; for heat treatment workshop The generated wastewater is discharged to the standard by treatment, the waste gas is wet adsorbed, and the waste residue is sent to the government specialized agency for treatment. Doing a good job of environmental governance is a conscious action of people.

Zhao Buqing will report questions and answers at the 2014 Advanced Energy Saving Heat Treatment Technology and Equipment Symposium , for more information, welcome to attend!

　　 Notice No. 2 of the "5th Advanced Energy Saving Heat Treatment Technology and Equipment Seminar" in 2014

Meeting time: June 30-July 2, 2014

Location: Changsha

Meeting fee: 1,600 yuan (200 yuan before the remittance offer before June 15)

Contact: Zhang Jing 13683315133