JPH11279635A - Method for hardening metallic member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously execute a hardening treatment and a shot blast treatment or a shot peening treatment, to improve the workability and to lower the cost by containing shot particles into hardening liquid having cooling capacity and jetting this hardening liquid at a prescribed speed to a metallic member heated to the hardening temp. SOLUTION: In a water vessel, cooling water is stored as the hardening liquid 3 and in a hopper, glass beads 4 having 10-100 μm average particle diameter, are stored as the shot particles and a nozzle 2 is connected with the water vessel and the hopper through a pump. A steel plate 5 is heated to the hardening temp. with a high frequency induction coil 1 and the hardening liquid 3 containing the glass beads 4 is jetted at e.g. 200 MPa from the nozzle 2. In such a way, the hardening treatment of the steel plate 5 is executed with the hardening liquid 3 and simultaneously the shot blast treatment is executed to remove the oxidizing scale on the surface of the steel plate 5. In this way, the workability under consideration of the hardening of the steel plate 5, the improvement of corrosion resistance or the improvement of fatigue strength, is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in a method for quenching a metal member.

[0002]

2. Description of the Related Art When it is desired to harden a metal member such as a steel plate by a quenching structure such as martensite, the metal member is first heated to a quenching temperature, and then the metal member is quenched with a quenching liquid having a cooling ability such as cooling water. Can be quenched. At that time, Japanese Patent Application Laid-Open Nos.
As described in JP-A-73926, heating of a metal member is performed by a high-frequency coil, and a quenching liquid is sprayed on the metal member at a predetermined speed.

[0003]

However, the metal member which has been quenched as described above has an oxide scale or so-called black scale remaining on its surface. It is difficult to secure the corrosion resistance of the coating, and rust is generated at an early stage.
Therefore, in order to improve the corrosion resistance of the quenched metal member, it is necessary to perform a shot blast process of projecting shot grains at a predetermined speed on the quenched metal member.

Further, in order to improve the fatigue strength of the quenched metal member, a shot peening process for projecting shot grains at a predetermined speed on the quenched metal member may be performed. In these cases, since shot blasting and shot peening are performed after the quenching, the workability is poor and the production cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and solves the problem of improving workability in consideration of the hardening of metal members and the improvement of corrosion resistance of coating or improvement of fatigue strength. It should be an issue to be done.

[0006]

According to the present invention, there is provided a method for quenching a metal member, the method comprising: spraying a quenching liquid having a cooling ability onto a metal member heated to a quenching temperature at a predetermined speed. The quenching liquid is characterized by including shot grains. In the quenching method of the present invention, in order to spray a quenching liquid containing shot grains at a predetermined speed on a metal member heated to a quenching temperature, quenching and shot blasting or shot peening are performed simultaneously. Become. For this reason, according to this quenching method, the workability can be improved in consideration of the hardening of the metal member and the improvement of the corrosion resistance of the coating or the improvement of the fatigue strength, and the manufacturing cost can be reduced.

The shot grains include (1) general steel grains which can be used for shot blasting or shot peening such as tempered cast iron shot grains, chilled tempered shot grains, cut wire shot grains, and the like. ) Glass grains,
(3) Ceramic particles such as alumina particles and silicon nitride particles can be used. When the metal member is heated by a high-frequency coil, it is preferable to use glass particles or ceramic particles. Because, in this case, the shot particles in the quenching liquid are located near the high-frequency coil, and the shot particles made of metal such as steel particles may generate heat due to the effect of the high-frequency coil and adversely affect the quenching process. Because there is.

If shot grains having no sharp corners are employed, compressive stress can be left in the metal member as shot peening treatment, and the fatigue strength of the metal member can be improved. On the other hand, if shot grains having sharp corners are employed, an effect as shot peening can be obtained, and oxide scale and black scale on the surface of the metal member can be removed as shot blasting.

The quenching solution, the quenching temperature, the average particle size of the shot particles, the speed at which the shot particles are sprayed together with the quenching solution,
Conditions such as the pressure of the quenching liquid containing shot particles can be selected depending on the material of the metal member and the like. When the metal member is made of a steel plate, a quenching temperature of 750 to 1150 ° C can be adopted. In this case, the average particle size of the shot particles can be selected from 10 to 100 μm which is usually employed in shot blasting or shot peening. Further, in this case, the speed at which the shot grains are sprayed together with the quenching liquid can be selected from the range of 20 to 50 m / sec normally employed in shot blasting or shot peening. In this case, the pressure of the quenching liquid containing shot particles can be selected from 50 to 300 MPa.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 embodying the present invention will be described below with reference to the drawings. (Embodiment 1) First, as shown in FIG. 1, a commercially available induction hardening apparatus having a nozzle 2 on the side of the high frequency coil 1 is prepared. The high-frequency coil 1 is connected to a power supply or the like (not shown), and the nozzle 2 is connected to a water tank and a hopper via a valve and a pump (not shown). Cooling water 3 as a quenching liquid is stored in a water tank, and glass beads 4 as shot particles are stored in a hopper. The average particle size of the glass beads 4 is 10 to 100 μm. Also, J
A steel plate 5 made of ISSCP440 is prepared.

Then, the steel plate 5 is heated by the high-frequency coil 1 to a quenching temperature of 1050 ° C. After a lapse of a predetermined time, energization of the high-frequency coil 1 is stopped, and cooling water 3 containing glass beads 4 is sprayed from the nozzle 2. At this time, the pressure of the cooling water 3 including the glass beads 4 is 200 MPa. Thus, the steel sheet 5 is quenched by the cooling water 3. At the same time, the glass beads 4 collide with the steel plate 5 to remove oxide scale on the surface of the steel plate 5 as a shot blast process. For this reason, it turns out that this steel plate 5 can exhibit excellent corrosion resistance of coating. "Measurement of residual stress"

[0012]

Example 1 A steel sheet 5 subjected to a quenching process and a shot blasting process according to the first embodiment was subjected to a front x-direction (F
r. The residual stress (kg / mm ² ) was measured in the x direction on the front side (Y on the Fr. side), the x direction on the rear side (x on the Rr. Side), and the y direction on the rear side (F on the Fr. side).

[0013]

Comparative Example 1 On the other hand, the residual stress was measured in the same manner as in Example 1 for a steel sheet which was not subjected to any treatment after purchase.

[0014]

Comparative Example 2 The residual stress was measured in the same manner as in Example 1 for the steel sheet subjected to only the quenching treatment as in Embodiment 1. The results are shown in FIG. As shown in FIG.
Since the steel sheet 5 of Example 1 is given a larger residual stress than the steel sheets of Comparative Examples 1 and 2, it can be seen that excellent fatigue strength can be exhibited.

Therefore, according to the first embodiment, since shot blasting and shot peening can be performed simultaneously with the quenching, the case where the hardening of the steel sheet 5 and the improvement of the corrosion resistance of the coating and the improvement of the fatigue strength are considered. It can be seen that the workability in the above can be improved. (Embodiment 2) As shown in FIG.
A rear upper arm 6 formed by welding a steel plate made of The arm 6 is subjected to quenching, shot blasting, and shot peening as in the first embodiment. "Evaluation of corrosion resistance of paint"

[0016]

Example 2 Salt water was sprayed over a range of 80 cm ² of the coated arm 6 to evaluate the corrosion resistance of the coating. The concentration of the salt water was 5.0%, the pH of the salt water was 6.8, the amount of the salt water was 1.4 ml / hour, the spray air pressure was 98 kPa,
The temperature in the spray chamber is 35 ° C and the relative humidity in the spray chamber is 98.
%, Evaluation time is 480 hours. As a result, no rust was generated on the arm 6 even after 30 days.

[0017]

COMPARATIVE EXAMPLE 3 On the other hand, the arm which was obtained by simply welding a purchased steel plate was similarly coated, and the corrosion resistance of the arm was evaluated. As a result, for this arm,
No rust was generated after 0 days.

[0018]

COMPARATIVE EXAMPLE 4 In the same manner as in the first embodiment, the arm subjected to only the quenching treatment was coated similarly, and the corrosion resistance of the coating of the arm was evaluated. As a result, rust was generated on the portion of the arm that had been induction hardened on the 10th day. Therefore, according to the second embodiment, it is understood that the curing of the arm 6 and the improvement of the corrosion resistance of the coating can be simultaneously realized. "Evaluation of Fatigue Strength" As shown in FIG. 3, for the arm 6 of Example 2 and the arms of Comparative Examples 3 and 4, two feet were fixed to the base 7, and a load of ± 150 kg was applied in the direction of the arrow. Load was applied and a bending fatigue test was performed. As a result, in the arm of Comparative Example 3, breakage occurred at the stress concentration portion after 200,000 times, and
In the arm No. 1, the damage was caused at the stress concentration portion after 1,000,000 times, whereas in the arm 6 of Example 2, no damage was caused at the stress concentration portion even after 10,000,000 times.

Therefore, according to the second embodiment, it is understood that the hardening of the arm 6 and the improvement of the fatigue strength can be simultaneously realized. As described above, according to the first and second embodiments, it is possible to improve the workability in consideration of the hardening of the metal member and the improvement of the corrosion resistance of the coating or the improvement of the fatigue strength, and it is possible to reduce the manufacturing cost. I understand.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an induction hardening device used in Embodiments 1 and 2.

FIG. 2 is a graph showing residual stress in Example 1 and Comparative Examples 1 and 2.

FIG. 3 is a schematic elevation view of a rear upper arm in Example 2 and Comparative Examples 3 and 4.

[Explanation of symbols]

 5, 6: metal member (5: steel plate, 6: rear upper arm) 3: quenching liquid (cooling water) 4: shot particles (glass beads)

Claims (1)

[Claims] 1. A method of quenching a metal member heated at a quenching temperature to a metal member heated at a quenching temperature at a predetermined speed, wherein the quenching solution contains shot grains. How to quench components.