Hot coil spring heat treatment parts straightening process code

(A) General

1. Hot coil spring heat treatment, due to thermal stress and the formation of stress will cause bending or warping deformation, the deformation is often beyond the tolerance range, therefore, must be used to compensate for this change in shape to So that the size and shape of the hot coil spring within the specified range.
2. Our factory straightening methods are: cold straightening, hot straightening, hot straightening, tempering straightening and cold straightening five, according to the hot coil spring material, shape and mechanical properties of the right Choose alignment process.
3. Hot coil spring straightening should generally include heat treatment before (in the machining shop) and heat treatment after straightening, thin and thin plate shape of the coil spring parts, should pay attention to the amount of deformation before quenching should be controlled in the process Within the specified range.
4. I plant general quenching hot coil spring parts, after straightening should keep their swing less than grinding the remaining 1/2, quenching and tempering coil spring parts should be less than 1-1.5mm.
5. Where straightening hot spring parts, should be in addition to stress treatment to eliminate straightening stress, the general hot spring parts can be carried out in the pit furnace, quenched and tempered hot coil spring parts should be below its tempering Temperature 50-100 ℃ within.

(B) pre-school preparation

1. straightening hot coil spring parts, must first be cleaned to remove the surface oxide and grease.
2. Check the measurement part is flat, two center hole for dirt or other filth blocked.
3. Check the measuring tools such as: dial indicator, flat, triangular iron, the center frame is accurate.
4 understand the hot coil spring material, hardness and heat treatment process.

(C) hot coil spring parts measurement method:

1. Rod-shaped hot coil spring parts: the hot coil spring parts top firmly with the top, and then use the dial gauge to measure the outer circle, find the highest point, with chalk marks.
2. Sheet-shaped hot coil spring parts: The hot coil spring parts on the flat, with a feeler to measure the gap to check the curvature of the coil spring.
3. On the irregular shape of the hot coil spring parts available dial indicator to measure the parallelism.
4. For centerless hot coil spring parts, use a triangular iron to rest both ends and measure with a dial indicator.

(D) the principle of process selection

1. Where not quenched, or the shape of the hardness of less than HRC38 hot coil spring parts, cold straightening method can be used. (On a 60 ton hydraulic press)
2. Carburizing or surface hardening hot coil spring parts, the hardened layer is less than one-fifth of its diameter or thickness of the thickness can be cold straightening method, more than 1/5 of the process allows the use of hot straightening can be adopted law.
3. Alloy steel and alloy tool steel, requiring high hardness hot straightening method should be used.
4. Carbon steel, hot-rolled alloy spring steel parts, the quenching and tempering, the hardness above HRC38 allow some soft spots, can be hot straightening method.
5. Sheet hot coil spring parts, clamps can be used, using the "tempering process alignment method" in the tempering straighten.
6. On the curving of the hot coil spring parts, cold straightening method can be used.

(E) operation

1. cold straightening method:
a) The measured hot coil spring parts, with the triangular iron level, and then to the hot coil spring bending side of the pressure exerted, so that it produces plastic deformation, the size of the pressure, according to the shape of the hot coil spring and the degree of bending To decide, usually a little bend over the horizontal line can be a little time, the pressure can not be completely straightened can be repeated.
B) For hot coil spring parts with pin grooves, threads and sharp corners, copper parts must be padded at the pressure-proof and support points to prevent damage to the surface of the coil spring.
C) After quenching, tempering the hot coil spring parts, especially alloy steel, its toughness is very good, in the cold pressure must be more than the horizontal line pressure in order to achieve good results.
D) carburizing quenching hot coil spring parts can be quenched immediately after cooling to room temperature, can improve efficiency.
2 hot school method
A) After quenching the hot coil spring, cooled to about 200 ℃ that is not completely transformed in the austenite temperature range, immediately straightening, then plastic better, the pressure need not be too large.
B) The operation must be rapid. During the cooling process, the straightening should be continuously measured until the final temperature is reached.
C) to control the temperature of the final school, not too low, or easily crushed. Generally based on actual experience to decide, about 60 ℃, close to the final temperature, the pressure is small, long time.
3 hot law
A) At the center of the bent high side of the hot coil spring part, heat it with a neutral oxy-acetylene flame at a hot spot temperature of approx. 800 ° C and quickly cover it with wet cotton yarn and give it cooling.
B) Hot-rolled alloy spring steel parts around the hot first preheating, the temperature is about 150 ℃, and then the hot spots, the hot spot temperature of not more than 700 ℃ is appropriate.
C) hot spots should try to choose at the scapula or other not very important position, the heating rate as soon as possible, generally not more than 20 seconds is not appropriate.
D) In ​​the hot spots have been burned, usually only repeat once, otherwise the effect is not big, and easily lead to cracks.
4. tempering process of alignment
A) Place the hot coil spring part in the clamp, slightly press it with the plate screw and place it in the furnace for tempering. After about 10 minutes, remove the clamp from the furnace and place it in the furnace for tempering.
B) Alignment must be performed on the first tempering, but not on the second tempering.
C) Hot rolled spring parts that are severely deformed by warpage must be pre-calibrated several times below the tempering temperature prior to clamping in order to avoid brittle fracturing.
Cold straightening
A) Place the measured hot coil spring part on a flat plate, and then hammer the protruding part of the hot coil spring part with a hammer.
B) To use a specially made hammerhead, the hammerhead must not exceed HRC25, or a brass hammerhead.
C) before and after hammering, hot coil spring parts must be treated in addition to stress.
6. Operation should pay attention to safety matters
A) During cold pressing, the coil spring part bracket must be stabilized before applying pressure.
B) All horns and triangles used on the press shall not be made of pig iron.
C) In the pressure, to prevent the hot coil spring parts broken pop-up wounding.
7. Technical inspection
A) All straightened hot coil spring parts must be inspected to comply with the process swing or warpage requirements.
B) Any part of a coil spring that is technically required to have a pendulum or warpage requirement without a straightening procedure shall be inspected by the inspector and, if required, an alignment procedure should be added by the craftman.
C) For hot coil spring parts with sharp corners, pin grooves or fine lines, check whether the shape of the coil spring is damaged by such as dimples or cracks.