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Improve the craft measure that one set of circles quenches quality of GCr15 steel bearing

30th September 2010 Bearing Technology 0 Comments

The common defect expands the craft when first, the intersection of bearing and suits of lap quench and cool

The part of the bearing adopts the oil as quenching mediums extensively, the main reason is the third stage convection one of the oil in the course of cooling The cooling speed is very slow. It is 20~50 ℃/ s when the 10th when use in past production, machinery oil No. 20 are among 650~500 ℃. Unless begin since 300 ℃ probably convection issues of stage, keep sustaining until by room temperature,just and the horses of bearing steel body be required speeds cooleds smaller not to be identical to be lasted temperatured, thus enable the part of the bearing out of shape in the course of quenching and fracturing and inclined to greatly reducing. Hang, enter in the oil with manual calabash sets of circle at operation mode, sets of circle up and down frequency and range of movement control manually by the operator in oil, this very difficult to meet technological requirement, namely sets of circle flee, work up time, no less than 3s/mm in oil. So, the following quality problems often appear in one set of circles in the course of cooling: 1The hardness homogeneity is bad: Criticize envelopes the samely and enclose the hardness scattered degree of HRC> 2, the same set of circle hardness even HRC> 1 or 2. 2The surface of one set of circles appears in the area a bit softer or some and a bit softer. 3As to effective the intersection of wall and thick> suits of circle of 7mm, present netted to crook the body organize, while being micro-.

Through the quality analysis of the heat treatment of 1998, because cooled the bad stove that needed to reprocess to count and quench 51.5% of the reprocessing rate, the defect that one set of circles produces in the course of cooling, lead to the fact the bearing hardness, intensity are reduced, wearability and resisting fatigue performance to drop.

As to the question that one set of circles appears while cooling, have taken the following measure.

1.Under not changing cooling way, improve the heating temperature of quenching select the temperature of upper limit for use between one set of circles ,To increase the stability of the body of of the subcooling in the steel, thus reduce the critical cooling speed of GCr15 steel. But with the improvement of the heating temperature, carbide two times is dissolved too much in the steel, lead to the fact the intersection of body and crystalline grain grow relatively large, hinder horse from function that body grows up subside, lack the same sets of hardness bad and relatively large circle, differ by HRC2 greatly most, quench, flash back appear part have the intersection of small quantity and little bulk crook body store in frequently still organize; Begin, have tiny needle horse body appear, can see obvious the intersection of needle and the intersection of horse and overheated to organize body under 500 the intersection of metallography and microscope at the same time . Quench deformation amount and rise sharply, the ultra difference rate of the change quantity of the diameter is from rising to more than 20% less than 10% equally, relative degradation of mechanics performance of the part.

2.Using has quenching the kerosene fast of very fast cooling speed. Because of the limitations of objective condition, in not producing, oil groove inevitable to enter a small amount of ink, will make the oil emulsify gradually in the course of using, performance changes, lose the good cooled result, make it reach the ideal result not to quench quality.

Second, research and application of new craft of heat treatment of one set of circles of bearing

It is important factors which influences the heat treatment quality of one set of circles of the bearing to quench the cooled ability of the medium and harden ability. Obviously this relates to metallurgical factor, shape and cooling condition of C curve at the time of cooling of the work piece,etc.. Cool the intersection of ability and strong the intersection of quenching and medium, can hardness to harden layer to be relatively dark make work piece quench. Here in fact, guarantee to cold and big enough rapidly in the nose place of C curve when quenching the hard key, but require the cooling speed is relatively small when horse’s body is changed. The application of the new craft is to meet this characteristic. Through changing the work piece and quenching the speed of relative motion of the kerosene, change the cooling which quenches the medium and harden ability, the organization forms the requirements for different cooling speeds to meet the work piece at different temperatures, thus obtained ideal quenching quality.

1.Test analysis of the cooling intensity

Through testing and analyzing that shows many times, adopting the new craft changes cooling way, can improve the cooled intensity of the oil, thus improve the quality of heat treatment. It is a parameter which reflects the medium cooling ability, H to cool strong H =

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