JPH0122116B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to organic polymer bonded grinding wheels. More specifically, the present invention relates to a grinding wheel bonded with a phenolic resin cured with hexamethylenetetramine, which is used, for example, in snagging wheels and cut-off wheels. BACKGROUND PRIOR ART The following patents are representative of the most relevant prior art known to applicant at the time of filing. U.S. Patent No. 3406020, November 15, 1968 W.J.
D'Alessandro UK Patent No. 1207766, November 7th,
1970Vnited Kingdom When manufacturing resin-bonded grinding wheels, the amount of abrasive grains is measured and mixed with powdered phenolic resin based on the bonding component, and then the resulting mixture is used to form the mold of the grinding wheel. Then, the resin is cured. It has been found useful to wet the abrasive grain with furfural prior to mixing it with the resin bonding component to further enhance the modification and bonding of the resin to the abrasive grain. US Patent No.
No. 3406020, D′Alessandro, November 15, 1968 and British Patent No. 1207766, Norton Company;
1207766, published October 7, 1970, describes a method for manufacturing such a grinding wheel. D'Alessandro asserts that bonded wheels with high bending strength can be produced and teaches a method for producing phenolic bonded abrasive wheels with various additives mixed with abrasive grains and binders. Various abrasives such as alumina, corundum, silicone carbide, diamond grains, etc. have been mentioned as inclusions in novolac resin bonded wheels with hexamethylenetetramine hardeners.
The curing agent is used in a range of about 2 to 50% based on the weight of the novolac, with a preferred range of about 3 to 20%, and more preferably a range of 7 to 15%. This patent describes the use of 0 to 100 parts of wetting agent per 100 parts of novolac, the wetting agent selected from the group consisting of liquid resol resins, cresols, furfural and furfural alcohol. The wetting agent is a ratio of approximately 40 parts liquid phenolic resin wetting agent to 80 parts powdered novolak binder, and 120 parts solid novolak resin and 10 parts solid novolak resin.
It is mixed with abrasive grains at another blending ratio of ~20 parts furfural. The formulation is such that the abrasive mixture of abrasive grains, wetting agent, and binder is free-flowing at room temperature, and the only criterion for determining how much wetting agent is used is that the mixture remains in a relatively free-flowing state until it is charged into a mold. The British patent relates to a method for manufacturing an improved self-dressing hand-conditioned cast snagging wheel with a resin binder, the wheel having a porosity of 22-26% by volume, The material is spinel or mullite granules or a mixture of such abrasive particles. The manufacture of such porous wheels is described, with one comment regarding the use of furfural in the preparation of the abrasive grains and resin binder from which the wheel is molded, and that furfural is a dry resin binder. per pound
It is stated that it is used in a conventional manner as a plasticizer in an amount of 55 cubic centimeters. Nothing is said regarding the amount of hexamethylenetetramine used. DISCLOSURE OF THE INVENTION The present invention provides an improvement over the prior art in explaining the relationship between the amount of furfural wetting agent used in the abrasive grains in relation to the amount of curing agent used in the resin binder. It is something. The word "mixture" is used here in the sense well known in grinding wheel technology, i.e., a more or less granulated mixture of abrasive grains coated with powdered, uncured polymer or resin. , means. Similarly, when the words "binder" or "resin binder" are used, these terms include the resin alone and one or more of the many fillers, grinding aids, and reinforcing agents known in the art. It is meant to include a binder consisting of. Maximum grinding for a given wheel specification when a preferred amount of furfural wetting agent is applied to the abrasive grain before mixing it with a powdered phenolic resin binder. It has been found that the ratio can be achieved more reliably. Furfural is used to wet the abrasive grain and is added to the abrasive grain in a proportion relative to the hardening agent used, hexamethylenetetramine. The curing agent itself is added in a certain amount to the resin binder in order to control the durability characteristics of the hardened whetstone. Durability of phenol-bonded grinding wheels, such as snagging wheels or cut-off wheels, is achieved by increasing the amount of hexamethylenetetramine, a hardening agent used with novolac resins, to cross-link the phenolic resin binder. It is known that improvements can be made by increasing the density. It has been found that there is a unique relationship between the amount of wetting agent furfural applied to the abrasive grain in relation to the amount of curing agent used in the binder component of the novolak resin. The amount of wetting agent then varies according to the behavior taught herein to control grinding ratio characteristics in hardened wheels. It is therefore an object of this invention to provide a grinding wheel with improved durability and grinding ratio characteristics. Another objective is to produce a grinding wheel with improved durability and grinding ratio.
It is an object of the present invention to provide a mixing procedure for relating the amount of furfural used to wet the abrasive grains and hexamethylenetetramine as a curing agent in the binder. Another object of this invention is to teach how snagging and cutoff wheels, etc., can be manufactured to have maximum grinding ratios for each particular configuration. Other objectives will be detailed next. Preferred Embodiments Although the following discussion of preferred embodiments is directed specifically to novolac resins or phenol-formaldehyde condensates, other phenol-based polymers are within the scope of the invention, such as modified phenol-formaldehyde resins, phenolfurfural resins, etc. It is understood that entering
As used herein, the term "phenolic resin" is meant to include such resins that can be cured with hexamethylenetetramine. Ordinary resin-bonded grinding wheels, which are subjected to the most difficult grinding operations, are cut-off wheels, millet wheels, used for the production of steel pieces for steel cutting, rolling, etc. and for cutting operations in castings, respectively. Includes grinding wheels such as Tsuto snagging wheels and cast snagging wheels. Most of such grinding wheels are also bonded with a novolak resin based bonding agent with a hardening agent of hexamethylenetetramine in the bonding agent to produce a thermoset bonding agent with good durability. It is made of abrasive grains. The amount of hardening agent used is known to be directly related to the durability of the hardened wheel structure since the crosslinking density of the wheel will depend on the use of more or less of this hardening agent. However, heretofore durability has not been related to the amount of furfural as much as the amount of hexamethylenetetramine in the novolak resin. Now the grinding ratio of the wheel, i.e. the amount of metal ground from the workpiece per unit volume of the wheel consumed in the grinding operation, is proportional to the hardening agent hexamethylenetetramine present in the binder component of the resin. It has been found that the optimum amount of furfural to wet the abrasive grains mixed with the agent can be maximized for a given phenolic resin binder. Wetting the abrasive grains with furfural prior to mixing the abrasive grains with a binder containing a powdered novolac resin and possibly a filler has been used in the past; There was no indication that the proportions were related to the amount of curing agent used in the binder component of the phenolic resin. More particularly, the grinding ratio of the hardened abrasive wheel can be controlled by varying the amount of wetting agent furfural used in the abrasive grain, in an amount that is related to the amount of the hardening agent hexamethylenetetramine in the novolak resin binder. This was not known until now. With reference to the data presented in the figure, when furfural is used as a wetting agent for the abrasive grains in a grinding wheel bonded with a novolak resin containing hexamethylenetetramine as a hardening agent, the best The grinding ratio is between 9 and 9 in the phenolic resin binder mixture.
Using a hardener amount of hexamethylenetetramine in the range of 14% and 20 to 60 cubic centimeters of furfural per pound of phenolic resin to wet the abrasive grains before mixing with the powdered resin binder component. It can be seen that by using , it can be realized consistently from beginning to end. It can be seen in the figure that as the amount of hexamethylenetetramine increases in the novolak binder component, the amount of furfural increases at which point the grinding ratio is optimized in the resulting wheel. For each percentage of curing agent in resin binder component within the range of 9-14%, the powder is There is an optimum amount of furfural used to wet the abrasive grains before mixing with the embodied resin binder. According to the present invention, the phenolic resin binder provides the desired durability in the grinding wheel by using some hexamethylenetetramine curing agent and a corresponding specific amount of furfural to create optimal grinding properties in the finished grinding wheel. can be configured for use with a given group of abrasive grains so as to obtain For comparison purposes, a pair of snagging wheels were constructed to demonstrate the convenience of relating the amount of wetting agent to the hardening agent used. Steel Conditioning Snugs wheels were made with 16 grit alumina-zirconia abrasive grains and bonded with a phenolic resin binder, which is commonly used to create fairly dense wheels. The abrasive grains in each wheel were also wetted with furfural before being mixed with a powdered novolac resin formulation containing 14% hexamethylenetetramine curing agent. In one wheel the amount of furfural was 17 cubic centimeters per pound of resin in the wheel, while in the other wheel the amount of furfural was 40 cubic centimeters per pound of resin. The wheels were heat pressed and conventionally hardened to produce a 16 inch diameter, 2 inch thick wheel with a 6 inch hole in the center. Both whetstones
It was installed on a 30 horsepower snagging machine and operated at a tip force of 400 pounds and a surface velocity of 9500 feet per minute. The whetstone was used to grind low alloy steel AISI4140. Wheel wear rate in cubic inches per hour and metal removal in pounds per hour were measured along with the power required to run each wheel throughout the test. The comparative grinding results are expressed as follows. (a) An abrasive wheel made from abrasive grains wetted with 17 c.c. per pound of resin mixture before mixing will
Showing a grinding wheel that wears out at a rate of 25.51 cubic inches,
Metal gives a grinding ratio of 4.57
It was removed at a rate of 116.6 pounds/hour at 20.40KW. (b) A wheel with the same formulation as the previous 17 c.c. wheel, except that the abrasive grains were wetted with 40 c.c. of furfural, wore out the wheel at a rate of 20.82 cubic inches per hour. Shown, metal is 18.88KW and 5.34
giving a more effective grinding ratio of
removed at a rate of 111.13 pounds/hour. These results show an improved grinding ratio for the 40 c.c. wheel, as expected from the 14% hexamethylenetetramine curve in the figure. Approximately the same amount of metal is removed in each test, but less effort is required for the 40 c.c. wheel. Large amounts of furfural cannot be added to the abrasive grains because the mixing preparation or mixing results are difficult and impossible to handle for the grinding wheel formulation. To overcome this problem, some of the total amount of furfural can be added directly to the abrasive grain, and the remainder, either alone or mixed with a second liquid, can be added to the abrasive after the binder has been added to the abrasive. added to the mixture. Below is a detailed example of this type of grindstone. In a second test, hot pressed cutoff wheels were made with a novolak resin binder with 9% hexamethylenetetramine hardener. The two wheels were made with 24-grit alumina abrasive, and each wheel had a diameter of 24 inches and was 3/16
inch thick with a 1-3/4 inch hole in the center. In the first wheel, 15 cubic centimeters of furfural is used to wet the abrasive grains before mixing with the powdered resin binder, and the resin is added so that the amount of total furfural is 55.9 cc per pound of resin. Furfural is added to the abrasive mixture. It takes 30c.c. to make other whetstones in the same way.
of furfural, the amount of total furfural is resin 1
A second amount of furfural was added directly to the abrasive grains, which was added to the resin-abrasive mixture at 70 c.c. per pound. Some tests were performed on the resulting grindstone. Dry Cutting Tabor Hydraulic Chop Machine
Used to drive the grindstone at 2200RPM. Each 2 inch diameter 304 stainless steel round bar was cut taking 6 seconds to cut. The data shows that, as expected from the 9% curve in the figure, a wheel made with abrasive grains wetted with 59.9 cc of furfural per pound of resin has an average grinding ratio of 3.21, and 70.9 cc of furfural per pound of resin. shows that wheels made with abrasive grains wetted with abrasive grains have an average grinding ratio of 2.50. Another test was conducted with these cutoff wheels on the grinder to produce plunge cuts using a 20KW power rating to drive a Fox swing frame grinder. 2 inch plunge cut
Made from C1018CR steel. This machine was operated at 1900 RPM. Throughout this test, the wheel made with 59.9 cc of furfural had a grinding ratio of 0.99, and the wheel made with 70.9 cc of furfural had a grinding ratio of 0.86. These tests showed that the preferred lower amount of furfural was 9% when the same processing rate was applied to different cut-off wheels made with various amounts of furfural proportional to the amount of hexamethylenetetramine curing agent present. Hexamethylenetetramine was shown to give a higher grinding ratio when used in a binder, demonstrating the relationship between furfural and furfural. Several different laboratory tests are performed under controlled conditions to compare the relative strengths of hardened resin bonded grinding wheel components. Bars with the same abrasive grain and resin binder compositions used in the standard wheel composition for these tests are formed and cured in the same manner as the snagging wheels described above. The flexural strength of each of the hardened bars is measured using a 2-inch flexural span in three-point bending on an Instron testing machine to determine average breaking strength.
This bending test shows that the durability increases, yet the strength of the wheel is maintained even when the amount of furfural to optimize the grinding ratio is changed, as evidenced by the following data: A number of 5" x 1/2" x 1/4" rods were combined with a modified resin containing the wetting agent Carbosorter used, along with powdered phenolic resin in an amount of approximately 20 c.c. per pound of resin. In these bars, the abrasives were 17 c.c., 40 c.c. and 60 grit to wet the abrasive grains.
It was also bonded with novolacs containing 9% and 14% additions of the curing agent hexamethylenetetramine with cc of furfural. The mixture is:

[Table] The resulting hardened rods have an average of 4 rods to break at each furfural amount.
Tested to determine psi. The average strength at 17c.c. is 14490psi and at 40c.c. it is 15400psi and at 60c.c.
It was 14150psi. This data shows that the strength of the wheel remains high with the addition of larger amounts of hexamethylenetetramine curing agent. The addition of furfural to the abrasive grain during mixing which is proportional to the amount of hexamethylenetetramine present causes the strength of the bond to remain as the content of hexamethylenetetramine increases. The ideal amount of furfural added to the abrasive grains is
The realization that the amount of hexamethylenetetramine curing agent in the binder is related to the durability and durability of new grinding wheels is desired with the introduction of new high efficiency steel conditioning grinders into the industry. This is important because it plays a role in improving the grinding ratio. When these heavy machines are operated at full capacity, for example to cut pieces of steel, a durable grinding wheel is desired. A more durable grinding wheel than previously known is produced according to the invention by combining appropriate amounts of furfural and hexamethylenetetramine. Generally, in bonding agents for manufacturing grinding wheels, a combination of amounts of furfural wetting agent used with abrasive grains bonded with a novolac phenolic resin with a hexamethylenetetramine hardening agent is used to improve the hardened grinding wheel grinds. It has been found that the deterioration ratio, durability and strength are affected. When the amount of hexamethylenetetramine is 12% or more by weight in the resin and up to 20% addition of this curing agent, the amount of furfural ranges from 20 c.c. It varies proportionately up to about 60 c.c. per pound of furfural. Grinding wheels made in accordance with the teachings of this invention may be prepared by mixing or other methods such as the use of additives such as fillers, grinding aids, hot or cold pressing, or curing of the phenolic resin mixture to produce the desired grinding wheels. It can also be manufactured by known techniques. While the above describes the preferred form of the invention, variations thereon may occur to those skilled in the art that are within the scope of the following claims. The invention is independent of the type of abrasive used, and thus includes, for example, fused sintered alumina, fused sintered alumina-zirconia, silicon carbide, spinel, sinter, mullite, equiaxed boron nitride. , boron carbide,
It will be understood that this includes abrasives such as diamond and mixtures thereof.

[Brief explanation of drawings]

The figure shows the polishing of the final product made in accordance with this invention by varying the amount of furfural, a wetting agent added to the abrasive grains, in relation to the amount of hexamethylenetetramine (HEXA), a hardening agent, in the resin. It is a graph showing a change in grinding ratio of a whetstone.

Claims (1)

[Claims] 1. A grinding wheel bonded with a phenolic resin, wherein hexamethylenetetramine is a curing agent,
Furfural is a wetting agent applied at least partially to the abrasive grains in the manufacture of the abrasive wheel mixture, said furfural is used in an amount of 20 to 60 cubic centimeters per pound of resin, and said furfural is used in an amount of hexamethylenetetramine in the resin. is increased from 12% to 20% by weight,
A whetstone characterized by being contained in a whetstone compound. 2 The hexamethylenetetramine is added to the resin.
The abrasive wheel of claim 1, wherein said furfural is present in said resin in an amount of 14% by weight and said furfural is added in an amount of 40 c.c. per pound of resin mixture. 3. The grindstone according to claim 1, wherein the phenolic resin is a novolak resin. 4 The abrasive grains are bonded with a phenolic resin, hexamethylenetetramine is the curing agent, and furfural is the wetting agent applied at least partially to the abrasive grains in the manufacture of the abrasive wheel mixture. Wet with furfural, then mix the furfural-wet abrasive grains with a powdered novolak resin binder containing a hexamethylenetetramine hardener, add additional amounts of furfural if necessary to the resin-abrasive mixture, and mix Before wetting the grains, measure out the total amount of fufural in an amount related to the amount of hexamethylenetetramine in the resin binder, and make sure that the amount is such that the hardener is in the resin mixture.
A method characterized in that it is in the range of 20 to 60 c.c. of furfural per pound of resin when present at 12 to 20% by weight.