A Comprehensive Guide To 35# Steel

What is 35# Steel?

35# steel, also known as 35CrMo steel or 35CrMo4, is a high-quality carbon structural steel with good plasticity, appropriate strength, process performance, and acceptable welding performance. It is mostly used in the normalized and quenched, and tempered states.

Chemical composition of 35# steel

35# steel is a type of carbon steel with a carbon content of 0.32-0.40%. Its chemical composition also includes:

С	Si	Mn	Ni	S	P	Cr	Cu	As
0.32-0.40	0.17-0.37	0.50-0.80	≤0.30	≤0.035	≤0.030	≤0.25	≤0.30	≤0.08

Mechanical properties of 35 steel

35# steel exhibits the following mechanical properties:

Mechanical properties at elevated temperatures

Test t, ° C	σ0.2, MPa	σB, MPa	δ5 ,%	ψ,%	KCU, J/m2
Hot rolled condition
200	300	580	nine	39	78
300	205	580	21	52	69
400	185	500	23	64	59
500	145	350	24	70	39
600	78	195	35	83	69
Sample 6 mm in diameter, 30 mm long, rolled. Deformation rate 16 mm/min. Strain rate 0.0091/s.
700	100	150	34	75
800	69	110	56	100
900	55	74	54	100
1000	30	51	69	100
1100	21	39	74	100
1200	15	27	85	100
1300	18	23	58	100

Mechanical properties of rolled products

Heat treatment, delivery condition	Section, mm	σB, MPa	δ5 ,%	δ4 ,%	ψ,%	HB
Hot-rolled steel, forged, calibrated and silver grade 2 after normalization	25	25	20		45
Calibrated steel grade 5 after work-hardening			6		35
Calibrated steel grade 5 after annealing or high tempering			15		45
Calibrated and calibrated steel with special finishing after spheroidizing annealing		<540			45	187
Steel calibrated and calibrated with a special finish, work-hardened without heat treatment		590	5		40	207
Annealed or highly tempered sheets	80	480	22
Normalized or hot rolled strips	6−25	530	20		45
Hot rolled sheet	<2	490−640		17
Cold rolled sheet	2−3.9	490−640		19
Heat-treated sheet of the 1st-2nd category	4−14	480−630	22			163
Cold rolled annealed strip	0.1−4	400−650		16
Cold-rolled cold-worked strip, strength class H2	0.1−4	800−950
Pipes hot-, cold- and heat-deformed, heat-treated		510	17			187

Mechanical properties of forgings

Heat treatment, delivery condition	Section, mm	σ0.2, MPa	σB, MPa	δ5 ,%	ψ,%	KCU, J/m2	HB
Normalization
KP 195	300−500	195	390	20	45	49	111−156
KP 195	500−800	195	390	18	38	44	111−156
KP 215	100−300	215	430	20	48	49	123−167
KP 215	300−500	215	430	18	40	44	123−167
KP 215	500−800	215	430	16	35	39	123−167
KP 245	<100	245	470	22	48	49	143−179
KP 245	100−300	245	470	19	42	39	143−179
KP 245	300−500	245	470	17	35	39	143−179
Hardening. Vacation.
KP 275	<100	275	530	20	40	44	156−197
KP 275	100−300	275	530	17	38	34	156−197
KP 315	<100	315	570	17	38	39	167−207

Mechanical properties depending on the tempering temperature

Vacation t, °С	σ0.2, MPa	σB, MPa	δ5 ,%	ψ,%	KCU, J/m2	HB
Billet with a diameter of 60 mm, quenching at 850 ° C in water
200	600	760	13	60	29	226
300	560	735	14	63	29	212
400	520	690	15	64	98	200
500	470	660	17	67	137	189
600	410	620	18	71	176	175
700	340	580	19	73	186	162

Technological properties of steel 35#

Forging temperature

Beginning 1280, end 750. Billets with a cross section up to 800 mm are cooled in air.

Weldability

Limited weldability. Methods of welding RDS, ADS submerged arc and gas shielded, EShS. Heating and subsequent heat treatment is recommended. KTS without restrictions.

Machinability by cutting

In the hot-rolled state at HB 144–156 and σB = 510 MPa, Kυb.st. = 1.3.

Tendency to release ability

Not inclined.

Flock sensitivity

Not sensitive.

Temperature of critical points of steel 35#

Critical point	°C
Ac1	730
Ac3	810
Ar3	796
Ar1	680
Mn	360

Impact strength of steel 35#

Impact strength, KCU, J/cm²

Delivery status, heat treatment	20	-20	-20	-50	-60
Normalization	63	47	45	14	12

Endurance limit steel 35#

σ-1, MPa	τ-1, MPa	σB, MPa	Heat treatment, steel condition
265		570	Normalization 850 C.
245	147		Normalization 850−890 C. Vacation 650−680 C.
402		710	Hardening 850 C. Ottpusk 650 C.

Physical properties of steel 35#

The physical properties of 35# steel include:

Test temperature, °С	20	100	200	300	400	500	600	700	800	900
Normal elastic modulus, E, GPa	206	197	187	156	168
Density of steel, pn, kg / m 3	7826	7804	7771	7738	7700	7662	7623	7583	7600	7549
Thermal conductivity coefficient W / (m ° С)		49	49	47	44	41	38	35	29	28
Ud. electrical resistance (p, Nom. m)		251	321	408	511	629	759	922	1112	1156
Test temperature, ° С	20−100	20−200	20−300	20−400	20−500	20−600	20−700	20−800	20−900	20−1000
Linear expansion coefficient (a, 10−6 1 / ° С)	12	12.9	13.6	14.2	14.6	15	15.2	12.7	13.9
Specific heat (C, J / (kg ° C))	469	490	511	532	553	578	611	708	699

Strength and Durability of 35# steel

One of the primary advantages of 35# steel is its excellent strength and durability. It’s high tensile and yield strengths allow it to withstand substantial loads and resist deformation, making it suitable for applications requiring a high mechanical performance level.

Weldability of 35# steel

35# steel has good weldability, which enables it to be easily joined to other materials through various welding techniques. This characteristic is particularly useful in the construction and automotive industries, where components often need to be welded together.

Affordability of 35# steel

Compared to other high-performance steel alloys, 35# steel is relatively affordable. This cost-effectiveness makes it an attractive option for large-scale projects and budget-conscious manufacturers.

Usage of 35 # steel

35 # steel is widely used in the manufacturing of various forgings and hot pressed parts, cold drawn and top forged steel, seamless steel pipes, and parts in mechanical manufacturing, such as crankshafts, shafts, pins, levers, connecting rods, crossbeams, sleeves, wheels, washers, screws, nuts, motorcycle frames, etc.

The difference between 35 # steel and 45 # steel

45 # steel is a high-quality carbon structural steel with a strength of 61 and an HRC of 48-55, which is commonly used in machinery; 35# steel is also a high-quality carbon structural steel, but its strength is only 54, and HRC is 38-45. Sparks can distinguish their differences. Sparks with low carbon content have a drooping tail, slightly darker color, and sometimes have pointed tail flowers. The amount of flowers is not large, and the awn line is thicker. On the 45th, the tail is straight, and the streamline at the tip has a bifurcation phenomenon, resulting in a higher ejection force and more flowers. 45# steel has a higher carbon content than 35# steel, but 45# steel is harder.

The Effect of Annealing Process on the Structure and Hardness of 35# Steel

Normally, annealing reduces hardness and improves toughness, plasticity, and processability. This is because annealing can eliminate the internal stresses in the steel so that the steel organization is homogeneous in preparation for the next process.
The annealing process can change the organization of steel and toughness and other mechanical properties; the original austenite grain determines the size of the fracture unit small plane, the toughness of steel plays a decisive role; the pearlite domain interface does not form a big obstacle to crack expansion, the contribution to toughness is not large. For the toughness of fracture shrinkage as an indicator, the influence of original austenite grain size is the largest, the influence of lamellar spacing is the second, and the smallest influence is the pearlite domain size. The influence on the tissue morphology of lamellar pearlite mainly realizes the influence of austenite grain size on toughness. The pearlite lamellar spacing corresponds to the impact toughness, and the refinement of the lamellar spacing is beneficial to improving toughness. Coarse grain austenite can form several pearlite spheres composed of pearlite domains. The orientation difference between adjacent pearlite domains in the pearlite spheres is small, with less resistance to crack expansion and lower resistance toughness. When the austenite grain refinement, the pearlite organization and the orientation difference between adjacent pearlite domains are larger, which increases the resistance to crack expansion and improves the toughness.
The annealing process’s effect on steel’s hardness has yet to be reported. With the development of the industry, the hardness of steel parts is required to be controlled more and more precisely. The hardness requirements of some small parts are also diversified, such as the pins of automotive clutch assemblies, which are small in size and require a hardness of 12 HRB higher in the middle part than in the ends and 65-80 HRB in the ends.
We study the effect of the annealing process on the organization and hardness of 35# steel to achieve precise control of 35# steel hardness.

Experimental materials and methods

The experimental material is rolled 35# steel cold pier coil steel with a hardness of 93HRB and basic composition (mass fraction, %) of 0.32-0.40C, 0.17-0.37Si, 0.50-0.80Mn, S≤0.035, P≤0.035, Cr≤0.25, Ni≤0.25, Cu≤0.25.
The experimental process is divided into seven groups:

• No.1: specimens with the furnace temperature rise annealing, 820 ℃ insulation 10min, with the furnace cooling to 500 ℃ out of the furnace air cooling;
• No.2: specimens with the furnace temperature rise annealing, 860 ℃ insulation 10min, with the furnace cooling to 500 ℃ out of the furnace air cooling;
• No.3: specimens with the furnace temperature rise annealing, 925 ℃ insulation 10min, with the furnace cooling to 500 ℃ out of the furnace air cooling;
• No.4: the starting furnace temperature is 150 ℃, holding temperature 925 ℃, holding time 10min, with the furnace cooling to 500 ℃ out of the furnace air-cooling;
• No.5: the starting furnace temperature 850 ℃, holding temperature 925 ℃, holding time 10min, with the furnace cooling to 500 ℃ out of the furnace air-cooling;
• No.6: the specimen with the furnace heating annealing, holding temperature 860 ℃, holding time 10min, with the furnace cooling to Room temperature;
• No.7: specimen with the furnace temperature annealing, holding temperature of 925 ℃, holding 10min, with the furnace cooling to room temperature.

Metallographic specimens were corroded with a dilute acid solution to determine the grain size, and the grain appearance and size of the tissue were observed under the metallographic microscope (OM). The hardness was measured by a Rockwell Meter.

Experimental results and analysis

The effect of holding temperature on the annealing organization and hardness of  35# steel
The hardness of  35# steel is 62HRB after process No.1 treatment; the grain size is small, the recrystallization is not sufficient, the microstructure of pearlite and ferrite grains are small and uniformly distributed; the hardness of process No.2 treatment is 58HRB, compared with process No.1 grains gradually become larger; the hardness of process No.3 treatment is 57HRB. With the increase in heating temperature, the average hardness value decreases. The average hardness value decreases as the heating temperature increases; the grains have been fully recrystallized, and the number of coarse grains increases. It can be seen that with the increase in heating temperature, the grains of pearlite and ferrite in the microstructure become more and more coarse, and the distribution becomes uneven.
With the increase of heating temperature, the grains of 35# steel ferrite and pearlite after heat treatment are coarser, and the hardness value becomes smaller. During the cooling process, the pearlite generated by the eutectic reaction is generally nucleated at the austenite grain boundaries because the austenite grains at high temperatures are larger and the grain boundaries are less. Hence, the nucleation site of pearlite is less, and the nucleation rate is lower.

Figure.1 Metallographic organization after different processes (No.1-3) × 200
The effect of starting furnace temperature on the annealing organization and hardness of 35# steel
The average hardness of process No.4 and process No.5 are 57 and 56HRB, respectively, and the coarse grains in the microstructure are more, see Fig.2. It can be seen that the annealing of different starting furnace temperatures has little effect on the organization and hardness of 35# steel.
Effect of cooling mode on the organization and hardness of 35# steel
The annealed hardness of process No.6 and process No.7 are 50 and 45HRB, respectively, and compared with process No.2, the hardness of the specimens cooled with the furnace is lower than that of the air-cooled specimens. Compared with air-cooled, the ferrite and pearlite with furnace cooling are coarser and the content of ferrite is less, and the content of pearlite is more, and the hardness value is smaller.

Figure.2 Metallographic organization after different processes (No.4-5)

Figure.3 Metallographic organization after the different processes (No.6-7)
The comparison of the metallographic grain size shows that the grain size with the furnace’s cooling is coarser than that of the air-cooled grains. The grain size of the heating temperature of 925℃ is coarser than that of 860℃. The grain size of the annealed specimen will become coarser as the heating temperature increases. This is because the nucleation and growth process of austenite in 35# steel after heating is the process of carbon atom diffusion and migration of grain boundaries. In the furnace cooling conditions, the 35# steel cooling rate is lower; the high-temperature residence time is longer, carbon atoms have a longer time to diffuse, grain boundaries have a longer time to migrate, austenite grains obtained after austenitization is larger, on the other hand, in the occurrence of co-dialysis reaction to generate pearlite, due to air-cooled cooling rate is a larger, co-dialysis reaction to getting more pearlite, ferrite phase is less, the organization is also more than the furnace cooling to get The organization is more uniform and smaller than that of furnace cooling. At the same time, because the hardness of the ferrite phase is lower and that of pearlite is higher, the room-temperature tissue obtained under air cooling is harder than that obtained under furnace cooling.

• (1) As the annealing temperature increases from 820℃ to 925℃, the hardness of 35# steel gradually decreases, and the grains of pearlite and ferrite in the microstructure become coarser and more and more unevenly distributed. The grains of annealed tissue become coarser with the increase in heating temperature.
• (2) The starting furnace temperature of the loaded sample is increased from room temperature to 850℃, which does not affect the hardness of 35# steel.
• (3) The hardness of 35# steel cooled with the furnace is lower than that of air-cooled 35# steel annealed at 860°C and 925°C, and the grain size cooled with the furnace is coarser than that of air-cooled 35# steel. The hardness of 35# steel can be controlled by controlling the holding temperature and cooling method of annealing.

Purchasing Tips of 35# steel

Purchasing 35# steel requires careful consideration of various factors, including the metal material‘s properties, supplier reputation, grades and specifications, pricing, and quality control measures. By following these comprehensive purchasing tips, you can ensure that you select the highest-quality 35# steel for your project, guaranteeing exceptional performance and longevity.

Comparing 35# Steel Grades and Specifications

It’s crucial to compare various grades and specifications of 35# steel to determine the most suitable option for your project. These factors include chemical composition, mechanical properties, and heat treatment methods. Always ensure that the chosen metal material complies with the required industry standards.

Negotiating Price and Terms

Request Multiple Quotes
To get the best deal on 35# steel, request quotes from multiple suppliers. This will allow you to compare prices and terms, ensuring you select the most cost-effective option.
Consider Bulk Purchasing
Purchasing 35# steel in bulk can often lead to significant discounts. You can negotiate a better price per unit by ordering larger quantities, leading to overall cost savings.
Review Payment and Delivery Terms
Thoroughly review the payment and delivery terms offered by the supplier. This includes shipping costs, lead times, and any additional charges that may be incurred. Ensure the terms are acceptable and align with your project timeline and budget.

Inspecting and Verifying 35# Steel Quality

Visual Inspection
Upon receiving your 35# steel order, perform a thorough visual inspection to check for any surface defects or inconsistencies. This includes examining the steel for cracks, indentations, and other imperfections that could compromise its performance.
Material Testing
Consider conducting material tests to verify the mechanical properties and chemical composition of your 35# steel. These tests might include hardness testing, tensile testing, and chemical analysis. This ensures that the material meets the required specifications and is suitable for your intended application.
Third-Party Inspection Services
If you want added assurance of the quality and compliance of your 35# steel, consider hiring third-party inspection services. These professionals can perform an unbiased material assessment, ensuring it meets the necessary standards and specifications.

Maintaining and Storing 35# Steel

Proper Storage
To preserve the quality and longevity of your 35# steel, store it in a dry, well-ventilated area away from direct sunlight and moisture. Proper storage prevents corrosion and other potential damage to the material.
Cleaning and Maintenance
Regularly clean and maintain your 35# steel components for optimal performance and durability. This includes removing dirt, debris, and any surface contaminants that could cause corrosion or compromise the material’s integrity.
Protective Coatings
Applying protective coatings, such as paint or galvanization, can enhance the corrosion resistance of your 35# steel. This additional layer of protection helps extend the material’s lifespan and ensures that it remains in optimal condition for its intended application.

Conclusion

35# steel is a versatile carbon structural steel with a wide range of applications, good mechanical properties, and excellent weldability. It is commonly used in the automotive, construction, and manufacturing industries. Understanding its properties, heat treatment processes, and comparison with other steels can help you make informed decisions when choosing the right material for your project.

Source: China 35# Steel Forgings Manufacturer – Yaang Pipe Industry (www.epowermetals.com)